ExamGOAL
Books
82
Subjective

Match the items of Column I and Column II.

Column I Column II
A. $\mathrm{S_N 1}$ reaction 1. vic-dibromides
B. Chemicals in fire extinguisher 2. gem-dihalides
C. Bromination of alkenes 3. Racemisation
D. Alkylidene halides 4. Saytzeff rule
E. Elimination of HX from alkylhalide 5. Chlorobromocarbons

Explanation

A. $\rightarrow(3)$ B. $\rightarrow$ (5) C. $\rightarrow$ (1) D. $\rightarrow$ (2) E. $\rightarrow$ (4)

A. 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 $\mathrm{S}_{\mathrm{N}} 1$ mechanism then racemisation takes place while if it follows $\mathrm{S}_{\mathrm{N}} 2$ mechanism than inversion takes places.

B. Chlorobromocarbons are used in fire extinguishers.

C. In vicinal dihalides, halogen atoms are present on the adjacent carbon atom. Bromination of alkenes will give vicinal dihalides.

D. Alkylidene halides are named as gem-dihalides. In gem-dihalides halogen atoms are present on same carbon atom.

E. 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".

83
Subjective

Match the structures of compounds given in Column I with the classes of compounds given in Column II.

Column I Column II
A. 1. Aryl halide
B. $\mathrm{CH}_2=\mathrm{CH}-\mathrm{CH}_2-X$ 2. Alkyl halide
C. 3. Vinyl halide
D. $\mathrm{CH}_2=\mathrm{CH}-X$ 4. Allyl halide

Explanation

A. $\rightarrow(2)$ B. $\rightarrow(4)$ C. $\rightarrow$ (1) D. $\rightarrow(3)$

A. In alkyl halide, halogen atom is bonded to $s p^3$ hybridised carbon atom, which may be further bonded to one, two or three alkyl group, i.e., $\mathrm{CH}_3 \mathrm{CH}(\mathrm{X})-\mathrm{CH}_3$

B. Allyl halides are the compounds in which the halogen atom is bonded to $s p^3$ hybridised carbon atom next to carbon-carbon double bond. i.e., $\mathrm{CH}_{2-}=\mathrm{CH}-\mathrm{CH}_2-X$

C. Aryl halides are the compounds in which the halogen atom is bonded to $s p^2$ hybridised carbon atom of an aromatic ring, i.e., $\mathrm{C}_6 \mathrm{H}_5 \mathrm{X}$

D. Vinyl halides are the compounds in which the halogen atom is bonded to an $s p^2$ hybridised carbon atom of a carbon-carbon double bond, i.e., $\mathrm{CH}_2=\mathrm{CH}-X$

84
Subjective

Match the reactions given in Column I with the types of reactions given in Column II.

Column I Column II
A. 1. Nucleophilic aromatic substitution
B. 2. Electrophilic aromatic substitution
C. 3. Saytzeff elimination
D. 4. Electrophilic addition
E. 5. Nucleophilic substitution $\mathrm{(S_N 1)}$

Explanation

A. $\rightarrow(2)$ B. $\rightarrow$ (4) C. $\rightarrow$ (5) D. $\rightarrow$ (1) E. $\rightarrow$ (3)

A. In this reaction, an electrophile $\mathrm{Cl}^{+}$attacks on to the benzene ring and substitution takes place.

B. In this reaction, addition of HBr takes place on to the doubly bonded carbons of propene in accordance with Markownikoff's rule and electrophilic addition takes place.

C. In this reaction, the reactant is secondary halide. Here, halogen atom is substituted by hydroxy ion. As it is secondary halide so it follows $\mathrm{S}_{\mathrm{N}} 1$ mechanism.

D. In this reaction, halogen atom is directly bonded to aromatic ring. So, It is nucleophilic aromatic substitution as ${ }^{-} \mathrm{OH}$ group has substituted halogen of given compound.

E. It is an elimination reaction. It follows Saytzeff elimination rule.

85
Subjective

Match the structures given in Column I with the names in Column II.

Column I Column II
A. 1. 4-bromopent-2-ene
B. 2. 4-bromo-3-methylpent-2-ene
C. 3. 1-bromo-2-methylbut-2-ene
D. 4. 1-bromo-2-methylpent-2-ene

Explanation

$A \rightarrow(1)$ B. $\rightarrow$ (2) C. $\rightarrow(3)$ D. (4)

A. The IUPAC name of compound (A) is 4-bromopent-2-ene.

B. The IUPAC name of compound (B) is 4-bromo-3-methyl pent-2-ene.

C. The IUPAC name of compound (C) is 1-bromo-2- methyl but-2-ene.

D. The IUPAC name of compound (D) is 1-bromo-2-methylpent-2-ene.

86
Subjective

Match the reactions given in Column I with the names given in Column II.

Column I Column II
A. 1. Fittig reaction
B. 2. Wurtz-Fittig reaction
C. 3. Finkelstein reactioin
D. $\mathrm{C}_2 \mathrm{H}_5 \mathrm{Cl}+\mathrm{Nal} \xrightarrow{\text { Dry acetone }} \mathrm{C}_2 \mathrm{H}_5 \mathrm{I}+\mathrm{NaCl}$ 4. Sandmeyer reaction

Explanation

A. $\rightarrow(2)$ B. $\rightarrow(1)$ C. $\rightarrow(4)$ D. $\rightarrow(3)$

A. A mixture of an alkyl halide and aryl halide gives an alkylarene when treated with sodium in dry ether and this is called Wurtz-Fittig reaction.

B. Aryl halides give analogous compounds when treated with sodium in dry ether, in which two aryl groups are joined together. It is called Fittig reaction.

C. Diazonium salt when treated with cuprous chloride or cuprous bromide gives chlorobenzene or bromobenzene. The reaction is known as Sandmeyer's reaction.

D. Alkyl iodides are prepared by the reaction of alkyl chlorides with sodium iodide in dry acetone. The reaction is known as Finkelstein reaction.