TRB PG Assistant - Principles of stereochemistry: configurational and conformational isomerism Online Test (MCQ Quiz)

1. What is stereoisomerism?

A) Isomers that differ in the connectivity of atoms. B) Isomers that have the same molecular formula but differ in the spatial arrangement of atoms. C) Isomers that are non-superimposable mirror images of each other. D) Isomers that have different functional groups.

2. Which type of isomerism involves different arrangements of atoms in space?

A) Structural isomerism B) Stereoisomerism C) Tautomerism D) Positional isomerism

3. Stereoisomers that are non-superimposable mirror images of each other are called:

A) Diastereomers B) Enantiomers C) Meso compounds D) Conformational isomers

4. Stereoisomers that are not mirror images of each other are called:

A) Enantiomers B) Meso compounds C) Diastereomers D) Anomers

5. A carbon atom bonded to four different atoms or groups is known as a:

A) Primary carbon B) Secondary carbon C) Tertiary carbon D) Chiral center

6. What is a chiral molecule?

A) A molecule that is superimposable on its mirror image. B) A molecule that is non-superimposable on its mirror image. C) A molecule with a plane of symmetry. D) A molecule with an axis of symmetry.

7. A molecule that is superimposable on its mirror image is called:

A) Chiral B) Achiral C) Optically active D) Enantiomerically pure

8. Which of the following is NOT a chiral molecule?

A) 2-butanol B) Lactic acid C) Methane D) Alanine

9. The relationship between two enantiomers is that they are:

A) Identical B) Superimposable mirror images C) Non-superimposable mirror images D) Positional isomers

10. Enantiomers have identical physical properties except for their interaction with:

A) Plane-polarized light B) Non-chiral reagents C) Acids D) Bases

11. A mixture containing equal amounts of two enantiomers is called a:

A) Diastereomeric mixture B) Meso mixture C) Racemic mixture D) Enantiomeric excess

12. A racemic mixture is optically:

A) Active B) Inactive C) Partially active D) Strongly active

13. The R/S system is used to assign the absolute configuration of:

A) Diastereomers B) Enantiomers C) Meso compounds D) Geometric isomers

14. In the R/S system, the priority of substituents is determined by the:

A) Atomic number of the directly attached atom. B) Molecular weight of the substituent. C) Number of atoms in the substituent. D) Electronegativity of the atom.

15. If, after assigning priorities, the lowest priority group is pointing away from the viewer and the sequence from highest to lowest is clockwise, the configuration is:

A) R B) S C) M D) P

16. If, after assigning priorities, the lowest priority group is pointing away from the viewer and the sequence from highest to lowest is counterclockwise, the configuration is:

A) R B) S C) M D) P

17. A meso compound is a stereoisomer that:

A) Is chiral and has a plane of symmetry. B) Is achiral and has a plane of symmetry. C) Is chiral and lacks a plane of symmetry. D) Is achiral and lacks a plane of symmetry.

18. A molecule with multiple chiral centers can be achiral if it possesses:

A) An enantiomeric relationship between the chiral centers. B) A plane of symmetry (internal compensation). C) A single chiral center. D) A rotational axis of symmetry.

19. Which of the following has a meso form?

A) 2,3-dichlorobutane B) 2,3-butanediol C) Tartaric acid D) All of the above

20. Configurational isomers are stereoisomers that:

A) Can be interconverted by rotation about single bonds. B) Cannot be interconverted by rotation about single bonds without breaking bonds. C) Are mirror images of each other. D) Are non-mirror images of each other.

21. Enantiomers and diastereomers are types of:

A) Constitutional isomers B) Configurational isomers C) Conformational isomers D) Tautomers

22. Conformational isomers are stereoisomers that:

A) Cannot be interconverted by rotation about single bonds. B) Can be interconverted by rotation about single bonds. C) Are mirror images of each other. D) Are non-mirror images of each other.

23. The different spatial arrangements of a molecule that arise due to rotation about single bonds are called:

A) Configurational isomers B) Conformational isomers C) Geometric isomers D) Stereoisomers

24. Which conformation of ethane is the most stable?

A) Eclipsed B) Staggered C) Skew D) Partially eclipsed

25. Which conformation of ethane is the least stable?

A) Staggered B) Eclipsed C) Gauche D) Anti

26. In the staggered conformation of ethane, the dihedral angle between the hydrogen atoms on adjacent carbons is:

A) 0 degrees B) 60 degrees C) 120 degrees D) 180 degrees

27. In the eclipsed conformation of ethane, the dihedral angle between the hydrogen atoms on adjacent carbons is:

A) 0 degrees B) 60 degrees C) 120 degrees D) 180 degrees

28. The 'gauche' conformation of butane has a dihedral angle between the two methyl groups of:

A) 0 degrees B) 60 degrees C) 120 degrees D) 180 degrees

29. The 'anti' conformation of butane has a dihedral angle between the two methyl groups of:

A) 0 degrees B) 60 degrees C) 120 degrees D) 180 degrees

30. The most stable conformation of n-butane is the:

A) Fully eclipsed B) Gauche C) Anti D) Partially eclipsed

31. Cyclohexane exists predominantly in which conformation?

A) Boat B) Twist-boat C) Half-chair D) Chair

32. In the chair conformation of cyclohexane, substituents can be in either axial or equatorial positions. Which position is generally more stable for a bulky substituent?

A) Axial B) Equatorial C) Both are equally stable D) Depends on the other substituents

33. An axial bond in cyclohexane is oriented:

A) Parallel to the approximate plane of the ring. B) Perpendicular to the approximate plane of the ring. C) At an angle to the ring. D) Within the plane of the ring.

34. An equatorial bond in cyclohexane is oriented:

A) Perpendicular to the approximate plane of the ring. B) Parallel to the approximate plane of the ring. C) Above the ring. D) Below the ring.

35. The interconversion of the chair conformations of cyclohexane by flipping the ring is called:

A) Rotation B) Inversion C) Ring flip D) Epimerization

36. During a ring flip in cyclohexane, axial bonds become equatorial and vice versa. This is an example of interconversion between:

A) Enantiomers B) Diastereomers C) Configurational isomers D) Conformational isomers

37. Geometric isomerism (cis-trans isomerism) is a type of stereoisomerism that arises due to:

A) Rotation about a single bond. B) Restricted rotation about a double bond or in a ring. C) The presence of a chiral center. D) Mirror image relationships.

38. Cis-trans isomerism is typically observed in compounds with:

A) Single bonds and free rotation. B) Double bonds or in cyclic structures. C) Chiral centers only. D) Meso structures.

39. In cis-trans isomerism, 'cis' refers to substituents that are:

A) On opposite sides of the double bond or ring. B) On the same side of the double bond or ring. C) In axial positions. D) In equatorial positions.

40. In cis-trans isomerism, 'trans' refers to substituents that are:

A) On the same side of the double bond or ring. B) On opposite sides of the double bond or ring. C) In axial positions. D) In equatorial positions.

41. Which of the following can exhibit cis-trans isomerism?

A) Ethane B) Propane C) 1,2-dichlorocyclopropane D) Methanol

42. The E/Z notation is a more unambiguous system for describing geometric isomerism, especially when there are more than two different substituents. 'Z' configuration corresponds to:

A) Substituents with higher priority on opposite sides. B) Substituents with higher priority on the same side. C) Substituents with lower priority on opposite sides. D) Substituents with lower priority on the same side.

43. The 'E' configuration in the E/Z notation indicates:

A) Substituents with higher priority on the same side. B) Substituents with higher priority on opposite sides. C) Substituents with lower priority on the same side. D) Substituents with lower priority on opposite sides.

44. Which of the following is an example of configurational isomerism?

A) Ethane staggered vs. eclipsed B) Cyclohexane chair vs. boat C) cis-2-butene vs. trans-2-butene D) Butane anti vs. gauche

45. Which of the following is an example of conformational isomerism?

A) 1,2-dichlorocyclopropane cis vs. trans B) 2-butanol R vs. S C) Cyclohexane chair vs. boat D) Tartaric acid meso vs. enantiomers

46. Stereoisomers that differ in configuration at only one stereocenter are called:

A) Enantiomers B) Epimers C) Anomers D) Diastereomers

47. In carbohydrate chemistry, epimers that differ in configuration at the anomeric carbon are called:

A) Enantiomers B) Epimers C) Anomers D) Diastereomers

48. Fischer projections are commonly used to represent the stereochemistry of molecules with multiple chiral centers, particularly in:

A) Alkanes B) Alkenes C) Carbohydrates D) Aromatic compounds

49. In a Fischer projection, horizontal lines represent bonds coming:

A) Away from the viewer (towards the back). B) Towards the viewer (out of the plane). C) In the plane of the paper. D) Parallel to the plane of the paper.

50. In a Fischer projection, vertical lines represent bonds going:

A) Towards the viewer (out of the plane). B) Away from the viewer (towards the back). C) In the plane of the paper. D) Perpendicular to the plane of the paper.

Principles of stereochemistry: configurational and conformational isomerism - Online Test

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