ISOMERISM
Single answer type questions:
1. The correct statement about the compounds A, B and C
COOCH 3 COOH COOH
H OH H OH H OH
H OH H OH HO H
COOH COOCH 3 COOCH 3
(A) (B) (C)
(A) A and B are identical (B)A and B are diastereomers
(C) A and C are enantiomers (D)A and B are enantiomers
2. Which one of the following has no stereogenic center?
3. The chiral molecules are
A) 1, 2 B) 2, 3 C) 1, 3 D) 1, 2, 3
4. How are the following compounds related?
CHO HOH2 C
OH
H OH
H
HO
H OH
H OH
HO H
H
CH2 OH OHC
A) Enantiomers B) Diastereomers
C) Epimers D) They are identical
5. Which of the following is/are incorrect about keto-enol tautomerism?
(A) acid catalysed enolisation involve the intermediate carbanion
(B) Racemisation occurs on keeping aqueous solution of carbonyl compounds
in which carbon is asymmetric containing one enolisable proton
(C) Enol form is less stable than keto form in cyclopent-1,2-dione
(D) Keto form is more stable than enol in butan-1,2-dione
6. The structure of (S)-2-fluorobutane is best represented by :
Page No 1
A) B)
C) D)
7. Identify, which of the following molecule does not have R configuration :
F CH2Cl
A) Cl D B) H3C CH2OH
H H
NH2 NH2
C) H3C COOH D) HOOC CH3
H H
8. Keto-enol tautomerism is an example of
A) Anionotropism B) Cationotropism
C) Prototropism D) Both b and c
9. For the compound :
The absolute configuration of numbered chiral carbon centre are
A) 2 S, 3 S, 5 S B) 2 S, 3 R, 5 S
C) 2 R, 3 S, 5 S D) 2 R, 3 R, 5 R
10. Geometry in the given compound is
A) Cis B) Trans
C) cis as well as trans D) No geometrical isomerism
11. Which compound will not show optical isomerism
A) 2-Butanol B) 2-Aminobutane
C) Lactic acid D) 2,2-dichloro pentane 1,5-dioic acid
Page No 2
12. syn and anti nomenclature is used in
A) Structural isomerism B) Optical isomerism
C) Geometrical isomerism D) Conformal isomerism
13. Which pair of isomerism is not possible together :
A) Functional and position B) Ring-chain and functional
C) Metamerism and functional D) chain and functional
14. The compound is
A) -1, 2-dichlorohexane B) -1, 2-dichlorocyclohexane
C) -1, 2-dichlorohexane D) -1, 2-dichlorocyclohexane
15. The half life for a reaction is .. of temperature :
A) Independent B) Increased with increase
C) Decreased with increase D) dependent
16. A compound contains 2 dissimilar asymmetric carbon atoms. The number
of optical isomers is :
A) 2 B) 3 C) 4 D) 5
17. Which of the following compounds would exhibit cis-trans isomerism
A) CH3 CH2 CH = CH2 B) ClCH = CHCl
C) ClCH = CCl2 D) CH2 = CH COOH
18. R-alanine is represented by
A) B)
C) D)
19. Which of the following pairs of compounds are geometrical isomers?
A) B)
C) D)
Page No 3
20. Which of the following statements is not true regarding the cis-trans
isomers :
A) They are stereoisomers
B) The are diastereomers
C) The cis isomer has a higher dipole-
moment than the trans isomer
D) The cis isomer usually has a lower b.p.
than the trans isomer
21. Which one of the following compounds will show enantiomerism?
A) B)
C) D)
22.
Translating this eclipsed Newman projection formula of 2, 3
dibromobutane into eclipsed sawhorse projection appears as
A) B)
C) D)
23.
, I and II are
A) A pair of optical isomers B) A pair of conformers
C) A pair of geometrical isomers D) Identical
24. Increasing stability order for Butane conformers
A) Gauche > Staggered > Eclipsed > partially eclipsed
Page No 4
B) Partially elipsed < eclipsed < Gauche < staggered
C) Eclipsed < Gauche < Staggared < Partially ellipsed
D) Staggered < Gauche < Partially ellipsed < eclipsed
25. Which of the following conformers of n-butane has torsional strain ?
A) B)
C) D)
Both B and C
26. Which of the following compound is optically active?
a) ( E ) 4 methylcyclohexanol b) ( Z ) 3 methylcyclohexanol
c) ( Z ) 4 methylcyclohexanol d) ( E ) 4 chlorocyclohexanol
27. The Fischer projection representation of C6 H 5CH ( OH ) CH ( OH ) C6H 5
corresponds to its
a) Gauche conformation b) Anti conformation
c) Eclipsed conformation d) staggered conformation
28. Which of the following are enol tautomers of 3 – methylcyclohexanone ?
a) I & II b) I & IV c) II & III d) only I
29. Tautomerism is not exhibited by:
CH = CH - OH O O
a) b)
O O
c) O d) O
30. Identify, which of the following molecule does not have ‘R’ configuration :
Page No 5
a) b)
c) d)
31. Which of the following is a trans isomer ?
a) b)
c) d)
32. Which of the following is more stable conformer of cyclohexane ?
a) b)
c) d)
33. Which of the following does not show chain isomerism
a) C4 H10 b) C4 H 8 c) C4 H 6 d) C4 H 9 OH
34. Maximum enolisation takes place in:
a) CH 3COCH 3 b) CH 3COCH 2CHO
CH 3COCH 2COCH 3 O
c) d)
35. The compound whose stereo-chemical formula is written below exhibits ‘x’
geometrical isomers and ‘y’ optical isomers:
The value of x and y are :
a) 4 and 4 b) 2 and 2 c) 2 and 4 d) 4 and 2
36. Ketoximes and aldoxime exhibits
a) Geometrical isomerism b) Functional isomerism
Page No 6
c) Optical isomerism d) Tautomerism
37. In which compound ,cis-trans nomenclature cannot be used ?
a) CH 3 CH = CH CH 3 b) CH 3 CH = CH COOH
c) d) C6 H 5 CH = CH CHO
38. Butyne and Butadiene are
a) Chain isomers b) Functional isomers
c) Positional isomers d) Metamers
39. Fumaric acid and Maleic acids are
a) Ring chain isomers b) Isotopic isomers
c) Optical isomers d) Geometrical isomers
40. Total number of chain isomers can be shown by C4 H 9Cl
a) One b) Two c) Three d) Four
41. Tautomerism exhibited by
a) ( CH 3 ) 3 CNO b) ( CH 3 ) 2 NH
c) R3CNO2 d) R CH 2 NO2
42. How many isomers are possible for C3 H 8O
a) 1 b) 2 c) 3 d) None
43. Keto-enol tautomerism is an example of
a) Anionotropism b) Cationotropism
c) Prototropism d) Both b and c
44. Molecules having same molecular formula. But differing in their structure are
known as.
a) Structural isomers b) Optical isomers
c) Geometrical isomers d) Cis-trans isomerism
45. Isomerism exhibited by secondary butyl chloride and tertiary butyl chloride is
a) Chain isomerism b) Geometrical isomerism
c) Optical isomerism d) Positional isomerism
46. Compound exhibit
a) Structural isomerism b) Geometrical isomerism
c) Functional isomerism d) Tautomerism
47. Ortho nitro phenol and paranitro phenol are
a) Cis-trans isomerism b) E, Z configuration
c) Positional isomerism d) Tautomerism
48. Keto-enol isomerism also known as
a) Positional isomerism b) Tautomerism
c) Geometrical isomerism d) Metamerism
49. Functional group R COO R known as
a) Ester b) Ether c) Carboxyl acid d) Ketone
Page No 7
50. HNO2 converts amino acids into hydroxy acids with retention of
configuration. Estimation of nitrogen gas evolved in the reaction is the basis
of Van Slyke estimation of amino acid
NH 2 OH
| |
R CH COOH ���
HNO 2
� R CH COOH + N 2 + H 2O
Among
(I) cysteine (II) Proline
NH 2 CO O H ,
| N
HS CH 2 CH COOH
H ,
(III) Histidine (IV) Valine
C H -C H -C O O H NH 2
|
N H 2 CH3 CH CH COOH
H -N N |
CH 3
aminoacids that cannot be analysed by van slyke method
(A) only I (B) only II (C) I and III (D) I, II and III
H H Cl H Cl Br H Br
51. Cl Br H Br H H Cl H
(A) (B) (C) (D)
(I) (A) and (B) are diastereomers
(II) (B) and (D) are enantiomers
(III) (A) and (D) are geometric isomer
(IV) (A) and (C) are optical isomer
(a) only I is true (b) I, II & III are true
(c) I & II are true (d) all are true
52. Let us consider, three types of disubstituted cyclohexanes
L1 L1 L1
L2 L2
L2
These compounds may exist in vaiours stereoisomeric forms (both geometric
and optical). What is the total number of stereoisomers that exist if L 1 and L2
are two different groups?
(A) six (B) eight (C) ten (D) twelve
53. Which of the following contains maximum enol form?
CH3 O O
(A) (B)
Page No 8
O
(C) (D) O O
54. Which of the following compound is not chiral?
(A) DCH2CH-2CH2Cl (B)CH3CHDCH2Cl
(C)CH3CHClCH2D (D) CH3CH2CHDCl
55. Which is a pair of geometrical isomers?
Cl Br Cl Br Cl H H Br
C C C C C C C C
H Br H CH3 Br H Cl CH3
(I) (II) (III) (IV)
(A) I and II (B)I and III
(C)II and IV (D) III and IV
56. Which of the following compound will exhibit geometrical isomersm?
(A) 1-Phenyl-2-butene (B)3-Phenyl-1-butene
(C) 2-Phenyl-1-butene (D) 1, 1-Diphenyl-1-propene
57. CH3 CH3
HO H and H OH are
CH2 CH2
CH3 CH3
(A) enantiomers (B) diastereomers (C) tautomers (D) position iosmers
58. The conformer in which 2 – Amino ethanol exist to the maximum extent is
a) Gauche b) Anti c) fully eclipsed d) partially eclipsed
59. The relationship between the two stereoisomeric forms of 2-bromo-3-
chlorobutane is
CH3 CH3
H Cl Cl H
and
H Br Br H
CH3 CH3
A) identical B) diastereomers C) enantiomers D) constitutional isomers
60. The number of isomers of C6 H14 is
A) 4 B) 5 C) 6 D) 7
61. Which of the following compound can not exhibit geometrical isomerism
(A) N N (B) C6 H5 C C6 H5
C6 H5 C6 H5
N OH
Page No 9
(C) H (D)
CH3
C2 H5
62. Correct relationship between the two structures given below is
OH
OH
(A) enantiomers (B) tautormers
(C) geometrical isomers (D) constitutional isomers
63.
64. Among the following, the Newmann projections of meso-2, 3-butanediol are:
a) P,Q b) P,R c) R,S d) Q,S
65. Which of the following structures represents the lowest-energy form of 1,2,4
–trimethyl –cyclohex-ane ?
Page No 10
a) b)
c) d)
66. The geometrical isomerism is shown by
CH 2
CH 2 CHCl
a) b) c) d) CHCl
67. How are the following compounds related?
CHO HOH2 C
OH
H OH
H
HO
H OH
H OH
HO H
H
CH2 OH OHC
A) Enantiomers B) Diastereomers
C) Epimers D) They are identical
68. Which of the following is/are incorrect about keto-enol tautomerism?
(A) acid catalysed enolisation involve the intermediate carbanion
(B) Racemisation occurs on keeping aqueous solution of carbonyl compounds
in which
carbon is asymmetric containing one enolisable proton
(C) Enol form is less stable than keto form in cyclopent-1,2-dione
(D) Keto form is more stable than enol in butan-1,2-dione
69.
70.
Page No 11
71. The chiral molecules are
A) 1, 2 B) 2, 3 C) 1, 3 D) 1,2,3
72. The correct statement about the compounds A, B and C
COOCH 3 COOH COOH
H OH H OH H OH
H OH H OH HO H
COOH COOCH 3 COOCH 3
(A) (B) (C)
(A) A and B are identical (B)A and B are diastereomers
(C)A and C are enantiomers (D) A and B are enantiomers
Page No 12
ISOMERISM – KEY SHEET
Single Answers
1 D 2 C 3 D 4 D 5 C 6 C
7 D 8 D 9 D 10 B 11 D 12 C
13 A 14 B 15 B 16 C 17 B 18 A
19 D 20 D 21 C 22 A 23 B 24 D
25 D 26 B 27 A 28 B 29 B 30 D
31 B 32 A 33 C 34 D 35 B 36
37 38 39 40 41 42
43 44 45 46 47 48
49 50 B 51 D 52 C 53 C 54 A
55 C 56 A 57 A 58 A 59 C 60 B
61 B 62 C 63 D 64 B 65 C 66 D
67 D 68 C 69 B 70 B 71 D 72 D
ISOMERISM – SOLUTIONS
Single solutions
1. (d)
Conceptual
2. Key: C
Hint:
4=3 3=4
2=5
5=2 1
H OH
The sequence of atoms 1 � 2 � 3 � 4 � 5 is equivalent regardless of whether
one proceeds clockwise (or) anti clock wise
3. Conceptual
4. Conceptual
5. Conceptual
6. Conceptual
7. Conceptual
8. Conceptual
9. Conceptual
10. Two methyl groups are on opposite sides. One up and one down.
11. Remaining all contains chiral carbon
12. Syn anti are synonymom to cis & trans respectively
13. Conceptual
Page No 13
14. Conceptual
15. Half life depends upon rate constant and rate constant (K) varies with
temperature. Since ; thus K increases with temperature. Also
.
16. , where n is no. of dissimilar asymmetric carbon atoms.
17. Carbon possessing double bond having two different group.
18. Even rotations are carried out to bring least priority group to the bottom
19. As per E, Z notation
20. Conceptual
21.
22. Fact
23. Fact
24. Fact
25. Fact
26. Trans alkene is more stable than cis
27. Dipolemoment of symmetrical molecule is zero
28. Conceptual
29. Conceptual
30. Conceptual
31. Conceptual
32. Conceptual
33. Conceptual
34. Conceptual
35. Conceptual
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
Page No 14
49.
50. Presence of secondary amine group.
51. Conceptual
52.
enantiomer
L2
L1
L1
enantiomer
L2
enantiomer
L1
L2
L1
enantiomer
L2
L2 L1 L2
No chiral carbon
L1
53. Conceptual
54. Conceptual
55. Conceptual
56. Conceptual
57. Conceptual
58.
Page No 15
59. The two compounds given
CH3 CH3
S R
H Cl Cl H
and
H R Br Br S H
CH3 CH3
(as they are non superimposable mirror images to each other)
CH 3
|
60. (1) CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 (2) CH 3 C CH 2 CH 3
|
CH 3
CH 3 CH CH CH 3 CH 3 CH CH 2 CH 2 CH 3
(3) | | (4) |
CH 3 CH 3 CH 3
CH 3 CH 2 CH CH 2 CH 3
(5) |
CH 3
61. Ketoxime having identical aryl group bonded to the carbon do not show GI
62. Conceptual
63. D
64. Conceptual
65. Conceptual
66. Conceptual
67. Conceptual
68. (C)
Conceptual
69. (b) Explanation : (b) is right because the molecule is chiral. This isomerism is
also called Atropisomerism.
(a) is wrong because it does not satisfy condition of geometrical isomerism.
70.
71. Conceptual
72. Conceptual
Page No 16
