1.
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
2.
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
3.
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
4.
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
5.
Succinic acid
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Succinic acid is a dicarboxylic acid with the chemical formula 22. The name derives from Latin succinum, meaning amber, succinate is generated in mitochondria via the tricarboxylic acid cycle, an ancient energy-yielding process shared by all organisms. As such, succinate links cellular metabolism to the regulation of cellular function, dysregulation of succinate synthesis and degradation can lead to pathological conditions, such as malignant transformation, inflammation and tissue injury. Succinic acid is a white, odorless solid with an acidic taste. In an aqueous solution, succinic acid readily ionizes to form its conjugate base, succinate. As a diprotic acid, succinic acid undergoes two successive reactions,22 → 2− + H+ 2− → 222− + H+ The pKa of these processes are 4.3 and 5.6. Both anions are colorless and can be isolated as the salts, e. g. Na2, in living organisms, primarily succinate, not succinic acid, is found. As a radical group it is called a succinyl group, like most simple mono- and dicarboxylic acids, it is not harmful but can be an irritant to skin and eyes. Succinic acid can be oxidized to fumaric acid or be converted to diesters and this diethyl ester is a substrate in the Stobbe condensation. Dehydration of succinic acid gives succinic anhydride, succinate can be used to derive 1, 4-butanediol, maleic anhydride, succinimide, 2-pyrrolidinone and tetrahydrofuran. Historically, succinic acid was obtained from amber by distillation and has thus been known as spirit of amber, today, succinic acid is generated for human use synthetically or converted from biomass via fermentation. Common industrial routes of synthesis include partial hydrogenation of maleic acid, oxidation of 1, 4-butanediol, succinate is also produced petrochemically from butane via maleic anhydride. Additionally, genetic engineering of bacteria, such as Escherichia coli or Saccharomyces cerevisiae, has allowed for the high-yielding. Global production is estimated at 16,000 to 30,000 tons a year, in 2004, succinate was placed on the US Department of Energys list of top 12 platform chemicals from biomass. Succinic acid is a precursor to polyesters and a component of some alkyd resins. A key derivative of succinic acid,1, 4-butanediol, has industrial applications. The global market size for BDO was estimated at USD4.72 billion in 2013, BDO is a precursor to the common organic solvent THF and a precursor to polybutylene terephthalate, an engineering-grade thermoplastic. The automotive and electronics industries heavily rely on PBT to produce connectors, insulators, wheel covers, gearshift knobs, Succinic acid also serves as the bases of certain biodegradable polymers, which are of interest in tissue engineering applications
6.
Malic acid
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Malic acid is an organic compound with the molecular formula C4H6O5. It is an acid that is made by all living organisms, contributes to the pleasantly sour taste of fruits. Malic acid has two forms, though only the L-isomer exists naturally. The salts and esters of malic acid are known as malates, the malate anion is an intermediate in the citric acid cycle. L-Malic acid is the naturally occurring form, whereas a mixture of L-, malate plays an important role in biochemistry. In the C4 carbon fixation process, malate is a source of CO2 in the Calvin cycle, in the citric acid cycle, -malate is an intermediate, formed by the addition of an -OH group on the si face of fumarate. It can also be formed from pyruvate via anaplerotic reactions, malate is also synthesized by the carboxylation of phosphoenolpyruvate in the guard cells of plant leaves. Malate, as an anion, often accompanies potassium cations during the uptake of solutes into the guard cells in order to maintain electrical balance in the cell. The accumulation of these solutes within the cell decreases the solute potential, allowing water to enter the cell. Malic acid was first isolated from apple juice by Carl Wilhelm Scheele in 1785, antoine Lavoisier in 1787 proposed the name acide malique, which is derived from the Latin word for apple, mālum—as is its genus name Malus. In German it is named Äpfelsäure after plural or singular of the fruit apple, Malic acid contributes to the sourness of green apples. It is present in grapes and in most wines with concentrations sometimes as high as 5 g/l and it confers a tart taste to wine, although the amount decreases with increasing fruit ripeness. The taste of malic acid is very clear and pure in rhubarb and it is also a component of some artificial vinegar flavors, such as salt and vinegar flavored potato chips. The process of malolactic fermentation converts malic acid to much milder lactic acid, Malic acid occurs naturally in all fruits and many vegetables, and is generated in fruit metabolism. Malic acid, when added to products, is denoted by E number E296. Malic acid is the source of extreme tartness in United States-produced confectionery and it is also used with or in place of the less sour citric acid in sour sweets. These sweets are sometimes labeled with a warning stating that excessive consumption can cause irritation of the mouth and it is approved for use as a food additive in the EU, US and Australia and New Zealand. Malic acid provides 10 kJ of energy per gram during digestion, racemic malic acid is produced industrially by the double hydration of maleic anhydride
7.
Maleic anhydride
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Maleic anhydride is an organic compound with the formula C2H22O. It is the anhydride of maleic acid. It is a colorless or white solid with an acrid odor and it is produced industrially on a large scale for applications in coatings and polymers. Maleic anhydride is produced by oxidation of n-butane. The overall process converts the methyl groups to carboxylate and dehydrogenates the backbone, the selectivity of the process reflects the robustness of maleic anhydride, with its conjugated double-bond system. Traditionally maleic anhydride was produced by the oxidation of benzene or other aromatic compounds, as of 2006, only a few smaller plants continue to use benzene. In both cases, benzene and butane are fed into a stream of hot air, and the mixture is passed through a catalyst bed at high temperature, the ratio of air to hydrocarbon is controlled to prevent the mixture from igniting. The traditional method using benzene became uneconomical due to the high and still rising benzene prices, in addition, in the production of maleic anhydride a third of the original carbon atoms is lost as carbon dioxide when using benzene. The modern catalytic processes start from a 4-carbon molecule and only oxygen and removes water. Overall, the method is therefore more material efficient. Parallels exist with the production of phthalic anhydride, While older methods use naphthalene, the chemistry of maleic anhydride is very rich, reflecting its ready availability and bifunctional reactivity. It hydrolyzes, producing maleic acid, cis-HOOC–CH=CH–COOH, with alcohols, the half-ester is generated, e. g. cis-HOOC–CH=CH–COOCH3. Maleic anhydride is a substrate for Diels-Alder reactions. It was used for work in 1928, on the reaction between maleic anhydride and 1, 3-butadiene, for which Otto Paul Hermann Diels and Kurt Alder were awarded the Nobel Prize in 1950 and it is through this reaction that maleic anhydride converted to many pesticides and pharmaceuticals. Michael reaction of maleic anhydride with active methylene or methine compounds such as malonate or acetoacetate esters in the presence of sodium acetate catalyst and these intermediates were subsequently used for the generation of the Krebs cycle intermediates aconitic and isocitric acids. Maleic anhydride dimerizes in a reaction to form cyclobutane tetracarboxylic dianhydride. This compound is used in the production of polyimides and as an alignment film for liquid crystal displays and it is also a ligand for low-valent metal complexes, examples being Pt2 and Fe4. Maleic anhydride is used in many applications, around 50% of world maleic anhydride output is used in the manufacture of unsaturated polyester resins
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.
Safety data sheet
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A safety data sheet, material safety data sheet, or product safety data sheet is an important component of product stewardship, occupational safety and health, and spill-handling procedures. SDS formats can vary from source to source within a country depending on national requirements, SDSs are a widely used system for cataloging information on chemicals, chemical compounds, and chemical mixtures. SDS information may include instructions for the use and potential hazards associated with a particular material or product. The SDS should be available for reference in the area where the chemicals are being stored or in use, there is also a duty to properly label substances on the basis of physico-chemical, health and/or environmental risk. Labels can include hazard symbols such as the European Union standard symbols, a SDS for a substance is not primarily intended for use by the general consumer, focusing instead on the hazards of working with the material in an occupational setting. It is important to use an SDS specific to country and supplier, as the same product can have different formulations in different countries. The formulation and hazard of a product using a name may vary between manufacturers in the same country. Safety data sheets have made an integral part of the system of Regulation No 1907/2006. The SDS must be supplied in a language of the Member State where the substance or mixture is placed on the market. The 16 sections are, SECTION1, Identification of the substance/mixture, relevant identified uses of the substance or mixture and uses advised against 1.3. Details of the supplier of the safety data sheet 1.4, Emergency telephone number SECTION2, Hazards identification 2.1. Classification of the substance or mixture 2.2, Other hazards SECTION3, Composition/information on ingredients 3.1. Mixtures SECTION4, First aid measures 4.1, Description of first aid measures 4.2. Most important symptoms and effects, both acute and delayed 4.3, indication of any immediate medical attention and special treatment needed SECTION5, Firefighting measures 5.1. Special hazards arising from the substance or mixture 5.3, advice for firefighters SECTION6, Accidental release measure 6.1. Personal precautions, protective equipment and emergency procedures 6.2, methods and material for containment and cleaning up 6.4. Reference to other sections SECTION7, Handling and storage 7.1, conditions for safe storage, including any incompatibilities 7.3. Specific end use SECTION8, Exposure controls/personal protection 8.1, Exposure controls SECTION9, Physical and chemical properties 9.1
10.
Acid dissociation constant
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An acid dissociation constant, Ka, is a quantitative measure of the strength of an acid in solution. It is the constant for a chemical reaction known as dissociation in the context of acid–base reactions. In the example shown in the figure, HA represents acetic acid, and A− represents the acetate ion, the chemical species HA, A− and H3O+ are said to be in equilibrium when their concentrations do not change with the passing of time. The definition can then be more simply H A ⇌ A − + H +, K a = This is the definition in common usage. A weak acid has a pKa value in the approximate range −2 to 12 in water, pKa values for strong acids can, however, be estimated by theoretical means. The definition can be extended to non-aqueous solvents, such as acetonitrile and dimethylsulfoxide. Denoting a solvent molecule by S H A + S ⇌ A − + S H +, K a = When the concentration of solvent molecules can be taken to be constant, K a =, as before. The value of pKa also depends on structure of the acid in many ways. For example, Pauling proposed two rules, one for successive pKa of polyprotic acids, and one to estimate the pKa of oxyacids based on the number of =O and −OH groups. Other structural factors that influence the magnitude of the dissociation constant include inductive effects, mesomeric effects. Hammett type equations have frequently applied to the estimation of pKa. The quantitative behaviour of acids and bases in solution can be only if their pKa values are known. These calculations find application in different areas of chemistry, biology, medicine. Acid dissociation constants are essential in aquatic chemistry and chemical oceanography. In living organisms, acid–base homeostasis and enzyme kinetics are dependent on the pKa values of the acids and bases present in the cell. According to Arrheniuss original definition, an acid is a substance that dissociates in solution, releasing the hydrogen ion H+. The equilibrium constant for this reaction is known as a dissociation constant. Brønsted and Lowry generalised this further to an exchange reaction
11.
Dicarboxylic acid
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A dicarboxylic acid is an organic compound containing two carboxyl functional groups. The general molecular formula for dicarboxylic acids can be written as HO2C−R−CO2H, in general, dicarboxylic acids show similar chemical behavior and reactivity to monocarboxylic acids. Dicarboxylic acids are used in the preparation of copolymers such as polyamides. The most widely used dicarboxylic acid in the industry is adipic acid, other examples of dicarboxylic acids include aspartic acid and glutamic acid, two amino acids in the human body. The PubChem links gives access to a wealth of information on the compounds, adipic acid, despite its name, is not a normal constituent of natural lipids but is a product of oxidative rancidity. It was first obtained by oxidation of castor oil with nitric acid and it is now produced industrially by oxidation of cyclohexanol or cyclohexane, mainly for the production of Nylon 6-6. Pimelic acid was also first isolated from oxidized oil, derivatives of pimelic acid are involved in the biosynthesis of lysine. Suberic acid was first produced by nitric acid oxidation of cork and this acid is also produced when castor oil is oxidised. Suberic acid is used in the manufacture of alkyd resins and in the synthesis of polyamides, azelaic acids name stems from the action of nitric acid oxidation of oleic acid or elaidic acid. It was detected among products of rancid fats and its origin explains for its presence in poorly preserved samples of linseed oil and in specimens of ointment removed from Egyptian tombs 5000 years old. Azelaic acid was prepared by oxidation of oleic acid with potassium permanganate, azelaic acid is used, as simple esters or branched-chain esters) in the manufacture of plasticizers, lubricants and greases. Azelaic acid is now used in cosmetics and it displays bacteriostatic and bactericidal properties against a variety of aerobic and anaerobic micro-organisms present on acne-bearing skin. Azelaic acid was identified as a molecule that accumulated at elevated levels in parts of plants and was shown to be able to enhance the resistance of plants to infections. Thenard isolated this compound from distillation products of beef tallow in 1802 and it is produced industrially by alkali fission of castor oil. Sebacic acid and its derivatives have a variety of uses as plasticizers, lubricants, diffusion pump oils, cosmetics, candles. It is also used in the synthesis of polyamide, as nylon, brassylic acid can be produced from erucic acid by ozonolysis but also by microorganisms from tridecane. This diacid is produced on a commercial scale in Japan for the manufacture of fragrances. Dodecanedioic acid is used in the production of nylon, polyamides, coatings, adhesives, greases, polyesters, dyestuffs, detergents, flame retardants and it is now produced by fermentation of long-chain alkanes with a specific strain of Candida tropicalis
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