2
$\begingroup$

If the leaving of the leaving group creates a secondary carbocation, and a tertiary carbocation has the possibility of being formed through a 1,2 methyl shift:

1) Will the methyl shift? I'm guessing the answer is an emphatic yes. Tertiary carbocations are more stable than secondary carbocations.

2) Will there still be some secondary carbocation left over? I.e. will there be both major and minor products? I'm guessing yes.

I ask because I was watching a video on E1 elimination and the narrator ignored the possibility of a shift, and I was wondering if this was because he forgot or because it was irrelevant.

$\endgroup$
2
$\begingroup$

1) Will the methyl shift? I'm guessing the answer is an emphatic yes. Tertiary carbocations are more stable than secondary carbocations.

Yes, if that is the only way to generate a tertiary carbocation and the C-Methyl bond can more or less line up with the carbocation p orbital, then the methyl would likely shift. If there are other alkyl groups attached to the carbon initially bearing the methyl group, they could shift too.

2) Will there still be some secondary carbocation left over? I.e. will there be both major and minor products? I'm guessing yes

An equilibrium exists between the various carbocations. At 300 K, an energy difference of 1.4 kcal/mol results in a power of ten difference in the equilibrium (e.g. from 50:50 to 90:10). So it really depends on the energy difference between the various carbocations involved, as well as the rate they are captured or proceed to the next step.

Finally, if there is a hydrogen on the carbon adjacent to the carbocation center, then elimination to create a double bond becomes a competing pathway,

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.