Quiznetik

Pharmaceutical Organic Chemistry 3 | Set 1

1. 1 Hexane and 3-methylpentane are examples of:

A. Enantiomers.

B. Stereoisomer.

C. Diastereomers.

D. Constitutional isomers.

Correct : D. Constitutional isomers.

2. Cis-trans isomers are:

A. Diastereomers.

B. Enantiomers.

C. Geometric isomers.

D. Constitutional isomers.

Correct : C. Geometric isomers.

3. (2R,4S) –2,4–Dichloropentane and (2S,4R)-2,4-dichloropentane are:

A. Enantiomers

B. Diastereomers

C. identical

D. conformational isomers

Correct : C. identical

4. Which of the following molecules is achiral?

A. (2R,3R)-2,3-Dichloropentane

B. (2R,3S)-2,3-Dichloropentane

C. (2S,4S)-2,4-Dichloropentane

D. (2S,4R)-2,4-Dichloropentane

Correct : D. (2S,4R)-2,4-Dichloropentane

5. Which statement is not true for a meso compound?

A. The specific rotation is 0º.

B. There are one or more planes of symmetry.

C. More than one stereogenic center must be present.

D. The stereo chemical labels, (R) and (S), must be identical for each stereogenic centre.

Correct : D. The stereo chemical labels, (R) and (S), must be identical for each stereogenic centre.

6. Which is a meso compound?

A. (2R,3R)-2,3-Dibromobutane

B. (2R,3S)-2,3-Dibromopentane

C. (2R,4R)-2,4-Dibromopentane

D. (2R,4S)-2,4-Dibromopentane

Correct : D. (2R,4S)-2,4-Dibromopentane

7. What is the percent composition of a mixture of (S)-(+)-2-butanol,[!] D/25 = +13.52º, and (R)-(-)-2-butanol,[!] D/25 = -13.52º, with a specific rotation [!] D/25 = +6.76º?

A. 75%(R) 25%(S)

B. 25%(R) 75%(S)

C. 50%(R) 50%(S)

D. 67%(R) 33%(S)

Correct : B. 25%(R) 75%(S)

8. Which one of the following can exist in optically active forms?

A. cis-1,3-Dichlorocyclohexane

B. trans-1,3-Dichlorocyclohexane

C. cis-1,4-Dichlorocyclohexane

D. tr

Correct : D. tr

9. Which of these is a comparatively insignificant factor affecting the magnitude of Specific optical rotation?

A. Concentration of the substance of interest

B. Purity of the sample

C. Temperature of the measurement

D. Length of the sample tube

Correct : C. Temperature of the measurement

10. What can be said with certainty if a compound has [!] D/25 = -9.25º ?

A. The compound has the (S) configuration.

B. The compound has the (R) configuration.

C. The compound is not a meso form.

D. The compound possesses only one stereogenic center.

Correct : C. The compound is not a meso form.

11. An alkane which can exhibit optical activity is:

A. Neopentane

B. Isopentane

C. 3–Methylpentane

D. 3–Methylhexane

Correct : D. 3–Methylhexane

12. In the absence of specific data, it can only be said that (R)–2–bromopentane is:

A. Dextrorotatory (+).

B. Levorotatory (–).

C. Optically inactive.

D. Chiral.

Correct : D. Chiral.

13. If a solution of a compound (30.0 g/100 mL of solution) has a measured rotation of +15º in a 2 dm tube, the specific rotation is:

A. +50º

B. +25º

C. +15º

D. +7.5º

Correct : B. +25º

14. Which compound would show optical activity?

A. cis 1,4- Dimethylcyclohexane

B. trans 1,4- Dimethylcyclohexane

C. cis 1,4- Dimethylcycloheptane

D. tr

Correct : D. tr

15. Of the compounds which correspond to the general name "dichlorocyclobutane", how many are optically active?

A. 0

B. 1

C. 2

D. 3

Correct : C. 2

16. Which of the following is true of any (S)-enantiomer?

A. It rotates plane-polarized light to the right.

B. It rotates plane-polarized light to the left.

C. It is a racemic form.

D. It is the mirror image of the corresponding (R)-enantiomer.

Correct : D. It is the mirror image of the corresponding (R)-enantiomer.

17. Enantiomers are:

A. Molecules that have a mirror image.

B. Molecules that have at least one stereogenic center.

C. Non-superposable molecules.

D. Non-superposable molecules that are mirror images of each other.

Correct : D. Non-superposable molecules that are mirror images of each other.

18. Which of the following is NOT true of enantiomers? They have the same:

A. Boiling point.

B. Melting point.

C. Specific rotation.

D. Density.

Correct : C. Specific rotation.

19. Which statement is true of 1,3-dimethylcyclobutane?.

A. Only one form of the compound is possible.

B. Two diastereomeric forms are possible.

C. Two sets of Enantiomers are possible.

D. Two enantiomeric forms and one meso comp.

Correct : B. Two diastereomeric forms are possible.

20. CH3CHBrCH2CHClCH3 is the generalized representation of what number of stereo isomers?

A. 3

B. 4

C. 5

D. 6

Correct : B. 4

21. For the generalized structure BrCH2CHClCH2CHClCH2Br there exists what number of stereoisomers?

A. 2

B. 3

C. 4

D. 6

Correct : C. 4

22. How many discrete dimethylcyclopropanes are there?

A. 2

B. 3

C. 4

D. 5

Correct : C. 4

23. What is the molecular formula for the alkenes of smallest molecular weight which possesses a stereogenic center?

A. C4H10

B. C5H12

C. C6H14

D. C7H16

Correct : D. C7H16

24. How many chiral stereoisomers can be drawn for CH3CHFCHFCH (CH3)2?

A. 1

B. 2

C. 3

D. 4

Correct : D. 4

25. How many different compounds are there which correspond to the general name "3-(1- methylbutyl) cyclobutanol”?

A. 2

B. 4

C. 6

D. 8

Correct : B. 4

26. Which of the statements below correctly describes an achiral molecule?

A. The molecule has a nonsuperimposable mirror image.

B. The molecule exhibits optical activity when it interacts with plane-polarized light.

C. The molecule has an enantiomer.

D. The molecule might be a meso form.

Correct : D. The molecule might be a meso form.

27. Which of the following statements correctly pertains to a pair of enantiomers?

A. They rotate the plane of polarized light by exactly the same amount and in opposite directions.

B. They rotate the plane of polarized light by differing amounts and in opposite directions.

C. They rotate the plane of polarized light by differing amounts and in the same direction.

D. They have different melting points.

Correct : A. They rotate the plane of polarized light by exactly the same amount and in opposite directions.

28. A mixture of equal amounts of two enantiomers __________.

A. is called a racemic mixture

B. is optically inactive

C. implies that the enantiomers are meso forms

D. both A and B

Correct : D. both A and B

29. __________ is the use of an optically active reagent or catalyst to convert an optically inactive starting material into an optically active product.

A. Asymmetric induction

B. Racemization

C. Optical reduction

D. Meso effection

Correct : A. Asymmetric induction

30. Which of the following statements is (are) true for the compound (R)-2-butanol?

A. This compound is chiral.

B. This compound is optically active.

C. This compound has an enantiomer.

D. all of the above

Correct : D. all of the above

31. Which of the following statements is (are) true for the compound (3R, 4R)-3,4-dimethylhexane?

A. This compound is chiral.

B. The enantiomer of this compound is (3S, 4S)-3,4-dimethylhexane.

C. This compound is a diastereomer of (3R, 4S)-3,4-dimethylhexane.

D. all of the above

Correct : D. all of the above

32. Which of the following statements is (are) true for the compound cis-1,2-dichlorocyclopropane?

A. This compound is chiral.

B. The enantiomer of this compound is trans-1,2-dichlorocyclopropane.

C. This compound contains no asymmetric carbons.

D. none of the above

Correct : D. none of the above

33. How many asymmetric carbon atoms are present in the following compound?

A. 0

B. 1

C. 2

D. 3

Correct : B. 1

34. How many chiral carbon atoms are present in the following compound?

A. 0

B. 1

C. 2

D. 3

Correct : A. 0

35. Which of the following terms correctly describe(s) the structural relationship between cis-1,3- dimethylcyclopentane and trans-1,3-dimethylcyclopentane?

A. enantiomers

B. diastereomers

C. geometric isomers

D. both B and C

Correct : D. both B and C

36. How many diastereomers are there of the molecule shown below?

A. 0

B. 2

C. 4

D. 6

Correct : D. 6

37. How many enantiomers are there of the molecule shown below?

A. 0

B. 2

C. 4

D. 6

Correct : A. 0

38. What term describes the structural relationship between (E)- and (Z)-2-pentene?

A. Constitutional isomers

B. Enantiomers

C. Geometric isomers

D. Conformers

Correct : C. Geometric isomers

39. Compounds which have different arrangements of atoms in space while having same atoms bonded to each other are said to have

A. position isomerism

B. functional group isomerism

C. chain isomerism

D. stereoisomerism

Correct : D. stereoisomerism

40. Which of the following can make difference in optical isomers?

A. heat

B. temperature

C. polarized light

D. pressure

Correct : C. polarized light

41. Which of the following terms best describes the following pair of molecules?

A. Isomers

B. Constitutional isomers

C. Configurational isomers

D. Geometrical isomers

Correct : D. Geometrical isomers

42. What is the relationship between the two groups in the following molecules?

A. They are equatorial to one another

B. They are axial to one another

C. They are cis to one another

D. They are trans to one another

Correct : A. They are equatorial to one another

43. What is the stereochemical relationship between the following two molecules?

A. Geometrical isomers

B. Enantiomers

C. Diastereomers

D. Identical

Correct : D. Identical

44. Which of the following is an alkane which can exhibit optical activity?

A. Neopentane

B. Isopentane

C. 3–Methylpentane

D. 3–Methylhexane

Correct : D. 3–Methylhexane

45. Hexane and 3-methylpentane are examples of:

A. enantiomers.

B. stereoisomers.

C. diastereomers.

D. constitutional isomers.

Correct : D. constitutional isomers.

46. Which of these is a comparatively insignificant factor affecting the magnitude of specific optical rotation.

A. Concentration of substance of interest

B. Temperature of measurement

C. Length of the sample tube

D. All of the above

Correct : D. All of the above

47. How many chiral stereoisomers can be drawn for CH3CHFCHFCH(CH3)2?

A. 2

B. 4

C. 6

D. 8

Correct : B. 4

48. How many different compounds are there which correspond to the general name "3-(1- methylbutyl)cyclobutanol”?

A. 2

B. 4

C. 6

D. 8

Correct : B. 4

49. Which of the following is NOT true of enantiomers? They have the same:

A. boiling point.

B. melting point.

C. specific rotation.

D. chemical reactivity toward achiral reagents.

Correct : D. chemical reactivity toward achiral reagents.

50. Which statement is true for 1,3-dimethylcyclobutane?

A. Only one form of the compound is possible

B. Two diastereomeric forms are possible.

C. Two enantiomeric forms and one meso compound are possible.

D. None of the above.

Correct : B. Two diastereomeric forms are possible.

51. If a solution of a compound (30.0 g/100 mL of solution) has a measured rotation of +15º in a 2 dm tube, the specific rotation is:

A. +50º

B. +25º

C. +15º

D. +7.5º

Correct : B. +25º

52. In the absence of specific data, it can only be said that (R)–2–bromopentane is:

A. dextrorotatory (+).

B. levorotatory (–).

C. analogous in absolute configuration to (R)–2–bromopentane.

D. optically inactive.

Correct : C. analogous in absolute configuration to (R)–2–bromopentane.

53. Those stereoisomers which can be interconverted only by breaking and remaking of covalent bonds are called as____

A. Chain isomers

B. Positional isomers

C. Configurational isomers

D. Conformational isomers

Correct : C. Configurational isomers

54. Those stereoisomers which can be interconverted by simple rotation about sigma bonds are called as____

A. Conformational isomers

B. Functional isomers

C. Geometric isomers

D. Tautomers

Correct : A. Conformational isomers

55. A beam of light having a particular wavelength and having vibrations only in one plane is____

A. Ordinary light

B. Plane polarized light

C. Monochromatic light

D. None of above

Correct : B. Plane polarized light

56. Optically active compound can rotate_____

A. Ordinary light

B. Plane polarized light

C. Monochromatic light

D. None of above

Correct : B. Plane polarized light

57. Which instrument is used to measure angle of rotation?

A. Polarimeter

B. UV spectrometer

C. pH meter

D. Conductometer

Correct : A. Polarimeter

58. For being chiral compound, chemical compound should not possess following characteristic

A. Plane of symmetry

B. Centre of symmetry

C. Axis of symmetry

D. All of the above

Correct : D. All of the above

59. Followings are types of optical isomers except__

A. Enantiomers

B. Diasteromers

C. Conformers

D. Meso compounds

Correct : C. Conformers

60. How many possible stereoisomers for the compound CH3CH(OH)COOH.

A. 1

B. 2

C. 3

D. 4

Correct : B. 2

61. Which is the true option for Diastereomers?

A. They have only one chiral centre.

B. They have identical physical properties

C. They have two or more chiral centre.

D. All of the above.

Correct : C. They have two or more chiral centre.

62. Ratio of dextro and levo isomers (d:l) of compound present in raceme mixture is__

A. 50:50

B. 40:60

C. 30:70

D. 20:80

Correct : A. 50:50

63. The process of separation of a racemic mixture into optically active d and l isomers is___

A. Racemization

B. Resolution

C. Both (a) and (b)

D. None of the above

Correct : B. Resolution

64. Absolute configuration of stereoisomer is denoted by__

A. R and S isomers

B. D and L isomers

C. d and l isomers

D. cis and tr

Correct : A. R and S isomers

65. Relative configuration of stereoisomer is denoted by__

A. R and S isomers

B. D and L isomers

C. d and l isomers

D. cis and tr

Correct : A. R and S isomers

66. The necessary conditions for geometric isomers are__

A. Presence of at least one double bond.

B. Each carbon atom of the double bond should be linked to two different atoms or groups.

C. Both (a) and (b)

D. None of the above.

Correct : C. Both (a) and (b)

67. By studying which physical property, configuration of geometric isomers can be determined

A. Melting point

B. Solubility

C. Dipole moment

D. All of the above

Correct : D. All of the above

68. From the followings, which is true about conformational isomers?

A. Eclipsed conformation is more stable than staggered conformation.

B. Eclipsed conformation is less stable than staggered conformation.

C. Eclipsed conformation has low energy than staggered conformation.

D. None of the above

Correct : B. Eclipsed conformation is less stable than staggered conformation.

69. Most stable conformation of cyclohexane is___

A. Chair conformation

B. Boat conformation

C. Twist boat conformation

D. Half chair conformation

Correct : A. Chair conformation

70. The hydrogens lying in the plane of the cyclohexane ring are called____

A. Axial hydrogens

B. Chiral hydrogens

C. Equatorial hydrogens

D. None of the above

Correct : C. Equatorial hydrogens

71. The hydrogens lying above or below the plane of the cyclohexane ring are called____

A. Axial hydrogens

B. Chiral hydrogens

C. Equatorial hydrogens

D. None of the above

Correct : A. Axial hydrogens

72. Which is the true sentence for stereospecific reactions from the followings,

A. Reactants react at different rate i.e. they have different rate of reaction.

B. They give different stereoisomers as products.

C. They have different paths to give different types of compounds as products.

D. All of the above

Correct : D. All of the above

73. Which of the following statements most accurately describes the stereochemistry between the various cyclohexanes?

A. Cis-1,2-dichlorocyclohexane and trans-1,2-dichlorocyclohexane rotate plane-polarized light in opposite directions, and together in equal proportions form a racemic mixture.

B. The diaxial and diequatorial forms of trans-1,3-dichlorohexane can be separated by their differing physical properties.

C. Only cis-1,4-dichlorocyclohexane is achiral due to a plane of symmetry, and cis-1,4- dichlorocyclohexane is diastereomeric to trans-1,4-dichlorocyclohexane.

D. The conformational isomers of tr

Correct : D. The conformational isomers of tr

74. Which of the following is the definition of a pair of diastereomers?

A. A pair of stereoisomers each of which has two chirality centers

B. Any pair of stereoisomers

C. A pair of stereoisomers that are not mirror images of one another

D. A pair of stereoisomers that are non-superimposable mirror images of one another

Correct : C. A pair of stereoisomers that are not mirror images of one another

75. What is the relation between the given compound?

A. constitutional isomers

B. enantiomers

C. Diastereomers

D. Identical

Correct : C. Diastereomers

76. What is the relation between the given compounds?

A. Diastereomers

B. constitutional isomers

C. enantiomers

D. identical

Correct : A. Diastereomers

77. Which of the following statements regarding enantiomers not true?

A. All (+) enantiomers are levorotatory

B. All (-) enantiomers rotate plane polarized light in a clockwise direction

C. (+) and (-) enantiomers rotate plane polarized light in opposite directions

D. All R enantiomers are dextrorotatory

Correct : C. (+) and (-) enantiomers rotate plane polarized light in opposite directions

78. Which of the following is/are the S-enantiomer of alanine?

A. Only 1

B. Only 2

C. 1 and 3

D. 2 and 3

Correct : C. 1 and 3

79. Which of the following is capable of existing as a pair of enantiomers?

A. 2-methylpropane

B. 2-methylpentane

C. 3-methylpentane

D. 3-methylhexane

Correct : D. 3-methylhexane

80. Which statement about a chiral compound A is incorrect?

A. A racemate contains equal amounts of (+)-A and (–)-A

B. If A is resolved, it is separated into its enantiomers

C. (+)-A can also be labelled R-A, because (+) means the same as R

D. (+)-A and (–)-A will rotate polarized light equally but in opposite directions

Correct : D. (+)-A and (–)-A will rotate polarized light equally but in opposite directions

81. Which of the following is the definition of chirality?

A. The superimposability of an object on its mirror image

B. A molecule with a mirror image

C. The non-superimposability an object on its mirror image

D. A molecule that has a carbon atom with four different substituents

Correct : D. A molecule that has a carbon atom with four different substituents

82. Which symmetry element makes the given compound achiral?

A. Plane of symmetry (POS)

B. Center of symmetry (COS)

C. Axis of symmetry (AOS)

D. Alternating axis of symmetry (AAOS)

Correct : A. Plane of symmetry (POS)

83. Which of the following is the definition for enatiomerism?

A. A pair of stereoisomers each of which has two chirality centres

B. A pair of stereoisomers that are not mirror images of one another

C. A pair of stereoisomers that are non-superimposable mirror images of one another

D. Any pair of stereoisomers

Correct : C. A pair of stereoisomers that are non-superimposable mirror images of one another

84. Which of the following notations is not used to distinguish between pairs of enantiomers?

A. R and S

B. E and Z

C. + and –

D. D and L

Correct : B. E and Z

85. Which among the following is not true about enantiomerism?

A. Assignments of R and S labels and (+) and (–) labels are not connected

B. The labels R and S refer to different conformers

C. The labels (+) and (–) are used to distinguish enantiomers

D. The specific rotation of enantiomers is equal and opposite

Correct : B. The labels R and S refer to different conformers

86. Which of the following molecules does not possess enantiomers?

A. CH3CH2CH2CHBrCH3

B. CH3CH2CBr2CH3

C. CH3CHBrCH2CH3

D. CHBr2CH2CHBrCH3

Correct : B. CH3CH2CBr2CH3

87. What does a polarimeter measure?

A. Polarity of the substance

B. Angle of rotation of an optical active compound

C. Concentration of the substance

D. pH of the substance

Correct : B. Angle of rotation of an optical active compound

88. A solution of 0.1 g/mL of a pure R enantiomer in a 1.0 dm (i.e., 10 cm) polarimeter rotates plane polarized light by +4.8°. What is the rotation observed on this solution in a 2 dm polarimeter?

A. +2.4°

B. +4.8°

C. +19°

D. +9.6°

Correct : D. +9.6°

89. . Polarimeter works on the principle of which of the following?

A. polarization of light

B. change of the electrical conductivity of solution with composition

C. change of angle of refraction with composition

D. change of electrical conductivity of solution with temperature

Correct : A. polarization of light

90. Which of the following groups has the highest priority according to the Cahn-Ingold-Prelog sequence rules?

A. CH3

B. CH2Cl

C. CH2OH

D. CHO

Correct : D. CHO

91. What is the percent composition of a mixture of (S)-(+)-2-butanol, α= +13.52°, and (R)-(-)-2-butanol, α = -13.52°, with a specific rotation α = +6.76°?

A. 75%(R) 25%(S)

B. 25%(R) 75%(S)

C. 50%(R) 50%(S)

D. 67%(R) 33%(S)

Correct : A. 75%(R) 25%(S)

92. What can be said with certainty if a compound has α= -9.25°?

A. The compound has the (S) configuration

B. The compound has the (R) configuration

C. The compound is not a meso form

D. The compound possesses only one stereogenic center

Correct : C. The compound is not a meso form

93. Which of the following compounds can exhibit geometrical isomerism?

A. 1-Hexene

B. 2-Methyl-2-Pentene

C. 3-methyl-1-pentene

D. 2-Hexene

Correct : D. 2-Hexene

94. How many stereoisomers are there for the following structure?

A. 1

B. 2

C. 3

D. 4

Correct : C. 3

95. How many stereoisomers of 3-bromo-2-butanol, CH3CH(OH)CHBrCH3, exist?

A. 3

B. 1

C. 2

D. 4

Correct : D. 4

96. How many stereoisomers of 2,3-butanediol, CH3CH(OH)CH(OH)CH3, exist?

A. 3

B. 4

C. 1

D. 2

Correct : A. 3

97. How many number of stereoisomers possible for 2, 3-pentanediol?

A. 3

B. 4

C. 5

D. 6

Correct : B. 4

98. Which of the following is a not a five membered ring?

A. Pyridine

B. Pyrrole

C. Furan

D. Thiophene

Correct : A. Pyridine

99. Which of the following five membered a ring is most resonance stabilized?

A. Furan

B. Thiophene

C. Pyrrole

D. Pyridine

Correct : B. Thiophene

100. Five membered rings come under which category of heterocycle classification on the basis of chemical behavior?

A. -excessive heterocycle

B. -deficient heterocycle

C. -equivalent heterocycle

D. Can’t say about the five membered rings

Correct : A. -excessive heterocycle