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.
Occupational safety and health
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These terms of course also refer to the goals of this field, so their use in the sense of this article was originally an abbreviation of occupational safety and health program/department etc. The goals of occupational safety and health programs include to foster a safe, OSH may also protect co-workers, family members, employers, customers, and many others who might be affected by the workplace environment. In the United States, the occupational health and safety is referred to as occupational health and occupational and non-occupational safety. In common-law jurisdictions, employers have a common law duty to take care of the safety of their employees. As defined by the World Health Organization occupational health deals with all aspects of health, Health has been defined as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity. Occupational health is a field of healthcare concerned with enabling an individual to undertake their occupation. Health has been defined as It contrasts, for example, with the promotion of health and safety at work, since 1950, the International Labour Organization and the World Health Organization have shared a common definition of occupational health. It was adopted by the Joint ILO/WHO Committee on Occupational Health at its first session in 1950, the concept of working culture is intended in this context to mean a reflection of the essential value systems adopted by the undertaking concerned. Such a culture is reflected in practice in the systems, personnel policy, principles for participation, training policies. Professionals advise on a range of occupational health matters. The research and regulation of safety and health are a relatively recent phenomenon. As labor movements arose in response to concerns in the wake of the industrial revolution. The initial remit of the Inspectorate was to police restrictions on the hours in the textile industry of children. The commission sparked public outrage resulted in the Mines Act of 1842. Otto von Bismarck inaugurated the first social insurance legislation in 1883, similar acts followed in other countries, partly in response to labor unrest. Although work provides many economic and other benefits, an array of workplace hazards also present risks to the health. Personal protective equipment can protect against many of these hazards. Physical hazards affect many people in the workplace, Falls are also a common cause of occupational injuries and fatalities, especially in construction, extraction, transportation, healthcare, and building cleaning and maintenance
3.
Ferrocene
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Ferrocene is an organometallic compound with the formula Fe2. It is the prototypical metallocene, a type of chemical compound consisting of two cyclopentadienyl rings bound on opposite sides of a central metal atom. Such organometallic compounds are known as sandwich compounds. The rapid growth of organometallic chemistry is often attributed to the excitement arising from the discovery of ferrocene, in 1951, Pauson and Kealy at Duquesne University reported the reaction of cyclopentadienyl magnesium bromide and ferric chloride with the goal of oxidatively coupling the diene to prepare fulvalene. Instead, they obtained a light orange powder of remarkable stability, a second group at British Oxygen also unknowingly discovered ferrocene. Miller, Tebboth and Tremaine were trying to synthesise amines from hydrocarbons such as cyclopentadiene and they published this result in 1952 although the actual work was done three years earlier. The stability of the new compound was accorded to the aromatic character of the negatively charged cyclopentadienyls. Robert Burns Woodward and Geoffrey Wilkinson deduced the structure based on its reactivity, independently Ernst Otto Fischer also came to the conclusion of the sandwich structure and started to synthesize other metallocenes such as nickelocene and cobaltocene. The structure of ferrocene was confirmed by NMR spectroscopy and X-ray crystallography, in 1973 Fischer of the Technische Universität München and Wilkinson of Imperial College London shared a Nobel Prize for their work on metallocenes and other aspects of organometallic chemistry. The carbon–carbon bond distances are 1.40 Å within the rings. The staggered conformation is believed to be most stable in the condensed phase due to crystal packing, the point group of the staggered conformation is D5d and the point group of the eclipsed conformation is D5h. The Cp rings rotate with a low barrier about the Cp–Fe–Cp axis, as observed by measurements on substituted derivatives of ferrocene using 1H, for example, methylferrocene exhibits a singlet for the C5H5 ring. In terms of bonding, the center in ferrocene is usually assigned to the +2 oxidation state. Each cyclopentadienyl ring is then allocated a single charge, bringing the number of π-electrons on each ring to six. These twelve electrons are shared with the metal via covalent bonding. When combined with the six d-electrons on Fe2+, the complex attains an 18-electron configuration, the first reported syntheses of ferrocene were nearly simultaneous. Pauson and Kealy synthesised ferrocene using iron chloride and a Grignard reagent, iron chloride is suspended in anhydrous diethyl ether and added to the Grignard reagent, which is prepared by reacting cyclopentadiene with magnesium and bromoethane in anhydrous benzene. The other early synthesis of ferrocene was by Miller et al. who reacted metallic iron directly with gas-phase cyclopentadiene at elevated temperature, an approach using iron pentacarbonyl was also reported
4.
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
5.
Palladium(II) chloride
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Palladium chloride, also known as palladium dichloride and palladous chloride, are the chemical compounds with the formula PdCl2. PdCl2 is a starting material in palladium chemistry – palladium-based catalysts are of particular value in organic synthesis. It is prepared by chlorination of palladium, two forms of PdCl2 are known. In both forms, the palladium centres adopt the square-planar coordination geometry that is characteristic of Pd, furthermore, in both forms, the Pd centres are linked by μ2-chloride bridges. The α-form of PdCl2 is a polymer, consisting of infinite slabs or chains, the β-form of PdCl2 is molecular, consisting of an octahedral cluster of six Pd atoms. Each of the edges of this octahedron is spanned by Cl−. PtCl2 adopts similar structures, whereas NiCl2 adopts the CdCl2 motif, palladium chloride is prepared by dissolving palladium metal in aqua regia or hydrochloric acid in the presence of chlorine. Alternatively, it may be prepared by heating palladium sponge metal with chlorine gas at 500 °C, even when dry, palladium chloride is able to rapidly stain stainless steel. Thus, palladium chloride solutions are used to test for the corrosion-resistance of stainless steel. Palladium chloride is used in carbon monoxide detectors. Palladium chloride can also be used for cosmetic tattooing of leukomas in the cornea
6.
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
7.
N-Butyllithium
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It is widely used as a polymerization initiator in the production of elastomers such as polybutadiene or styrene-butadiene-styrene. Also, it is employed as a strong base in the synthesis of organic compounds as in the pharmaceutical industry. Butyllithium is commercially available as solutions in such as pentane, hexanes. Solutions in diethyl ether and THF can be prepared, but are not stable enough for storage, annual worldwide production and consumption of butyllithium and other organolithium compounds is estimated at 1800 tonnes. Although butyllithium is colorless, n-butyllithium is usually encountered as a yellow solution in alkanes. Such solutions are stable indefinitely if properly stored, but in practice, fine white precipitate is deposited and the color changes to orange. N-BuLi exists as a cluster both in the state and in a solution. The tendency to aggregate is common for organolithium compounds, the aggregates are held together by delocalized covalent bonds between lithium and the terminal carbon of the butyl chain. In the case of n-BuLi, the clusters are tetrameric or hexameric, the cluster is a distorted cubane-type cluster with Li and CH2R groups at alternating vertices. An equivalent description describes the tetramer as a Li4 tetrahedron interpenetrated with a tetrahedron 4, bonding within the cluster is related to that used to describe diborane, but more complex since eight atoms are involved. Reflecting its electron-deficient character, n-butyllithium is highly reactive toward Lewis bases, due to the large difference between the electronegativities of carbon and lithium, the C-Li bond is highly polarized. The charge separation has been estimated to be 55-95%, for practical purposes, n-BuLi can often be considered to react as the butyl anion, n-Bu−, and a lithium cation, Li+. Solvents used for this preparation include benzene, cyclohexane, and diethyl ether, when BuBr is the precursor, the product is a homogeneous solution, consisting of a mixed cluster containing both LiBr and BuLi, together with a small amount of octane. BuLi forms a complex with LiCl, so that the reaction of BuCl with Li produces a precipitate of LiCl. The concentration of butyllithium in commercially available solutions tends to decrease over time as the BuLi reacts with air, subsequently, butyllithium is often titrated prior to use to ascertain its true concentration. The BuLi is added to an amount of a weakly acidic compound. Because butyllithium is a base, it quickly and quantitatively reacts with weak acids to give the corresponding lithium salts. An indicator, such as 1, 10-phenanthroline or 2, 2-bipyridine, is used to signal the endpoint of the titration
8.
Google Books
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Books are provided either by publishers and authors, through the Google Books Partner Program, or by Googles library partners, through the Library Project. Additionally, Google has partnered with a number of publishers to digitize their archives. The Publisher Program was first known as Google Print when it was introduced at the Frankfurt Book Fair in October 2004, the Google Books Library Project, which scans works in the collections of library partners and adds them to the digital inventory, was announced in December 2004. But it has also criticized for potential copyright violations. As of October 2015, the number of scanned book titles was over 25 million, Google estimated in 2010 that there were about 130 million distinct titles in the world, and stated that it intended to scan all of them. Results from Google Books show up in both the universal Google Search as well as in the dedicated Google Books search website, if Google believes the book is still under copyright, a user sees snippets of text around the queried search terms. All instances of the terms in the book text appear with a yellow highlight. The four access levels used on Google Books are, Full view, Books in the domain are available for full view. In-print books acquired through the Partner Program are also available for full view if the publisher has given permission, usually, the publisher can set the percentage of the book available for preview. Users are restricted from copying, downloading or printing book previews, a watermark reading Copyrighted material appears at the bottom of pages. All books acquired through the Partner Program are available for preview and this could be because Google cannot identify the owner or the owner declined permission. If a search term appears many times in a book, Google displays no more than three snippets, thus preventing the user from viewing too much of the book. Also, Google does not display any snippets for certain reference books, such as dictionaries, Google maintains that no permission is required under copyright law to display the snippet view. No preview, Google also displays search results for books that have not been digitized, in effect, this is similar to an online library card catalog. Google also stated that it would not scan any in-copyright books between August and 1 November 2005, to provide the owners with the opportunity to decide which books to exclude from the Project. It can let Google scan the book under the Library Project and it can opt out of the Library Project, in which case Google will not scan the book. If the book has already been scanned, Google will reset its access level as No preview and this information is collated through automated methods, and sometimes data from third-party sources is used. This information provides an insight into the book, particularly useful when only a view is available
9.
Organophosphorus compound
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Organophosphorus compounds are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment, organophosphorus chemistry is the corresponding science of the properties and reactivity of organophosphorus compounds. Phosphorus, like nitrogen, is in group 15 of the periodic table and these compounds are highly effective insecticides, though some are also lethal to humans at minuscule doses and include some of the most toxic substances ever created by man. The definition of organophosphorus compounds is variable, which can lead to confusion, in industrial and environmental chemistry, an organophosphorus compound need contain only an organic substituent, but need not have a direct phosphorus-carbon bond. Thus a large proportion of pesticides, are included in this class of compounds. In a descriptive but only intermittently used nomenclature, phosphorus compounds are identified by their coordination number δ, in this system, a phosphine is a δ3λ3 compound. Phosphate esters have the general structure P3 feature P, such species are of technological importance as flame retardant agents, and plasticizers. Lacking a P−C bond, these compounds are in the technical sense not organophosphorus compounds, many derivatives are found in nature, such as phosphatidylcholine. Phosphate ester are synthesized by alcoholysis of phosphorus oxychloride, a variety of mixed amido-alkoxo derivatives are known, one medically significant example being the anti-cancer drug cyclophosphamide. Also derivatives containing the group include the pesticide malathion. The organophosphates prepared on the largest scale are the zinc dithiophosphates, several million kilograms of this coordination complex are produced annually by the reaction of phosphorus pentasulfide with alcohols. In the environment, these compounds break down via hydrolysis to eventually afford phosphate, phosphonates are esters of phosphonic acid and have the general formula RP2. Phosphonates have many applications, a well-known member being glyphosate. With the formula 2PCH2NHCH2CO2H, this derivative of glycine is one of the most widely used herbicides, bisphosphonates are a class of drugs to treat osteoporosis. The nerve gas agent sarin, containing both C–P and F–P bonds, is a phosphonate, phosphinates feature two P–C bonds, with the general formula R2P. A commercially significant member is the herbicide Glufosinate, similar to glyphosate mentioned above, it has the structure CH3PCH2CH2CHCO2H. The Michaelis–Arbuzov reaction is the method for the synthesis of these compounds. For example, dimethylmethylphosphonate arises from the rearrangement of trimethylphosphite, which is catalyzed by methyl iodide, in the Horner–Wadsworth–Emmons reaction and the Seyferth–Gilbert homologation, phosphonates are used in reactions with carbonyl compounds
10.
Borrowing hydrogen
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Borrowing hydrogen catalysis, also called hydrogen autotransfer, is an important catalytic concept. Borrowing hydrogen can be seen as an example of Green chemistry, the method is highly atom economic, because is circumvents the activation of the alcohol. The method is not limited to the preparation of amines, it can also be used to form Carbon–carbon bonds, alcohols can be temporarily converted into carbonyl compounds by the metal-catalysed removal of hydrogen. The carbonyl compounds are reactive in a range of transformations than the precursor alcohols and can react in situ to give imines, alkenes. Nitroaromatics can also give this reaction, reducing nitro to amine and imine giving secondary amines, ruthenium dichloride dimer Dichlorotrisruthenium dppf Eschweiler-Clarke reaction
11.
Ligand
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In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the electron pairs. The nature of bonding can range from covalent to ionic. Furthermore, the bond order can range from one to three. Ligands are viewed as Lewis bases, although rare cases are known to involve Lewis acidic ligand, metals and metalloids are bound to ligands in virtually all circumstances, although gaseous naked metal ions can be generated in high vacuum. Ligands in a complex dictate the reactivity of the atom, including ligand substitution rates, the reactivity of the ligands themselves. Ligand selection is a consideration in many practical areas, including bioinorganic and medicinal chemistry, homogeneous catalysis. Ligands are classified in many ways, including, charge, size, the identity of the atom. The size of a ligand is indicated by its cone angle, the composition of coordination complexes have been known since the early 1800s, such as Prussian blue and copper vitriol. The key breakthrough occurred when Alfred Werner reconciled formulas and isomers and he showed, among other things, that the formulas of many cobalt and chromium compounds can be understood if the metal has six ligands in an octahedral geometry. The first to use the term ligand were Alfred Stock and Carl Somiesky, the theory allows one to understand the difference between coordinated and ionic chloride in the cobalt ammine chlorides and to explain many of the previously inexplicable isomers. He resolved the first coordination complex called hexol into optical isomers, in general, ligands are viewed as electron donors and the metals as electron acceptors. This is because the ligand and central metal are bonded to one another, bonding is often described using the formalisms of molecular orbital theory. The HOMO can be mainly of ligands or metal character, ligands and metal ions can be ordered in many ways, one ranking system focuses on ligand hardness. Metal ions preferentially bind certain ligands, in general, soft metal ions prefer weak field ligands, whereas hard metal ions prefer strong field ligands. According to the orbital theory, the HOMO of the ligand should have an energy that overlaps with the LUMO of the metal preferential. Metal ions bound to strong-field ligands follow the Aufbau principle, whereas complexes bound to weak-field ligands follow Hunds rule. Binding of the metal with the results in a set of molecular orbitals, where the metal can be identified with a new HOMO and LUMO
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