Phenol and Deuterated Sulphuric Acid
The deuteration of phenol and aniline hydrochloride has been investigated by Werstiuk and Kadai by the High Temperature/Dilute Acid (HTDA) method. For phenol, ortho/para substitution is faster than meta (2.7 D/3.0 H vs. 1.3 D/2.0 H). OD/OH exchange was conducted at the end of the reaction. The presence of conc. HCl undoubtedly lowers the efficiency of incorporation of deuterium.
Incorporation of deuterium without the presence of conc. HCl allows for efficient deuteration of aniline hydrochloride. [RND3+ to RNH3+ exchange was conducted.] The authors note that conversion of aniline hydrochloride-d5 to phenol-d5 is efficient via diazotization.


Werstiuk, N. H.; Kadai, T., Can. J. Chem., 1974, 52, 2169.