Phenol is an aromatic organic compound with the molecular formula C6H5OH. It is a white crystalline solid, volatile; the molecule consists of a phenyl group bonded to a hydroxy group. It requires careful handling due to its propensity for causing chemical burns. Phenol was first extracted from coal tar, it is an important industrial commodity as a precursor to useful compounds. It is used to synthesize plastics and related materials. Phenol and its chemical derivatives are essential for production of polycarbonates, Bakelite, detergents, herbicides such as phenoxy herbicides, numerous pharmaceutical drugs. Phenol is an organic compound appreciably soluble in water, with about 84.2 g dissolving in 1000 mL. Homogeneous mixtures of phenol and water at phenol to water mass ratios of ~2.6 and higher are possible. The sodium salt of phenol, sodium phenoxide, is far more water-soluble. Phenol is weakly acidic and at high pHs gives the phenolate anion C6H5O−: PhOH ⇌ PhO− + H+ Compared to aliphatic alcohols, phenol is about 1 million times more acidic, although it is still considered a weak acid.
It reacts with aqueous NaOH to lose H+, giving the salt sodium phenoxide, whereas most alcohols react only partially. One explanation for the increased acidity over alcohols is resonance stabilization of the phenoxide anion by the aromatic ring. In this way, the negative charge on oxygen is delocalized on to the ortho and para carbon atoms through the pi system. An alternative explanation involves the sigma framework, postulating that the dominant effect is the induction from the more electronegative sp2 hybridised carbons. In support of the second explanation, the pKa of the enol of acetone in water is 10.9, making it only less acidic than phenol. Thus, the greater number of resonance structures available to phenoxide compared to acetone enolate seems to contribute little to its stabilization. However, the situation changes. A recent in silico comparison of the gas phase acidities of the vinylogues of phenol and cyclohexanol in conformations that allow for or exclude resonance stabilization leads to the inference that about 1⁄3 of the increased acidity of phenol is attributable to inductive effects, with resonance accounting for the remaining difference.
The phenoxide anion has a similar nucleophilicity to free amines, with the further advantage that its conjugate acid does not become deactivated as a nucleophile in moderately acidic conditions. Phenolate esters are more stable toward hydrolysis than acid anhydrides and acyl halides but are sufficiently reactive under mild conditions to facilitate the formation of amide bonds. Phenol exhibits keto-enol tautomerism with its unstable keto tautomer cyclohexadienone, but only a tiny fraction of phenol exists as the keto form; the equilibrium constant for enolisation is 10−13, which means only one in every ten trillion molecules is in the keto form at any moment. The small amount of stabilisation gained by exchanging a C=C bond for a C=O bond is more than offset by the large destabilisation resulting from the loss of aromaticity. Phenol therefore exists entirely in the enol form. Phenoxides are enolates stabilised by aromaticity. Under normal circumstances, phenoxide is more reactive at the oxygen position, but the oxygen position is a "hard" nucleophile whereas the alpha-carbon positions tend to be "soft".
Phenol is reactive toward electrophilic aromatic substitution as the oxygen atom's pi electrons donate electron density into the ring. By this general approach, many groups can be appended to the ring, via halogenation, acylation and other processes. However, phenol's ring is so activated—second only to aniline—that bromination or chlorination of phenol leads to substitution on all carbon atoms ortho and para to the hydroxy group, not only on one carbon. Phenol reacts with dilute nitric acid at room temperature to give a mixture of 2-nitrophenol and 4-nitrophenol while with concentrated nitric acid, more nitro groups get substituted on the ring to give 2,4,6-trinitrophenol, known as picric acid. Aqueous solutions of phenol are weakly acidic and turn blue litmus to red. Phenol is neutralized by sodium hydroxide forming sodium phenate or phenolate, but being weaker than carbonic acid, it cannot be neutralized by sodium bicarbonate or sodium carbonate to liberate carbon dioxide. C6H5OH + NaOH → C6H5ONa + H2OWhen a mixture of phenol and benzoyl chloride are shaken in presence of dilute sodium hydroxide solution, phenyl benzoate is formed.
This is an example of the Schotten-Baumann reaction: C6H5OH + C6H5COCl → C6H5OCOC6H5 + HClPhenol is reduced to benzene when it is distilled with zinc dust, or when phenol vapour is passed over granules of zinc at 400 °C: C6H5OH + Zn → C6H6 + ZnOWhen phenol is reacted with diazomethane in the presence of boron trifluoride, anisole is obtained as the main product and nitrogen gas as a byproduct. C6H5OH + CH2N2 → C6H5OCH3 + N2When phenol reacts with iron chloride solution, an intense violet-purple solution is formed; because of phenol's commercial importance, many methods have been developed for its production. The dominant current route, accounting for 95% of production, is the cumene process, which uses benzene and propene as feedstock and involves the partial oxidation of cumene vi
A formylation reaction in organic chemistry refers to organic reactions in which an organic compound is functionalized with a formyl group. The reaction is a route to aldehydes and formate esters. A reagent that delivers the formyl group is called a formylating agent. A important formylation process is hydroformylation which converts alkenes to the homologated aldehyde; the conversion of benzene to benzaldehyde is the basis of the Gattermann–Koch reaction: Formylation reactions are a form of electrophilic aromatic substitution and therefore work best when the aromatic starting materials are electron-rich. Phenols are commonly encountered as they can be deprotonated to form phenoxides which are excellent nucleophiles, other electron rich substrates such as mesitylene, pyrrole, or fused aromatic rings can be expected to react. Benzene will react under aggressive conditions but deactivated rings such as pyridine are difficult to formylate effectively. Phenol would be expected to react to give a mixture of ortho and para products, however many formylation reactions will selectively give only the otho product.
This can be explained by strong attractive interactions between the phenoxide and the formylating reagent during the reaction, for example ionic interactions with cationic nitrogen centres in the Vilsmeier–Haack reaction and Duff reaction or coordination to high oxidation metals in the Casiraghi formylation and Rieche formylation. The direct reaction between phenol and paraformaldehyde is possible via the Casiraghi formylation, all other methods used masked forms of formaldehyde, in part to limit the formation of phenol formaldehyde resins. Aldehydes are deactivating and as such phenols only react once, however certain reactions, such as the Duff reaction, can give double addition. Formylation can be applied to other aromatic rings; as it begins with nucleophilic attach by the aromatic group, the electron density of the ring is an important factor. Some aromatic compounds, such as pyrrole, are known to formylate regioselectively. Formylation reactions benzene rings can be achieved via the Gattermann reaction and Gattermann-Koch reaction.
These proceed in a manner similar to the Friedel -- Crafts reaction. Dimethylformamide and phosphorus oxychloride in the Vilsmeier-Haack reaction. Hexamethylenetetramine in the Duff reaction and the Sommelet reaction Carbon monoxide and hydrochloric acid in the Gattermann-Koch reaction Cyanides in the Gattermann reaction; this method synthetizes aromatic aldehydes using hydrogen chloride and hydrogen cyanide in the presence of Lewis acid catalysts: Chloroform in the Reimer-Tiemann reaction dichloromethyl methyl ether in Rieche formylation. Formylation of 3-methylamino-1-propanol with formamide as a protecting group in the preparation of Protriptyline. Formamide was used in the synthesis of primidone. Hydroformylation is the the most important method for the formylation of aliphatic compounds, however it can be achieved by the Sommelet reaction, Bouveault aldehyde synthesis or Bodroux–Chichibabin aldehyde synthesis. Hydroformylation Hydroacylation
A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei, can be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur; the substance involved in a chemical reaction are called reactants or reagents. Chemical reactions are characterized by a chemical change, they yield one or more products, which have properties different from the reactants. Reactions consist of a sequence of individual sub-steps, the so-called elementary reactions, the information on the precise course of action is part of the reaction mechanism. Chemical reactions are described with chemical equations, which symbolically present the starting materials, end products, sometimes intermediate products and reaction conditions.
Chemical reactions happen at a characteristic reaction rate at a given temperature and chemical concentration. Reaction rates increase with increasing temperature because there is more thermal energy available to reach the activation energy necessary for breaking bonds between atoms. Reactions may proceed in the forward or reverse direction until they go to completion or reach equilibrium. Reactions that proceed in the forward direction to approach equilibrium are described as spontaneous, requiring no input of free energy to go forward. Non-spontaneous reactions require input of free energy to go forward. Different chemical reactions are used in combinations during chemical synthesis in order to obtain a desired product. In biochemistry, a consecutive series of chemical reactions form metabolic pathways; these reactions are catalyzed by protein enzymes. Enzymes increase the rates of biochemical reactions, so that metabolic syntheses and decompositions impossible under ordinary conditions can occur at the temperatures and concentrations present within a cell.
The general concept of a chemical reaction has been extended to reactions between entities smaller than atoms, including nuclear reactions, radioactive decays, reactions between elementary particles, as described by quantum field theory. Chemical reactions such as combustion in fire and the reduction of ores to metals were known since antiquity. Initial theories of transformation of materials were developed by Greek philosophers, such as the Four-Element Theory of Empedocles stating that any substance is composed of the four basic elements – fire, water and earth. In the Middle Ages, chemical transformations were studied by Alchemists, they attempted, in particular, to convert lead into gold, for which purpose they used reactions of lead and lead-copper alloys with sulfur. The production of chemical substances that do not occur in nature has long been tried, such as the synthesis of sulfuric and nitric acids attributed to the controversial alchemist Jābir ibn Hayyān; the process involved heating of sulfate and nitrate minerals such as copper sulfate and saltpeter.
In the 17th century, Johann Rudolph Glauber produced hydrochloric acid and sodium sulfate by reacting sulfuric acid and sodium chloride. With the development of the lead chamber process in 1746 and the Leblanc process, allowing large-scale production of sulfuric acid and sodium carbonate chemical reactions became implemented into the industry. Further optimization of sulfuric acid technology resulted in the contact process in the 1880s, the Haber process was developed in 1909–1910 for ammonia synthesis. From the 16th century, researchers including Jan Baptist van Helmont, Robert Boyle, Isaac Newton tried to establish theories of the experimentally observed chemical transformations; the phlogiston theory was proposed in 1667 by Johann Joachim Becher. It postulated the existence of a fire-like element called "phlogiston", contained within combustible bodies and released during combustion; this proved to be false in 1785 by Antoine Lavoisier who found the correct explanation of the combustion as reaction with oxygen from the air.
Joseph Louis Gay-Lussac recognized in 1808 that gases always react in a certain relationship with each other. Based on this idea and the atomic theory of John Dalton, Joseph Proust had developed the law of definite proportions, which resulted in the concepts of stoichiometry and chemical equations. Regarding the organic chemistry, it was long believed that compounds obtained from living organisms were too complex to be obtained synthetically. According to the concept of vitalism, organic matter was endowed with a "vital force" and distinguished from inorganic materials; this separation was ended however by the synthesis of urea from inorganic precursors by Friedrich Wöhler in 1828. Other chemists who brought major contributions to organic chemistry include Alexander William Williamson with his synthesis of ethers and Christopher Kelk Ingold, among many discoveries, established the mechanisms of substitution reactions. Chemical equations are used to graphically illustrate chemical reactions, they consist of chemical or structural formulas of the reactants on the left and those of the products on the right.
They are separated by an arrow which indicates the type of the reaction.
Johann Karl Wilhelm Ferdinand Tiemann was a German chemist and together with Karl Reimer discoverer of the Reimer-Tiemann reaction. Beginning in 1866, Tiemann studied pharmacy at the TU Braunschweig where he graduated in 1869, his professor in Brunswick wrote a letter of recommendation to August Wilhelm von Hofmann at the University of Berlin where Tiemann started as assistant of von Hofmann in 1869. In 1874 Wilhelm Haarmann and Tiemann started a company, after they discovered the synthesis of vanillin from coniferyl alcohol; the vanillin plant Holzminden was not successful before Karl Reimer discovered the Reimer-Tiemann reaction which opened an alternative synthesis route to vanillin. In 1882 Tiemann became professor at the University of Berlin, he was involved in the first synthesis of Jonon a compound of the sweet violet, which became a huge success for Harmann & Reimer company. August Wilhelm von Hofmann married Berta the younger sister of Ferdinand Tiemann. Tiemann-Gärtner's Handbuch der Untersuchung und Beurtheilung der Wässer: zum Gebrauch für Apotheker, Ärzte, Fabrikanten, Medicinalbeamte und Techniker.
Vieweg, Braunschweig 4. Aufl. / bearb. von Georg Walter und August Gärtner 1895 Digital edition by the University and State Library Düsseldorf
Royal Society of Chemistry
The Royal Society of Chemistry is a learned society in the United Kingdom with the goal of "advancing the chemical sciences". It was formed in 1980 from the amalgamation of the Chemical Society, the Royal Institute of Chemistry, the Faraday Society, the Society for Analytical Chemistry with a new Royal Charter and the dual role of learned society and professional body. At its inception, the Society had a combined membership of 34,000 in the UK and a further 8,000 abroad; the headquarters of the Society are at Burlington House, London. It has offices in Thomas Graham House in Cambridge where RSC Publishing is based; the Society has offices in the United States at the University City Science Center, Philadelphia, in both Beijing and Shanghai and Bangalore, India. The organisation carries out research, publishes journals and databases, as well as hosting conferences and workshops, it is the professional body for chemistry in the UK, with the ability to award the status of Chartered Chemist and, through the Science Council the awards of Chartered Scientist, Registered Scientist and Registered Science Technician to suitably qualified candidates.
The designation FRSC is given to a group of elected Fellows of the society who have made major contributions to chemistry and other interface disciplines such as biological chemistry. The names of Fellows are published each year in The Times. Honorary Fellowship of the Society is awarded for distinguished service in the field of chemistry; the president is elected biennially and wears a badge in the form of a spoked wheel, with the standing figure of Joseph Priestley depicted in enamel in red and blue, on a hexagonal medallion in the centre. The rim of the wheel is gold, the twelve spokes are of non-tarnishable metals; the current president is Dame Carol V. Robinson. Past presidents of the society have been: The following are membership grades with post-nominals: Affiliate: The grade for students and those involved in chemistry who do not meet the requirements for the following grades. AMRSC: Associate Member, Royal Society of Chemistry The entry level for RSC membership, AMRSC is awarded to graduates in the chemical sciences.
MRSC: Member, Royal Society of Chemistry Awarded to graduates with at least 3 years' experience, who have acquired key skills through professional activity FRSC: Fellow of the Royal Society of Chemistry Fellowship may be awarded to nominees who have made an outstanding contribution to chemistry. HonFRSC: Honorary Fellow of the Society Honorary Fellowship is awarded for distinguished service in the field of chemistry. CChem: Chartered Chemist The award of CChem is considered separately from admission to a category of RSC membership. Candidates need to be MRSC or FRSC and demonstrate development of specific professional attributes and be in a job which requires their chemical knowledge and skills. CSci: Chartered Scientist The RSC is a licensed by the Science Council for the registration of Chartered Scientists. EurChem: European Chemist The RSC is a member of the European Communities Chemistry Council, can award this designation to Chartered Chemists. MChemA: Mastership in Chemical Analysis The RSC awards this postgraduate qualification, the UK statutory qualification for practice as a Public Analyst.
It requires candidates to submit a portfolio of suitable experience and to take theory papers and a one-day laboratory practical examination. The qualification GRSC was awarded from 1981 to 1995 for completion of college courses equivalent to an honours chemistry degree and overseen by the RSC, it replaced the GRIC offered by the Royal Institute of Chemistry. The society is organised around 9 divisions, based on subject areas, local sections, both in the United Kingdom and overseas. Divisions cover broad areas of chemistry but contain many special interest groups for more specific areas. Analytical Division for analytical chemistry and promoting the original aims of the Society for Analytical Chemistry. 12 Subject Groups. Dalton Division, named after John Dalton, for inorganic chemistry. 6 Subject Groups. Education Division for chemical education. 4 Subject Groups. Faraday Division, named after Michael Faraday, for physical chemistry and promoting the original aims of the Faraday Society. 14 Subject Groups.
Organic Division for organic chemistry. 6 Subject Groups. Chemical Biology Interface Division. 2 Subject Groups. Environment and Energy Division. 3 Subject Groups. Materials Chemistry Division. 4 Subject Groups. Industry and Technology Division. 13 Subject Groups. There are 12 subjects groups not attached to a division. There are 35 local sections covering the United Ireland. In countries of the Commonwealth of Nations and many other countries there are Local Representatives of the society and some activities; the society is a not-for-profit publisher: surplus made by its publishing business is invested to support its aim of advancing the chemical sciences. In addition to scientific journals, including its flagship journals Chemical Communications, Chemical Science and Chemical Society Reviews, the society publishes: Education in Chemistry for teachers. A free online journal for chemistry educators, Chemistry Education Research and Practice. A general chemistry magazine Chemistry World, sent monthly to all members of the Society throughout the world.
The editorial board consists of 10 industrial chemists. It was first published in January 2004, it replaced C
Carbon tetrachloride known by many other names is an organic compound with the chemical formula CCl4. It is a colourless liquid with a "sweet" smell, it has no flammability at lower temperatures. It was widely used in fire extinguishers, as a precursor to refrigerants and as a cleaning agent, but has since been phased out because of toxicity and safety concerns. Exposure to high concentrations of carbon tetrachloride can affect the central nervous system, degenerate the liver and kidneys. Prolonged exposure can be fatal. Carbon tetrachloride was synthesized by the French chemist Henri Victor Regnault in 1839 by the reaction of chloroform with chlorine, but now it is produced from methane: CH4 + 4 Cl2 → CCl4 + 4 HClThe production utilizes by-products of other chlorination reactions, such as from the syntheses of dichloromethane and chloroform. Higher chlorocarbons are subjected to "chlorinolysis": C2Cl6 + Cl2 → 2 CCl4Prior to the 1950s, carbon tetrachloride was manufactured by the chlorination of carbon disulfide at 105 to 130 °C: CS2 + 3Cl2 → CCl4 + S2Cl2The production of carbon tetrachloride has steeply declined since the 1980s due to environmental concerns and the decreased demand for CFCs, which were derived from carbon tetrachloride.
In 1992, production in the U. S./Europe/Japan was estimated at 720,000 tonnes. In the carbon tetrachloride molecule, four chlorine atoms are positioned symmetrically as corners in a tetrahedral configuration joined to a central carbon atom by single covalent bonds; because of this symmetrical geometry, CCl4 is non-polar. Methane gas has the same structure, making carbon tetrachloride a halomethane; as a solvent, it is well suited to dissolving other non-polar compounds and oils. It can dissolve iodine, it is somewhat volatile, giving off vapors with a smell characteristic of other chlorinated solvents, somewhat similar to the tetrachloroethylene smell reminiscent of dry cleaners' shops. Solid tetrachloromethane has two polymorphs: crystalline II below −47.5 °C and crystalline I above −47.5 °C. At −47.3 °C it has monoclinic crystal structure with space group C2/c and lattice constants a = 20.3, b = 11.6, c = 19.9, β = 111°. With a specific gravity greater than 1, carbon tetrachloride will be present as a dense nonaqueous phase liquid if sufficient quantities are spilled in the environment.
In organic chemistry, carbon tetrachloride serves as a source of chlorine in the Appel reaction. One specialty use of carbon tetrachloride is in stamp collecting, to reveal watermarks on postage stamps without damaging them. A small amount of the liquid was placed on the back of a stamp, sitting in a black glass or obsidian tray; the letters or design of the watermark could be seen. Carbon tetrachloride was used as a dry cleaning solvent, as a refrigerant, in lava lamps. In case of the latter, carbon tetrachloride is a key ingredient that adds weight to the otherwise buoyant wax, it once was a popular solvent in organic chemistry, because of its adverse health effects, it is used today. It is sometimes useful as a solvent for infrared spectroscopy, because there are no significant absorption bands > 1600 cm−1. Because carbon tetrachloride does not have any hydrogen atoms, it was used in proton NMR spectroscopy. In addition to being toxic, its dissolving power is low, its use has been superseded by deuterated solvents.
Use of carbon tetrachloride in determination of oil has been replaced by various other solvents, such as tetrachloroethylene. Because it has no C-H bonds, carbon tetrachloride does not undergo free-radical reactions, it is a useful solvent for halogenations either by the elemental halogen or by a halogenation reagent such as N-bromosuccinimide. In 1910, the Pyrene Manufacturing Company of Delaware filed a patent to use carbon tetrachloride to extinguish fires; the liquid was vaporized by the heat of combustion and extinguished flames, an early form of gaseous fire suppression. At the time it was believed the gas displaced oxygen in the area near the fire, but research found that the gas inhibits the chemical chain reaction of the combustion process. In 1911, Pyrene patented a portable extinguisher that used the chemical; the extinguisher consisted of a brass bottle with an integrated handpump, used to expel a jet of liquid toward the fire. As the container was unpressurized, it could be refilled after use.
Carbon tetrachloride was suitable for liquid and electrical fires and the extinguishers were carried on aircraft or motor vehicles. In the first half of the 20th century, another common fire extinguisher was a single-use, sealed glass globe known as a "fire grenade," filled with either carbon tetrachloride or salt water; the bulb could be thrown at the base of the flames to quench the fire. The carbon tetrachloride type could be installed in a spring-loaded wall fixture with a solder-based restraint; when the solder melted by high heat, the spring would either break the globe or launch it out of the bracket, allowing the extinguishing agent to be automatically dispersed into the fire. A well-known brand was the "Red Comet,", variously manufactured with other fire-fighting equipment in the Denver, Colorado area by the Red Comet Manufacturing Company from its founding in 1919 until manufacturing operations were closed in the early 1980s. Prior to the Montreal Protocol, large quantities of carbon tetrachloride were used to produce the chlorofluorocarbon re