KINETIC EPR STUDIES OF THE ADDITION OF ALIPHATIC RADICALS TO ACRYLIC-ACID AND RELATED ALKENES - THE INTERPLAY OF STERIC AND ELECTRONIC FACTORS

A continuous flow system approach with EPR detection and steady-state analysis has been employed to determine the rate constants for additio n of a range of aliphatic radicals to acrylic acid and related alkenes in aqueous solution at room temperature. For acrylic and methacrylic acids the rate constants (in the range 2 x 10(5)-ca. 10(8) dm3 mol-1 s -1) are governed largely by polar effects in the transition state, tho ugh the deviation from planarity of the attacking species may be impor tant for .CHMeOH and related radicals. As expected, steric effects pla y a prominent role in causing retardation in the reactions of crotonic and 3,3-dimethylacrylic acids, and in addition of .CMe2OH.