Question

A mixture of two chlorine organic compounds was treated with sodium metal in ether solution. Isobutane was obtained as one of the products. The two chlorine compounds are:

• A. Methyl chloride and Propyl chloride
• B. Methyl chloride and Ethyl chloride
• C. Isopropyl chloride and Methyl chloride
• D. Isopropyl chloride and Ethyl chloride

Answer 1

The correct option is C Isopropyl chloride and Methyl chloride

In Wurtz reaction, alkane is prepared by reducing alkyl halide using Na in dry ether. It is a coupling reaction where two alkyl group will combine to form higher alkanes.

$RX+2Na+RX\underset{\text{ether}}{\overset{\text{pure \& dry}}{\to }}R-R+2NaX$
The obtained product is isobutane so it has four carbon chain and it is a branched chain.
To get a branched chain product, the reactant should be a branced one.
Thus, (c) and (d) has branched reactant, isopropyl.
In Wurtz reaction of reactant (d), the isopropyl chloride will combine with ethyl chloride to give 5 membered carbon chain. Isopropyl chloride react with itself to give 6 membered carbon chain and ethyl choride will react itself to give four membered carbon chain.

In Wurtz reaction of reactant (c), the isopropyl chloride will react with methyl chloride to give isobutane.

$RX+2Na+X{R}^{\prime }\underset{\text{ether}}{\overset{\text{pure \& dry}}{\to }}\text{Mixture of}{R}^{\prime }-R^{\prime }+R^{\prime }-R+R-R$
(a),
$C{H}_{3}Cl+2Na+ClC{H}_{2}C{H}_{2}C{H}_3\underset{\text{ether}}{\overset{\text{pure \& dry}}{\to }}C{H}_{3}C{H}_{2}C{H}_{2}C{H}_3+C{H}_{3}C{H}_3+C{H}_{3}C{H}_{2}C{H}_{2}C{H}_{2}C{H}_{2}C{H}_3$
(b),
$C{H}_{3}Cl+2Na+Cl{C}_2{H}_5\underset{\text{ether}}{\overset{\text{pure \& dry}}{\to }}C{H}_{3}C{H}_3+C{H}_{3}C{H}_{2}C{H}_3+C{H}_{3}C{H}_{2}C{H}_{2}C{H}_3$
(c),
(d)

Thus, option (d) has the suitable reactant for the product obtained by Wurtz reaction.