Important Questions Class 12 Chemistry Chapter 10 Haloalkanes and Haloarenes 1 Mark Questions

1. Give IUPAC names of following compounds

(i).

(ii).

(iii).

(iv).

(v).

 

(vi).

(vii). 

(viii).

(ix).

(x).

Ans.

(i). 1, 3- Dibromobutane
(ii). 1- Cholopropan-2-ol
(iii). 2, 3 – Dibromo-1-chloro-3-methylpentane
(iv). 2-Choloro-3-ethyl-2-methyl pentane
(v). 1-Chloro-2-phenylethane
(vi). 1-Chloro-1-phenyl ethane
(vii). 1, 2, 3, 4, 5, 6- hexachlorocyclohexane
(viii). 2, 2- Dihexyl 1, 1, 1-Trichloro ethane
(ix). 4, 4-dibromobiphenyl
(x). 1, 3-Dibromo -3- methyl butane

(2). Give the structures of following.:

(i). 1,3-Dichloro -2-(bromomethyl) propane
(ii). Isobutylchloride
(iii). Ortho bromotoluene
(iv). 1 – Bromo – 4 – chlorobutane
(v). 3 – Bromo – 5 – chloro – 3,5 – dimethyloctane
(vi). 2,3 – Dibromo – 1 – chloro -3- methylpentane
(vii). 2 – Chloro – 3 – ethyl -1, 4- pentadieme
(viii). 2,3 – Dibromo – 1 – chloro -3- methylpentane
(ix). 2 – Chloro – 1 – phemylpropane
(x). Tert – butylchloride

Ans.(i)

(ii).

(iii).

(iv).

(v).

(vi).

(vii).

(viii).

(ix).

(x).

3. Convert

(i). 1 – Butene to 1 — chlorobutane.

Ans. 

(ii). Ethene to ethanol.

Ans. 

(iii). Chlorobenzene to phenol.

Ans. 

(iv). Methyl bromide to acetic acid.

Ans. 

(v). 2- chlorobutane to sec- butyl ethyl ether.

Ans. 

(vi). Chlorobenzene to benzyl chloride.

Ans. 

(vii). Chlorobenzene   to Benzene.

Ans. 

(viii).  Methane to Ethane.

Ans. 

(ix). Benzene to o- chlorotoluene.

Ans. 

(x).  1- chloropropane  to 2- iodopropane.

Ans. 

4. What is lucas reagent?

Ans. A mixture of HCl and anhydrous ZnCl₂ is known as Lucas reagent.

5. Which of the following will show optical is omerism

1 – bromobutane or 2 – bromobutane?

Ans. 2- bromobutane will be optically active as it has one chiral carbon(C₂).

6. Arrange CH₃CH₂CH₂CH₂Br, (CH₃)₃C-Br, CH₃CH(CH₃)CH₂Br in order of increasing boiling points.

Ans. The order of increasing boiling points is

Boiling point decreases with increase in branching as it reduces the surface area.

7. Give an example of

(a)  Fittig reaction

 (b)  Finkelstein reaction.

Ans. (a) Fittig reaction

(b) Finkelstein reaction

Overview

Haloalkanes and haloarenes are the hydrocarbons in which one or more hydrogen atoms have been replaced with halogen atoms. The primary difference between haloalkanes and haloarenes is that haloalkanes are derived from open-chain hydrocarbons i.e., alkanes whereas haloarenes are derived from aromatic hydrocarbons.

Haloalkanes are commonly referred to as alkyl halides whereas haloarenes are commonly referred to as aryl halides.

Alkyl halides and aryl halides can be classified based on the following parameters:

1. Number of halogen atoms in the molecule
2. sp³ hybridized carbon-halogen bond.
3. sp² hybridized carbon-halogen bond.

Reactivity of Haloalkanes & Haloarenes

Haloarenes are less reactive than haloalkanes because in case of aryl halides the carbon is sp² hybridised while in haloalkanes it is sp³  hybridised. As sp² is more electronegative than sp³  due to more S character in sp². Therefore haloarenes are more stable than haloalkanes and hence less reactive.

Uses of Haloalkanes and Haloarenes

Some of the important applications of these compounds are listed below.

• These organic compounds can dissolve non-polar compounds and are therefore used as solvents.
• Many derivatives of alkyl and aryl halides are used in medicine. One such example is the compound chloramphenicol, which is used to treat cases of typhoid.
• Another example is chloroquine, which is very useful in the treatment of malaria.
• Dichlorodiphenyltrichloroethane (commonly referred to as DDT) is used as an insecticide.

Some haloalkanes and haloarenes have adverse effects on the environment and are labeled as pollutants. One such example is chlorofluorocarbons (or CFCs), which lead to the depletion of the ozone layer which protects the Earth from the harmful radiation coming from the sun.