Kinetic isotope effect, decarbonylation

That alkenes are formed from those alkyl groups containing a jS-hydrogen atom strongly implies that the mechanism of alkene formation involves a /3-hydride abstraction step. There is a very pronounced kinetic isotope effect when C6D5CD2CH2COCI is decarbonylated, which indicates that not only does a jS-deuteride abstraction take place but that it is also rate determining. Further evidence for the participation of a /3-hydride abstraction comes from the decarbonylation of erythro- or t/ reo-2,3-diphenylbutanoyl chloride, where the former yields the (ii)-alkene and the latter the (Z)-isomer. 

Provided care is taken to avoid exchange with water, a kinetic isotope effect is noted when CDO groups are decarbonylated. This indicates that the rate-determining step of the reaction is the scission of the C-D bond. Deuteration studies have also shown that decarbonylation of RCDO yields RD. Further, decarbonylation of Ar CDO and Ar CHO mixtures yields only Ar D and Ar H. ... 

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