Aromatic sulphonation. Part 71. Sulphonation and protonation of 1,2-diphenylcyclopropenone

Abstract

The oxygen protonation and the phenyl substitution of 1,2-diphenylcyclopropenone in sulphuric acid as well as the sulphur trioxide sulphonation in CCl₃F as solvent have been studied. 1,2-Diphenylcyclopropenone is half protonated at ca. 63 wt-% H₂SO₄. Sulphonation in 105 wt-% sulphuric acid yields the 1,2-diphenylcyclopropenone-3′,3″-disulphonic acid. The sulphonation with 5 equivalents of sulphur trioxide in CCl₃F led to a substrate conversion of 64% with formation of 45 ± 3% 3′-sulphonic acid and 19 + 3% 3′,3″-disulphonic acid. The entity undergoing substitution in fuming sulphuric acid is identified as it is for aprotic sulphonation.