Aromatic hydrocarbons with acid derivatives

By oxidation of the methyl derivative of an aromatic hydrocarbon with a solution of chromic anhydride in acetic anhydride and acetic acid. The aldehyde formed is immediately converted into the (/m-diacetate, which is stable to oxidation. The diacetate is collected and hydrolysed with sulphuric acid, for example ... 

An excess of crotonaldehyde or aUphatic, ahcyhc, and aromatic hydrocarbons and their derivatives is used as a solvent to produce compounds of molecular weights of 1000—5000 (25—28). After removal of unreacted components and solvent, the adduct referred to as polyester is decomposed in acidic media or by pyrolysis (29—36). Proper operation of acidic decomposition can give high yields of pure /n j ,/n7 j -2,4-hexadienoic acid, whereas the pyrolysis gives a mixture of isomers that must be converted to the pure trans,trans form. The thermal decomposition is carried out in the presence of alkaU or amine catalysts. A simultaneous codistillation of the sorbic acid as it forms and the component used as the solvent can simplify the process scheme. The catalyst remains in the reaction batch. Suitable solvents and entraining agents include most inert Hquids that bod at 200—300°C, eg, aUphatic hydrocarbons. When the polyester is spHt thermally at 170—180°C and the sorbic acid is distilled direcdy with the solvent, production and purification can be combined in a single step. The solvent can be reused after removal of the sorbic acid (34). The isomeric mixture can be converted to the thermodynamically more stable trans,trans form in the presence of iodine, alkaU, or sulfuric or hydrochloric acid (37,38). 

Chloral condensations with aromatic hydrocarbons (and related derivatives) give rise to diaryltrichloroethane compounds, and are brought about in the presence of acid catalysts, proceeding with the formation of carbinol intermediates (Scheme 2.1). Commonly used catalysts include concentrated H2SO4 and its monohydrate, HCl, HF, I O,-, Lewis acids and a series of other acid agents [1, 2]. 

Konovalov [15] nitrated aliphatic hydrocarbons in sealed tubes at 120-130°C, using dilute nitric acid of concentration 6.5-19%. From normal hydrocarbons he obtained secondary nitro compounds in yields varying from 40% (2-nitro-hexane from hexane) to 49-50% (2-nitrooctane from octane). Aromatic hydrocarbons with an aliphatic substituted group when nitrated under the same conditions gave nitro derivatives with a nitro group in the side chain. For example, ethylbenzene, when nitrated with 12.5% nitric acid at 105-108°C, gives phenyl-nitroethane in 44% yield. The optimum yield is obtained with 13% acid. 

Creosote. The major portion of creosote is derived from coal and is a complex mixture of aromatic hydrocarbons with condensed ring systems. The remaining components are tar acids, which are phenolic derivatives of these compounds, and tar bases, which are heterocyclic compounds containing nitrogen plus some neutral oxygenated compounds. At least 200 chemical compounds have been identified in coal-tar creosote, but many of these are present in small amounts. The chemical composition is variable, but some idea of a typical creosote is given in Table I (2). 

The conventional method for preparation of these aromatic ketones involves reaction of the aromatic hydrocarbon with a carboxylic acid derivatives using a Lewis acid (AICI3, FeCl3, BF3, ZnCl2, TiCl4, etc.) ora Bronsted acid (polyphosphoric... 

The conventional method for preparation of these aromatic ketones involves reaction of the aromatic hydrocarbon with a carboxylic acid derivative in the presence of a Lewis acid (AICI3, FeClj, BF3, ZnCl2, TiCy or Brpnsted acids (poly-phosphoric acid, FIF). The major drawback of the Friedel-Crafts reaction is the need to use a stoichiometric quantity of Lewis acid relative to the ketone formed. This stoichiometric quantity is required because the ketone (product of the reaction) forms a stable stoichiometric complex with the Lewis acid. The decomposition of this complex is generally performed with water, leading to total destruction and loss of the Lewis acid. 

Friedel and Crafts also discovered that treating an aromatic hydrocarbon with an acyl halide in the presence of aluminum chloride gives a ketone. An acyl halide is a derivative of a carboxylic acid in which the —OH of the carboxyl group is replaced by a halogen, most commonly chlorine. Acyl halides are also referred to as acid halides. An RCO— group is known as an acyl group hence, the reaction of an acyl halide with an aromatic hydrocarbon is known as Friedel-Crafts acylation, eis illustrated by the reaction of benzene and acetyl chloride in the presence of aluminum chloride to give acetophenone ... 

In the second mechanism proposed as an alternative to the previous one, radical-cations are involved as active intermediate species [11]. In this case it is postulated that a Lewis acid (A), considered as an electron acceptor, reacts with the aromatic hydrocarbon and its derivatives to give a radical-cation species (9), which couples with another aromatic substrate to produce a dimer (10). Such a mechanism was proposed in order to interpret the oxidative dimerization of anisole by Lewis acids, involving addition of a radical-cation to the substrate (Scheme 6.3) [12,13]. 

It is noteworthy that there is no single wavelength that alone will unambiguously give all information about the nature and content of the DOC. It is well known that tt-tt electron transition, specific for phenolic arenes, benzoic acids, aniline derivatives, polyenes, and polycyclic aromatic hydrocarbons with two or more rings, occurs between the wavelengths approximately from 270 to 280 nm. For that reason, the application of UV absorbances within 270-280 nm is more suitable for describing aromatic carbon moieties and offers also a possibility to estimate their total quantity [14]. A detailed research about... 

Bassin, Cremlyn and Swinboume. Details of kinetic and mechanistic studies on sulfonation and chlorosulfonation of aromatic hydrocarbons and other derivatives have been described in Chapter 2. Chlorosulfonic acid is a very active sulfonating agent and when benzene is added to an excess of the reagent at room temperature, benzenesulfonyl chloride is formed (> 70%) with only a trace of diphenyl sulfone. " On the other hand, when an excess of benzene is present, the major products are diphenyl sulfone and benzenesulfonic acid. " ... 

Unsaturated cyclic hydrocarbons, aromatic hydrocarbons and their derivatives, and polycyclic hydrocarbons give a very sensitive reaction with sulfuric acid and formaldehyde, in which deeply colored resinous substances are formed. In this manner as little as 0.1% of benzene in solvent mixtures can be detected. Saturated hydrocarbons, unsaturated aliphatic hydrocarbons, and cyclic saturated hydrocarbons do not give this reaction. 

Unlike aliphatic hydrocarbons, aromatic hydrocarbons can be sul-phonated and nitrated they also form characteristic molecular compounds with picric acid, styphnic acid and 1 3 5-trinitrobenzene. Many of the reactions of aromatic hydrocarbons will be evident from the following discussion of crystalline derivatives suitable for their characterisation. 

An additional useful test is to distil the acid or its sodium salt with soda lime. Heat 0.5 g. of the acid or its sodium salt with 0 2 g. of soda lime in an ignition tube to make certain that there is no explosion. Then grind together 0-5 g. of the acid with 3 g. of soda hme, place the mixture in a Pyrex test-tube and cover it with an equal bulk of soda hme. Fit a wide dehvery tube dipping into an empty test-tube. Clamp the tube near the mouth. Heat the soda lime first and then the mixture gradually to a dull-red heat. Examine the product this may consist of aromatic hydrocarbons or derivatives, e.g., phenol from sahcyUc acid, anisole from anisic acid, toluene from toluic acid, etc. 

The physical properties of cyanoacetic acid [372-09-8] and two of its ester derivatives are Hsted ia Table 11 (82). The parent acid is a strong organic acid with a dissociation constant at 25°C of 3.36 x 10. It is prepared by the reaction of chloroacetic acid with sodium cyanide. It is hygroscopic and highly soluble ia alcohols and diethyl ether but iasoluble ia both aromatic and aUphatic hydrocarbons. It undergoes typical nitrile and acid reactions but the presence of the nitrile and the carboxyUc acid on the same carbon cause the hydrogens on C-2 to be readily replaced. The resulting malonic acid derivative decarboxylates to a substituted acrylonitrile ... 

Preparation of Arylcarboxylic Acids and Derivatives. The general Friedel-Crafts acylation principle can be successfully appHed to the preparation of aromatic carboxyUc acids. Carbonyl haUdes (phosgene, carbonyl chloride fluoride, or carbonyl fluoride) [353-50-4] are diacyl haUdes of carbonic acid. Phosgene [75-44-5] or oxalyl chloride [79-37-8] react with aromatic hydrocarbons to give aroyl chlorides that yield acids on hydrolysis (133) ... 

Reaction with Organic Compounds. Aluminum is not attacked by saturated or unsaturated, aUphatic or aromatic hydrocarbons. Halogenated derivatives of hydrocarbons do not generally react with aluminum except in the presence of water, which leads to the forma tion of halogen acids. The chemical stabiUty of aluminum in the presence of alcohols is very good and stabiUty is excellent in the presence of aldehydes, ketones, and quinones. 

Impurities can sometimes be removed by conversion to derivatives under conditions where the major component does not react or reacts much more slowly. For example, normal (straight-chain) paraffins can be freed from unsaturated and branched-chain components by taking advantage of the greater reactivity of the latter with chlorosulfonic acid or bromine. Similarly, the preferential nitration of aromatic hydrocarbons can be used to remove e.g. benzene or toluene from cyclohexane by shaking for several hours with a mixture of concentrated nitric acid (25%), sulfuric acid (58%), and water (17%). 

Participation of fluorocarbocations, derived from carboxylic acids and from halo acetones, in reactions of carbonyl compounds with sulfur tetrafluoride has been directly evidenced by trapping them with aromatic hydrocarbons [207, 20S],... 

Benzyl-type carbanions and their metallo compounds, derived from aromatic or hetero-aromatic precursors, bearing carbon- or hetero-substituents, are readily available with variable substitution patterns due to their mesomeric stabilization (see Section 1.3.2.2)2. Even dicarbanions are accessible without difficulty3,4. The equilibrium acidities of many aromatic hydrocarbons have been determined5-7. The acidities of a-hetero-substituted toluenes8 are similar to those of the corresponding allylic compounds and can usually be generated by the same methods. 

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