Chemistry Class 12 NCERT Solutions: Chapter 10 Haloalkanes and Haloarenes Part 16

Download PDF of This Page (Size: 185K)

Q: 6. Arrange each set of compounds in order of increasing boiling points.

(i) Bromomethane, Bromoform, Chloromethane, Dibromoethane.

(ii) 1-Chloropropane, Isopropyl chloride, 1-Chlorobutane.

Answer:

For alkyl halides containing the same alkyl group, the boiling point increases with an increase in the atomic mass of the halogen atom.

Since the atomic mass of is greater than that of , the boiling point of bromomethane is higher than that of chloromethane.

Further, for alkyl halides containing the same alkyl group, the boiling point increases with an increase in the number of halides. Therefore, the boiling point of Dibromomethane is higher than that of chloromethane and bromomethane, but lower than that of bromoform.

Hence, the given set of compounds can be arranged in the order of their increasing boiling points as:

.

(ii)

For alkyl halides containing the same halide, the boiling point increases with an increase in the size of the alkyl group. Thus, the boiling point of chlorobutane is higher than that of isopropyl chloride and chloropropane.

Further, the boiling point decreases with an increase in branching in the chain. Thus, the boiling point of isopropyl alcohol is lower than that of chloropropane.

Hence, the given set of compounds can be arranged in the increasing order of their boiling points as:

Q 6 i Melting And Bioling Point Of Compounds.

Q 6 I Melting and Bioling Point of Compounds.

Q 6 i Melting And Bioling Point Of Compounds.

Q: 7. Which alkyl halide from the following pairs would you expect to react more rapidly by an mechanism? Explain your answer.

(i)

(ii)

(iii)

Answer:

(i)

2-bromobutane is a alkylhalide whereas is a alkyl halide. The approaching of nucleophile is more hindered in than in 1-bromobutane. Therefore, reacts more rapidly than 2-bromobutane by an mechanism.

(ii)

Bromobutane is alkylhalide whereas methylpropane is alkyl halide. Therefore, greater numbers of substituents are present in alkyl halide than in alkyl halide to hinder the approaching nucleophile. Hence, reacts more rapidly than methylpropane by an mechanism.

(iii)

Both the alkyl halides are primary. However, the substituent is at a greater distance to the carbon atom linked to Br in than in methylbutane. Therefore, the approaching nucleophile is less hindered in case of the former than in case of the latter. Hence, the former reacts faster than the latter by mechanism.