Why is hydride shift preferred over methyl?

In general hydride shift is more favourable over methyl shift because of its smaller size. The example proposed by James was not known to me but its truly an amazing example. James: It’s possible for multiple hydride/alkyl shifts to occur.

Which has highest migratory aptitude?

Migratory aptitude depends on how much a group can donate electron. The group which can donate easily will have higher migratory aptitude thus aromatic groups like para hydroxy benzene will have greater migratory apptitude than propanol. Only exception is the hydride ion it has highest migratory apptitude.

What is the difference between methyl shift and hydride shift?

The key difference between hydride and methyl shift is that a hydride shift can occur when a hydrogen atom moves to a carbon atom bearing a positive charge from an adjacent carbon in the same molecule, whereas methyl shift occurs when a methyl group moves to a carbon atom bearing a positive charge from an adjacent …

What is meant by hydride shift?

– Hydride shift is the movement of a hydrogen atom from one carbon to an adjacent charged carbon atom of the same compound. If a secondary carbocation is vicinal to a tertiary carbon atom bearing a hydrogen atom then a hydride shift occurs.

What is migratory aptitude in Baeyer Villiger Oxidation?

Migratory aptitude is the relative ability of a migrating group to migrate in a rearrangement reaction. In the Baeyer-Villiger reaction, the more substituted group, in general, migrates.

Is phenyl shift easier than methyl shift?

Originally Answered: Why is phenyl shift preferred over methyl shift? During the shift there is a partial +ve charge on the migrating group, due to resonance effect, it is more preferred for phenyl than less stable methyl cation.

What is the advantage of rearrangement reaction?

Rearrangement reactions can be powerful methods for the relay of stereochemistry, functional group interconversion, and altering the atomic connectivity.

Why does methyl have a higher migratory aptitude than phenyl?

The methyl group is smaller and should have a higher migratory aptitude. Despite the mechanism shown in your question, which is commonly used to depict a phenyl shift, phenyl shifts occur by a slightly different mechanism. Phenyl shifts do not usually happen by the normal 1,2-sigmatropic “hop”. Instead, the phenyl group shifts by more of a “walk”.

What is a methyl shift and why is it done?

Yes, a methyl shift is done to stabilise a carbocation. And it is done in this case for the same reason, to increase the relative stability. Now you might think, “How can a secondary carbocation be more stable than a tertiary carbocation?

What is the mechanism of phenyl shift?

Despite the mechanism shown in your question, which is commonly used to depict a phenyl shift, phenyl shifts occur by a slightly different mechanism. Phenyl shifts do not usually happen by the normal 1,2-sigmatropic “hop”. Instead, the phenyl group shifts by more of a “walk”.

Why phenyl cation is more stable than methyl cation?

During the shift there is a partial +ve charge on the migrating group, due to resonance effect, it is more preferred for phenyl than less stable methyl cation. If migrating group is tert. methyl, having same migratory aptitude as phenyl, the partial +ve charge is stabilized by +ve inductive effect.