1. Which type of isomerism involves compounds with the same molecular formula but different alkyl groups on each side of a divalent atom?

A. Metamerism B. Functional isomerism C. Ring-chain isomerism D. Tautomerism

2. What factor primarily leads to geometric isomerism in nitrogen-nitrogen double bonds?

A. Free rotation around the bond B. Possibility of differing spatial arrangements due to restricted rotation C. Presence of chiral centers D. Presence of a racemic mixture

3. A carbon atom bonded to four different substituents is called:

A. Achiral center B. Stereogenic center C. Chiral center D. Both B and C

4. What happens to the optical rotation when equal amounts of two enantiomers are mixed?

A. The rotation doubles B. The rotation is halved C. The rotations cancel out, resulting in no rotation D. The rotation reverses direction

5. When two molecules are mirror images and not superimposable, they are called:

A. Diastereomers B. Enantiomers C. Conformers D. Isotopes

6. Which of the following is generally not a factor in conformational isomerism?

A. Free rotation around single bonds B. Restricted rotation around double bonds C. Stereogenic centers D. Different spatial arrangements because of bond rotation

7. Why can double bonds between nitrogen-nitrogen or carbon-nitrogen exhibit geometric isomerism?

A. Because of free rotation around the bond B. Because of restricted rotation about the double bond C. Because they have chiral centers attached D. Because they form racemic mixtures

8. What type of isomerism occurs because of different positions of a functional group on the carbon chain?

A. Positional isomerism B. Functional group isomerism C. Geometric isomerism D. Tautomerism

9. The term "Dextro-rotatory" refers to a substance that:

A. Rotates plane polarized light to the left B. Rotates plane polarized light to the right C. Does not rotate plane polarized light D. Is racemic

10. What does stereochemistry primarily study in molecules?

A. Molecular weight differences B. The position of electrons in orbitals C. The three-dimensional arrangement of atoms D. Types of chemical bonds

11. Why are enantiomers optically active?

A. Because they have different molecular weights B. Because they rotate plane-polarized light in opposite directions C. Because they differ in their functional groups D. Because they are achiral molecules

12. What is the relationship between enantiomers?

A. They are identical in every way B. They are mirror images that are superimposable C. They are mirror images that are not superimposable D. They differ only in ring size

13. What distinguishes a racemic mixture denoted as (±) from a pure enantiomer?

A. It contains only one enantiomer B. It contains equal proportions of both enantiomers and is optically inactive C. It rotates light only to the left D. It is more reactive than pure enantiomers

14. Which of the following is true about a compound with a chiral center?

A. It always exists as a racemic mixture B. It cannot rotate plane-polarized light C. It has non-superimposable mirror images called enantiomers D. It is always optically inactive

15. Which is true about optical isomerism?

A. Optical isomers have different molecular formulas B. They differ only in light rotation but have identical physical and chemical properties C. They are always geometric isomers D. They are superimposable on mirror images

16. What is the relationship between the optical activities of pure enantiomers?

A. They rotate plane polarized light in the same direction B. Their rotations are equal in magnitude but opposite in direction C. Only one enantiomer is optically active D. They are optically inactive

17. Which statement best describes the concept of ring-chain isomerism?

A. Isomers differ by the position of substituents on a ring B. One isomer contains a ring structure, the other has an open chain C. Both isomers contain ring structures but differ in size D. Isomers differ only in optical activity

18. Enantiomers are identical in all properties except:

A. Molecular formula B. Configuration at all stereogenic centers C. Direction in which they rotate plane polarized light D. Connectivity of atoms

19. What is a stereogenic (chiral) center typically characterized by?

A. A carbon atom bonded to four identical atoms B. A carbon atom bonded to four different substituents C. A carbon atom with a double bond D. A carbon atom in a ring system

20. Why is a racemic mixture optically inactive?

A. Because it absorbs light fully B. Because the rotations of the two enantiomers cancel each other C. Because it contains different functional groups D. Because it has no stereogenic centers

21. What defines a molecule as chiral?

A. It has at least one double bond B. It is superimposable on its mirror image C. It is not superimposable on its mirror image D. It contains a ring structure

22. Which is NOT true about tautomerism?

A. It involves an intramolecular proton transfer B. The tautomers rapidly interconvert and exist in equilibrium C. It involves changes in the molecular formula D. Keto-enol tautomerism is a classic example

23. Which characteristic is true of geometric (cis-trans) isomers?

A. They differ in the order of bonded atoms B. They have free rotation around the double bond C. They arise from restricted rotation about a double bond or ring D. They are mirror images of each other

24. What is the key criterion for a molecule to be chiral?

A. It must contain a double bond B. It must have at least one chiral center and be non-superimposable on its mirror image C. It must be symmetrical D. It must rotate plane polarized light anticlockwise only

25. Which is true about achiral molecules?

A. They are not superimposable on their mirror images B. They rotate plane polarized light C. They are superimposable on their mirror images D. They must contain a chiral center

26. Optical isomers differ in:

A. Their physical and chemical properties B. Their ability to rotate plane polarized light in different directions C. Their molecular formula D. Their functional group arrangement

27. Which statement best describes an enantiomeric pair of molecules?

A. They are superimposable mirror images B. They have the same physical properties but differ chemically C. They are non-superimposable mirror images that rotate plane polarized light in opposite directions D. They have the same 3D structure

28. What distinguishes structural isomers from stereoisomers?

A. Structural isomers have different molecular formulas B. Stereoisomers differ in the sequence of bonded atoms C. Structural isomers differ in connectivity; stereoisomers differ in spatial arrangement D. Structural isomers always have chiral centers

29. What is a racemic mixture?

A. A mixture of diastereomers B. A mixture with unequal enantiomeric amounts C. A mixture containing equal amounts of both enantiomers D. A pure enantiomeric compound

30. Which tool is used to measure the degree of rotation of plane polarized light by a substance?

A. Spectrophotometer B. Polarimeter C. Chromatograph D. Calorimeter

31. How is the direction of optical rotation determined using a polarimeter described?

A. Clockwise rotation is laevo-rotatory B. Counterclockwise rotation is dextro-rotatory C. Clockwise rotation is dextro-rotatory D. The direction depends on temperature only

32. What results when a pair of enantiomers are mixed in equal amounts?

A. They form a new compound B. Their optical activities add up C. The mixture becomes optically inactive due to mutual cancellation D. They form a diastereomer

33. What distinguishes stereoisomers from other isomers?

A. They have different molecular formulas B. They differ in the spatial arrangement of atoms, not connectivity C. They have different functional groups D. They differ in molecular weight

34. Which of the following statements correctly describes a racemic mixture?

A. It contains only one enantiomer and is optically active. B. It contains unequal amounts of enantiomers and is optically active. C. It contains equal amounts of (+) and (−) enantiomers and is optically inactive. D. It contains only achiral molecules and does not rotate plane-polarized light.

35. Geometric isomers differ in:

A. Their molecular weight B. The sequence of bonded atoms C. Their spatial arrangement around a double bond or ring D. Their functional groups

36. Diastereomers:

A. Are non-superimposable mirror images B. Have identical physical and chemical properties C. Are stereoisomers that are not mirror images D. Always contain chiral centers

37. Which of the following statements about chiral centers is true?

A. They must be carbon atoms bonded to four different groups B. They include any carbon atom in a molecule C. Only carbons in double bonds can be chiral centers D. Presence of a chiral center ensures a molecule is achiral

38. Which of the following best defines structural isomers?

A. Have the same molecular formula but differ in connectivity of atoms B. Have the same spatial arrangement but differ in functional groups C. Have different molecular formulas D. Are always chiral

39. Which is characteristic of chiral molecules?

A. Plane polarized light passes through without change B. They are optically inactive C. They have non-superimposable mirror images D. They have mirror symmetry

40. Which type of stereoisomerism arises from restricted rotation around double bonds?

A. Structural isomerism B. Geometric isomerism C. Optical isomerism D. Tautomerism

41. An example of functional group isomerism would be:

A. C3H6O existing as propanal and acetone B. Different positions of a hydroxyl group in an alcohol C. Two geometric isomers of an alkene D. Enantiomers of amino acids

42. Which is an example of ring-chain isomerism?

A. Ethanol and dimethyl ether B. Propene and cyclopropane C. Butane and isobutane D. Glucose and fructose

43. Which of the following is true about the specific rotation of an enantiomer?

A. It depends only on the solvent B. It is temperature-dependent and substance-specific C. It remains constant irrespective of wavelength D. It is always clockwise

44. Metamerism arises due to:

A. Different alkyl groups on each side of a functional group B. Different positions of substituent atoms C. Different functional groups present D. Different numbers of pi bonds

45. Tautomers differ mainly in:

A. The molecular formula B. The position of protons and electrons C. The sequence of bonded atoms D. The presence of chiral centers

46. Enantiomers are related similarly to how:

A. Two plants of different species are related B. Left and right hands are related C. Two isotopes of the same element are related D. Two polymers are related

47. How does ring-chain isomerism affect the number of pi bonds in the isomers?

A. Both isomers have the same number of pi bonds B. The ring form has fewer pi bonds than the open-chain isomer C. The open-chain form has fewer pi bonds D. It does not affect pi bonds

48. In optical isomerism, how are enantiomers related in terms of symmetry?

A. They have an internal plane of symmetry B. They are mirror images but lack identical symmetry elements C. They are identical in every way D. They are both achiral

49. Which of the following best describes a racemic mixture?

A. A mixture of two different compounds with different formulas B. Equal amounts of two enantiomers that cancel optical rotation C. A compound with two or more chiral centers D. A mixture of geometric isomers

50. What type of isomerism is illustrated by keto-enol tautomers?

A. Functional isomerism B. Ring-chain isomerism C. Tautomerism D. Geometric isomerism