Formaldehyde, reactions with chlorosulfonic acid

Extensive studies of the reaction of chlorosulfonic acid and other formaldehyde-generating chemicals, have been carried out by Fuchs Mid Katscher. The results have been reviewed in detail by Jackson, and they demonstrate that formaldehyde can react with chlorosulfonic acid to give a variety of different products 82-85 depending on the reaction conditions. When the reaction is carried out below 70 °C, followed by distillation of the mixture under reduced pressure (14 mmHg), the products were chloromethyl chlorosulfonate 84 and methylene sulfate 82. The initial step of the reaction probably involves protonation of the carbonyl group of the aldehyde by chlorosulfonic acid and addition of the chlorosulfonate anion giving hydroxymethyl chlorosulfonate which, by chlorination, yields chloromethyl chlorosulfonate 84 (Scheme 7). 

Addition of chlorosulfonic acid (one equivalent) to a solution of / -cresol 127 in carbon disulfide at —15 °C, gave p-tolyl hydrogen sulfate 128 (Equation 41). Reaction of p-cresol 127 with excess chlorosulfonic acid at room temperature yields 2-hydroxy-5-methylbenzene-1,3-disulfonyl chloride 129. o-, m- and p-Cresols were sulfonated by the action of chlorosulfonic acid at 25-105 °C and the isomeric mixture of cresolsulfonic acids by treatment with formaldehyde (2 1) gave condensation products which were useful pharmaceuticals. ... 

Another preparative method involves the treatment of oleum with either carbon tetrachloride or dichloromethane as the chlorinating agent. The reaction of dichloromethane on 70% oleum initially yields a mixture of formaldehyde, sulfur trioxide and hydrogen chloride the latter two products subsequently combine to form chlorosulfonic acid (Scheme 2). This reaction provides a convenient laboratory preparation of chlorosulfonic acid which is obtained in excellent yield (86%). The analogous reaction between carbon tetrachloride and oleum presumably follows a similar mechanistic pathway. 

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