Consider the following transformations

${\mathrm{CH}}_3\mathrm{CH}\left(\mathrm{OH}\right){\mathrm{CH}}_3\underset{\mathrm{PCC}}{\overset{\left(\mathrm{O}\right)}{\to }}\mathrm{A}\underset{\mathrm{NaOH}}{\overset{{\mathrm{I}}_2}{\to }}\mathrm{B}$

The molecular formula of B is

Iodoform turns yellow and emits a distinctive odour as a result of the haloform reaction, which also signifies the existence of a methyl ketone derivative. When the $-{\mathrm{COCH}}_3$group is present, haloform reaction results. 

$C{H}_{3}CH\left(OH\right)C{H}_3\underset{PCC}{\overset{\left(O\right)}{\to }}{\mathrm{CH}}_3\mathrm{COC}{\mathrm{H}}_3\stackrel{{\mathrm{I}}_2+\mathrm{NaOH}}{\to }{\mathrm{CHI}}_3+{\mathrm{H}}_2\mathrm{O}+{\mathrm{Na}}_2{\mathrm{CO}}_3$