Explanation

(a)
The compound containing
O OH
$\ \ \ \ \ \ \ \ \ \ \ \ \ \parallel \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ |$
$CH_{3} - C - and - CH - CH_{3}$
groups on heating with sodium hypoiodite (NaOI) or $I_{2}\$with aq. NaOH or aq. $Na_{2}\ CO_{3}$ gives yellow ppt. of iodoform and the reaction is known as iodoform.
$H_{3}C - {CH}_{2} - CH - CH_{3} + OI^{-} \longrightarrow$
|
OH
O
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \parallel$
$CH_{3} - {CH}_{2} - C - CH_{3} + I^{-} + H_{2}O$
O
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \parallel$
$CH_{3} - {CH}_{2} - C - CH_{3} + {OI}^{-} \longrightarrow$
O
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \parallel$
$\ \ \ \ \ \ \ \ \ \ {CH}_{3} - {CH}_{2} - C - {CI}_{3} + \overline{O}H$
O
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \parallel$
$CH_{3}{CH}_{2} - C - CI_{3} + HONa$
O
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \parallel$
$CH_{3} - {CH}_{2} - C - ONa + {CHI}_{3}$
iodoform