Abstract Aryltrimethylsilanes, ArSiMe 3, react with sulphur trioxide in carbon tetrachloride to give the sulphonic esters, ArSO 2 OSiMe 3, which undergo hydrolysis readily to the sulphonic acids ArSO 3 H. The reaction provides a means of introducing a sulpho group at a specific position of the aromatic ring; thus from m-tolyltrimethylsilane, m-toluenesulphonic acid is obtained in 80% yield.
