RATE CONSTANTS FOR THE ADDITION OF THE 2-CYANO-2-PROPYL RADICAL TO ALKENES IN SOLUTION

Absolute rate constants for the addition of the 2-cyano-2-propyl radical to 26 alkenes CH2 = CXY at 315 K were determined in solution by time-resolved electron-spin-resonance spectroscopy. They vary with the alkene substituents from 30 M-1 s-1 to 7'010 M-1 s-1. For styrene the temperature dependence is given by log k/M-1 s-1 = 7.7 - 26.1/THETA where THETA = 2.303 RT in kJ/mol. An analysis of the substituent effects in terms of polar and enthalpic factors reveals a dominant influence of the overall reaction enthalpy.