Question

What is the order of the SN2 reaction for the compounds: \[ \text{2-methyl-2-bromo-butene}, \quad \text{2-bromo-butene}, \quad \text{1-bromo-butane} \]

• A. 1, 2, 3
• B. 3, 2, 1
• C. 2, 1, 3
• D. 3, 1, 2

Hint:

In SN2 reactions, less steric hindrance leads to faster reactions. Look for less hindered carbons to predict reactivity.

Answer 1

The Correct Option is B

In an SN2 reaction, the order of reactivity depends on the steric hindrance of the carbon attached to the leaving group.

1. Step 1: Consider the steric hindrance. - 2-methyl-2-bromo-butene: The carbon attached to the leaving group is highly hindered due to the bulky methyl group. Thus, it will react slowly in an SN2 reaction. - 2-bromo-butene: The carbon attached to the leaving group has moderate steric hindrance, making it more reactive than the 2-methyl compound but less reactive than 1-bromo-butane. - 1-bromo-butane: The carbon attached to the leaving group is the least hindered, making it the most reactive in an SN2 reaction.

2. Step 2: Determine the order. Based on the steric hindrance, the order of reactivity is: \[ 1-bromo-butane>2-bromo-butene>2-methyl-2-bromo-butene \] Thus, the order of reactivity is 3, 2,
1.