Consider the reaction of 2-bromobutane (where the stereocenter is in the \"R\" c
ID: 697353 • Letter: C
Question
Consider the reaction of 2-bromobutane (where the stereocenter is in the "R" configuration) with OH. How many of the following statements are true? 1. If the reaction proceeds through an SN2 mechanism one alcohol product will be formed, the "S" isomer 2. If the reaction proceeds through an SN1 mechanism one alcohol product will be formed, the "S" isomer 3. If the reaction goes through an SNl mechanism it means the pathway for secondary carbocation formation was higher in energy than the pathway for the attack of a nucleophile on the secondary alkyl halide 4. An inversion of stereochemistry would indicate the reaction proceeded through a first order process 5. The reaction could proceed through either an SN1 or SN2 mechanism. Information about the stereochemistry of the reaction or rate law would be needed to determine which mechanism was used O o 0 1Explanation / Answer
1. SN2 mechanism always leads to an inversion in configuration at the chiral center; hence, the (R)- alkyl halide will give the (S)- alkyl halide via SN2 mechanism. Therefore, statement 1 is true.
2. SN1 mechanism leads to racemization; therefore, both (R)- and (S)- alkyl halides will be produced. Consequently, statement 2 is false.
3. If a reaction proceeds via SN1 pathway, then it indicates that the formation of the secondary carbocation is less energy-demanding process as compared to the concerted pathway for the nucleophile attacking the secondary alkyl halide (SN2). Therefore, statement 3 is false.
4. An inversion in configuration at the chiral center indicates that the reaction proceeds via SN2 pathway. The SN2 mechanism depends on the concentrations of both the starting alkyl halide and the nucleophile. Consequently, a SN2 reaction is second order overall. Therefore, statement 4 is false.
5. A secondary alkyl halide can undergo nucleophilic substitution via both SN1 as well as SN2 pathways; hence, statement 5 is true.
Therefore, two statements are correct.