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Amines — NEET & JEE MCQs with answers
Amines are nitrogen-containing organic compounds derived from ammonia by replacing one, two or all three hydrogen atoms by alkyl and/or aryl groups; they are classified as primary (1°), secondary (2°) or tertiary (3°). Amines are basic because of the unshared electron pair on nitrogen: aliphatic amines are stronger bases than ammonia ($pKb$ 3 to 4.22 against 4.75), while aromatic amines such as aniline ($pKb$ 9.38) are weaker. Arenediazonium salts, formed from primary aromatic amines, are useful intermediates for introducing –F, –Cl, –Br, –I, –CN, –OH and –NO₂ into the benzene ring.
Topics in this chapter
- 9.1 Structure of Amines
- 9.2 Classification
- 9.3 Nomenclature
- 9.4 Preparation of Amines
- 9.5 Physical Properties of Amines
- 9.6 Chemical Reactions of Amines
- 9.7 Preparation of Diazonium Salts
- 9.8 Physical Properties of Diazonium Salts
- 9.9 Chemical Reactions of Diazonium Salts
- 9.10 Importance of Diazonium Salts in Synthesis of Aromatic Compounds
Free practice questions
Which of the following best describes the role played by amines in the substances listed as "synthetic examples" in Unit 9?
- A. They act only as catalysts in the manufacture of ammonia
- B. They are used exclusively as fuels
- C. They serve only as laboratory solvents
- D. They occur in polymers, dye stuffs and drugs, and serve commercially as intermediates for medicines and fibres
Show answer
Answer: D — Option D is correct. NCERT lists polymers, dye stuffs and drugs as synthetic materials in which amines feature, and the chapter epigraph adds that their chief commercial use is as intermediates in the synthesis of medicines and fibres.
NCERT Class 12 Chemistry Part-2 · Ch 9 · §9.1 ("and hormones. Synthetic examples include polymers,")
At which stage of the Gabriel synthesis is the bond between nitrogen and the alkyl group actually made?
- A. When the potassium salt of phthalimide is heated with the alkyl halide
- B. When phthalimide is treated with ethanolic potassium hydroxide
- C. During the alkaline hydrolysis of the alkylated product
- D. During diazotisation of the liberated amine
Show answer
Answer: A — The alkyl group becomes attached to nitrogen when the potassium salt of phthalimide is heated with the alkyl halide, so option A is correct. The first stage only generates the anion, the hydrolysis stage releases the amine, and no diazotisation is involved.
NCERT Class 12 Chemistry Part-2 · Ch 9 · §9.4 ("potassium salt of phthalimide which on heating with alkyl halide")
Aniline reacts with bromine water at room temperature to give
- A. a white precipitate of p-bromoaniline
- B. a red precipitate of 2,4,6-tribromoaniline
- C. a white precipitate of 2,4,6-tribromoaniline
- D. a colourless solution of o-bromoaniline
Show answer
Answer: C — Option C is correct. NCERT: aniline reacts with bromine water at room temperature to give a white precipitate of 2,4,6-tribromoaniline. All three activated positions are brominated at once.
NCERT Class 12 Chemistry Part-2 · Ch 9 · §9.6 ("white precipitate of 2,4,6-tribromoaniline")
Among the following, the compound in which all three hydrogen atoms of ammonia have been replaced by alkyl groups is
- A. $\mathrm{(CH_3)_3N}$
- B. $\mathrm{CH_3CH_2CH_2NH_2}$
- C. $\mathrm{(C_2H_5)_2NH}$
- D. $\mathrm{C_6H_5NH_2}$
Show answer
Answer: A — Option A is correct. In $\mathrm{(CH_3)_3N}$ all three hydrogen atoms of ammonia have been replaced by methyl groups, leaving no N–H bond. $\mathrm{CH_3CH_2CH_2NH_2}$ has one replacement and $\mathrm{C_6H_5NH_2}$ one, while $\mathrm{(C_2H_5)_2NH}$ has two.
NCERT Class 12 Chemistry Part-2 · Ch 9 · §9.2 ("group leads to the formation of tertiary amine. Amines are said to be")
NCERT places the reactions in which the diazo group is retained under which heading?
- A. Heading (A)
- B. Both headings equally
- C. Heading (B)
- D. Neither of the two headings
Show answer
Answer: C — Option C is correct. Category (B) is defined in the text as reactions involving retention of the diazo group; these are the coupling reactions.
NCERT Class 12 Chemistry Part-2 · Ch 9 · §9.9 ("(B) reactions involving retention of diazo group.")
Which reagent is printed on the FIRST arrow of the scheme in Example 9.5, acting on 4-nitrotoluene itself?
- A. $\mathrm{Sn/HCl}$
- B. $\mathrm{NaNO_2/HCl}$
- C. $\mathrm{KMnO_4}$ with $\mathrm{OH^-}$
- D. $\mathrm{Br_2}$
Show answer
Answer: D — The scheme on p. 277 begins with $\mathrm{Br_2}$, which puts a bromine on the ring carbon next to the one carrying $\mathrm{-CH_3}$. $\mathrm{Sn/HCl}$ is the second arrow, $\mathrm{NaNO_2/HCl}$ the third and $\mathrm{KMnO_4/OH^-}$ the last.
NCERT Class 12 Chemistry Part-2 · Ch 9 · §9.10, Example 9.5 scheme ("How will you convert 4-nitrotoluene to 2-bromobenzoic acid ?")
The IUPAC name of $\mathrm{CH_3{-}CH(NH_2){-}CH_2{-}NH_2}$ is
- A. Propane-1,2-diamine
- B. Propane-1,3-diamine
- C. Propan-1,2-diamine
- D. N-Methylethane-1,2-diamine
Show answer
Answer: A — Option A is correct. The chain has three carbons; numbering to give the amino groups the lowest locants places them at C1 and C2, and the 'e' of propane is retained before the prefix di, giving propane-1,2-diamine.
NCERT Class 12 Chemistry Part-2 · Ch 9 · §9.3 ("amino group is present at different positions in the parent chain, their")
The lower aliphatic amines are best described as:
- A. Colourless solids
- B. High-boiling liquids with a pleasant smell
- C. Gases with a fishy odour
- D. Completely odourless gases
Show answer
Answer: C — NCERT opens the section on physical properties with the statement that 'the lower aliphatic amines are gases with fishy odour', so option C is correct. They are neither colourless solids nor high-boiling liquids, and their smell is distinctly unpleasant rather than absent.
NCERT Class 12 Chemistry Part-2 · Ch 9 · §9.5 ("The lower aliphatic amines are gases with fishy odour. Primary amines")
Diazotisation, as defined in NCERT, is carried out on which class of amines?
- A. Primary aromatic amines
- B. Secondary aromatic amines
- C. Tertiary aliphatic amines
- D. Quaternary ammonium salts
Show answer
Answer: A — Option A is correct. The definition given is 'the conversion of primary aromatic amines into diazonium salts'. Secondary, tertiary and quaternary nitrogen compounds are outside that definition.
NCERT Class 12 Chemistry Part-2 · Ch 9 · §9.7 ("conversion of primary aromatic amines into diazonium salts is known")
What is the behaviour of benzenediazonium chloride in the dry state?
- A. It is perfectly stable
- B. It absorbs moisture and dissolves
- C. It melts without decomposition
- D. It decomposes easily
Show answer
Answer: D — Option D is correct. The text says 'It decomposes easily in the dry state', which is why the salt is handled in solution rather than isolated dry.
NCERT Class 12 Chemistry Part-2 · Ch 9 · §9.8 ("It decomposes easily in the dry state")
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