THE KINETICS AND MECHANISM(S) OF NUCLEOPHILIC ATTACK BY CATECHOLATE ANION ON EPIBROMOHYDRIN-d2

Article abstract of DOI:10.1002/poc.610070802

The reaction which forms hydroxymethylbenzodioxane from epibromohydrin and catecholate anion was examined by ultraviolet spectroscopy for the kinetics and by proton nuclear magnetic resonance spectroscopy to follow the fate of CD2 from reactant to product.Over the practical temperature range it was found that both CH2 positions in the epihalohydrin are attacked by catecholate anion to give product.Therefore, the difference in energy for the two pathways was small.The individual rate constants were obtained from the total rate constants.Further, the individual ΔH(excit.) and ΔS(excit.) values were calculated.It was found that the pathway of higher ΔH(excit.) had the less negative ΔS(excit.), which explains the subtlety of two mechanisms being operative over the available temperature range.Interestingly, it proved impossible to prepare epibromohydrin with two deuteriums at only one position in what appeared to be a relatively straightforward synthesis.