High-level ab initio calculations at the QCISD/6-311G∗∗ + ZPVE level have been carried out to study the addition reactions of CH3∗, CH2OH∗, and CH2CN∗ radicals to the substituted alkenes CH2=CHX (X = H, NH2, F, CI, CHO, and CN) and the results analyzed with the aid of the curve-crossing model. We find that the reactivity of CH3∗ is primarily governed by enthalpy effects, whereas both enthalpy and polar effects are important for the reactions of CH2OH∗ and CH2CN∗ There is no general barrier height-enthalpy correlation for the latter two radicals because of the presence in some cases of polar effects that stabilize the transition states without a corresponding stabilization of the products. The polar effects are not sufficient, however, to significantly shift the location of the transition states, so a general structure-enthalpy correlation is observed.
ASJC Scopus subject areas
- Chemistry (all)
- Colloid and Surface Chemistry