# What is the effect of leaving group and solvent on the reaction rate of S_N2 reaction?

Oct 16, 2015

Greater rate: Better leaving group & polar aprotic solvent .

#### Explanation:

${S}_{N 2}$ is a bimolecular molecule and the reaction rate depends on the alkyl halide and the nucleophile.

${S}_{N 2}$ has a concerted mechanism which means that it occurs in one step which is itself the rate determining step:

$R = k \left[R - X\right] \left[N {u}^{-}\right]$

Effect of leaving group:
The better the leaving group the faster the reaction and therefore greater reaction rate.

Effect of solvent:
${S}_{N 2}$ favours polar aprotic solvents.
Polar aprotic solvents do not affect the strength of the nucleophile (${S}_{N 2}$ favours strong nucleophiles), therefore, the reaction will proceed at a faster rate.