Syntheses of formylmethylcobalamin and the kinetics and mechanism of decomposition of the aldehyde and its acetals are reported. Two different pathways were observed for the acid-catalyzed decomposition of the cobalamin acetals: direct cobalt-carbon bond cleavage to B12b and a vinyl ether, and normal acetal hydrolysis to formylmethylcobalamin, followed by a rate-determining fission of the cobalt-carbon bond to B12b and acetaldehyde. The rate law of decomposition of formylmethylcobalamin (A) is d[A]/dt = -K [A][H3O+]; the acid sensitivity and bimolecularity of the decomposition were rationalized as an initial protonation of the formyl carbonyl followed by a direct cleavage of the cobalt-carbon bond.
ASJC Scopus subject areas
- Colloid and Surface Chemistry