Question

When R-X is treated with KCN (alcoholic, heat), find the type of attack found, when the major product is formed in this reaction?

• A. Attack occurs through nitrogen \(\rightarrow\) Forming isocyanide.
• B. Attack occurs through carbon \(\rightarrow\) Forming nitrile.
• C. Free radical substitution
• D. Elimination

Hint:

KCN is ionic, so the cyanide ion attacks through carbon, since the C-C bond formed is stronger than the C-N bond.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
Cyanide ion is an ambident nucleophile; it can attack through carbon or nitrogen.

Step 2: Role of KCN
KCN is predominantly ionic and gives free \(\text{CN}^{-}\) ions in alcoholic solution.
Attack through carbon forms a C-C bond, which is stronger than the C-N bond formed by attack through nitrogen.

Step 3: Compare the options
The major product is an alkyl cyanide (nitrile) formed by attack through carbon, the second option.

Final Answer:
Attack occurs through carbon, giving a nitrile. \[ \boxed{\text{(B) }\text{Attack occurs through carbon}\rightarrow\text{Forming nitrile}} \]