ADDITION OF METHYL RADICAL TO SUBSTITUTED ALKENES - A THEORETICAL-STUDY OF THE REACTION-MECHANISM

Ab initio calculations at the QCISD(T)/6-311G** level have been carried out to study the addition of the methyl radical to a series of substituted alkenes, and the results analyzed with the aid of the curve-crossing model. It is found that (a) reaction exothermicity is the main factor that dominates reactivity, (b) polar contributions to the transition states are generally small and of minor energetic consequences, and (c) the general observation that pi-electron-accepting substituents in the alkene enhance reactivity is a secondary correlation that is a consequence of the effect of these substituents on reaction exothermicity. There is no evidence for the prevalent view that the methyl radical is generally nucleophilic towards alkenes.