21. Aniline when treated with excess bromine water gives:
a) 2,4,6-Tribromoaniline
b) p-Bromoaniline
c) m-Bromoaniline
d) o-Bromoaniline
Answer: a) 2,4,6-Tribromoaniline
Explanation: Aniline is highly reactive towards bromine due to the strong activating nature of the -NH₂ group. When treated with bromine water, it forms 2,4,6-tribromoaniline by substitution at the ortho and para positions.
22. The major product obtained when nitrobenzene is reduced using iron and HCl is:
a) Aniline
b) Hydrazobenzene
c) Phenylhydroxylamine
d) Benzylamine
Answer: a) Aniline
Explanation: Reduction of nitrobenzene (C₆H₅NO₂) using iron and hydrochloric acid gives aniline (C₆H₅NH₂) as the major product. This is a common method of reducing the nitro group to an amino group.
23. The Sandmeyer reaction is used for the synthesis of:
a) Halogenated aromatic compounds
b) Aliphatic amines
c) Nitro compounds
d) Alcohols
Answer: a) Halogenated aromatic compounds
Explanation: The Sandmeyer reaction involves the replacement of the diazonium group in an aromatic diazonium salt with a halogen (Cl, Br, or I) using copper salts (CuCl or CuBr). It is commonly used to synthesize halogenated aromatic compounds.
24. Which of the following statements is correct about nitro compounds?
a) Nitro compounds are basic
b) Nitro compounds are acidic
c) Nitro compounds are neutral
d) Nitro compounds show neither basic nor acidic character
Answer: b) Nitro compounds are acidic
Explanation: Nitro compounds, especially nitroalkanes, have an acidic hydrogen at the α-carbon due to the electron-withdrawing nature of the nitro group, which stabilizes the conjugate base.
25. Which of the following amines can be synthesized using the Hoffmann degradation?
a) Primary amines
b) Secondary amines
c) Tertiary amines
d) Quaternary amines
Answer: a) Primary amines
Explanation: The Hoffmann degradation (also known as Hoffmann bromamide reaction) converts an amide to a primary amine with one fewer carbon atom. Secondary, tertiary, and quaternary amines cannot be synthesized by this method.
26. Which of the following is true about the basicity of aromatic amines?
a) Aromatic amines are more basic than aliphatic amines
b) Aromatic amines are less basic than aliphatic amines
c) Aromatic amines do not act as bases
d) Aromatic amines have the same basicity as aliphatic amines
Answer: b) Aromatic amines are less basic than aliphatic amines
Explanation: Aromatic amines (like aniline) are less basic than aliphatic amines because the lone pair of electrons on the nitrogen atom is delocalized into the aromatic ring, making it less available for protonation.
27. Which of the following reactions will give nitrobenzene as a product?
a) Nitration of benzene
b) Reduction of aniline
c) Oxidation of phenol
d) Friedel-Crafts acylation
Answer: a) Nitration of benzene
Explanation: Nitrobenzene is formed by the nitration of benzene using a mixture of concentrated nitric acid (HNO₃) and sulfuric acid (H₂SO₄). This introduces a nitro group (-NO₂) onto the benzene ring.
28. Which of the following reactions involves the formation of a free radical?
a) Sandmeyer reaction
b) Hoffmann bromamide reaction
c) Diazotization
d) Acetylation of aniline
Answer: a) Sandmeyer reaction
Explanation: The Sandmeyer reaction involves the formation of free radicals when the diazonium salt is reacted with copper(I) halide (CuCl or CuBr), which replaces the diazonium group with a halogen.
29. Which of the following amines does not undergo diazotization?
a) Aniline
b) Methylamine
c) Phenylamine
d) Benzylamine
Answer: d) Benzylamine
Explanation: Benzylamine is a primary aliphatic amine, and only aromatic primary amines (like aniline) undergo diazotization. Aliphatic amines generally decompose when treated with nitrous acid, forming alcohols.
30. The reduction of nitrobenzene under strongly acidic conditions gives:
a) Phenylhydroxylamine
b) Hydrazobenzene
c) Azobenzene
d) Aniline
Answer: d) Aniline
Explanation: Nitrobenzene (C₆H₅NO₂) is reduced to aniline (C₆H₅NH₂) under strongly acidic conditions using a reducing agent such as tin and hydrochloric acid (Sn/HCl).
Leave a comment