Question

Which of the following yield both alkahe and alkene?

• A. Kolbe's reaction
• B. Williamson's synthesis
• C. Wurtz reaction
• D. Sandmeyer reaction

Answer 1

Answer: (A)

Kolbe's method of electrolysis of organic acid can be used to prepare alkane (except methane) alkene and alkyne. This reaction follows free radical mechanism.
Preparation of ethane

For ethyne

For ethene

Williamson synthesis
$\underset{\text{Sodium alkoxide}}{R-\bar{O}-\stackrel{+}{N}a}+\underset{\text{Alkyl halide}}{X-R^{\prime }}\to \underset{\text{Ether}}{RO{R}^{\prime }}+NaX$
Wurtz reaction is used to prepare higher alkanes
$RX+Na+RX\stackrel{\text{ dry ether}}{\to }R-R+NaX$
$RX+Na+R^{\prime }X⟶$
$\underset{\text{mixture of alkanes }}{\underbrace{R-R+R-R^{\prime }+R^{\prime }}}-R^{\prime }+NaX$
Sandmeyer reaction is used for preparation of chloroarenes and bromo arenes