o-Toluidine hydrochloride

o-Toluidine hydrochloride is the hydrochloride salt of o-toluidine (2-methylaniline), formed by protonation of the amine nitrogen [1]. It is used in analytical chemistry as a standard for colorimetric assays (the o-toluidine blood glucose assay, now largely replaced by enzymatic methods), as a pharmaceutical intermediate, and in research settings [2]. Like its free base counterpart, it was used as a dye intermediate and in rubber chemical manufacturing. The toxicological concerns are identical to o-toluidine — metabolic N-hydroxylation produces reactive intermediates that form bladder DNA adducts [1].

Laboratory chemists and pharmaceutical synthesis workers using o-toluidine hydrochloride as a reagent [1]. Historical exposure through o-toluidine-producing industries, particularly rubber antioxidant manufacturing (same cohort as o-toluidine free base) [2].

In vivo, the hydrochloride proton dissociates, and o-toluidine hydrochloride behaves identically to the free base in terms of metabolic activation and carcinogenicity [1]. IARC Group 1 carcinogen (same classification as free base) [2].

Laboratory chemists and pharmaceutical workers [1]. Same occupational cohort as o-toluidine in rubber manufacturing [2].

1. Handle in fume hood with impermeable gloves [1]. 2. Same precautions as o-toluidine free base [2].