Question

What is the number of moles of hydrogen atoms needed to obtain one mole ethanamine from acetamide using \(\text{LiAl H}_4\) /ether as reducing agent.

• A. \(4\)
• B. \(3\)
• C. \(2\)
• D. \(1\)

Hint:

LiAlH4 reduces an amide to an amine: RCONH2 + 4[H] gives RCH2NH2 + H2O.

Answer 1

The Correct Option is A

Step 1: Balance the equation:
Write $\text{CH}_3\text{CONH}_2 + n\,\text{H} \to \text{CH}_3\text{CH}_2\text{NH}_2 + \text{H}_2\text{O}$.

Step 2: Balance hydrogens:
Left: 5 from acetamide, plus $n$. Right: 5 from ethanamine's $\text{CH}_3\text{CH}_2$ and $\text{NH}_2$ (that is 3 + 2 + 2 = 7), plus 2 from water, total 9.
$5 + n = 9$, so $n = 4$.

Step 3: Interpretation:
Two H atoms convert $\text{C=O}$ into $\text{CH}_2$, and two more combine with oxygen to leave as water.

Final Answer:
$n = 4$, option (A). \[ \boxed{4 \text{ (A)}} \]