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The SN2 reaction mechanism is more favorable for primary and secondary alkyl halides due to less steric hindrance. Which of the following correctly represents the order of reactivity for SN2 reactions?

1. CH3CH2Br > CH3CH2CH2Br > CH3—CH—CH2Br > CH3—C—Br
2. CH3—CH—CH2Br > CH3CH2Br > CH3CH2CH2Br > CH3—C—Br
3. CH3CH2CH2Br > CH3CH2Br > CH3—CH—CH2Br > CH3—C—Br
4. CH3CH2Br > CH3CH2CH2Br > CH3—CH—CH2Br > CH3—C—Br

Correct answer: CH3CH2Br > CH3CH2CH2Br > CH3—CH—CH2Br > CH3—C—Br

Solution

The SN2 mechanism is favored by less steric hindrance, so primary halides react faster than secondary or tertiary halides. The given order correctly reflects this trend.

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