A-LevelChemistryHalogen derivatives9701/12 · May/June 2023 · Q321 Mark

Halogenoalkanes react with hot ethanolic potassium cyanide. The reaction mechanism is either Sɴ1 or Sɴ2. Which statement is correct?

AAll secondary halogenoalkanes react by the Sɴ2 mechanism only.

BBoth the halogenoalkane and the cyanide ion are involved in the initial step of the Sɴ1 mechanism.

CChloroethane reacts with cyanide ions by the Sɴ1 mechanism only.

DThe Sɴ2 mechanism involves a short-lived negatively charged transition state.

✓ Correct answer

D: The Sɴ2 mechanism involves a short-lived negatively charged transition state.

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Topic: Halogen derivatives, A-Level Chemistry (syllabus 9701). Multiple choice, 1 mark.
Source: A-Level Chemistry, May/June 2023 Paper 1 Variant 2, question 32.

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