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Explanation: The lone pair of electrons on the nitrogen atom in amines allows them to donate electrons, making them Lewis bases.
2. Aniline is a weaker base than methylamine mainly because:
A. The lone pair on nitrogen is delocalized into the benzene ring
B. Aniline has a much higher molecular weight
C. Methylamine lacks a lone pair on nitrogen
D. Aniline is aromatic and therefore chemically neutral
Answer: A. The lone pair on nitrogen is delocalized into the benzene ring
Explanation: Delocalization of the nitrogen lone pair into the aromatic ring in aniline reduces its availability for protonation, lowering basicity.
3. The Hofmann bromamide degradation reaction converts:
A. An amide into a primary amine with one carbon less
B. An amine into an amide
C. A nitrile into an amine
D. An amide into a nitrile
Answer: A. An amide into a primary amine with one carbon less
Explanation: Treating an amide with Br2 and NaOH causes rearrangement to give a primary amine with one fewer carbon atom than the starting amide.
4. The carbylamine (isocyanide) test is a positive characteristic test for:
A. Primary amines
B. Secondary amines
C. Tertiary amines
D. All classes of amines equally
Answer: A. Primary amines
Explanation: Only primary amines react with chloroform and alcoholic KOH to give a foul-smelling isocyanide; secondary and tertiary amines do not.
5. Aromatic diazonium salts are prepared by treating a primary aromatic amine with:
A. NaNO2 and HCl at 273-278 K
B. NaOH at room temperature
C. Concentrated H2SO4 alone
D. KMnO4
Answer: A. NaNO2 and HCl at 273-278 K
Explanation: Diazotization requires nitrous acid (generated in situ from NaNO2 and HCl) at low temperature (0-5°C) to prevent decomposition of the diazonium salt.
6. The Gabriel phthalimide synthesis is a method used to prepare:
A. Pure primary amines, free from secondary/tertiary contamination
B. Secondary amines selectively
C. Tertiary amines selectively
D. Quaternary ammonium salts
Answer: A. Pure primary amines, free from secondary/tertiary contamination
Explanation: Since aromatic primary amines cannot be prepared this way, the Gabriel synthesis is valued for producing pure aliphatic primary amines.
7. Considering basicity in the gas phase, the general order among methylamine, dimethylamine, trimethylamine and ammonia is:
A. Tertiary > Secondary > Primary > Ammonia
B. Ammonia > Primary > Secondary > Tertiary
C. Primary > Secondary > Tertiary > Ammonia
D. All four show identical basicity
Answer: A. Tertiary > Secondary > Primary > Ammonia
Explanation: In the gas phase, without solvation effects, increasing alkyl substitution steadily increases electron density on nitrogen, raising basicity.
8. Amines can be distinguished from amides mainly on the basis of their:
A. Basic character, since amides are essentially neutral
B. Equal basicity, since both behave identically
C. Amides being more basic than amines
D. The complete absence of any distinguishing test
Answer: A. Basic character, since amides are essentially neutral
Explanation: Amines are basic due to the available lone pair on nitrogen, whereas in amides this lone pair is delocalized into the carbonyl group, making amides essentially neutral.
9. The coupling reaction of a diazonium salt with phenol produces a(n):
A. Azo dye
B. Simple amine
C. Nitro compound
D. Alcohol
Answer: A. Azo dye
Explanation: Diazonium salts undergo electrophilic coupling with phenols (or aromatic amines) to form brightly coloured azo compounds used as dyes.
10. Aniline, obtained by reduction of nitrobenzene, is an important starting material in the synthesis of:
A. Sulfa drugs (via sulfanilamide)
B. Simple alkanes
C. Ethers
D. Carboxylic acids directly
Answer: A. Sulfa drugs (via sulfanilamide)
Explanation: Aniline is a key precursor used in the industrial synthesis of sulfonamide (sulfa) drugs.
11. Reaction of a primary amine with chloroform and alcoholic KOH produces:
A. An isocyanide (carbylamine) with a foul smell
B. An amide
C. A nitrile
D. A diazonium salt
Answer: A. An isocyanide (carbylamine) with a foul smell
Explanation: This carbylamine reaction is a classic qualitative test that is specific to primary amines.
12. Catalytic or chemical reduction of nitrobenzene gives:
A. Aniline
B. Nitrosobenzene as the final stable product
C. Benzene
D. Phenol
Answer: A. Aniline
Explanation: Complete reduction of the nitro group (-NO2) on nitrobenzene converts it into the amino group (-NH2), forming aniline.
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