Question

Which of the following is not true for $S_{N}1$ reaction?

• A. Favoured by polar solvents.
• B. $3^{\circ }$ alkyl halides generally react through $S_{N}1$ reaction.
• C. The rate of the reaction does not depend upon the molar concentration of the nucleophile.
• D. $1^{\circ }$ alkyl halides generally react through $S_{N}1$ reaction.

Answer 1

The correct option is D $1^{\circ }$ alkyl halides generally react through $S_{N}1$ reaction.

$\text{(1)}$ Polar protic solvent solvates the halide ion (leaving group) formed due to $C-X$ bond breaking.
$\therefore \text{Polar protic solvents favour}{S}_{N}1\text{reaction.}$.

$\text{(2) Rate of}{S}_{N}1\text{reaction}\propto \text{Stability of carbocation}\text{Carbocation stability order:}{3}^o>2^o>1^o>\text{Methyl}$
Therefore, primary alkyl halides generally do not react through $S_{N}1$ reaction.

$\text{(3) Rate of}{S}_{N}1\text{reaction}\propto [R-X][Nu{]}^0$.Since, the nucleophile is not involved in the RDS.It does not affect the rate of $S_{N}1$ reaction