Question

Consider the reaction :
$C{H}_{3}C{H}_{2}C{H}_{2}Br+NaCN\to C{H}_{3}C{H}_{2}C{H}_{2}CN+NaBr$
This reaction will be fastest in :

• A. N,N'-dimethylformamide (DMF)
• B. Water
• C. ethanol
• D. Methanol

Answer 1

The correct option is A N,N'-dimethylformamide (DMF)

(Polar aprotic solvent)

$C{H}_{3}C{H}_{2}C{H}_{2}Br+NaCN\to C{H}_{3}C{H}_{2}C{H}_{2}CN+NaBr$This is a $S_{N}2$ reaction frow which polar aprotic medium is suitable for faster rate of reaction.

$H^{+}$ in polar protic solvent will solvate the nucleophile so that the nucleophilic attacking efficiency is lowered and reduce the rate of $S_{N}2$ reaction.
Hence, option (d) is correct.