Nucleophilic and electrophilic radical attack on maleic and fumaric acids in aqueous solution

Rate coefficients (k) of CH2OH, CH 3 CHOH , ( CH 3 ) 2 COH and Cl 2 - radical addition to maleic and fumaric acids were investigated between pH 1 and 8. Strong pH dependences observed were attributed to changes in protonation states of acids: H2X, HX− and X2−. k of CH2OH, CH 3 CHOH , ( CH 3 ) 2 COH addition to fumaric acid decreased in the order k H 2 F > k HF - > k F 2 - in agreement with the nucleophilic character of reaction. The electrophilic Cl 2 - radical showed opposite tendency. With maleic acid the monoanion had the highest reactivity towards nucleophilic and the lowest one towards electrophilic radicals. This is attributed to a prevalence of steric over polar effects for HM−.