Chapter-9 Amines — Online MCQ Test
CHEMISTRY · Grade 12 · CBSE(NCERT)
Practice Chapter-9 Amines with a free chapter-wise online MCQ test.
This chapter covers: preparation of amines - properties of amines - diazonium salts.
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Chapter-9 Amines — Important Questions & Answers
Amines are organic compounds derived from ammonia by replacement of one or more hydrogen atoms with alkyl or aryl groups. Which of the following is a primary amine?
- A. CH₃-NH₂
- B. CH₃-NH-CH₃
- C. (CH₃)₃N
- D. C₆H₅-N(CH₃)₂
Answer: A. CH₃-NH₂
Primary amines have one alkyl/aryl group attached to nitrogen (RNH₂). CH₃-NH₂ (methylamine) is a primary amine with one methyl group and two hydrogen atoms bonded to nitrogen.
Primary amines have one alkyl/aryl group attached to nitrogen (RNH₂). CH₃-NH₂ (methylamine) is a primary amine with one methyl group and two hydrogen atoms bonded to nitrogen.
Which classification is correct for (CH₃)₂NH?
- A. Primary amine
- B. Secondary amine
- C. Tertiary amine
- D. Quaternary amine
Answer: B. Secondary amine
Secondary amines have two alkyl/aryl groups attached to nitrogen (R₂NH). In (CH₃)₂NH, two methyl groups are bonded to nitrogen with one hydrogen, making it a secondary amine.
Secondary amines have two alkyl/aryl groups attached to nitrogen (R₂NH). In (CH₃)₂NH, two methyl groups are bonded to nitrogen with one hydrogen, making it a secondary amine.
Amines are basic in nature because the nitrogen atom possesses a lone pair of electrons. Arrange the following amines in order of increasing basicity in water: NH₃, CH₃NH₂, (CH₃)₂NH, (CH₃)₃N
- A. (CH₃)₃N < (CH₃)₂NH < CH₃NH₂ < NH₃
- B. NH₃ < CH₃NH₂ < (CH₃)₂NH < (CH₃)₃N
- C. (CH₃)₃N < NH₃ < CH₃NH₂ < (CH₃)₂NH
- D. NH₃ < (CH₃)₃N < (CH₃)₂NH < CH₃NH₂
Answer: C. (CH₃)₃N < NH₃ < CH₃NH₂ < (CH₃)₂NH
In aqueous solution, basicity order is (CH₃)₂NH > CH₃NH₂ > NH₃ > (CH₃)₃N. Secondary amines are most basic in water due to balance between electron donation and hydrogen bonding effects; tertiary amines are least basic due to steric hindrance.
In aqueous solution, basicity order is (CH₃)₂NH > CH₃NH₂ > NH₃ > (CH₃)₃N. Secondary amines are most basic in water due to balance between electron donation and hydrogen bonding effects; tertiary amines are least basic due to steric hindrance.
Which of the following amines will NOT undergo the Hofmann elimination reaction?
- A. Primary aliphatic amines
- B. Secondary aliphatic amines
- C. Tertiary aliphatic amines
- D. Primary aromatic amines
Answer: D. Primary aromatic amines
Primary aromatic amines do not undergo Hofmann elimination because the aromatic ring is not broken under these conditions. Hofmann elimination is specific for aliphatic amines and converts them to alkenes.
Primary aromatic amines do not undergo Hofmann elimination because the aromatic ring is not broken under these conditions. Hofmann elimination is specific for aliphatic amines and converts them to alkenes.
The reaction of diazonium salts with cuprous iodide produces iodobenzene, while the same reaction with hypophosphorous acid produces benzene. What does this tell us about the reactivity of these reagents toward diazonium salts?
- A. CuI is a nucleophile; H₃PO₂ is a reducing agent
- B. Both are equally reactive nucleophiles
- C. H₃PO₂ is more reactive than CuI
- D. Neither is reactive; the products form spontaneously
Answer: A. CuI is a nucleophile; H₃PO₂ is a reducing agent
CuI acts as a nucleophile, replacing the diazo group with I⁻ (Sandmeyer reaction); H₃PO₂ acts as a reducing agent, replacing the diazo group with H⁻ (Gattermann reaction), demonstrating different reaction mechanisms.
CuI acts as a nucleophile, replacing the diazo group with I⁻ (Sandmeyer reaction); H₃PO₂ acts as a reducing agent, replacing the diazo group with H⁻ (Gattermann reaction), demonstrating different reaction mechanisms.