Question

Match the items of Column I and Column II.

	Column I	Column II
(i)	SN1 reaction	(a) vic-dibromides
(ii)	Chemicals in fire extinguisher	(b) gem-dihalides
(iii)	Bromination of alkenes	(c) Racemisation
(iv)	Alkylidene halides	(d) Saytzeff rule
(v)	Elimination of HX from alkylhalide	(e) Chlorobromocarbons

Answer 1

	Column I	Column II
(i)	SN1 reaction	(c) Racemisation
(ii)	Chemicals in fire extinguisher	(e) Chlorobromocarbons
(iii)	Bromination of alkenes	(a) vic-dibromides
(iv)	Alkylidene halides	(b) gem-dihalides
(v)	Elimination of HX from alkylhalide	(d) Saytzeff rule

Explanation:

(i) A mixture containing two enantiomers in equal proportions will have zero optical rotation, such a mixture is known as racemic mixture. The process of conversion of enantiomer into a racemic mixture is known as racemisation. If an alkyl halide follows S_N1 mechanism then racemisation takes place while if it follows S_N2 mechanism than inversion takes places.

(ii) Chlorobromocarbons are used in fire extinguishers.

(iii) In vicinal dihalides, halogen atoms are present on the adjacent carbon atom. Bromination of alkanes will give vicinal dihalides.

(iv) Alkylidene halides are named gem-dihalides. In gem-dihalides halogen atoms are present on same carbon atom.

(v) Elimination of HX from alkylhalide follows Saytzeff rule. This rule states that “in dehydrohalogenation reactions, the preferred product is that alkene which has the greater number of alkyl groups attached to the doubly bonded carbon atoms”.