Aromatic sulfonation XI: Sulfonation of benzene and toluene with sulfur trioxide; sulfone formation and sulfonic acid isomer distribution.

Abstract

The sulfonation of benzene and toluene with sulfur trioxide without solvent has been studied extensively.With benzene at low conversion benzenesulfonic acid and diphenylsulfone arc the only products. At 25" the sulfone: sulfonic acid ratio changes from 0.2 to 0.6 on varying the so3 : CaHs ratio from 0.13 to 1.3. AtaSO3:CsHRratio . 1.3benzene-] .3-disulfonic acid and diphenylsulfonesulfonic acid are found among the reaction products as well. With toluene the sulfone formation is less than with benzene. The isomer distribution of the monosulfonic acids formed in the sulfonation of toluene has been determined at various temperatures between -44 and 65'.Under all conditions the degree of mefa-substitution is low ( I -5 % ) whereas that of para-substitution is high (-80%). The difference in activation enthalpy between paru-and meta-substitution is -2.7 f 0.4 kcal . mole-1, that between para-and orrho-substitution 1.3 kcal . mole-'. The latter enthalpy difference is explainable by an intramolecular hyperconjugative proximity effect in the transition state leading to ortho-substitution. The entropy of activation is greater for pora-than for ortho-substitution, indicating steric hindrance for ortho-su bs t i tu tion.The formation of sulfonic acid and sulfone is discussed in terms of the niechanism : H / \

Diatom type material in permanent slides does not need to be permanently unavailable for electron microscopy examination

“…To further simplify and shorten the process, fuming sulfuric acid (oleum) can be used instead of sulfuric acid (Cerfontain et al. 1964). Using fuming sulfuric acid, the reaction will be completed after ca.…”

“…Similar to benzene, this solvent can be sulphonated in reaction with either concentrated sulfuric acid or fuming sulfuric acid (Cerfontain et al. 1964). Therefore, slightly modified methods may be used to extract diatoms from permanent slides prepared with different standard mounting media.…”