Greetings,
This is a short introduction to the SN1 reaction. SN1 has the following characteristics:
- Monomolecular - 1st Order
- Rate only depends on the leaving-group concentration
- Leaving group on second or third degreee carbon atom
- Products are a mix of mirror-image optical isomers
Monomolecular 1st Order
The kinetics of SN1 is a simple one-to-one relationship between reaction rate and leaving group concentration. For example, doubling the concentration of the leaving group (in essence, doubling the concentration of the substrate-electrophilic reactant) doubles the reaction rate. Changing the nucleophile concentration has no effect on reaction rate.
Rate change only depends on changes in the leaving-group concentrationThe overall reaction happens in two steps: 1. Leaving group departs (fast) & 2. Nucleophile attacks the remaining carbocation (slow). Step 1 is the rate-determining part of the SN1 reaction and therefore the only step affecting reaction rate.
Leaving group on second or third degreee carbon atom
Products are a mix of mirror-image optical isomers
The SN1 reaction happens when a stable intermediate carbocation can form (in addition to a leaving group that can have a stable solvated form). Leaving groups on second and third degree carbon atoms create a more stable carbocation.
Products are a mix of mirror-image optical isomers
The carbocation intermediate can be attacked by the nucleophile from both sides. This causes a pair of optical isomers (enantiomeric mirror-image) to form.
Thant's all for now. As always, thank you for reading!
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