Question

Write a test to differentiate between pentan-2-one and pentan-3-one.

Answer 1

Pentan--one having a group forms a yellow ppt. of iodoform with an alkaline solution of iodine (i.e., iodoform test) while pentan-3-one does not.

\[\begin{array}{cc}
\ce{O}\phantom{.....................................}\\
||\phantom{.....................................}\\
\ce{CH3CH2\underset{Pentan-2-one}{CH2 - C - CH3} ->[I2/NaOH][(Iodoform test)] \underset{Yellow ppt.}{CHI3} + \underset{Sodium butanoate}{CH3CH2CH2COONa}}
\end{array}\]