Higher Alkylbenzenes

The reaction is claimed to be improved by use of an equimolar mixture of chlorosulfonic acid and sulfuryl chloride apparently chlorinated byproducts were not formed. o-Xylene (1,2-dimethylbenzene) reacts with excess chlorosulfonic acid to give the expected 4-sulfonyl chloride (74-86% yield), and by treatment with the reagent (seven equivalents) at 8 °C, the reaction also produces some of the 3-sulfonyl chloride (26%).  

This orientation of sulfonation would be unfavourable on steric grounds and, indeed, it is known that on heating, the 3-sulfonic acid rearranges to the 4-isomer. 

Mesitylene (1,3,5-trimethylbenzene), by heating with a mixture of chlorosulfonic acid and sulfuryl chloride at 100 °C (10 hours), gives a high yield of 2,4,6-trimethylbenzene-l,3-disulfonyl chloride the same compound (70% yield) also 

5-Tertiary butyl-1,3-dimethylbenzene reacts with excess chlorosulfonic acid in chloroform solution to give a high yield of the 2-sulfonyl chloride.  

4- and 1,3,5-Triisopropylbenzene react with chlorosulfonic acid in carbon tetrachloride (30-50 °C) to yield the 5- and 2-sulfonyl chlorides respectively, and 1-methyl-3,5-diisopropylbenzene gives the 2-sulfonyl chloride.  

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Isomerization is promoted by either acids or bases. Higher alkylbenzenes are isomerized in the presence of AlCb/HCl or BF3/HF olefins with most mineral acids, acid salts and silica-alumina saturated hydrocarbons with AlCb or AlBr,3 promoted by 0.1 percent of olefins. 

Table 6.1 presents the purity specifications. The target of design is achieving over 99.9% purity. It may be seen that higher alkylbenzenes impurities are undesired. Ethyl- and butylbenzene can be prevented by avoiding olefins and butylenes in the propylene feed. N-propylbenzene appears by equilibrium between isomers and can be controlled by catalyst selectivity. 

The in situ generation of bromine from H202 and HBr provides an extremely versatile indirect method for oxidizing toluenes and higher alkylbenzenes. It is... 

Of the n-alkylbenzenes the effect of toluene equalled that of benzene. The higher alkylbenzenes inhibited both cracking and isomerization. 

Podall and Foster reported that the reaction of toluene with olefins with KCs, a graphite inclusion compound, gave the alkylation of the side chain. A 50% conversion of toluene to 3-phenylpentane was obtained together with higher alkylbenzenes at 298 K from toluene and ethylene. At 323 K, the main product was propylbenzene (48%) together with 3-phenylpentane and a small quantity of higher alkylated products. Similarly, the reaction of isopropylbenzene with ethylene gave a 42% yield of <-amylbenzene at 473 K. 

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