Free Radical Additions. Kinetics of Free Radical Additions of Bromomalononitrile to Alkenes and PMO Treatment of the Reactivity and Regioselectivity

Article abstract of DOI:10.1021/jo00378a009

The addition rate of dicyanomethyl (DCM) radicals to 2-methyl-1-pentene (2) was found to be k₄=(1.6 +/- 0.4)*10⁶ L*mol^-1*s^-1.Relative rates (k_rel) of additions to 11 alkenes were measured.Obviously steric effects do not influence the addition rates with n-alkyl-substituted alkenes.The ln k_rel values correlate linearly (r=0.98) with the superdelocalizabilities, S_r^(R), a measure for binding molecular orbital interactions between the reactants (Fukui).The S_r^(R) values for the DCM radical attack at the two sp² C atoms of unsymmetrically substituted alkenes show significant differences.On the basis of the S_r^(R) values, i.e., polar effects, a prediction of regioselectivities is made.The found regioselectivities are in accord with the predicted ones within the limits of error.A more accurate experimental verification seems to be of considerable interest because up to now only steric effects have been considered to be the reason for the anti-Markovnikov orientation in free radical additions to n-alkyl-substituted alkenes.