Rate constants for the addition of the 2‐hydroxy‐2‐propyl radical to alkenes in solution

Absolute rate constants for the addition of the 2‐hydroxy‐2‐propyl radical to 18 substituted alkenes (CH2 = CXY) were determined at (296 ± 1) K in 2‐propanol by time‐resolved electronspin‐resonance spectroscopy. With alkene substitution the rate constants vary by more than 6 orders of magnitude. For 3,3‐dimethyl‐but‐1‐ene the temperature dependence is given by log k/M−1 · s−1 = 6.4 minus;; 19.1/Θ where Θ = 2.303 RT in kJ/mol−1. As shown by a good correlation with the alkene electron affinities, log k296/M−1 · s−1 = 6.46 + 1.71 · EA/eV (r = 0.930), 2‐hydroxy‐2‐propyl is a very nucleophilic radical, and its addition rates are highly governed by polar effects.