Abstract
Sulfonation of aromatic compounds (Phenols, Anilines) is triggered by Vilsmeier Haack (VH) reagent (DMF/POCl3) or (DMF/SOCl2) in the presence of NaHSO3 under Sonication and conventional stirred conditions at room temperature. The reactions afforded corresponding Sulfonic acid derivatives in very good yields. The results obtained under Sonication were enhanced when compared with the yields of the conventional method.
Highlights
Aromatic sulfonation is an electrophilic substitution in which a hydrogen atom on arene is replaced by SO3H group [1]
P-toluene sulfonic acid, is about a million times stronger acid than benzoic acid; while methane sulfonic acid is about one million times stronger acid than acetic acid. Even though both alkyl and aryl sulfonic acids are well known in literature, there has been an up surging interest in the synthetic chemistry of aromatic sulfonic acids most of the applications are associated with the aromatic derivatives
Sulfonation of aniline produces p-amino benzene sulfonic acid or sulfanilic acid which is a zwitterion with an unusual high melting point
Summary
Aromatic sulfonation is an electrophilic substitution in which a hydrogen atom on arene is replaced by SO3H group [1]. Aromatic sulfonic acids are intermediates for the preparation of dyes and pharmaceuticals. These acids are much stronger acids than the corresponding carboxylic acids. The amides of p-amino benzene sulfonic acid and related compounds are known to form a large group of sulfa drugs. Among various sulfonating agents sulfuric acid [2,3], oleum [4,5] and SO3 [6] are widely used, but some of them could cause polymer chain degradation during the reaction due to their high reactivity and toxicity level. SO3 is an aggressive electrophile (sulfonating agent) that rapidly reacts with any organic compound containing an electron donor group. It has been proposed to develop an alternate path way for sulfonation of aromatic compounds using (DMF + Oxychloride)/NaHSO3
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