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1. But-1-ene and but-2-ene are which type of isomers?
Position isomers: same skeleton, the C=C moves.
2. Cyclopentane and pent-1-ene (both C₅H₁₀) are which type of isomers?
Ring-chain isomers (functional isomers if ring-chain is not offered).
3. n-Propyl alcohol and isopropyl alcohol are: ((a) position isomers (b) chain isomers (c) tautomers (d) geometrical isomers)
Option (a): position isomers.
4. Give two isomers of C₃H₆O that are not carbonyl compounds.
Any two of allyl alcohol, methyl vinyl ether, oxetane, 1,2-epoxypropane, cyclopropanol.
5. Ethyl acetate is C₄H₈O₂. Name a functional isomer from a different class.
Butanoic acid (or 2-methylpropanoic acid): a carboxylic acid.
6. Are nitroethane and ethyl nitrite functional isomers?
Yes: a nitroalkane (bonded through N) and an alkyl nitrite (bonded through O).
7. Which pair are NOT functional isomers? ((a) CH₃CN and CH₃NC (b) propanal and propanone (c) ethanol and dimethyl ether (d) propan-1-amine and propan-2-amine)
Option (d): propan-1-amine and propan-2-amine.
8. Which of the following are examples of metamerism? (a) Ethoxyethane and 1-methoxypropane (b) Pentan-2-one and pentan-3-one (c) N-Methylpropan-1-amine and N-ethylethanamine (d) All of the above
(d) All of the above (GRB Ch 4, Illustration Q3).
9. Write a metamer of diethylamine.
Methyl propyl amine (CH₃NHC₃H₇).
10. Are ethyl acetate and methyl propanoate metamers?
Yes: both C₄H₈O₂ esters with the carbons split differently around –COO–.
11. Metamers of ethyl propionate are: ((a) C₄H₉COOH and HCOOC₄H₉ (b) C₄H₉COOH and CH₃COOC₃H₇ (c) CH₃COOCH₃ and CH₃COOC₃H₇ (d) CH₃COOC₃H₇ and C₃H₇COOCH₃)
Option (d): CH₃COOC₃H₇ and C₃H₇COOCH₃.
12. Which of the following is a dynamic isomerism? (a) Metamerism (b) Geometrical isomerism (c) Tautomerism (d) Optical isomerism
(c) Tautomerism (GRB Ch 4, Illustration Q1).
13. Which shows no keto-enol tautomerism: acetone, benzaldehyde, acetophenone, butan-2-one?
Benzaldehyde: it has no α-hydrogen.
14. Arrange by increasing enol content: acetylacetone, acetone, ethyl acetoacetate.
Acetone < ethyl acetoacetate < acetylacetone.
15. Why is ethyl acetoacetate 46 % enol in hexane but 0.4 % in water?
Water H-bonds to the keto C=O and competes with the enol's internal H-bond; hexane leaves the chelate intact.
16. Enol content is maximum in: ((a) acetone (b) acetophenone (c) acetic acid (d) acetylacetone)
Option (d): acetylacetone.
17. Name the tautomer of nitromethane.
Aci-nitromethane, CH₂=N(O)OH.
18. For acetamide, which form dominates, amide or imidol?
The amide form.
19. Which pair are tautomers? ((a) CH₃CH₂NO₂ and CH₃CH₂–O–N=O (b) CH₃CH=NOH and CH₃CONH₂ (c) CH₃CH₂CH=NH and CH₃CH=CH–NH₂ (d) CH₃CN and CH₃NC)
Option (c): CH₃CH₂CH=NH and CH₃CH=CH–NH₂.
20. The number of isomeric pentyl alcohols possible is: (a) two (b) four (c) six (d) eight
(d) eight (GRB Ch 4, Illustration Q13).
21. Find the D.B.E. of C₆H₆.
[6(2) + 6(−1)]/2 + 1 = 4.
22. Find the D.B.E. of C₄H₉N.
[4(2) + 9(−1) + 1(1)]/2 + 1 = 1.
23. How many structurally isomeric alkenes have the formula C₄H₈?
3: but-1-ene, but-2-ene, 2-methylpropene.
24. Constitutional isomers of C₅H₈ (excluding ring-chain isomers): ((a) 5 (b) 6 (c) 7 (d) 9)
Option (d): 9.
25. Which type of isomerism is shown by the product of benzaldehyde and hydroxylamine? (a) syn and anti (b) cis and trans (c) E and Z (d) None
(a) syn and anti (GRB Ch 4, Illustration Q9).
26. Which will form two isomeric semicarbazones? (a) Benzaldehyde (b) Acetone (c) Benzoquinone (d) Benzophenone
(a) Benzaldehyde (GRB Ch 4, Illustration Q14).
27. How many geometrical isomers does CH₃–(CH=CH)₃–Cl have?
Ends differ, n = 3: 2³ = 8.
28. Which boils higher, cis- or trans-1,2-dichloroethene?
cis (333.3 K vs 320.5 K): it is polar.
29. What does Br₂ give with trans-but-2-ene?
meso-2,3-Dibromobutane (anti addition).
30. Which will show geometrical isomerism? ((a) 1,1,2-Trimethylcyclopropane (b) 1,2-Dimethylcyclobutane (c) Methylcyclohexane (d) 3,4-Dimethylhexane)
Option (b): 1,2-Dimethylcyclobutane.
31. A sucrose solution (0.1 g/mL) in a 1 dm tube rotates the plane by +6.65°. Find [α].
[α] = 6.65 / (1 × 0.1) = +66.5°.
32. Is 3-methylhexane chiral?
Yes: C3 carries H, CH₃, C₂H₅ and C₃H₇.
33. Is 2-methylbutan-2-ol chiral?
No: C2 carries two CH₃ groups.
34. The optically active alkane with the lowest molecular mass is: ((a) CH₃CH₂CH₂CH₃ (b) CH₃CH₂CH(CH₃)CH₃ (c) CH₃–CH(C₂H₅)–cyclopropyl (d) CH₃CH₂C≡CH)
Option (c): CH₃–CH(C₂H₅)–cyclopropyl.
35. Is buta-1,2-diene (CH₂=C=CHCH₃) optically active?
No: one end carries two H atoms.
36. Which is resolvable: biphenyl-2,2′-dicarboxylic acid or 6,6′-dinitrobiphenyl-2,2′-dicarboxylic acid?
The dinitro compound: each ring has two different bulky ortho groups.
37. Which is optically inactive? ((a) abC=C=C=Cab (b) abC=C=Cab (c) hindered aryl amine, N(d)(e), ring groups a, b (d) None of these)
Option (a): abC=C=C=Cab.
38. How many stereoisomers does CH₃CHBrCHBrCH₃ have?
Symmetrical, n = 2: a = 2, m = 1 → 3.
39. How many stereoisomers does CH₃CHClCHBrCH₃ have?
Unsymmetrical, n = 2: 2² = 4.
40. How many racemic forms does open-chain glucose have?
a = 16, so r = 8.
41. How many stereoisomers does HOOC–(CHOH)₄–COOH have?
Symmetrical, n = 4: a = 8, m = 2 → 10.
42. How many stereoisomers does HOOC–(CHOH)₃–COOH have? ((a) 8 (b) 4 (c) 6 (d) 2)
Option (b): 4.
43. A mixture is 80 % (+) and 20 % (−). Find the ee.
60 %.
44. Pure (−)-enantiomer has [α] = −20°. What does a sample with 40 % ee of (−) show?
−8°.
45. Why can diastereomeric salts be separated by crystallisation but enantiomers can't?
Diastereomers have different solubilities; enantiomers have identical physical properties.
46. [α]obs = +6.75°, pure (+)-2-butanol = +13.5°. % of (+) form? ((a) 50% (b) 75% (c) 25% (d) 100%)
Option (b): 75%.
47. What does turning a Fischer projection by 90° in the plane give?
Its enantiomer.
48. Fischer projection: CHO on top, H left, OH right, CH₂OH at the bottom. D or L?
D-Glyceraldehyde (OH on the right).
49. How many stereoisomers does CH₃CH=CH–CH(OH)CH₃ have?
4: one chiral centre (×2) and a cis-trans double bond (×2).
50. Fischer projections (A), (B), (C): which is correct? ((a) (A) and (B) are identical (b) (A) and (B) are diastereomers (c) (A) and (C) are enantiomers (d) (A) and (B) are enantiomers)
Option (d): (A) and (B) are enantiomers.
51. Most stable conformation of n-butane?
Anti (180°).
52. μobs = 1.2 D, μgauche = 4.0 D, μanti = 0. Percentage of anti?
xg = 0.3, so 70 % anti.
53. Energy difference between staggered and eclipsed ethane?
About 12.5 kJ/mol (3 kcal/mol).
54. The most stable conformation of ethane-1,2-diol is: ((a) anti (b) gauche (c) fully eclipsed (d) partially eclipsed)
Option (b): gauche.
55. Which is more stable, cis- or trans-1,4-dimethylcyclohexane?
trans: it can be diequatorial.
56. Which ring has the greatest Baeyer angle strain?
Cyclopropane (d = 24°44′).
57. In the more stable chair of tert-butylcyclohexane, where is the tert-butyl group?
Equatorial; it is essentially never axial.
58. The most stable form of 1,3-dimethylcyclohexane: ((a) cis, diequatorial (b) trans, diequatorial (c) cis, diaxial (d) trans, axial-equatorial)
Option (a): cis, diequatorial.