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180+ Pharmaceutical Organic Chemistry 3 Solved MCQs
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Bachelor of Pharmacy (B. Pharma) , Pharmacy .
| 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 |
| Answer» 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. |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» B. Plane polarized light | |
| 56. |
Optically active compound can rotate_____ |
| A. | Ordinary light |
| B. | Plane polarized light |
| C. | Monochromatic light |
| D. | None of above |
| Answer» B. Plane polarized light | |
| 57. |
Which instrument is used to measure angle of rotation? |
| A. | Polarimeter |
| B. | UV spectrometer |
| C. | pH meter |
| D. | Conductometer |
| Answer» 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 |
| Answer» D. All of the above | |
| 59. |
Followings are types of optical isomers except__ |
| A. | Enantiomers |
| B. | Diasteromers |
| C. | Conformers |
| D. | Meso compounds |
| Answer» C. Conformers | |
| 60. |
How many possible stereoisomers for the compound CH3CH(OH)COOH. |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» 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. |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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. |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» C. Diastereomers | |
| 76. |
What is the relation between the given compounds?
|
| A. | Diastereomers |
| B. | constitutional isomers |
| C. | enantiomers |
| D. | identical |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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) |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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 |
| Answer» 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° |
| Answer» 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 |
| Answer» 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 |
| Answer» 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) |
| Answer» 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 |
| Answer» 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 |
| Answer» D. 2-Hexene | |
| 94. |
How many stereoisomers are there for the following structure?
|
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» C. 3 | |
| 95. |
How many stereoisomers of 3-bromo-2-butanol, CH3CH(OH)CHBrCH3, exist? |
| A. | 3 |
| B. | 1 |
| C. | 2 |
| D. | 4 |
| Answer» D. 4 | |
| 96. |
How many stereoisomers of 2,3-butanediol, CH3CH(OH)CH(OH)CH3, exist? |
| A. | 3 |
| B. | 4 |
| C. | 1 |
| D. | 2 |
| Answer» A. 3 | |
| 97. |
How many number of stereoisomers possible for 2, 3-pentanediol? |
| A. | 3 |
| B. | 4 |
| C. | 5 |
| D. | 6 |
| Answer» B. 4 | |
| 98. |
Which of the following is a not a five membered ring? |
| A. | Pyridine |
| B. | Pyrrole |
| C. | Furan |
| D. | Thiophene |
| Answer» A. Pyridine | |
| 99. |
Which of the following five membered a ring is most resonance stabilized? |
| A. | Furan |
| B. | Thiophene |
| C. | Pyrrole |
| D. | Pyridine |
| Answer» 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 |
| Answer» A. -excessive heterocycle | |
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