Question

n-pentane and iso-pentane can be distinguished by:

• A. $B{r}_2$
• B. $O_3$
• C. conc. $H_{2}S{O}_4$
• D. $KMn{O}_4$

Answer 1

Answer: (D)

On oxidation with $KMn{O}_4$ $n$-pentane and iso-pentane give different oxidation products.
So, by identifying these products we can distinguish $n$-pentane and iso-pentane.
$C{H}_{3}C{H}_{2}C{H}_{2}C{H}_{2}C{H}_3\stackrel{(\mathrm{O})}{\to }KMn{O}_4$
$\underset{1^{\circ }\text{alcohol}}{C{H}_{3}C{H}_{2}C{H}_{2}C{H}_{2}OH}\underset{\text{iso- pentane}}{C{H}_{3}C{H}_2-\underset{\stackrel{|}{C}{H}_3}{\mathrm{CH}}-C{H}_3}\stackrel{(\mathrm{O})}{\to }KMn{O}_4$
$\underset{3^{\circ }\text{alcohol}}{C{H}_{3}C{H}_2-\underset{\stackrel{|}{C}{H}_3}{\stackrel{\underset{|}{O}H}{C}}-C{H}_3}$
$n$ pentane gives $1^{\circ }$ alcohol and iso-pentane gives $3^{\circ }$ alcohol and the alcohols can be distinguished by Lucas test
$\therefore n$-pentane and iso-pentane can be distinguished by $KMn{O}_4$ .