Phenols, from sulphonic acids

From Sulphonic Acids.—As previously stated, the methods of formation of phenols are wholly different from those of alcohols, and, together with their reactions, prove the constitution to be as we have given it, viz.. Ring—OU. The synthesis which is most generally used industrially is that from sulphonic acids, i. 520). When a salt of benzene sulphonic acid is fused with potassium or sodium hydroxide, phenol is formed together with a sulphite salt of the metal, according to the following reaction ... 

The best methods of synthesis are the potash fusion of phenol ortho-sulphonic acid and from ortho-chlor phenol with alkali. 

Resorcinol, 1-3-Di-hydroxy Benzene.—The meta-di-hydroxy benzene is known as resorcinol or resorcin. It is also obtained from plant resins by alkali fusion. Synthetically it is prepared from phenol meta-sulphonic acid and from meta-chlor phenol. In the case of chlor phenol the para compound also yields meta-di-hydroxy benzene due to position rearrangement. 

Sulphonic acids of this series may also be obtained from sulphonic acids of the phenols. 

The paper describes work on the preparation of Ru/AljOj catalyst containing different amounts of Ru and the effect of ruthenium loading on the removal of NOx vapours from air stream. The effect of residence time on the efficiency of removal is also discussed. The NOx analysis was carried out using spectrophotometer. The Phenol-di-sulphonic acid method was used for the estimation of nitrate. It was found that 1 wt% loading was the best for the removal of NOx comparison to 0.2 wt% and 2 wt% loadings and a higher residence time of... 

Phenols are prepared from sulphonic acids or amines. When the sodium salt of benzenesulphonic acid, for example, is fused with sodium hydroxide, it is converted into the salt of phenol —... 

Artificial humic acids were produced, either chemically or enzymatically, from a variety of phenols, from sulphonated napthoquinone, and fromp-benzoquinone, together with numerous amino acids. Microbial decomposition of both natural and artificial humic acids was usually negligible. When model humic acids were prepared by reacting quinones formed from phenols, usually with amino acids present, it was observed that oxidation, polymerization, and polycondensation were more rapid in the presence of amino acids than in their absence. Evidently the amino acids participate in these reactions. Colorless products were formed initially which gradually darkened to reddish-brown and then brownish-black. These humic acids had many physical and chemical properties that corresponded closely to those of natural humic acids. 

Usually prepared from the corresponding sulphonic acids by alkali fusion, methylation of phenol or from the aminotoluene by treatment with nitrous acid followed by boiling. Both o- and p-cresol are used as end components in azo dyes. 

The most important reaction of the sulphonic acids is their conversion into phenols by fusion with caustic alkalis. When they are fused with potassium cyanide, nitriles are obtained, e.g. benzonitriie from ben-zenesulphonic acid. 

The procedure is not usually applicable to aminosulphonic acids owing to the interaction between the amino group and the phosphorus pentachloride. If, however, the chlorosulphonic acid is prepared by diazotisation and treatment with a solution of cuprous chloride in hydrochloric acid, the crystalline chlorosulphonamide and chlorosulphonanilide may be obtained in the usual way. With some compounds, the amino group may be protected by acetylation. Sulphonic acids derived from a phenol or naphthol cannot be converted into the sulphonyl chlorides by the phosphorus pentachloride method. 

At one time the requirement for phenol (melting point 41°C), eould be met by distillation of eoal tar and subsequent treatment of the middle oil with eaustic soda to extraet the phenols. Such tar acid distillation products, sometimes containing up to 20% o-cresol, are still used in resin manufacture but the bulk of phenol available today is obtained synthetically from benzene or other chemicals by such processes as the sulphonation process, the Raschig process and the cumene process. Synthetic phenol is a purer product and thus has the advantage of giving rise to less variability in the condensation reactions. 

The kinetics of desulphonation of sulphonic acid derivatives of m-cresol, mesitylene, phenol, p-cresol, and p-nitrodiphenylamine by hydrochloric or sulphuric acids in 90 % acetic acid were investigated by Baddeley et a/.701, who reported (without giving any details) that rates were independent of the concentration of sulphuric acid and nature of the catalysing anion, and only proportional to the hydrogen ion concentration. The former observation can only be accounted for if the increased concentration of sulphonic acid anion is compensated by removal of protons from the medium to form the undissociated acid this result implies, therefore, that reaction takes place on the anion and the mechanism was envisaged as rapid protonation of the anion (at ring carbon) followed by a rate-determining reaction with a base. 

Polymeric adsorbents have also been found to be very useful, and even highly water-loving undesired materials like p-toluene sulphonic acid from waste streams can be recovered via ad.sorption and regeneration with solvents like fv -propanol. In such instances, the regeneration of activated carbons is not satisfactory, even with aqueous sodium hydroxide. Solutes like phenols, substituted phenols, aromatic amines, heterocyclic amines (pyridine, picolines, etc.) can be recovered, in a rewarding way, from aqueous solutions. 

The crude product contains isomers other than that required and also nitrated phenolic compounds resulting from side reactions. The usual method of purification is to treat the crude product with sodium sulphite, which converts asymmetric trinitro compounds to sulphonic acid derivatives, and to wash out the resulting soluble products with alkaline water. The purity of the product is determined by the melting point, the minimum value for Grade I TNT commonly being 80-2°C. Unless adequate purity is achieved, slow exudation of impurities can occur during storage and the TNT then becomes insensitive. 

Naphthylamine and also its sulphonic acids are likewise employed technically for the manufacture of azo-dyes. In the same way a-naph-thol is made from naphthalene-a-sulphonic acid by fusion with sodium hydroxide although on a smaller scale than /3-naphthol. a-Naphthyla-mine, on the other hand, is obtained by the reduction of a-nitronaph-thalene (analogy to aniline). The fusion of alkali salts of arylsulphonic acids with alkali also serves technically for the production of pure phenol and of many phenol derivatives. 

The azo-dyes derived from phenols are called acid dyes, those derived from amines basic dyes. But since, in industry, the starting materials, not only diazo-components (diazotised amines), but also azocomponents (coupled phenols or amines), are nearly always sulphonic acids, this distinction is pointless. The vast majority of the azo-dyes... 

Alcohols may be prepared (1) by hydration of alkenes (1) in presence of an acid and (11) by hydroboratlon-oxidatlon reaction (2) from carbonyl compounds by (1) catalytic reduction and (11) the action of Grignard reagents. Phenols may be prepared by (1) substitution of (1) halogen atom In haloarenes and (11) sulphonic acid group In aiyl sulphonic acids, by -OH group (2) by hydrolysis of diazonium salts and (3) industrially from cumene. 

Alkali fusion of sulphonates Phenols can he prepared from the corresponding sulphonic acids hy fusion with alkali. 

Solid esters are easily crystallisable materials. It is important to note that esters of alcohols must be recrystallised either from non-hydroxylic solvents (e.g. toluene) or from the alcohol from which the ester is derived. Thus methyl esters should be crystallised from methanol or methanol/toluene, but not from ethanol, n-butanol or other alcohols, in order to avoid alcohol exchange and contamination of the ester with a second ester. Useful solvents for crystallisation are the corresponding alcohols or aqueous alcohols, toluene, toluene/petroleum ether, and chloroform (ethanol-free)/toluene. Carboxylic acid esters derived from phenols are more difficult to hydrolyse and exchange, hence any alcoholic solvent can be used freely. Sulphonic acid esters of phenols are even more resistant to hydrolysis they can safely be crystallised not only from the above solvents but also from acetic acid, aqueous acetic acid or boiling n-butanol. 

Polymeric phosphonium salt-bound carboxylate, benzenesulphinate and phenoxide anions have been used in nucleophilic substitution reactions for the synthesis of carboxylic acid esters, sulphones and C/O alkylation of phenols from alkyl halides. The polymeric reagent seems to increase the nucleophilicity of the anions376 and the yields are higher than those for corresponding polymer phase-transfer catalysis (reaction 273). 

Reaction LXXV. Fusion of Aromatic Sulphonic Acids with Caustic Alkalis. (Z. Ch (1876), 3, 299 J. pr., [2], 17, 394 20, 300.)—This method is of technical importance as it is employed to prepare phenols and naphthols from the parent hydrocarbons. These phenols and naphthols are much used as intermediates in the dye industry. The method cannot easily be applied to determine structure, owing to rearrangement liable to occur at the elevated temperatures. Caustic potash is more convenient than soda, since it generally yields a more easily fusible mixture. 

The constitution of picric acid was determined by Laurent [8] in 1841. He prepared it by reacting phenol with nitric acid. He was also able to isolate dinitro-phenol formed in an intermediate stage of the nitration. A further improvement in the method of preparation of picric acid from phenol was its sulphonation prior to nitration (Schmidt and Glutz [9]). 

The spent acid from the nitration of phenol by the methods described contains several by-products, among them 2,4-dinitrophenol-6-sulphonic acid in the proportions of 22 parts per 100 parts of phenol used for the process, which corresponds to a 8% loss of the phenol, and oxalic acid in the proportion of 5-6 parts per 100 parts of phenol. These are the principal by-products that lower the yield of picric acid. 

---