Question

Alkyl halides are formed when thionyl chloride and_______ are refluxed in presence of pyridine. The order of reactivity $(3^{°}>2^{°}>1^{°})$ is due to $+I$ effect of the alkyl group which_______the polarity of $C—X$ bond.

• A. acids, decreases
• B. alcohols, increases
• C. aldehydes, changes
• D. ketones, decreases

Answer 1

Answer: (B)

The reaction of thionyl chloride and alcohol in presence of pyridine is called as Darzen's reaction. The pyridine acts as a catalyst and this way alkyl halides are formed. the order of reactivity $3^{\circ }>2^{\circ }>1^{\circ }$ is due to the $+I$ effect of the alkyl group which increases the polarity of $CX$ bond. The $CX$ bond determines the reactivity of the compound.