H-shift transition states

The lifetime of 56 can be extended by deuteration CD3CCD3 lives 3.2 times longer in pentane than does CH3CCH3. This longevity is the result of a substantial primary kinetic isotope effect where k 2-n > 1,2-0- Tunneling is important here the H shift occurs in part by tunneling, a pathway not as available to the D shift. On the other hand, polar solvents increase / i, 2-h and decrease the lifetime of 56, in accord with the increase in charge stabilization in the 1,2-H shift transition state. 34 ... 

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