Question

A carbonyl compound A having molecular formula C₅H₁₀O forms crystalline precipitate with sodium bisulphate and gives positive iodoform test. A does not reduce Fehling's solution. Identify A.

Answer 1

1. \[\begin{array}{cc}
\phantom{.....................................................}\ce{OH}\\
\phantom{...................................................}|\\
\ce{CH3 - CH2 - CH2 - C - CH3 ->[NaHSO3] CH3 - CH2 - CH2 - C - CH3}\\
\phantom{..............}||\phantom{.....................................}|\phantom{.}\\
\phantom{.......................}\ce{\underset{(Pentan-2-one)}{O}}\phantom{.........................}\ce{\underset{(White crystalline precipitate)}{OSO2Na}}\phantom{}
\end{array}\]

2. Pentan-2-one gives a positive iodoform test, but it does not reduce Fehling’s solution.

3. Hence carbonyl compound A having molecular formula C₅H₁₀O is pentan-2-one.

\[\begin{array}{cc}
\ce{CH3 - CH2 - CH2 - C - CH3}\\
\phantom{..............}||\\
\phantom{..............}\ce{\underset{(2-pentanone)}{O}}
\end{array}\]