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Pharmaceutical Organic Chemistry-III (Part:-2) MCQs with Answers

PHARMACEUTICAL ORGANIC CHEMISTRY-III (BP401TT) MCQs with Answers

51) 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.
Ans. – d

52) 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
Ans. – b

53) 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.
Ans. – c

54) 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
Ans. – d

55) Which is achiral from the following molecules?

a. (2R,3R)-2,3-Dichloropentane
b. (2R,3S)-2,3-Dichloropentane
c. (2S,4S)-2,4-Dichloropentane
d. (2S,4R)-2,4-Dichloropentane
Ans. – d

56) 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
Ans. – c

57) 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
Ans. – a

58) 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
Ans. – b

59) Optically active compound can rotate_____
a. Ordinary light
b. Plane polarized light
c. Monochromatic light
d. None of above
Ans. – b

60) Which instrument is used to measure angle of rotation?
a. Polarimeter
b. UV spectrometer
c. pH meter
d. Conductometer
Ans. – a

61) 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
Ans. – d

62) Followings are types of optical isomers except__
a. Enantiomers
b. Diasteromers
c. Conformers
d. Meso compounds
Ans. – c

63) How many possible stereoisomers for the compound CH3CH(OH)COOH.
a. 1
b. 2
c. 3
d. 4
Ans. – b

64) 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.
Ans. – c

65) 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
Ans. – a

66) 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
Ans. – b

67) 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 trans isomers
Ans. – a

68) 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 trans isomers
Ans. – b

69) 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.
Ans. – c

70) 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
Ans. – d

71) 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 abovd

Ans. – b

72) Most stable conformation of cyclohexane is___
a. Chair conformation
b. Boat conformation
c. Twist boat conformation
d. Half chair conformation
Ans. – a

73) 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
Ans. – c

74) 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
Ans. – a

75) 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
Ans. – d

76) 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 trans-1,2-dichlorocyclohexane are enantiomers, which are not
interconvertible, but resolvable.
Ans. – d

77) Which of the following is a mesocompound?

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a. I
b. II
c. III
d. IV
Ans. – b

78) Which of the following is(are) not meso compound(s)?

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a. II
b. II and III
c. I and III
d. I and II
Ans. – d

79) Which of the following is(are) not meso compound(s)?

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a. I
b. II and III
c. I and III
d. I and Idd

Ans. – a

80) 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
Ans. – c

81) What is the relation between the given compound?

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a. constitutional isomers
b. enantiomers
c. Diastereomers
d. Identical
Ans. – c

82) What is the relation between the given compounds?

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a. Diastereomers
b. constitutional isomers
c. enantiomers
d. identical
Ans. – a

83) What is the relation between the given compounds?

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a. Diastereomers
b. constitutional isomers
c. enantiomers
d. identical
Ans. – a

84) 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
Ans. – c

85) Which of the following is/are the S-enantiomer of alanine?

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a. Only 1
b. Only 2
c. 1 and 3
d. 2 and 3
Ans. – c

86) Which of the following is the pair of enantiomer from the following substance?

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a. I and II
b. II and III
c. III and IV
d. I and V
Ans. – a

87) 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
Ans. – d

88) 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
Ans. – d

89) 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
Ans. – d

90) Which of the following compound(s) is/are chiral?

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a. Both A and B
b. Only B
c. Only A
d. Neither A nor B
Ans. – a

91) Which symmetry element makes the given compound achiral?

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a. Plane of symmetry (POS)
b. Center of symmetry (COS)
c. Axis of symmetry (AOS)
d. Alternating axis of symmetry (AAOS)
Ans. – a

92) 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
Ans. – c

93) 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
Ans. – b

94) 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
Ans. – b

95) Which of the following molecules does not possess enantiomers?
a. CH3CH2CH2CHBrCH3
b. CH3CH2CBr2CH3
c. CH3CHBrCH2CH3
d. CHBr2CH2CHBrCH3
Ans. – b

96) 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
Ans. – b

97) 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°
Ans. – d

98) . 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
Ans. – a

99) 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
Ans. – d

100) 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)

Ans. – a

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➡️ Pharmaceutical Organic Chemistry-III (Part:-2) MCQs with Answers:- Click here

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➡️ Organic Chemistry-III (Part:-4) MCQs with Answers:- Click here

Subject:- Pharmaceutical Organic chemistry:- 3 MCQs with Answers

Topic:- (Chapter 1 & 2 – Stereochemistry)
(Chapter 3 – Heterocyclic compound – I)

Semester:- 4th sem sem 4

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