Abstract:
Cob(I)alamin (vitamin B12s) has been generated by pulse radiolysis of N2O-saturated solutions of cob(II)alamin (vitamin B12r) containing sodium formate. It reacts with N2O with rate constants in the range 200–1200 dm3 mol–1 s–1, depending on pH and buffer concentration. The final product is cob(II)alamin, formed in 100 % yield. The initial product is thought to be cob(III)alamin (vitamin B12a or B12h) but this does not build up to significant concentrations. Cob(III)alamin (vitamin B12a or B12h) reacts with cob(I)alamin with a rate constant of 3.2 × 107 dm3 mol–1 s–1 independent of pH in the range 5.8–11.0. Cyanocobalamin (vitamin B12) does not react with cob(I)alamin.
