A molecular orbital study on the reactivity of L-ascorbic acid towards OH radical

Abstract

The reaction between L-ascorbic acid (AAH₂) and OH radical has been investigated theoretically. The addition site on AAH₂ and AAH^– is found to be the olefinic carbon adjacent to the carbonyl group, with much more distinct selectivity for AAH^–. Dehydration is found to occur readily not from the neutral ˙OH adduct AAH₂OH˙, but from the anion adduct, AAHOH˙^–, which leads to formation of the most probable key intermediate radical 17(ascorbate anion radical). The parent molecule of AAH₂, triose reductone TRH₂(2,3-dihydroxprop-2-enal), undergoes ˙OH addition and dehydration in a similar manner to AAH₂. The addition site has been confirmed by comparison of MO energies for four possible transition states of the TRH₂(ab initio and MNDO) and AAH₂(MNDO) systems. The importance of the conjugate bases, AAH^– and TRH^–, for yielding the key radicals is suggested.