Question

How many of the following responses are true?

1. S_N1 leads to a racemization of sterechemistry due to the nucleophile attacking from the backside and the leaving group leaving
2. S_N2 leads to an inversion of sterechemistry due to the nucleophile attacking from the backside and the leaving group leaving
3. A secondary alkyl halide could react through either an S_N1 or S_N2 mechanism because backside attack is possible (albeit slow) and a secondary carbocation is relatively stable (which would give a similar rate of reaction as for S_N2)
4. 3-bromo-3-methylpentane will undergo substitution through an S_N2 mechanism
5. If R-2-bromopentane is allowed to react with OH^- the product will be S-2-pentanol

Answer 1

statements 2, 3, 5 are correct.

Explanation: Reaction of alkyl halide with a strong nucleophile gives SN2 mechanism. The nucleophile attacks the carbon atom bearing leaving group from the back side and eliminates leaving group to form the product in SN2 mechanism. so statement 2 is correct.

3-bromo-3-methylpentane is a tertiary alkyl halide and it gives SN1 mechanism. so statement 4 is not correct.

Inversion of configuration occurs in SN2 mechanism so R-2-bromopentane gives S-2-pentanol with OH-. so statement 5 is correct.