Aromatic sulphonation. Part 93. Sulphonation of the three t-butylphenols, four di-t-butylphenols, and 2,4,6-tri-t-butylphenol

Abstract

The (homogeneous) sulphonation of the three t-butyl-phenols, 2,4-, 2,5-, 2,6-, and 3,5-di-t-butyl-phenol, and 2,4,6-tri-t-butylphenol with a number of sulphonating reagents has been studied, and product compositions have been determined. The formation of the several initial and eventual sulphonation products is explained in terms of sulphodeprotonation, protiode-t-butylation, sulphode-t-butylation, and isomerization, the relative importance of which is discussed for the various substrates. 2-(1) and 4-t-butylphenol (3), 2,4-(4), and 2,6-di-t-butylphenol (6), and 2,4,6-tri-t-butylphenol (8) in 98.5% H₂SO₄ at 35 °C after 10 days of reaction all yield 50 ± 2% 4-t-butylphenol-2,6-(9) and 50 ± 2% phenol-2,4-disulphonic acid (10). With both (1) and (6) the initial step is a rapid 1,3-shift of the t-butyl group from the 2- to the 4-position. With (1) this is then followed by sulphodeprotonation at the 2- and 6- position and with (6) by protiode-t-butylation at the 6-position followed by sulphodeprotonation at the 2- and 6-position. The formation of (9) from the substrates (3), (4), and (8) and the formation of (10) from (1), (3), (4), (6), and (8) is explained by protiode-t-butylation and subsequent sulphode-protonation.