when does a hydride shift happen

[houstongirl]

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can someone please explain when a hydride shift and methyl shift happen?

 

[doc toothache]

It referes to the downfield or upfield shift of the NMR signal of H or CH3. The position of the signal depends on the functional groups attached to the C atoms.

 

[bruinpredent]

i think she means the shifts involved in rearrangement, in which case you would shift an adjacent hydrogen or a methyl group in order to achieve the most stable carbocation (usually in Sn1 and E1 rxns)

 

[wigglytooth]

i think she means the shifts involved in rearrangement, in which case you would shift an adjacent hydrogen or a methyl group in order to achieve the most stable carbocation (usually in Sn1 and E1 rxns)

Yeah I think this too. If you have an Sn1 or E1 reaction forming a secondary carbocation, and an adjacent hydride or methyl could move over to form a tertiary carbocation, it's going to do it. Methyl shifts, I believe, are more common than hydride shifts.

 

[houstongirl]

Thank you guys