1.
Jmol
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Jmol is computer software for molecular modelling chemical structures in 3-dimensions. Jmol returns a 3D representation of a molecule that may be used as a teaching tool and it is written in the programming language Java, so it can run on the operating systems Windows, macOS, Linux, and Unix, if Java is installed. It is free and open-source software released under a GNU Lesser General Public License version 2.0, a standalone application and a software development kit exist that can be integrated into other Java applications, such as Bioclipse and Taverna. A popular feature is an applet that can be integrated into web pages to display molecules in a variety of ways, for example, molecules can be displayed as ball-and-stick models, space-filling models, ribbon diagrams, etc. Jmol supports a range of chemical file formats, including Protein Data Bank, Crystallographic Information File, MDL Molfile. There is also a JavaScript-only version, JSmol, that can be used on computers with no Java, the Jmol applet, among other abilities, offers an alternative to the Chime plug-in, which is no longer under active development. While Jmol has many features that Chime lacks, it does not claim to reproduce all Chime functions, most notably, Chime requires plug-in installation and Internet Explorer 6.0 or Firefox 2.0 on Microsoft Windows, or Netscape Communicator 4.8 on Mac OS9. Jmol requires Java installation and operates on a variety of platforms. For example, Jmol is fully functional in Mozilla Firefox, Internet Explorer, Opera, Google Chrome, fast and Scriptable Molecular Graphics in Web Browsers without Java3D
2.
ChemSpider
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ChemSpider is a database of chemicals. ChemSpider is owned by the Royal Society of Chemistry, the database contains information on more than 50 million molecules from over 500 data sources including, Each chemical is given a unique identifier, which forms part of a corresponding URL. This is an approach to develop an online chemistry database. The search can be used to widen or restrict already found results, structure searching on mobile devices can be done using free apps for iOS and for the Android. The ChemSpider database has been used in combination with text mining as the basis of document markup. The result is a system between chemistry documents and information look-up via ChemSpider into over 150 data sources. ChemSpider was acquired by the Royal Society of Chemistry in May,2009, prior to the acquisition by RSC, ChemSpider was controlled by a private corporation, ChemZoo Inc. The system was first launched in March 2007 in a release form. ChemSpider has expanded the generic support of a database to include support of the Wikipedia chemical structure collection via their WiChempedia implementation. A number of services are available online. SyntheticPages is an interactive database of synthetic chemistry procedures operated by the Royal Society of Chemistry. Users submit synthetic procedures which they have conducted themselves for publication on the site and these procedures may be original works, but they are more often based on literature reactions. Citations to the published procedure are made where appropriate. They are checked by an editor before posting. The pages do not undergo formal peer-review like a journal article. The comments are moderated by scientific editors. The intention is to collect practical experience of how to conduct useful chemical synthesis in the lab, while experimental methods published in an ordinary academic journal are listed formally and concisely, the procedures in ChemSpider SyntheticPages are given with more practical detail. Comments by submitters are included as well, other publications with comparable amounts of detail include Organic Syntheses and Inorganic Syntheses
3.
European Chemicals Agency
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ECHA is the driving force among regulatory authorities in implementing the EUs chemicals legislation. ECHA helps companies to comply with the legislation, advances the safe use of chemicals, provides information on chemicals and it is located in Helsinki, Finland. The Agency, headed by Executive Director Geert Dancet, started working on 1 June 2007, the REACH Regulation requires companies to provide information on the hazards, risks and safe use of chemical substances that they manufacture or import. Companies register this information with ECHA and it is freely available on their website. So far, thousands of the most hazardous and the most commonly used substances have been registered, the information is technical but gives detail on the impact of each chemical on people and the environment. This also gives European consumers the right to ask whether the goods they buy contain dangerous substances. The Classification, Labelling and Packaging Regulation introduces a globally harmonised system for classifying and labelling chemicals into the EU. This worldwide system makes it easier for workers and consumers to know the effects of chemicals, companies need to notify ECHA of the classification and labelling of their chemicals. So far, ECHA has received over 5 million notifications for more than 100000 substances, the information is freely available on their website. Consumers can check chemicals in the products they use, Biocidal products include, for example, insect repellents and disinfectants used in hospitals. The Biocidal Products Regulation ensures that there is information about these products so that consumers can use them safely. ECHA is responsible for implementing the regulation, the law on Prior Informed Consent sets guidelines for the export and import of hazardous chemicals. Through this mechanism, countries due to hazardous chemicals are informed in advance and have the possibility of rejecting their import. Substances that may have effects on human health and the environment are identified as Substances of Very High Concern 1. These are mainly substances which cause cancer, mutation or are toxic to reproduction as well as substances which persist in the body or the environment, other substances considered as SVHCs include, for example, endocrine disrupting chemicals. Companies manufacturing or importing articles containing these substances in a concentration above 0 and they are required to inform users about the presence of the substance and therefore how to use it safely. Consumers have the right to ask the retailer whether these substances are present in the products they buy, once a substance has been officially identified in the EU as being of very high concern, it will be added to a list. This list is available on ECHA’s website and shows consumers and industry which chemicals are identified as SVHCs, Substances placed on the Candidate List can then move to another list
4.
PubChem
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PubChem is a database of chemical molecules and their activities against biological assays. The system is maintained by the National Center for Biotechnology Information, a component of the National Library of Medicine, PubChem can be accessed for free through a web user interface. Millions of compound structures and descriptive datasets can be downloaded via FTP. PubChem contains substance descriptions and small molecules with fewer than 1000 atoms and 1000 bonds, more than 80 database vendors contribute to the growing PubChem database. PubChem consists of three dynamically growing primary databases, as of 28 January 2016, Compounds,82.6 million entries, contains pure and characterized chemical compounds. Substances,198 million entries, contains also mixtures, extracts, complexes, bioAssay, bioactivity results from 1.1 million high-throughput screening programs with several million values. PubChem contains its own online molecule editor with SMILES/SMARTS and InChI support that allows the import and export of all common chemical file formats to search for structures and fragments. In the text search form the database fields can be searched by adding the name in square brackets to the search term. A numeric range is represented by two separated by a colon. The search terms and field names are case-insensitive, parentheses and the logical operators AND, OR, and NOT can be used. AND is assumed if no operator is used, example,0,5000,50,10 -5,5 PubChem was released in 2004. The American Chemical Society has raised concerns about the publicly supported PubChem database and they have a strong interest in the issue since the Chemical Abstracts Service generates a large percentage of the societys revenue. To advocate their position against the PubChem database, ACS has actively lobbied the US Congress, soon after PubChems creation, the American Chemical Society lobbied U. S. Congress to restrict the operation of PubChem, which they asserted competes with their Chemical Abstracts Service
5.
International Chemical Identifier
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Initially developed by IUPAC and NIST from 2000 to 2005, the format and algorithms are non-proprietary. The continuing development of the standard has supported since 2010 by the not-for-profit InChI Trust. The current version is 1.04 and was released in September 2011, prior to 1.04, the software was freely available under the open source LGPL license, but it now uses a custom license called IUPAC-InChI Trust License. Not all layers have to be provided, for instance, the layer can be omitted if that type of information is not relevant to the particular application. InChIs can thus be seen as akin to a general and extremely formalized version of IUPAC names and they can express more information than the simpler SMILES notation and differ in that every structure has a unique InChI string, which is important in database applications. Information about the 3-dimensional coordinates of atoms is not represented in InChI, the InChI algorithm converts input structural information into a unique InChI identifier in a three-step process, normalization, canonicalization, and serialization. The InChIKey, sometimes referred to as a hashed InChI, is a fixed length condensed digital representation of the InChI that is not human-understandable. The InChIKey specification was released in September 2007 in order to facilitate web searches for chemical compounds and it should be noted that, unlike the InChI, the InChIKey is not unique, though collisions can be calculated to be very rare, they happen. In January 2009 the final 1.02 version of the InChI software was released and this provided a means to generate so called standard InChI, which does not allow for user selectable options in dealing with the stereochemistry and tautomeric layers of the InChI string. The standard InChIKey is then the hashed version of the standard InChI string, the standard InChI will simplify comparison of InChI strings and keys generated by different groups, and subsequently accessed via diverse sources such as databases and web resources. Every InChI starts with the string InChI= followed by the version number and this is followed by the letter S for standard InChIs. The remaining information is structured as a sequence of layers and sub-layers, the layers and sub-layers are separated by the delimiter / and start with a characteristic prefix letter. The six layers with important sublayers are, Main layer Chemical formula and this is the only sublayer that must occur in every InChI. The atoms in the formula are numbered in sequence, this sublayer describes which atoms are connected by bonds to which other ones. Describes how many hydrogen atoms are connected to each of the other atoms, the condensed,27 character standard InChIKey is a hashed version of the full standard InChI, designed to allow for easy web searches of chemical compounds. Most chemical structures on the Web up to 2007 have been represented as GIF files, the full InChI turned out to be too lengthy for easy searching, and therefore the InChIKey was developed. With all databases currently having below 50 million structures, such duplication appears unlikely at present, a recent study more extensively studies the collision rate finding that the experimental collision rate is in agreement with the theoretical expectations. Example, Morphine has the structure shown on the right, as the InChI cannot be reconstructed from the InChIKey, an InChIKey always needs to be linked to the original InChI to get back to the original structure
6.
Simplified molecular-input line-entry system
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The simplified molecular-input line-entry system is a specification in form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules, the original SMILES specification was initiated in the 1980s. It has since modified and extended. In 2007, a standard called OpenSMILES was developed in the open-source chemistry community. Other linear notations include the Wiswesser Line Notation, ROSDAL and SLN, the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. The Environmental Protection Agency funded the project to develop SMILES. It has since modified and extended by others, most notably by Daylight Chemical Information Systems. In 2007, a standard called OpenSMILES was developed by the Blue Obelisk open-source chemistry community. Other linear notations include the Wiswesser Line Notation, ROSDAL and SLN, in July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is generally considered to have the advantage of being slightly more human-readable than InChI, the term SMILES refers to a line notation for encoding molecular structures and specific instances should strictly be called SMILES strings. However, the term SMILES is also used to refer to both a single SMILES string and a number of SMILES strings, the exact meaning is usually apparent from the context. The terms canonical and isomeric can lead to confusion when applied to SMILES. The terms describe different attributes of SMILES strings and are not mutually exclusive, typically, a number of equally valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol, algorithms have been developed to generate the same SMILES string for a given molecule, of the many possible strings, these algorithms choose only one of them. This SMILES is unique for each structure, although dependent on the algorithm used to generate it. These algorithms first convert the SMILES to a representation of the molecular structure. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database, there is currently no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, and these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES
7.
Chemical formula
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These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, the simplest types of chemical formulas are called empirical formulas, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the numbers of each type of atom in a molecule. For example, the formula for glucose is CH2O, while its molecular formula is C6H12O6. This is possible if the relevant bonding is easy to show in one dimension, an example is the condensed molecular/chemical formula for ethanol, which is CH3-CH2-OH or CH3CH2OH. For reasons of structural complexity, there is no condensed chemical formula that specifies glucose, chemical formulas may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. A chemical formula identifies each constituent element by its chemical symbol, in empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound, as ratios to the key element. For molecular compounds, these numbers can all be expressed as whole numbers. For example, the formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of compounds, however, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the consists of simple molecules. These types of formulas are known as molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the formula for glucose is C6H12O6 rather than the glucose empirical formula. However, except for very simple substances, molecular chemical formulas lack needed structural information, for simple molecules, a condensed formula is a type of chemical formula that may fully imply a correct structural formula. For example, ethanol may be represented by the chemical formula CH3CH2OH
8.
Density
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The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume, ρ = m V, where ρ is the density, m is the mass, and V is the volume. In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity, osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka. As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume. As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.1,000 kg/m3 equals 1 g/cm3. In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density
9.
Celsius
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Celsius, also known as centigrade, is a metric scale and unit of measurement for temperature. As an SI derived unit, it is used by most countries in the world and it is named after the Swedish astronomer Anders Celsius, who developed a similar temperature scale. The degree Celsius can refer to a temperature on the Celsius scale as well as a unit to indicate a temperature interval. Before being renamed to honour Anders Celsius in 1948, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps. The scale is based on 0° for the point of water. This scale is widely taught in schools today, by international agreement the unit degree Celsius and the Celsius scale are currently defined by two different temperatures, absolute zero, and the triple point of VSMOW. This definition also precisely relates the Celsius scale to the Kelvin scale, absolute zero, the lowest temperature possible, is defined as being precisely 0 K and −273.15 °C. The temperature of the point of water is defined as precisely 273.16 K at 611.657 pascals pressure. This definition fixes the magnitude of both the degree Celsius and the kelvin as precisely 1 part in 273.16 of the difference between absolute zero and the point of water. Thus, it sets the magnitude of one degree Celsius and that of one kelvin as exactly the same, additionally, it establishes the difference between the two scales null points as being precisely 273.15 degrees. In his paper Observations of two persistent degrees on a thermometer, he recounted his experiments showing that the point of ice is essentially unaffected by pressure. He also determined with precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the point of his temperature scale, being the boiling point. This pressure is known as one standard atmosphere, the BIPMs 10th General Conference on Weights and Measures later defined one standard atmosphere to equal precisely 1013250dynes per square centimetre. On 19 May 1743 he published the design of a mercury thermometer, in 1744, coincident with the death of Anders Celsius, the Swedish botanist Carolus Linnaeus reversed Celsiuss scale. In it, Linnaeus recounted the temperatures inside the orangery at the University of Uppsala Botanical Garden, since the 19th century, the scientific and thermometry communities worldwide referred to this scale as the centigrade scale. Temperatures on the scale were often reported simply as degrees or. More properly, what was defined as centigrade then would now be hectograde.2 gradians, for scientific use, Celsius is the term usually used, with centigrade otherwise continuing to be in common but decreasing use, especially in informal contexts in English-speaking countries
10.
Melting point
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The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point the solid and liquid phase exist in equilibrium, the melting point of a substance depends on pressure and is usually specified at standard pressure. When considered as the temperature of the change from liquid to solid. Because of the ability of some substances to supercool, the point is not considered as a characteristic property of a substance. For most substances, melting and freezing points are approximately equal, for example, the melting point and freezing point of mercury is 234.32 kelvins. However, certain substances possess differing solid-liquid transition temperatures, for example, agar melts at 85 °C and solidifies from 31 °C to 40 °C, such direction dependence is known as hysteresis. The melting point of ice at 1 atmosphere of pressure is close to 0 °C. In the presence of nucleating substances the freezing point of water is the same as the melting point, the chemical element with the highest melting point is tungsten, at 3687 K, this property makes tungsten excellent for use as filaments in light bulbs. Many laboratory techniques exist for the determination of melting points, a Kofler bench is a metal strip with a temperature gradient. Any substance can be placed on a section of the strip revealing its thermal behaviour at the temperature at that point, differential scanning calorimetry gives information on melting point together with its enthalpy of fusion. A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window, the several grains of a solid are placed in a thin glass tube and partially immersed in the oil bath. The oil bath is heated and with the aid of the melting of the individual crystals at a certain temperature can be observed. In large/small devices, the sample is placed in a heating block, the measurement can also be made continuously with an operating process. For instance, oil refineries measure the point of diesel fuel online, meaning that the sample is taken from the process. This allows for more frequent measurements as the sample does not have to be manually collected, for refractory materials the extremely high melting point may be determined by heating the material in a black body furnace and measuring the black-body temperature with an optical pyrometer. For the highest melting materials, this may require extrapolation by several hundred degrees, the spectral radiance from an incandescent body is known to be a function of its temperature. An optical pyrometer matches the radiance of a body under study to the radiance of a source that has been previously calibrated as a function of temperature, in this way, the measurement of the absolute magnitude of the intensity of radiation is unnecessary. However, known temperatures must be used to determine the calibration of the pyrometer, for temperatures above the calibration range of the source, an extrapolation technique must be employed
11.
Boiling point
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The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the environmental pressure. A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high pressure has a boiling point than when that liquid is at atmospheric pressure. For a given pressure, different liquids boil at different temperatures, for example, water boils at 100 °C at sea level, but at 93.4 °C at 2,000 metres altitude. The normal boiling point of a liquid is the case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level,1 atmosphere. At that temperature, the pressure of the liquid becomes sufficient to overcome atmospheric pressure. The standard boiling point has been defined by IUPAC since 1982 as the temperature at which boiling occurs under a pressure of 1 bar, the heat of vaporization is the energy required to transform a given quantity of a substance from a liquid into a gas at a given pressure. Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation, evaporation is a surface phenomenon in which molecules located near the liquids edge, not contained by enough liquid pressure on that side, escape into the surroundings as vapor. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, a saturated liquid contains as much thermal energy as it can without boiling. The saturation temperature is the temperature for a corresponding saturation pressure at which a liquid boils into its vapor phase, the liquid can be said to be saturated with thermal energy. Any addition of energy results in a phase transition. If the pressure in a system remains constant, a vapor at saturation temperature will begin to condense into its liquid phase as thermal energy is removed, similarly, a liquid at saturation temperature and pressure will boil into its vapor phase as additional thermal energy is applied. The boiling point corresponds to the temperature at which the pressure of the liquid equals the surrounding environmental pressure. Thus, the point is dependent on the pressure. Boiling points may be published with respect to the NIST, USA standard pressure of 101.325 kPa, at higher elevations, where the atmospheric pressure is much lower, the boiling point is also lower. The boiling point increases with increased pressure up to the critical point, the boiling point cannot be increased beyond the critical point. Likewise, the point decreases with decreasing pressure until the triple point is reached
12.
Aqueous solution
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An aqueous solution is a solution in which the solvent is water. It is usually shown in chemical equations by appending to the relevant chemical formula, for example, a solution of table salt, or sodium chloride, in water would be represented as Na+ + Cl−. The word aqueous means pertaining to, related to, similar to, as water is an excellent solvent and is also naturally abundant, it is a ubiquitous solvent in chemistry. Substances that are hydrophobic often do not dissolve well in water, an example of a hydrophilic substance is sodium chloride. Acids and bases are aqueous solutions, as part of their Arrhenius definitions, the ability of a substance to dissolve in water is determined by whether the substance can match or exceed the strong attractive forces that water molecules generate between themselves. If the substance lacks the ability to dissolve in water the molecules form a precipitate, reactions in aqueous solutions are usually metathesis reactions. Metathesis reactions are another term for double-displacement, that is, when a cation displaces to form a bond with the other anion. The cation bonded with the latter anion will dissociate and bond with the other anion, aqueous solutions that conduct electric current efficiently contain strong electrolytes, while ones that conduct poorly are considered to have weak electrolytes. Those strong electrolytes are substances that are ionized in water. Nonelectrolytes are substances that dissolve in water yet maintain their molecular integrity, examples include sugar, urea, glycerol, and methylsulfonylmethane. When writing the equations of reactions, it is essential to determine the precipitate. To determine the precipitate, one must consult a chart of solubility, soluble compounds are aqueous, while insoluble compounds are the precipitate. Remember that there may not always be a precipitate, when performing calculations regarding the reacting of one or more aqueous solutions, in general one must know the concentration, or molarity, of the aqueous solutions. Solution concentration is given in terms of the form of the prior to it dissolving. Metal ions in aqueous solution Solubility Dissociation Acid-base reaction theories Properties of water Zumdahl S.1997, 4th ed. Boston, Houghton Mifflin Company
13.
Solubility
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Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent. The solubility of a substance depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure. The solubility of a substance is a different property from the rate of solution. Most often, the solvent is a liquid, which can be a substance or a mixture. One may also speak of solid solution, but rarely of solution in a gas, the extent of solubility ranges widely, from infinitely soluble such as ethanol in water, to poorly soluble, such as silver chloride in water. The term insoluble is often applied to poorly or very poorly soluble compounds, a common threshold to describe something as insoluble is less than 0.1 g per 100 mL of solvent. Under certain conditions, the solubility can be exceeded to give a so-called supersaturated solution. Metastability of crystals can also lead to apparent differences in the amount of a chemical that dissolves depending on its form or particle size. A supersaturated solution generally crystallises when seed crystals are introduced and rapid equilibration occurs, phenylsalicylate is one such simple observable substance when fully melted and then cooled below its fusion point. Solubility is not to be confused with the ability to dissolve a substance, for example, zinc dissolves in hydrochloric acid as a result of a chemical reaction releasing hydrogen gas in a displacement reaction. The zinc ions are soluble in the acid, the smaller a particle is, the faster it dissolves although there are many factors to add to this generalization. Crucially solubility applies to all areas of chemistry, geochemistry, inorganic, physical, organic, in all cases it will depend on the physical conditions and the enthalpy and entropy directly relating to the solvents and solutes concerned. By far the most common solvent in chemistry is water which is a solvent for most ionic compounds as well as a range of organic substances. This is a factor in acidity/alkalinity and much environmental and geochemical work. According to the IUPAC definition, solubility is the composition of a saturated solution expressed as a proportion of a designated solute in a designated solvent. Solubility may be stated in units of concentration such as molarity, molality, mole fraction, mole ratio, mass per volume. Solubility occurs under dynamic equilibrium, which means that solubility results from the simultaneous and opposing processes of dissolution, the solubility equilibrium occurs when the two processes proceed at a constant rate. The term solubility is used in some fields where the solute is altered by solvolysis
14.
Diethyl ether
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Diethyl ether or simply ether, is an organic compound in the ether class with the formula 2O. It is a colorless, highly flammable liquid. It is commonly used as a solvent in laboratories and as a fluid for some engines. It was formerly used as an anesthetic, until non-flammable drugs were developed. It has been used as a drug to cause intoxication. The compound may have created by either Jābir ibn Hayyān in the 8th century or Ramon Llull in 1275. At about the time, Paracelsus discovered ethers analgesic properties in chickens. The name ether was given to the substance in 1729 by August Sigmund Frobenius and it is particularly important as a solvent in the production of cellulose plastics such as cellulose acetate. Ether starting fluid is sold and used in countries with cold climates, for the same reason it is also used as a component of the fuel mixture for carbureted compression ignition model engines. In this way diethyl ether is very similar to one of its precursors, diethyl ether is a common laboratory aprotic solvent. It has limited solubility in water and dissolves 1.5 g/100 ml water at 25 °C and this, coupled with its high volatility, makes it ideal for use as the non-polar solvent in liquid-liquid extraction. When used with a solution, the diethyl ether layer is on top due to the fact that it has a lower density than the water. It is also a solvent for the Grignard reaction in addition to other reactions involving organometallic reagents. Morton participated in a demonstration of ether anesthesia on October 16,1846 at the Ether Dome in Boston. British doctors were aware of the properties of ether as early as 1840 where it was widely prescribed in conjunction with opium. Because of its associations with Boston, the use of ether became known as the Yankee Dodge, diethyl ether depresses the myocardium and increases tracheobronchial secretions. Diethyl ether could also be mixed with other agents such as chloroform to make C. E. mixture, or chloroform. In the 2000s, ether is rarely used, the use of flammable ether was displaced by nonflammable fluorinated hydrocarbon anesthetics
15.
Benzene
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Benzene is an important organic chemical compound with the chemical formula C6H6. The benzene molecule is composed of 6 carbon atoms joined in a ring with 1 hydrogen atom attached to each, because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is a constituent of crude oil and is one of the elementary petrochemicals. Because of the cyclic continuous pi bond between the atoms, benzene is classed as an aromatic hydrocarbon, the second -annulene. Benzene is a colorless and highly flammable liquid with a sweet smell and it is used primarily as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene, of which billions of kilograms are produced. Because benzene has a high number, it is an important component of gasoline. Because benzene is a carcinogen, most non-industrial applications have been limited. The word benzene derives historically from gum benzoin, a resin known to European pharmacists. An acidic material was derived from benzoin by sublimation, and named flowers of benzoin, the hydrocarbon derived from benzoic acid thus acquired the name benzin, benzol, or benzene. Michael Faraday first isolated and identified benzene in 1825 from the oily residue derived from the production of illuminating gas, in 1833, Eilhard Mitscherlich produced it by distilling benzoic acid and lime. He gave the compound the name benzin, in 1845, Charles Mansfield, working under August Wilhelm von Hofmann, isolated benzene from coal tar. Four years later, Mansfield began the first industrial-scale production of benzene, gradually, the sense developed among chemists that a number of substances were chemically related to benzene, comprising a diverse chemical family. In 1855, Hofmann used the word aromatic to designate this family relationship, in 1997, benzene was detected in deep space. The empirical formula for benzene was known, but its highly polyunsaturated structure. In 1865, the German chemist Friedrich August Kekulé published a paper in French suggesting that the structure contained a ring of six carbon atoms with alternating single and double bonds, the next year he published a much longer paper in German on the same subject. Kekulés symmetrical ring could explain these facts, as well as benzenes 1,1 carbon-hydrogen ratio. Here Kekulé spoke of the creation of the theory and he said that he had discovered the ring shape of the benzene molecule after having a reverie or day-dream of a snake seizing its own tail. This vision, he said, came to him years of studying the nature of carbon-carbon bonds
16.
Toluene
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Toluene /ˈtɒljuːiːn/, also known as toluol /ˈtɒljuːɒl/, is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a benzene derivative, consisting of a CH3 group attached to a phenyl group. As such, its IUPAC systematic name is methylbenzene, Toluene is widely used as an industrial feedstock and a solvent. In 2013, worldwide sales of toluene amounted to about 24.5 billion US-dollars, as the solvent in some types of paint thinner, contact cement and model airplane glue, toluene is sometimes used as a recreational inhalant and has the potential of causing severe neurological harm. The compound was first isolated in 1837 through a distillation of oil by a Polish chemist named Filip Walter. In 1843, Jöns Jacob Berzelius recommended the name toluin, in 1850, French chemist Auguste Cahours isolated from a distillate of wood a hydrocarbon which he recognized as similar to Devilles benzoène and which Cahours named toluène. Toluene reacts as an aromatic hydrocarbon in electrophilic aromatic substitution. Because the methyl group has greater electron-releasing properties than an atom in the same position. It undergoes sulfonation to give p-toluenesulfonic acid, and chlorination by Cl2 in the presence of FeCl3 to give ortho, importantly, the methyl side chain in toluene is susceptible to oxidation. Toluene reacts with Potassium permanganate to yield benzoic acid, and with chromyl chloride to yield benzaldehyde, the methyl group undergoes halogenation under free radical conditions. For example, N-bromosuccinimide heated with toluene in the presence of AIBN leads to benzyl bromide, the same conversion can be effected with elemental bromine in the presence of UV light or even sunlight. Toluene may also be brominated by treating it with HBr and H2O2 in the presence of light. C6H5CH3 + Br2 → C6H5CH2Br + HBr C6H5CH2Br + Br2 → C6H5CHBr2 + HBr The methyl group in toluene undergoes deprotonation only with strong bases. Catalytic hydrogenation of toluene gives methylcyclohexane, the reaction requires a high pressure of hydrogen and a catalyst. Final separation and purification is done by any of the distillation or solvent extraction processes used for BTX aromatics, Toluene is so inexpensively produced industrially that it is not prepared in the laboratory. In principle it could be prepared by a variety of methods, Toluene is mainly used as a precursor to benzene via hydrodealkylation, C6H5CH3 + H2 → C6H6 + CH4 The second ranked application involves its disproportionation to a mixture of benzene and xylene. When oxidized it yields benzaldehyde and benzoic acid, two important intermediates in chemistry, in addition to the synthesis of benzene and xylene, toluene is a feedstock for toluene diisocyanate, trinitrotoluene, and a number of synthetic drugs. Toluene is a solvent, e. g. for paints, paint thinners, silicone sealants, many chemical reactants, rubber, printing ink, adhesives, lacquers, leather tanners
17.
Xylene
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Xylene, xylol or dimethylbenzene is any one of three isomers of dimethylbenzene, or a combination thereof. With the formula 2C6H4, each of the three compounds has a benzene ring with two methyl groups attached at substituents. They are all colorless, flammable liquids, some of which are of great industrial value, the mixture is referred to as both xylene and, more precisely, xylenes. Xylenes are an important petrochemical produced by reforming and also by coal carbonisation in the manufacture of coke fuel. They also occur in oil in concentrations of about 0. 5–1%. Small quantities occur in gasoline and aircraft fuels, xylenes are produced mainly as part of the BTX aromatics extracted from the product of catalytic reforming known as reformate. The xylene mixture is a greasy, colorless liquid commonly encountered as a solvent. Several million tons are produced annually, in 2011, a global consortium began construction of one of the world’s largest xylene plants in Singapore. Xylene was first isolated and named in 1850 by the French chemist Auguste Cahours, Xylene exists in three isomeric forms. The isomers can be distinguished by the designations ortho-, meta-, and para-, of the three isomers, the p-isomer is the most industrially sought after since it can be oxidized to terephthalic acid. Xylenes are produced by the methylation of toluene and benzene, commercial or laboratory grade xylene produced usually contains about 40-65% of m-xylene and up to 20% each of o-xylene, p-xylene and ethylbenzene. The ratio of isomers can be shifted to favor the highly valued p-xylene via the patented UOP-Isomar process or by transalkylation of xylene with itself or trimethylbenzene and these conversions are catalyzed by zeolites. The chemical and physical properties of xylene differ according to the respective isomers, the melting point ranges from −47.87 °C to 13.26 °C. The boiling point for each isomer is around 140 °C, the density of each isomer is around 0.87 g/mL and thus is less dense than water. Xylene in air can be smelled at concentrations as low as 0.08 to 3.7 ppm, xylenes form azeotropes with water and a variety of alcohols. With water the azeotrope consists of 60% xylenes and boils at 94.5 °C, as with many alkylbenzene compounds, xylenes form complexes with various halocarbons. The complexes of different isomers often have different properties from each other. P-Xylene is the precursor to terephthalic acid and dimethyl terephthalate
18.
Vapor pressure
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Vapor pressure or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature in a closed system. The equilibrium vapor pressure is an indication of a liquids evaporation rate and it relates to the tendency of particles to escape from the liquid. A substance with a vapor pressure at normal temperatures is often referred to as volatile. The pressure exhibited by vapor present above a surface is known as vapor pressure. As the temperature of a liquid increases, the energy of its molecules also increases. As the kinetic energy of the molecules increases, the number of molecules transitioning into a vapor also increases, the vapor pressure of any substance increases non-linearly with temperature according to the Clausius–Clapeyron relation. The atmospheric pressure boiling point of a liquid is the temperature at which the pressure equals the ambient atmospheric pressure. With any incremental increase in temperature, the vapor pressure becomes sufficient to overcome atmospheric pressure. Bubble formation deeper in the liquid requires a pressure, and therefore higher temperature. More important at shallow depths, is the temperature required to start bubble formation. The surface tension of the wall lead to an overpressure in the very small initial bubbles. Thus, thermometer calibration should not rely on the temperature in boiling water, the vapor pressure that a single component in a mixture contributes to the total pressure in the system is called partial pressure. Vapor pressure is measured in the units of pressure. The International System of Units recognizes pressure as a unit with the dimension of force per area. One pascal is one newton per square meter, experimental measurement of vapor pressure is a simple procedure for common pressures between 1 and 200 kPa. Most accurate results are obtained near the point of substances. Better accuracy is achieved when care is taken to ensure that the entire substance and this is often done, as with the use of an isoteniscope, by submerging the containment area in a liquid bath. Very low vapor pressures of solids can be measured using the Knudsen effusion cell method, the Antoine equation is a mathematical expression of the relation between the vapor pressure and the temperature of pure liquid or solid substances
19.
Aromatic hydrocarbon
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An aromatic hydrocarbon or arene is a hydrocarbon with sigma bonds and delocalized pi electrons between carbon atoms forming a circle. In contrast, aliphatic hydrocarbons lack this delocalization, the term aromatic was assigned before the physical mechanism determining aromaticity was discovered, the term was coined as such simply because many of the compounds have a sweet or pleasant odour. The configuration of six carbon atoms in compounds is known as a benzene ring, after the simplest possible such hydrocarbon. Aromatic hydrocarbons can be monocyclic or polycyclic, some non-benzene-based compounds called heteroarenes, which follow Hückels rule, are also called aromatic compounds. In these compounds, at least one atom is replaced by one of the heteroatoms oxygen, nitrogen. Benzene, C6H6, is the simplest aromatic hydrocarbon, and it was the first one named as such, the nature of its bonding was first recognized by August Kekulé in the 19th century. Each carbon atom in the cycle has four electrons to share. One goes to the atom, and one each to the two neighbouring carbons. The structure is alternatively illustrated as a circle around the inside of the ring to show six electrons floating around in delocalized molecular orbitals the size of the ring itself. This depiction represents the equivalent nature of the six carbon–carbon bonds all of bond order 1.5, the electrons are visualized as floating above and below the ring with the electromagnetic fields they generate acting to keep the ring flat. The proper use of the symbol is debated, it is used to describe any cyclic π system in some publications, jensen argues that, in line with Robinsons original proposal, the use of the circle symbol should be limited to monocyclic 6 π-electron systems. In this way the symbol for a six-center six-electron bond can be compared to the Y symbol for a three-center two-electron bond. A reaction that forms a compound from an unsaturated or partially unsaturated cyclic precursor is simply called an aromatization. Many laboratory methods exist for the synthesis of arenes from non-arene precursors. Many methods rely on cycloaddition reactions, alkyne trimerization describes the cyclization of three alkynes, in the Dötz reaction an alkyne, carbon monoxide and a chromium carbene complex are the reactants. Diels–Alder reactions of alkynes with pyrone or cyclopentadienone with expulsion of carbon dioxide or carbon monoxide also form arene compounds, in Bergman cyclization the reactants are an enyne plus a hydrogen donor. Arenes are reactants in many organic reactions, in aromatic substitution one substituent on the arene ring, usually hydrogen, is replaced by another substituent. The two main types are electrophilic aromatic substitution when the reagent is an electrophile and nucleophilic aromatic substitution when the reagent is a nucleophile
20.
Alpha and beta carbon
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The alpha carbon in organic molecules refers to the first carbon atom that attaches to a functional group, such as a carbonyl. The second carbon atom is called the beta carbon, and the system continues naming in alphabetical order with Greek letters, the nomenclature can also be applied to the hydrogen atoms attached to the carbon atoms. A hydrogen atom attached to a carbon atom is called an alpha-hydrogen atom, a hydrogen atom on the beta-carbon atom is a beta hydrogen atom. Organic molecules with more than one group can be a source of confusion. Generally the functional group responsible for the name or type of the molecule is the group for purposes of carbon-atom naming. For example, the molecules nitrostyrene and phenethylamine are very similar, alpha-carbon is also a term that applies to proteins and amino acids. It is the carbon before the carbonyl carbon. Therefore, reading along the backbone of a protein would give a sequence of –n– etc. The α-carbon is where the different substituents attach to different amino acid. That is, the groups hanging off the chain at the α-carbon are what give amino acids their diversity and these groups give the α-carbon its stereogenic properties for every amino acid except for glycine. Therefore, the α-carbon is a stereocenter for every amino acid except glycine, glycine also does not have a β-carbon, while every other amino acid does. The α-carbon of an acid is significant in protein folding. When describing a protein, which is a chain of amino acids, in general, α-carbons of adjacent amino acids in a protein are about 3.8 ångströms apart. The α-carbon is important for enol- and enolate-based carbonyl chemistry as well, an exception is in reaction with silyl- chlorides, -bromides, and -iodides, where the oxygen acts as the nucleophile to produce silyl enol ether. ^ Hackhs Chemical Dictionary,1969, page 30, ^ Hackhs Chemical Dictionary,1969, page 95
21.
Keto group
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In chemistry, a ketone /ˈkiːtoʊn/ is an organic compound with the structure RCR, where R and R can be a variety of carbon-containing substituents. Ketones and aldehydes are simple compounds that contain a carbonyl group and they are considered simple because they do not have reactive groups like −OH or −Cl attached directly to the carbon atom in the carbonyl group, as in carboxylic acids containing −COOH. Many ketones are known and many are of importance in industry. Examples include many sugars and the industrial solvent acetone, which is the smallest ketone, the word ketone is derived from Aketon, an old German word for acetone. According to the rules of IUPAC nomenclature, ketones are named by changing the suffix -ane of the parent alkane to -anone, the position of the carbonyl group is usually denoted by a number. For the most important ketones, however, traditional names are still generally used. The common names of ketones are obtained by writing separately the names of the two alkyl groups attached to the group, followed by ketone as a separate word. The names of the groups are written alphabetically. When the two groups are the same, the prefix di- is added before the name of alkyl group. The positions of other groups are indicated by Greek letters, the α-carbon being the adjacent to carbonyl group. If both alkyl groups in a ketone are the same then the ketone is said to be symmetrical, although used infrequently, oxo is the IUPAC nomenclature for a ketone functional group. Other prefixes, however, are also used, for some common chemicals, keto or oxo refer to the ketone functional group. The term oxo is used widely through chemistry, for example, it also refers to an oxygen atom bonded to a transition metal. The ketone carbon is often described as sp2 hybridized, a description that includes both their electronic and molecular structure, ketones are trigonal planar around the ketonic carbon, with C−C−O and C−C−C bond angles of approximately 120°. Ketones differ from aldehydes in that the group is bonded to two carbons within a carbon skeleton. In aldehydes, the carbonyl is bonded to one carbon and one hydrogen and are located at the ends of carbon chains, ketones are also distinct from other carbonyl-containing functional groups, such as carboxylic acids, esters and amides. The carbonyl group is polar because the electronegativity of the oxygen is greater than that for carbon, thus, ketones are nucleophilic at oxygen and electrophilic at carbon. Because the carbonyl group interacts with water by bonding, ketones are typically more soluble in water than the related methylene compounds
22.
Skeletal formula
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A skeletal formula shows the skeletal structure or skeleton of a molecule, which is composed of the skeletal atoms that make up the molecule. It is represented in two dimensions, as on a page of paper and it employs certain conventions to represent carbon and hydrogen atoms, which are the most common in organic chemistry. The technique was developed by the organic chemist Friedrich August Kekulé von Stradonitz, Skeletal formulae have become ubiquitous in organic chemistry, partly because they are relatively quick and simple to draw. As in a Lewis structure, a doubled or tripled line segment indicates double or triple bonding, the skeletal structure of an organic compound is the series of atoms bonded together that form the essential structure of the compound. The skeleton can consist of chains, branches and/or rings of bonded atoms, Skeletal atoms other than carbon or hydrogen are called heteroatoms. The skeleton has hydrogen and/or various substituents bonded to its atoms, hydrogen is the most common non-carbon atom that is bonded to carbon and, for simplicity, is not explicitly drawn. For example, in the image below, the formula of hexane is shown. The carbon atom labeled C1 appears to have one bond. The carbon atom labelled C3 has two bonds to other carbons and is bonded to two hydrogen atoms as well. NOTE, It doesnt matter which end of the chain you start numbering from, the condensed formula or the IUPAC name will confirm the orientation. Some molecules will become familiar regardless of the orientation, any hydrogen atoms bonded to non-carbon atoms are drawn explicitly. In ethanol, C2H5OH, for instance, the hydrogen bonded to oxygen is denoted by the symbol H. Lines representing heteroatom-hydrogen bonds are usually omitted for clarity and compactness and these bonds are sometimes drawn out in full in order to accentuate their presence when they participate in reaction mechanisms. Shown below for comparison are a model of the actual three-dimensional structure of the ethanol molecule in the gas phase, the Lewis structure. All atoms that are not carbon or hydrogen are signified by their symbol, for instance Cl for chlorine, O for oxygen, Na for sodium. These atoms are known as heteroatoms in the context of organic chemistry. There are also symbols that appear to be chemical element symbols and these are known as pseudoelement symbols or organic elements. The most widely used symbol is Ph, which represents the phenyl group, boc for the t-butoxycarbonyl group Cbz or Z for the carboxybenzyl group Fmoc for the fluorenylmethoxycarbonyl group Two atoms can be bonded by sharing more than one pair of electrons
23.
Aristolochiaceae
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The Aristolochiaceae are a family, the birthwort family, of flowering plants with seven genera and about 400 known species belonging to the order Piperales. The type genus is Aristolochia L and they are mostly perennial, herbaceous plants, shrubs, or lianas. The membranous, cordate leaves are spread out, growing alternately along the stem on leaf stalks. The bizarre flowers are large to medium-sized, growing in the leaf axils and they are bilaterally or radially symmetrical. Aristolochiaceae are magnoliids, a group of angiosperms which are not part of the large categories of monocots or eudicots. As of APG IV APG IV, the former families Hydnoraceae and Lactoridaceae are included, many members of Aristolochia and some of Asarum contain the toxin aristolochic acid, which discourages herbivores and is known to be carcinogenic in rats. Aristolochia species are carcinogenic to humans, pipevine swallowtail butterflies lay their eggs on pipevine, and the larvae feed on the plant, but are not affected by the toxin, which then offers the adult butterfly protection against predators
24.
Traditional Chinese medicine
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It is primarily used as a complementary alternative medicine approach. TCM is widely used in China and is becoming prevalent in Europe. One of the tenets of TCM holds that the bodys vital energy circulates through channels, called meridians. Concepts of the body and of disease used in TCM reflect its ancient origins and its emphasis on dynamic processes over material structure, scientific investigation has not found histological or physiological evidence for traditional Chinese concepts such as qi, meridians, and acupuncture points. The TCM theory and practice are not based upon scientific knowledge, the effectiveness of Chinese herbal medicine remains poorly researched and documented. There are concerns over a number of toxic plants, animal parts. There are also concerns over illegal trade and transport of endangered species including rhinoceroses and tigers, a review of cost-effectiveness research for TCM found that studies had low levels of evidence, but so far have not shown benefit outcomes. Pharmaceutical research has explored the potential for creating new drugs from traditional remedies, proponents propose that research has so far missed key features of the art of TCM, such as unknown interactions between various ingredients and complex interactive biological systems. The doctrines of Chinese medicine are rooted in such as the Yellow Emperors Inner Canon and the Treatise on Cold Damage, as well as in cosmological notions such as yin-yang. Starting in the 1950s, these precepts were standardized in the Peoples Republic of China, including attempts to integrate them with modern notions of anatomy, in the 1950s, the Chinese government promoted a systematized form of TCM. TCMs view of the body places little emphasis on anatomical structures, while health is perceived as the harmonious interaction of these entities and the outside world, disease is interpreted as a disharmony in interaction. Traces of therapeutic activities in China date from the Shang dynasty, which Shang elites usually attributed to curses sent by their ancestors. There is no evidence that the Shang nobility used herbal remedies, according to a 2006 overview, the Documentation of Chinese materia medica dates back to around 1,100 BC when only dozens of drugs were first described. By the end of the 16th century, the number of drugs documented had reached close to 1,900, and by the end of the last century, published records of CMM had reached 12,800 drugs. Stone and bone found in ancient tombs led Joseph Needham to speculate that acupuncture might have been carried out in the Shang dynasty. The earliest evidence for acupuncture in this sense dates to the second or first century BC, the Yellow Emperors Inner Canon, the oldest received work of Chinese medical theory, was compiled around the first century BC on the basis of shorter texts from different medical lineages. It was also one of the first books in which the doctrines of Yinyang. The Treatise on Cold Damage Disorders and Miscellaneous Illnesses was collated by Zhang Zhongjing sometime between 196 and 220 CE, at the end of the Han dynasty
25.
Heinrich Holk
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Heinrich Holk was a Danish-German mercenary in both Christian IV of Denmarks and Albrecht von Wallensteins service during the Thirty Years War. Serving Christian IV, Holk was commander of the Danish-Scottish force in the Battle of Stralsund in 1628, when Christian was forced into a peace with Wallenstein in 1629, Holk entered the latters service. In 1632, he was given a cavalry command and his unit, referred to as Holks Horse, was known for their fierce attitude not only in battle, but also in pillage and rape - notorious even in an age of atrocities. He took part in the devastation and looting of the Electorate of Saxony, the battle marked the end of his active career, though he remained in office as a senior commander. The following year, he died of plague while negotiating a truce after a battle near Saxony. Holk retired after two weeks and, on Wallensteins orders, renewed talks with Arnim who was then visiting Johann Georg, the two generals met for dinner when Holk suddenly fell ill. Fearing poison, he was assured otherwise and left in his coach to confer with his subordinates, by now it was obvious he had the plague and they refused to see him. He died by the road alone, his coachman having gone to fetch a priest. Whos who in history, From 1453 to the present day. Military governors and imperial frontiers c, 1600-1800, A study of Scotland and empires. In Asmus, Ivo, Droste, Heiko, Olesen, Jens E. Gemeinsame Bekannte, the Thirty Years War, Europes Tragedy
26.
Tetralin
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Tetralin is a hydrocarbon having the chemical formula C10H12. This molecule is similar to the chemical structure except that one ring is saturated. The compound can be synthesized in a Bergman cyclization whereby cyclodeca-3-ene-1, 5-diyne reacts with 1, 3-cyclohexadiene to produce benzene, tetralin is produced by the catalytic hydrogenation of naphthalene. A large amount of work has been devoted to the hydrogenation of naphthalene into tetralin, mixtures containing different proportions of naphthalene, tetralin, and decalin can be produced depending on the pressure and temperature of the process. Tetralin has been obtained from pressed naphthalene isolated from coal tar by hydrogenating it over commercial catalyst WS2 + NiS + Al2O3, tetralin is used as a solvent. It is also used for the synthesis of dry HBr gas
27.
Hydroperoxide
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A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion, O2−2. The O−O group is called the group or peroxo group. In contrast to oxide ions, the atoms in the peroxide ion have an oxidation state of −1. The simplest stable peroxide is hydrogen peroxide, superoxides, dioxygenyls, ozones and ozonides are considered separately. Peroxide compounds can be classified into organic and inorganic. Whereas the inorganic peroxides have an ionic, salt-like character, the peroxides are dominated by the covalent bonds. The oxygen–oxygen chemical bond of peroxide is unstable and easily split into reactive radicals via homolytic cleavage, for this reason, peroxides are found in nature only in small quantities, in water, atmosphere, plants, and animals. Peroxides have an effect on organic substances and therefore are added to some detergents. Other large-scale applications include medicine and chemical industry, where peroxides are used in synthesis reactions or occur as intermediate products. With an annual production of over 2 million tonnes, hydrogen peroxide is the most economically important peroxide, many peroxides are unstable and hazardous substances, they cannot be stored and therefore are synthesized in situ and used immediately. Peroxides are usually very reactive and thus occur in only in a few forms. These include, in addition to hydrogen peroxide, a few products such as ascaridole. Hydrogen peroxide occurs in water, groundwater and in the atmosphere. It forms upon illumination or natural catalytic action by substances containing in water, sea water contains 0.5 to 14 μg/L of hydrogen peroxide, freshwater 1 to 30 μg/L and air 0.1 to 1 parts per billion. Hydrogen peroxide is formed in human and animal organisms as a product in biochemical processes and is toxic to cells. The toxicity is due to oxidation of proteins, membrane lipids, the class of biological enzymes called SOD is developed in nearly all living cells as an important antioxidant agent. They promote the disproportionation of superoxide into oxygen and hydrogen peroxide,2 O2 − +2 H + → SOD H2 O2 ⏞ hydrogen peroxide + O2 ⏞ oxygen Formation of hydrogen peroxide by superoxide dismutase Peroxisomes are organelles found in virtually all eukaryotic cells. This reaction is important in liver and kidney cells, where the peroxisomes neutralize various toxic substances that enter the blood, some of the ethanol humans drink is oxidized to acetaldehyde in this way
28.
Sodium phenylbutyrate
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Sodium phenylbutyrate is a salt of an aromatic fatty acid, 4-phenylbutyrate or 4-phenylbutyric acid. The compound is used to treat urea cycle disorders, because its metabolites offer an alternative pathway to the cycle to allow excretion of excess nitrogen. It is a drug, marketed by Ucyclyd Pharma under the trade name Buphenyl, by Swedish Orphan International as Ammonaps. Sodium phenylbutyrate is a salt of an aromatic fatty acid, made up of an aromatic ring. The chemical name for sodium phenylbutyrate is 4-phenylbutyric acid, sodium salt, sodium phenylbutyrate is taken orally or by nasogastric intubation as a tablet or powder, and tastes very salty and bitter. Uncontrolled, this causes mental retardation and early death, patients may need treatment for all their life. The treatment was introduced by researchers in the 1990s, and approved by the FDA on 13 May 1996, nearly 1/4 women may experience an adverse effect of amenorrhea or menstrual dysfunction. Appetite loss is seen is 4% of patients, body odor due to metabolization of pheylbutyrate affects 3% of patients, and 3% experience unpleasant tastes. Gastrointestinal symptoms and mostly mild indications of neurotoxicity are also seen in less than 2% of patients, the researchers spoke to Norman Radin about this finding, and he remembered a 1914 article on using sodium benzoate to reduce urea excretion. Another 1919 article had used sodium phenylacetate, and so the researchers treated 5 patients with hyperammonemia with benzoate and phenylacetate, in 1982 and 1984, the researchers published on using benzoate and arginine for urea cycle disorders in the NEJM. Use of sodium phenylbutyrate was introduced in the early 1990s, as it lacks the odor of phenylacetate and this lack of CFTR in the cell membrane leads to disrupted chloride transport and the symptoms of cystic fibrosis. Sodium phenylbutyrate can act as a chaperone, stabilising the mutant CFTR in the endoplasmic reticulum. While small-scale investigation is proceeding, there is to no published data to support the use of the compound in the clinical treatment of cancer. Sodium phenylbutyrate is also being studied as an option for the treatment of Huntingtons disease. Phenylbutyrate has been associated with longer lifespans in Drosophila, as of July 2011 they plan on testing phenylbutyrate for the treatment of Parkinsons disease in humans. In the human body it is first converted to phenylbutyryl-CoA and then metabolized by mitochondrial beta-oxidation, mainly in the liver and kidneys, to the active form, phenylacetate conjugates with glutamine to phenylacetylglutamine, which is eliminated with the urine. It contains the amount of nitrogen as urea, which makes it an alternative to urea for excreting nitrogen. A 5g tablet or powder of sodium phenylbutyrate taken by mouth can be detected in the blood within 15 minutes and it is metabolized into phenylacetate within half an hour
29.
Gamma-Butyrolactone
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γ-Butyrolactone is a hygroscopic colorless liquid with a weak characteristic odor. In humans it acts as a prodrug for γ-hydroxybutyric acid, GBL has been found in extracts from samples of unadulterated wines. This finding indicates that GBL is a naturally occurring component in some wines, the concentration detected was approximately 5 μg/mL and was easily observed using a simple extraction technique followed by GC/MS analysis. GBL can be found in cheese flavourings but typically results in a content of 0. 0002% GBL in the final foodstuff, GBL is produced industrially by dehydrogenation of 1, 4-butanediol. This route proceeds via dehydration of GHB, in the laboratory, it may also be obtained via the oxidation of tetrahydrofuran, for example with aqueous sodium bromate. As a lactone, GBL is hydrolyzed under basic conditions, for example in a sodium hydroxide solution into sodium gamma-hydroxybutyrate, in acidic water, a mixture of the lactone and acid forms coexist in an equilibrium. These compounds then may go on to form the polymer poly, when treated with a non-nucleophilic base, such as lithium diisopropylamide, GBL undergoes deprotonation alpha to the carbonyl. The related compound caprolactone can be used to make a polyester in this manner, a variety of catalysts promote the ring-opening polymerization of butyrolactone, poly. The resulting polybutyrolactone reverts to the monomer by thermal cracking and it is claimed that poly is competitive with commercial biomaterial poly, or P4HB. It is further claimed that poly is cheaper to make than P4HB, GBL is not active in its own right, its mechanism of action stems from its identity as a prodrug of GHB. The hypnotic effect of GHB is enhanced by combination with alcohol, a 2003 rat study showed that GBL in combination with ethanol showed a potentiated hypnotic effect, as the sleep-timing measure was longer than both of the individual components combined. GBL is rapidly converted into GHB by paraoxonase enzymes, found in the blood, animals which lack these enzymes exhibit no effect from GBL. GBL is more lipophilic than GHB, and so is absorbed faster and has higher bioavailability, the levels of lactonase enzyme can vary between individuals, meaning that first-time users can show unpredictable results, even from small doses. In many this manifests as slow onset of effects, followed by headaches, if the user decides to try again at a later date, they appear to be able to enjoy the effects normally. S. At least until the end of 1999, GBL is a prodrug of GHB and its recreational use comes entirely as a result of this. To bypass GHB restriction laws, home synthesis kits were introduced to transform GBL and/or 1, GBL overdose can cause irrational behaviour, severe sickness, coma and death. GBL has a taste and odour, described as being comparable to stale water. This differs significantly from GHB, which is described as having a salty taste
30.
Aluminium chloride
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Aluminium chloride is the main compound of aluminium and chlorine. It is white, but samples are often contaminated with iron chloride, the solid has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium metal, the compound is often cited as a Lewis acid. It is an example of a compound that cracks at mild temperature. AlCl3 adopts three different structures, depending on the temperature and the state, solid AlCl3 is a sheet-like layered cubic close packed layers. In this framework, the Al centres exhibit octahedral coordination geometry, in the melt, aluminium trichloride exists as the dimer Al2Cl6, with tetracoordinate aluminium. This change in structure is related to the density of the liquid phase vs solid aluminium trichloride. Al2Cl6 dimers are also found in the vapour phase, at higher temperatures, the Al2Cl6 dimers dissociate into trigonal planar AlCl3, which is structurally analogous to BF3. The melt conducts electricity poorly, unlike more ionic halides such as sodium chloride, the hexahydrate consists of octahedral 3+ centers and chloride counterions. Hydrogen bonds link the cation and anions, anhydrous aluminium chloride is a powerful Lewis acid, capable of forming Lewis acid-base adducts with even weak Lewis bases such as benzophenone and mesitylene. It forms tetrachloroaluminate AlCl4− in the presence of chloride ions, aluminium chloride reacts with calcium and magnesium hydrides in tetrahydrofuran forming tetrahydroaluminates. Aluminium chloride is hygroscopic, having a very pronounced affinity for water and it fumes in moist air and hisses when mixed with liquid water as the Cl− ions are displaced with H2O molecules in the lattice to form the hexahydrate Cl3. Such solutions are found to be acidic, indicative of partial hydrolysis of the Al3+ ion. 2 Al +3 Cl2 →2 AlCl32 Al +6 HCl →2 AlCl3 +3 H2 Aluminum chloride may be formed via a single displacement reaction between copper chloride and aluminum metal. 2 Al +3 CuCl2 →2 AlCl3 +3 Cu In the US in 1993, approximately 21,000 tons were produced, hydrated aluminium trichloride is prepared by dissolving aluminium oxides in hydrochloric acid. Metallic aluminum also readily dissolves in hydrochloric acid ─ releasing hydrogen gas, AlCl3 is probably the most commonly used Lewis acid and also one of the most powerful. It finds application in the industry as a catalyst for Friedel–Crafts reactions. Important products are detergents and ethylbenzene and it also finds use in polymerization and isomerization reactions of hydrocarbons
31.
Phosphoric acids and phosphates
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There are various kinds of phosphoric acids and phosphates. Of the many phosphorus oxoacids, the phosphoric acids constitute the largest and most diverse group, the simplest phosphoric acid series begins with monophosphoric acid, continues with many oligophosphoric acids such as diphosphoric acid and concludes in the polyphosphoric acids. But, phosphoric acid units can bind together into rings or cyclic structures, chains, or branched structures, each of these can form phosphates. It has also been called monophosphoric acid, the chemical formula of orthophosphoric acid is H3PO4 and its chemical structure is shown in the illustration below. Two or more orthophosphoric acid molecules can be joined by condensation into larger molecules by elimination of water and this way, a series of polyphosphoric acids can be obtained. Orthophosphoric acid has three hydrogen atoms bonded to oxygen atoms in its structure, all three hydrogens are acidic to varying degrees and can be lost from the molecule as H+ ions. When all three H+ ions are lost from orthophosphoric acid, an ion is formed. Orthophosphate is the simplest in a series of phosphates, and is usually just called phosphate by both people and many chemists alike, see a separate article on phosphate for details. Because orthophosphoric acid can undergo as many as three dissociations or ionizations, it has three dissociation constants called Ka1, Ka2, and Ka3. Another way to provide acid dissociation constant data is to list pKa1, pKa2, and pKa3 instead. Orthophosphate is in a sense the triple conjugate base of phosphoric acid and has three related basicity constants, Kb1, Kb2, and Kb3, which likewise have corresponding pKb1, pKb2, and pKb3 values. Three orthophosphoric acid molecules can condense in a row to obtain tripolyphosphoric acid and this condensation process can continue with additional orthophosphoric acid units to obtain tetrapolyphosphoric acid and so on. Note that each extra phosphoric unit adds 1 extra H atom,1 extra P atom, the backbone chain of these types of molecules consists of alternating P and O atoms covalently bonded together. Polyphosphoric acid molecules can have dozens of such phosphoric units bonded in a row, a general formula for such poly-acid compounds is HOxH, where x = number of phosphoric units in the molecule. The four oxygen atoms bonded to each atom are in a tetrahedral configuration with the phosphorus in the center of the tetrahedron. Polyphosphoric acids are used in synthesis for cyclizations and acylations. In a pyrophosphoric acid molecule, there are four hydrogens bonded to oxygens, when all four are lost from pyrophosphoric acid, a pyrophosphate ion is formed. Because pyrophosphoric acids can undergo four dissociations, there are four Ka values for it, similarly, pyrophosphate is a base with four Kb and, of course, four pKb values for regaining the H+ ions in reverse order
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Methanesulfonic acid
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Methanesulfonic acid is a colorless liquid with the chemical formula CH3SO3H. It is the simplest of the alkylsulfonic acids, salts and esters of methanesulfonic acid are known as mesylates. It is hygroscopic in its concentrated form, methanesulfonic acid may be considered an intermediate compound between sulfuric acid, and methylsulfonylmethane, effectively replacing an –OH group with a –CH3 group at each step. This pattern can no further in either direction without breaking down the –SO2– group. Methanesulfonic acid can dissolve a wide range of salts, many of them in significantly higher concentrations than in hydrochloric or sulphuric acid. Methanesulfonic acid is used as an acid catalyst in organic reactions because it is a non-volatile, methanesulfonic acid is convenient for industrial applications because it is liquid at ambient temperature, while the closely related p-toluenesulfonic acid is solid. However, in a setting, solid PTSA is more convenient. Methanesulfonic acid can be used in the generation of borane by reacting methanesulfonic acid with NaBH4 in a solvent such as THF or DMS, the complex of BH3. Methanesulfonic acid is also the electrolyte of choice in zinc-cerium and lead-acid flow batteries, methanesulfonic acid is also a primary ingredient in rust and scale removers. It is used to clean off surface rust from ceramic, tiles and porcelain which are usually susceptible to acid attack
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Lewis acids and bases
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A Lewis acid is a chemical species that reacts with a Lewis base to form a Lewis adduct. A Lewis base, then, is any species that donates a pair of electrons to a Lewis acid to form a Lewis adduct, for example, OH− and NH3 are Lewis bases, because they can donate a lone pair of electrons. In the adduct, the Lewis acid and base share an electron pair furnished by the Lewis base, usually the terms Lewis acid and Lewis base are defined within the context of a specific chemical reaction. For example, in the reaction of Me3B and NH3 to give Me3BNH3, Me3B acts as a Lewis acid, the terminology refers to the contributions of Gilbert N. Lewis. Another example is boron trifluoride etherate, BF3•Et2O, the center dot is also used to represent hydrate coordination in various crystals, as in MgSO4•7H2O for hydrated magnesium sulfate. In general, however, the bond is viewed as simply somewhere along a continuum between idealized covalent bonding and ionic bonding. Classically, the term Lewis acid is restricted to trigonal planar species with an empty p orbital, for the purposes of discussion, even complex compounds such as Et3Al2Cl3 and AlCl3 are treated as trigonal planar Lewis acids. Other reactions might simply be referred to as acid-catalyzed reactions, some compounds, such as H2O, are both Lewis acids and Lewis bases, because they can either accept a pair of electrons or donate a pair of electrons, depending upon the reaction. Simplest are those that react directly with the Lewis base, but more common are those that undergo a reaction prior to forming the adduct. Again, the description of a Lewis acid is used loosely. For example, in solution, bare protons do not exist, BF3 + OMe2 → BF3OMe2 Both BF4− and BF3OMe2 are Lewis base adducts of boron trifluoride. Well known cases are the aluminium trihalides, which are viewed as Lewis acids. Aluminium trihalides, unlike the boron trihalides, do not exist in the form AlX3, a simpler case is the formation of adducts of borane. Monomeric BH3 does not exist appreciably, so the adducts of borane are generated by degradation of diborane, B2H6 +2 H− →2 BH4− In this case, an intermediate B2H7− can be isolated. Many metal complexes serve as Lewis acids, but usually only after dissociating a more weakly bound Lewis base, 2+ +6 NH3 → 2+ +6 H2O The proton is one of the strongest but is also one of the most complicated Lewis acids. It is convention to ignore the fact that a proton is heavily solvated, the key step is the acceptance by AlCl3 of a chloride ion lone-pair, forming AlCl4− and creating the strongly acidic, that is, electrophilic, carbonium ion. RCl +AlCl3 → R+ + AlCl4− A Lewis base is an atomic or molecular species where the highest occupied molecular orbital is highly localized, typical Lewis bases are conventional amines such as ammonia and alkyl amines. Other common Lewis bases include pyridine and its derivatives, some of the main classes of Lewis bases are amines of the formula NH3−xRx where R = alkyl or aryl
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Acyl chloride
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In organic chemistry, an acyl chloride is an organic compound with the functional group -COCl. Their formula is usually written RCOCl, where R is a side chain and they are reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride, CH3COCl, Acyl chlorides are the most important subset of acyl halides. Where the acyl chloride moiety takes priority, acyl chlorides are named by taking the name of the parent carboxylic acid, for example, acetic acid boils at 118 °C, whereas acetyl chloride boils at 51 °C. Like most carbonyl compounds, infrared spectroscopy reveals a band near 1750 cm−1, the industrial route to acetyl chloride involves the reaction of acetic anhydride with hydrogen chloride. In this reaction, the dioxide and hydrogen chloride generated are both gases that can leave the reaction vessel, driving the reaction forward. Excess thionyl chloride is easily evaporated as well, the iminium intermediate reacts with the carboxylic acid, abstracting an oxide, and regenerating the DMF catalyst. Finally, methods that do not form HCl are also known, such as the Appel reaction, RCOOH + Ph3P + CCl4 → RCOCl + Ph3PO + HCCl3 and the use of cyanuric chloride, Acyl chlorides are very reactive. Consider the comparison to its RCOOH acid analogue, the ion is an excellent leaving group while the hydroxide is not under normal conditions. The use of a base, e. g. aqueous sodium hydroxide or pyridine, or excess amine is desirable to remove the hydrogen chloride byproduct, and to catalyze the reaction. While it is possible to obtain esters or amides from the carboxylic acid with alcohols or amines. In contrast, both involved in preparing esters and amides via acyl chlorides are fast and irreversible. This makes the route often preferable to the single step reaction with the carboxylic acid. With carbon nucleophiles such as Grignard reagents, acyl chlorides generally react first to give the ketone, a notable exception is the reaction of acyl halides with certain organocadmium reagents which stops at the ketone stage. The nucleophilic reaction with Gilman reagents also afford ketones, due to their lesser reactivity, acid chlorides of aromatic acids are generally less reactive those of alkyl acids and thus somewhat more rigorous conditions are required for reaction. Acyl chlorides are reduced by strong hydride donors such as lithium aluminium hydride, lithium tri-tert-butoxyaluminium hydride, a bulky hydride donor, reduces acyl chlorides to aldehydes, as does the Rosenmund reduction using hydrogen gas over a poisoned palladium catalyst. Because acyl chlorides are reactive compounds, precautions should be taken while handling them. They are lachrymatory because they can react with water at the surface of the eye producing hydrochloric and organic acids irritating to the eye, similar problems can result if one inhales acyl chloride vapors
35.
Phosphorus pentachloride
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Printer Command Language, more commonly referred to as PCL, is a page description language developed by Hewlett-Packard as a printer protocol and has become a de facto industry standard. Originally developed for early inkjet printers in 1984, PCL has been released in varying levels for thermal, matrix printer, HP-GL/2 and PJL are supported by later versions of PCL. PCL is occasionally and incorrectly said to be an abbreviation for Printer Control Language which actually is another term for page description language, PCL levels 1 through 5e/5c are command-based languages using control sequences that are processed and interpreted in the order they are received. At a consumer level, PCL data streams are generated by a print driver, PCL output can also be easily generated by custom applications. PCL1 was introduced in 1984 on the HP ThinkJet 2225 and provides basic text, PCL 1+ was released with the HP QuietJet 2227. PCL2 added Electronic Data Processing/Transaction functionality, PCL3 was introduced in 1984 with the original HP LaserJet. This added support for bitmap fonts and increased the resolution to 300 dpi. Other products with PCL3 support were the HP DeskJet ink jet printer, HP2932 series matrix printers, PCL3 is still in use on several impact printers which replaced the obsolete HP models. PCL 3+ and PCL 3c+ are used on later HP DeskJet, PCL 3GUI is used in the HP DesignJet and some DeskJet series printers. It uses a raster format that is not compatible with standard PCL3. PCL4 was introduced on the HP LaserJet Plus in 1985, adding macros, larger bitmapped fonts, PCL4 is still popular for many applications. PCL5 was released on the HP LaserJet III in March 1990, adding Intellifont font scaling, outline fonts, PCL 5e was released on the HP LaserJet 4 in October 1992 and added bi-directional communication between the printer and the PC and Windows fonts. PCL 5c introduced color support on the HP PaintJet 300XL and HP Color LaserJet in 1992, HP introduced PCL6 around 1995 with the HP LaserJet 4000 series printers. It consists of, PCL6 Enhanced, An object-oriented PDL optimized for printing from GUI interfaces such as Windows, PCL6 Standard, Equivalent to PCL 5e or PCL 5c, intended to provide backward compatibility. Font synthesis, Provides scalable fonts, font management and storage of forms, in early implementations, HP did not market PCL6 well, thus causing some confusion in terminology. PCL XL was renamed to PCL6 Enhanced, but many third-party products still use the older term, some products may claim to be PCL6 compliant, but may not include the PCL5 backward compatibility. PCL6 Enhanced is primarily generated by the printer drivers under Windows, due to its structure and compression methodology, custom applications rarely use it directly. PCL6 Enhanced is a stack-based, object-oriented protocol, similar to PostScript, however, it is restricted to binary encoding as opposed to PostScript, which can be sent either as binary code or as plain text
36.
Tin(IV) chloride
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Tin chloride, also known as tin tetrachloride or stannic chloride is a inorganic compound with the formula SnCl4. At room temperature it is a liquid, which fumes on contact with air. It is used as precursor to other tin compounds and it was first discovered by Andreas Libavius and was known as spiritus fumans libavii. It is prepared from reaction of gas with elemental tin at 115 °C. Sn +2 Cl2 → SnCl4 Anhydrous tin chloride solidifies at −33 °C to give monoclinic crystals with the P21/c space group, within this the molecules adopt near perfect tetrahedral symmetry with average Sn–Cl distances of 227. 9 pm. Several forms of hydrated tin tetrachloride are known and they all consist of molecules together with varying amouts of water of crystallization. The additional water molecules link together the molecules of hydrogen bonds. Although the pentahydrate is most common of the hydrates, lower hydrates have also been characterised, Anhydrous tin chloride is a Lewis acid. It forms adducts with ammonia, organophosphines, and other Lewis bases, when mixed with a small amount of water a semi-solid crystalline mass of the pentahydrate, SnCl4·5H2O is formed. This solid was formerly known as butter of tin, with hydrochloric acid the complex 2− is formed making the so-called hexachlorostannic acid. Anhydrous tin chloride is a precursor in organotin chemistry. Although a specialized application, SnCl4 is used in Friedel-Crafts reactions as a Lewis acidic catalyst for alkylation and cyclisation, stannic chloride is used in chemical reactions with fuming nitric acid for the selective nitration of activated aromatic rings in the presence of inactivated ones. The main application of SnCl4 is as a precursor to organotin compounds and it can be used in a sol-gel process to prepare SnO2 coatings, nanocrystals of SnO2 can be produced by refinements of this method. International Chemical Safety Card 0953 Use in glass industry
37.
Hydrogen bond
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Hydrogen bonds can occur between molecules or within different parts of a single molecule. Depending on geometry and environment, the hydrogen bond free energy content is between 1 and 5 kcal/mol and this makes it stronger than a van der Waals interaction, but weaker than covalent or ionic bonds. This type of bond can occur in molecules such as water and in organic molecules like DNA. Intermolecular hydrogen bonding is responsible for the boiling point of water compared to the other group 16 hydrides that have much weaker hydrogen bonds. Intramolecular hydrogen bonding is responsible for the secondary and tertiary structures of proteins. It also plays an important role in the structure of polymers, in 2011, an IUPAC Task Group recommended a modern evidence-based definition of hydrogen bonding, which was published in the IUPAC journal Pure and Applied Chemistry. An accompanying detailed technical report provides the rationale behind the new definition, a hydrogen atom attached to a relatively electronegative atom will play the role of the hydrogen bond donor. This electronegative atom is usually fluorine, oxygen, or nitrogen, a hydrogen attached to carbon can also participate in hydrogen bonding when the carbon atom is bound to electronegative atoms, as is the case in chloroform, CHCl3. An example of a hydrogen donor is the hydrogen from the hydroxyl group of ethanol. In a hydrogen bond, the electronegative atom not covalently attached to the hydrogen is named proton acceptor, because of the small size of hydrogen relative to other atoms and molecules, the resulting charge, though only partial, represents a large charge density. A hydrogen bond results when this positive charge density attracts a lone pair of electrons on another heteroatom. The hydrogen bond is described as an electrostatic dipole-dipole interaction. These covalent features are more substantial when acceptors bind hydrogens from more electronegative donors, the partially covalent nature of a hydrogen bond raises the following questions, To which molecule or atom does the hydrogen nucleus belong. And Which should be labeled donor and which acceptor, liquids that display hydrogen bonding are called associated liquids. Hydrogen bonds can vary in strength from weak to extremely strong. For example, the central interresidue N−H···N hydrogen bond between guanine and cytosine is much stronger in comparison to the N−H···N bond between the adenine-thymine pair, the length of hydrogen bonds depends on bond strength, temperature, and pressure. The bond strength itself is dependent on temperature, pressure, bond angle, the typical length of a hydrogen bond in water is 197 pm. The ideal bond angle depends on the nature of the hydrogen bond donor, moore and Winmill used the hydrogen bond to account for the fact that trimethylammonium hydroxide is a weaker base than tetramethylammonium hydroxide
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Hexafluoro-2-propanol
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Hexafluoroisopropanol, commonly abbreviated HFIP, is the organic compound with the formula 2CHOH. This fluorinated alcohol finds use as solvent and synthetic intermediate and it appears as a colorless, volatile liquid that is characterized by a strong, pungent odor. As a solvent hexafluoro-2-propanol is polar and exhibits strong hydrogen bonding properties enabling it to dissolve substances that serve as hydrogen-bond acceptors, such as amides, Hexafluoro-2-propanol is transparent to UV light with high density, low viscosity and low refractive index. Hexafluoro-2-propanol is prepared from hexafluoropropylene via hexafluoroacetone, which is reduced by hydrogenation or by hydride reagents. 2CO + H2 → 2CHOH Hexafluoro-2-propanol is a speciality solvent for some polar polymers and it has also found use in biochemistry to solubilize peptides and to monomerize β-sheet protein aggregates. Because of its acidity, it can be used as acid in volatile buffers for ion pair HPLC - mass spectrometry of nucleic acids and it is both the precursor and the chief metabolite of the inhalation anesthetic sevoflurane. Hexafluoro-2-propanol is a volatile, corrosive liquid that can cause severe burns, application note on quantification of HFIP in polymers
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