Class 12 Chemistry MCQ – Haloalkanes and Haloarenes

1. Which of the following compounds will have the highest dipole moment?

a) CH3Cl
b) CH3F
c) CH3Br
d) CH3I

Answer:

b) CH3F

Explanation:

Fluorine is highly electronegative, leading to a significant charge separation and a higher dipole moment in CH3F.

2. Which of the following is not a method for the preparation of haloalkanes?

a) From alcohols
b) From hydrocarbons
c) By free radical halogenation
d) From esters

Answer:

d) From esters

Explanation:

Haloalkanes are not typically prepared directly from esters.

3. Which type of isomerism is shown by 1-chloropropane and 2-chloropropane?

a) Functional isomerism
b) Chain isomerism
c) Positional isomerism
d) Tautomeric isomerism

Answer:

c) Positional isomerism

Explanation:

Both compounds have the same molecular formula but different positions of the chlorine atom.

4. Which of the following reactions involves the formation of a carbocation intermediate?

a) Williamson ether synthesis
b) Wurtz reaction
c) Elimination of haloalkanes
d) SN1 reaction

Answer:

d) SN1 reaction

Explanation:

The SN1 reaction involves the formation of a carbocation intermediate.

5. What product is formed when ethyl chloride reacts with sodium metal?

a) Ethylene
b) Ethane
c) Ethanol
d) Diethyl ether

Answer:

b) Ethane

Explanation:

The Wurtz reaction between ethyl chloride and sodium produces ethane.

6. Which reagent is used to convert alcohols to haloalkanes?

a) Sodium
b) Hydrochloric acid
c) Silver nitrate
d) Thionyl chloride

Answer:

d) Thionyl chloride

Explanation:

Thionyl chloride (SOCl2) is commonly used to convert alcohols to chloroalkanes.

7. What type of reaction does bromobenzene undergo with magnesium metal in dry ether?

a) Elimination reaction
b) Electrophilic substitution
c) Grignard reaction
d) Nucleophilic substitution

Answer:

c) Grignard reaction

Explanation:

Bromobenzene reacts with magnesium in dry ether to form phenylmagnesium bromide, a Grignard reagent.

8. Which of the following is a nucleophile?

a) Br+
b) Br−
c) HBr
d) Br2

Answer:

b) Br−

Explanation:

Br− has a lone pair of electrons which can be donated, making it a nucleophile.

9. Which of the following halogens is most reactive in electrophilic aromatic substitution reactions?

a) Fluorine
b) Chlorine
c) Bromine
d) Iodine

Answer:

a) Fluorine

Explanation:

Due to its high reactivity, fluorine is most reactive in electrophilic aromatic substitution reactions.

10. The hydrolysis of haloalkanes to alcohols is an example of which type of reaction?

a) Electrophilic substitution
b) Nucleophilic addition
c) Nucleophilic substitution
d) Free radical substitution

Answer:

c) Nucleophilic substitution

Explanation:

The hydrolysis of haloalkanes to produce alcohols involves nucleophilic substitution.

11. What is the product when chlorobenzene is treated with aqueous sodium hydroxide at 623 K and 300 atm pressure?

a) Benzene
b) Phenol
c) Benzoic acid
d) Sodium benzoate

Answer:

b) Phenol

Explanation:

Under these conditions, chlorobenzene is hydrolyzed to phenol.

12. Which of the following halides will react most rapidly in an SN2 reaction?

a) Methyl chloride
b) Ethyl chloride
c) Propyl chloride
d) Tert-butyl chloride

Answer:

a) Methyl chloride

Explanation:

Methyl halides are least hindered and thus react most rapidly in SN2 reactions.

13. In the presence of sunlight, chlorine reacts with methane to form:

a) Methyl chloride
b) Methylene chloride
c) Chloroform
d) All of the above

Answer:

d) All of the above

Explanation:

Chlorination of methane in the presence of sunlight can lead to the formation of a mixture of products, including methyl chloride, methylene chloride, and chloroform.

14. What is the IUPAC name of CH3-CH2-CH2-Br?

a) 3-Bromopropane
b) 1-Bromopropane
c) Isobromopropane
d) Methylethyl bromide

Answer:

b) 1-Bromopropane

Explanation:

According to IUPAC nomenclature, the compound is named as 1-Bromopropane.

15. What is the primary product when 2-bromo-2-methylbutane reacts with ethanolic potassium hydroxide?

a) 2-Methyl-2-butene
b) 2-Methyl-1-butene
c) 1-Butene
d) Butane

Answer:

a) 2-Methyl-2-butene

Explanation:

The reaction involves elimination to form the more substituted alkene, which is 2-Methyl-2-butene.

16. Which of the following haloalkanes will undergo racemization when reacted with a base?

a) 1-Chlorobutane
b) 2-Chlorobutane
c) Tert-butyl chloride
d) Methyl chloride

Answer:

b) 2-Chlorobutane

Explanation:

Chiral haloalkanes like 2-Chlorobutane undergo racemization in the presence of a base.

17. Which compound will not give a precipitate with AgNO3 solution?

a) Ethyl bromide
b) Vinyl bromide
c) Allyl bromide
d) Benzyl bromide

Answer:

b) Vinyl bromide

Explanation:

Vinyl halides do not typically undergo nucleophilic substitution reactions to give precipitates with AgNO3.

18. Haloarenes are less reactive towards nucleophilic substitution due to:

a) Greater bond energy of C-X bond
b) Electron withdrawing nature of the halogen
c) Resonance stabilization
d) Steric hindrance

Answer:

c) Resonance stabilization

Explanation:

The partial double bond character of the C-X bond in haloarenes due to resonance makes them less reactive towards nucleophilic substitution.

19. Which of the following compounds will have the shortest C-X bond length?

a) CH3F
b) CH3Cl
c) CH3Br
d) CH3I

Answer:

a) CH3F

Explanation:

Fluorine is the smallest halogen, and the C-F bond will be shorter than the bonds with the other halogens.

20. Which of the following reactions will give 2,2,2-trifluoroethanol as the main product?

a) Hydrolysis of 2,2,2-trifluoroethyl fluoride
b) Action of HF on ethene
c) Hydrolysis of hexafluoropropane
d) Reaction of ethanol with F2

Answer:

a) Hydrolysis of 2,2,2-trifluoroethyl fluoride

Explanation:

The hydrolysis of 2,2,2-trifluoroethyl fluoride will lead to the formation of 2,2,2-trifluoroethanol.

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