![Sample our Physical Sciences journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/110819/TOC-Subject-Sample-2021-Physical-Sciences.jpg"})
Abstract
The sulfonations of pentachlorobenzene (1) with 25% oleum at 40°C or 140°C, or with 65% oleum at 40°C give always excellent yields of pentachlorobenzenesulfonic anhydride (2). However, pentachlorobenzenesulfonic acid (3) is obtained when the working up of the reaction mixture is not mild enough to avoid the hydrolysis of the anhydride 2. Acid 3 is also synthesized starting from pentachlorophenol (4) via O-pentachlorophenyl dimethylthiocarbamate (6), its isomerization to S-pentachlorophenyl dimethylthiocarbamate (7) and final oxidation to 3. Pentachlorobenzenesulfonyl chloride (8) and anhydride (2) are also obtained from acid 3. Anhydride 2 reacts at 200°C with phenol 4 or pentachloroaniline (10) giving pentachlorophenyl pentachlorobenzenesulfonate (9), or a mixture of pentachlorobenzenesulfonyl pentachloroanilide (11) and pentachloroanilinium pentachlorobenzenesulfonate (12), respectively. Sulfonamide 11 can be obtained in two polymorphic forms and an ethyl ether solvate, for which interesting spectral and thermal differences are observed.