CBSE Class 12 Chemistry Amines Worksheet Set B

Assertion and Reason Based MCQs

Directions: In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R).
Mark the correct choice as:
(A) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(B) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(C) (A) is true, but (R) is false.
(D) (A) is false, but (R) is true.

Question. Assertion (A): Acylation of amines gives a monosubstituted product whereas alkylation of amines gives poly substituted product.
Reason (R): Acyl group sterically hinders the approach of further acyl groups. 
Answer : C

Question. Assertion (A): Acetanilide is less basic than aniline.
Reason (R): Acetylation of aniline results in decrease of electron density on nitrogen. 
Answer : A

Question. Assertion (A): N, N-Diethylbenzene sulphonamide is insoluble in alkali.
Reason (R): Sulphonyl group attached to nitrogen atom is strong electron withdrawing group. 
Answer : A

Question. Assertion (A): Aromatic 1° amines can be prepared by Gabriel Phthalimide synthesis.
Reason (R): Aryl halides do not undergo nucleophilic substitution with anion formed by phthalimide. 
Answer : D

Question. Assertion (A): Solubility of amines in water decreases with increase in molar mass.
Reason (R): Intermolecular H bonds formed by the higher amines are weaker. 
Answer : C

Case-based MCQs

I. Read the passage given below and answer the following questions: 
Greater is the stability of the substituted ammonium cation, stronger should be the corresponding amine as a base. Thus, the order of basicity of aliphatic amines should be: primary > secondary > tertiary, which is opposite to the inductive effect based order. Secondly, when the alkyl group is small, like –CH₃ group, there is no steric hindrance to H-bonding. In case the alkyl group is bigger than CH₃ group, there will be steric hinderance to H-bonding. Therefore, the change of nature of the alkyl group, e.g., from –CH₃ to –C₂H₅ results in change of the order of basic strength. In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices:
(A) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(B) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(C) Assertion is correct statement but reason is wrong statement.
(D) Assertion is wrong statement but reason is correct statement.

Question. Assertion (A): (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N > NH₃ is the order of basic strength in case of methyl substituted amines.
Reason (R): The inductive effect, solvation effect and steric hindrance of the alkyl group decide the basic strength of alkyl amines in the aqueous state.
Answer : A

Question. Assertion (A): (C₂H₅) 2NH > (C₂H₅) 3N > C₂H₅NH₂ > NH₃ is the order of basic strength in case of ethyl substituted amines.
Reason (R): The change of nature of the alkyl group, does not result in change of the order of basic strength. 
Answer : C

Question. Assertion (A): Greater is the stability of the substituted ammonium cation, stronger is the corresponding amine as a base.
Reason (R): The order of basicity of aliphatic amines is: primary > secondary > tertiary. 
Answer : C

Question. Assertion (A): Amines behave as a Lewis base.
Reason (R): Amines have an unshared pair of electrons on nitrogen atom. 
Answer : A

II. Read the passage given below and answer the following questions:
Benzene ring in aniline is highly activated. This is due to the sharing of lone pair of nitrogen with the ring which results in increase in the electron density on the ring and hence facilitates the electrophilic attack. The substitution mainly takes place at ortho and para positions because electron density is more at ortho and para positions. On reaction with aqueous bromine all the ortho and para positions get substituted resulting in the formation of 2,4,6-tribromoaniline. To get a monobromo compound, the amino group is acetylated before bromination. After bromination, the bromoacetanilide is acid hydrolysed to give the desired halogenated amine. In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices:
(A) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(B) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(C) Assertion is correct statement but reason is wrong statement.
(D) Assertion is wrong statement but reason is correct statement.

Question. Assertion (A): Benzene ring of aniline is highly deactivated.
Reason (R): In aniline, the sharing of lone pair of nitrogen with the ring increases the electron density on the ring. 
Answer : D

Question. Assertion (A): In aniline –NH2 group facilitates the electrophilic attack.
Reason (R): It is due to decrease in electron density on the ring. 
Answer : C

Question. Assertion (A): In aniline, the substitution mainly takes place at ortho and para positions.
Reason (R): The electron density is more at ortho and para positions. 
Answer : A

Question. Assertion (A): The amino group of aniline is acetylated before bromination.
Reason (R): It is due to the strong deactivating effect of –NH2 group. 
Answer : C

III. Read the passage given below and answer the following questions:
The main problem encountered during electrophilic substitution reactions of aromatic amines is that of their very high reactivity.
Substitution tends to occur at ortho and parapositions. To prepare monosubstituted aniline derivative, the activating affect of –NH₂ group be controlled. This can be done by protecting the –
NH₂ group by acetylation with acetic anhydride, then carrying out the desired substitution followed by hydrolysis of the substituted amide to the substituted amine.

Question. Why is the activating effect of -NHCOCH₃ group in the above reaction less than the activating effect of amino group?
(A) Due to mesomeric effect of benzene ring.
(B) Due to inductive effect of alkyl group.
(C) Due to resonance effect of acetanilide.
(D) All of the above 
Answer : C

Question. Aniline is a resonance hybrid of:
(A) 3 resonating structures
(B) 6 resonating structures
(C) 2 resonating structures
(D) 5 resonating structures 
Ans. Option (D) is correct.