SN1 Rxn: is hyrdride shift major product or the LG position?

In summary, the conversation discusses the major and minor products formed in a reaction involving a hydride shift and a secondary and tertiary carbocation. It is concluded that the tertiary carbocation will be the major product due to its higher thermodynamic stability, as long as there is enough activation energy for the hydride shift to occur. This reaction can also occur under kinetic control, where the major product is determined by the relative kinetics of rearrangement and reaction of the intermediates, rather than their thermodynamic stability.
  • #1
AMan24
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Homework Statement


So LG is on 2° position, and you have a hydride shift. So you form one product on 2° and one product on 3°.

Which product will be major which will be minor?

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Homework Equations


none.

The Attempt at a Solution


I know hydride shift will be more major than a methide shift, because it's not as energetically costly. But for hydride shift vs original LG position (2°), I'm not really sure. I know it does take extra energy to have the hydride shift, so that's making me think original LG position (2°) will be more major than the hydride shift. But i also know that 3° is better than 2°, so I'm really not sure
 
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  • #2
The extra energy required for the hydride shift to occur is merely the activation energy for the hydride shift, which does not change the fact that the tertiary carbocation will be more thermodynamically stable than the secondary carbocation. As long as enough activation energy is available for the hydride shift to occur, the more thermodynamically stable intermediate will be favored (under these conditions the reaction is said to occur under thermodynamic control). Sometimes, chemists will set up reactions to minimize the thermal energy available to promote rearrangements of intermediates to more stable intermediates such that the reaction to form product occurs much more quickly than the rearragement (not sure if that is possible in this case, howerver). Under those conditions, the reaction is said to occur under kinetic control as the major product will be dictated by the relative kinetics or rearrangement or reaction of the intermediate and not the thermodynamic stability of the two intermediates.
 
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What is an SN1 reaction?

An SN1 reaction is a type of nucleophilic substitution reaction in organic chemistry where the leaving group (LG) is replaced by a nucleophile. It involves a two-step process where the leaving group first dissociates to form a carbocation intermediate, which is then attacked by a nucleophile to form the final product.

What is a hydride shift?

A hydride shift is a rearrangement of atoms within a molecule where a hydrogen atom with two electrons shifts to an adjacent carbon atom with an electron-deficient center. This process is common in carbocations, where the positive charge can be stabilized by shifting a hydride ion (H-) to the adjacent carbon atom.

Is hydride shift the major product in an SN1 reaction?

In an SN1 reaction, the major product is typically formed through a hydride shift. This is because the intermediate carbocation is often unstable and can be stabilized by a hydride shift. However, there are cases where other factors, such as steric hindrance, can affect the product formation.

What is the role of the leaving group in an SN1 reaction?

The leaving group in an SN1 reaction is responsible for the initial dissociation from the substrate. This creates a carbocation intermediate, which is then attacked by a nucleophile to form the final product. The nature of the leaving group can affect the rate of the reaction and the stability of the intermediate.

What is the difference between SN1 and SN2 reactions?

SN1 and SN2 reactions are two types of nucleophilic substitution reactions. SN1 reactions involve a two-step process with a carbocation intermediate, while SN2 reactions involve a single-step process with simultaneous bond breaking and bond formation. Additionally, SN1 reactions are favored in polar solvents and with weak nucleophiles, while SN2 reactions are favored in aprotic solvents and with strong nucleophiles.

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