The catalytic role of acid and base in the rearrangement and the following decomposition of trimethylamine N-oxide to formaldehyde and dimethylamine has been investigated. The catalyzer which decomposed the N-oxide most extensively was tris (hydroxymethyl) aminomethane-malonate system, while several other tris (hydroxymethyl) aminomethane-dibasic carboxylic acid systems exhibited appreciable catalytic activities. Specific acid and base, hydrogen ion and hydroxide ion, scarcely showed the catalytic activity in the pH region from 0 to 14. The optimum pH of tris (hydroxymethyl) aminomethane-malonate system for the decomposition of trimethylamine Noxide was 11 and the amounts of the products, formaldehyde and dimethylamine, bore an equimolar relation to each other. On the other hand, several assumed schemes were simulated to elucidate the catalytic mechanism of tris (hydroxymethyl) aminomethane-malonate system. Based upon the reaction mechanism presumed from the experimental results, it has been concluded that the catalyzed rearrangement of trimethylamine N-oxide may occur through an intermediate to yield dimethylaminomethylo1 which gives spontaneously formaldehyde and dimethylamine as final products. In addition, the mechanism of rearrangement step was discussed from the standpoint of role of acid-base catalysis with emphasizing the action of base or hydride ion.
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