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Question
1) Which alkyl halide from the following pairs would you expect to react more rapidly by and SN2 mechanism?
Explain you answer.
2) Which alkyl halide from the following pairs would you expect to react more rapidly by and SN2 mechanism?
Explain you answer.
3) - Which alkyl halide from the following pairs would you expect to react more rapidly by and SN2 mechanism?
Explain you answer.
Explain you answer.
2) Which alkyl halide from the following pairs would you expect to react more rapidly by and SN2 mechanism?
Explain you answer.
3) - Which alkyl halide from the following pairs would you expect to react more rapidly by and SN2 mechanism?
Explain you answer.
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Solution
(1) In SN2 reactions, nucleophile attack on less hindered carbon from the back side in the transition state. The minimum hindrance is provided by the primary carbon and maximum hindrance is provided by the tertiary carbocation.
Thus, primary alkyl halide will give SN2 reaction faster than secondary which gives faster reaction than tertiary alkyl halide.
Here, 1 - Bromobutane is primary alkyl halide.
So, it readily undergoes SN2 reaction compared to 2 - bromobutane as it is secondary alkyl halide.
2) - In SN2 reactions, nucleophile attack on less hindered carbon from the back side in the transition state. The minimum hindrance is provided by the primary carbon and maximum hindrance is provided by the tertiary carbocation.
Thus, primary alkyl halide will give SN2 reaction faster than secondary which gives faster reaction than tertiary alkyl halide.
2 - Bromo - 2 - methylpropane is tertiary alkyl halide. So, it does not undergo SN2 reaction.
2- Bromobutane is secondary alkyl halide. So, it can undergo SN2 reaction faster as compared to 2 - bromo - 2 - methylpropane.
3) - In SN2 nucleophile attack on less hindered carbon from the back side in the transition state. The minimum hindrance is provided by the primary carbon and maximum hindrance is provided by the tertiary carbocation.
Thus, SN2 is faster when there is lesser steric crowding.
Both the alkyl halides are primary.
However, the substituent −CH3 is at a greater distance to the carbon atom linked to Br in 1-bromo-3-methylbutane than in 1-bromo-2-methylbutane.
Therefore, the approaching nucleophile is less hindered in 1-bromo-3-methylbutane than in 1-bromo-2-methylbutane.
Hence, 1-bromo-3-methylbutane reacts faster by SN2 mechanism.
Thus, primary alkyl halide will give SN2 reaction faster than secondary which gives faster reaction than tertiary alkyl halide.
Here, 1 - Bromobutane is primary alkyl halide.
So, it readily undergoes SN2 reaction compared to 2 - bromobutane as it is secondary alkyl halide.
2) - In SN2 reactions, nucleophile attack on less hindered carbon from the back side in the transition state. The minimum hindrance is provided by the primary carbon and maximum hindrance is provided by the tertiary carbocation.
Thus, primary alkyl halide will give SN2 reaction faster than secondary which gives faster reaction than tertiary alkyl halide.
2 - Bromo - 2 - methylpropane is tertiary alkyl halide. So, it does not undergo SN2 reaction.
2- Bromobutane is secondary alkyl halide. So, it can undergo SN2 reaction faster as compared to 2 - bromo - 2 - methylpropane.
3) - In SN2 nucleophile attack on less hindered carbon from the back side in the transition state. The minimum hindrance is provided by the primary carbon and maximum hindrance is provided by the tertiary carbocation.
Thus, SN2 is faster when there is lesser steric crowding.
Both the alkyl halides are primary.
However, the substituent −CH3 is at a greater distance to the carbon atom linked to Br in 1-bromo-3-methylbutane than in 1-bromo-2-methylbutane.
Therefore, the approaching nucleophile is less hindered in 1-bromo-3-methylbutane than in 1-bromo-2-methylbutane.
Hence, 1-bromo-3-methylbutane reacts faster by SN2 mechanism.
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