Question

(i) The hydrogen atom of chloroform is acidic. Explain.
(ii) Why is dehydrohalogenation reaction in haloalkanes termed as Beta - elimination reaction?

Answer 1

(i) (Refer to Image 1)

$Cl$ being electronegative attract shared pair of electrons between $C-Cl$ resulting in partial positive charge on carbon. Carbon being more electronegative than $H$ attract electrons from $H$ making loss of $H^{+}$ favourable making $CHC{l}_3$ acidic.

(Refer to Image 2)

Negative charge on carbon stabilized by back donation to $Cl$ due to presence of empty $3d-$ orbital.

(ii) $C{H}_3-\underset{\beta }{C{H}_2}-\underset{|}{\stackrel{\alpha }{C}}-C{H}_3+alc.KOH$

$Cl$

(Refer to Image 3)

Dehydrohalogenation involves removal of hydrogen from $\beta -$carbon so known as $\beta -$elimination.