Question

Chlorocyclohexane reacts with $NaCN$ in ethanol to give cyanocyclohexane. What happens when a small amount (catalytic) of iodide - $I^{-}$ is added to the solution?

• A. The rate of formation of cyanocyclohexane is unchanged
• B. The rate of formation of cyanocyclohexane decreases
• C. The rate of formation of cyanocyclohexane increases
• D. Cyanocyclohexane is depleted because iodocyclohexane is formed

Answer 1

The correct option is C

The rate of formation of cyanocyclohexane increases

The crux of this problem lies in recognizing that $I^{-}$ is $both$ a fantastic nucleophile as well as a terrific leaving group!

Without iodide, the formation of cyanocyclohexane happens in a slow to moderate manner.

See how the above reaction is "moderate" while the following (first of the bottom two)
is a faster one relatively speaking:

The reaction is truly catalytic in $I^{-}$.