2. For oxidative addition (OA) of an alkyl halide to a metal centre, which mecha

Question

2. For oxidative addition (OA) of an alkyl halide to a metal centre, which mechanism or mechanisms of oxidative addition are the following observations most consistent with (briefly explain): a) b) c) d) For a particular metal and RX combination, OA is much slower in the presence of a radical inhibitor. For a particular metal and RX combination, OA is significantly faster in more polar solvents. OA of R-PhHDC-I occurs with inversion of config. at carbon. OA ofR-PhMe(DsC)C-I occurs with racemization at carbon, and the rate of the reaction is not affected upon addition of radical initiators or inhibitors. OA of Cyclopropyl-CH2-Br to [Ni(COD)2] yields [(COD)NiBr(CH2CH2CH-CH2)] e)

Explanation / Answer

a.) Unlike the non-chain case, the reactions may slow down or stop in the presence of radical inhibitors, such as the hindered phenol, 2,6?di?t?butylphenol. (Chain Radical)

b.) In general, more electron-rich and more electron-poor polar organics react more rapidly in oxidative additions. (Ionic and SN2)

c.) Inversion at carbon is observable in (Ionic and SN2) reactions, and entropy of activation is negative (suggesting an associated transition state).

d.) Racemization generally ocuurs in Non-chain Radical reaction.

e.) Catalytic C-C bond activations are involved in the same. Also, cross-coupling occurs.

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