Question

$C_6{H}_5-\underset{H}{\underset{|}{\stackrel{C{H}_3}{\stackrel{|}{C}}}}-Br+H_{2}O\to HO-\underset{H}{\underset{|}{\stackrel{C{H}_3}{\stackrel{|}{C}}}}-C_6{H}_5+HBr$

The above reaction result in 98% racemization, the reaction mainly follows:

• A. $S_{N}1$ mechanism
• B. $S_{N}2$ mechanism
• C. $E^1$ mechanism
• D. $E^2$ mechanism

Answer 1

Answer: (A)

$S_{N}1$ mechanism

An alkyl halide with chiral carbon forms a racemic mixture through $S{N}^1$ mechanism.

$S{N}^2$ mechanism changes the configuration of a compound due to formation of the transition state.

$S{N}^1$ mechanism proceeds through carbocation formation so it's a two-step process and as stability of carbocation increases, reaction favours $S{N}^1$ mechanism.

$3^0$ carbocation are more stable than others and also polar solvent increases the stability of carbocation so they both favours $S{N}^1$ mechanism.

Also, the rate of $S{N}^1$ mechanism depends on nucleophile concentration only so as conc. of nucleophile increases, reaction favours $S{N}^1$ mechanism.