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/Θ where Θ = 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. © 1993 John Wiley & Sons, Inc.