Question

Which of the following reactions is used to prepare isobutane?

• A. Wurtz reaction of $C_2{H}_{5}Br$
• B. Hydrolysis of n-butylmagnesium iodide
• C. Reduction of propanol with red phosphorus and $HI$
• D. Decarboxylation of 3-methylbutanoic acid

Answer 1

The correct option is D Decarboxylation of 3-methylbutanoic acid

$\underset{\text{3-methylbutanoic acid}}{C{H}_3-\underset{C{H}_3}{\underset{|}{C}H}-C{H}_{2}COOH}\underset{\Delta }{\overset{NaOH/CaO}{\to }}\underset{Isobutane}{C{H}_3-\underset{C{H}_3}{\underset{|}{C}H}-C{H}_3}+C{O}_2\uparrow$

3-methylbutanoic acid gives isobutane on decarboxylation i.e.,
While Wurtz reaction of $C_2{H}_{5}Br$ gives $n$-butane and hydrolysis of $n$-butyl magnesium bromide gives $n$-butane but reduction of propanol with $HI/P$ gives propane.