Ethyl derivatives, hyperconjugation

The beta-tritium secondary isotope effect for elimination from the propyl-trimethylammonium ion (8, Table 7) seems most probably explained in terms of reduced acidity of the beta hydrogen caused by the greater inductive effect of the bond to the heavier isotope. A hyperconjugative effect also fits the observed data as in the transition state the developing double bond would be more effectively stabilised by the methyl than the monotritiomethyl group. However, the latter explanation seems less likely as the elimination from the propyl compound is slightly slower than that from the ethyl derivative . 

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