Publication Date:
2011-03-24
Description:
Among the genotoxic halofuranones formed by chlorination in water are mucochloric acid (MCA, 3,4-dichloro-5-hydroxyfuran-2(5 H )-one) and mucobromic acid (MBA, 3,4-dibromo-5-hydroxyfuran-2(5 H )-one). These acids are direct genotoxins and potential carcinogens, with the capacity to alkylate the DNA bases. In recent years, they have also attracted attention in the synthesis of furanone derivatives. Mucohalic acids (MXA) exist in solution as an equilibrium between three species; a cyclic lactone-lactol , an open-chain aldehyde-acid , and the dissociated form of the latter . The distribution of the three species in the equilibrium has synthetic, toxicological, and environmental implications owing to their different functionalization. The case of the neutral open-chain form is of special interest, since it is expected to be highly reactive. We have experimentally determined the apparent dissociation constant of the cyclic species . Their values suggest that at neutral pH MXA are mostly present as the dissociated carboxylate-aldehyde. The dissociation constant of the open-chain neutral species and the cyclization equilibrium constant were determined in water and organic solvents, using density functional theory and ab initio methods. The results suggest that the undissociated aldehyde is a minor species at any given pH. The structure of MXA in solution and the influence of the level of theory on the calculated geometry are discussed. Copyright © 2011 John Wiley & Sons, Ltd. Mucohalic acids exist in solution as an equilibrium between three species; a cyclic lactone-lactol, an open-chain aldehyde-acid, and the dissociated form of the later. The distribution of the three species in equilibrium has synthetic, toxicological, and environmental implications and thus, we have determined by a combined experimental and computational approach, the respective equilibrium constants.
Print ISSN:
0894-3230
Electronic ISSN:
1099-1395
Topics:
Chemistry and Pharmacology
,
Physics
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