Geometrical isomerism and E-Z nomenclature for double bonds - Question Bank

1. A molecule that exhibits geometrical isomerism has:
A) A single bond with restricted rotation.
B) A double bond (or ring system) with restricted rotation and different groups on at least one of the carbons involved.
C) A chiral center.
D) Only sp3 hybridized carbons.
2. Which type of isomerism is exhibited by 1,2-dibromocyclohexane?
A) Positional isomerism
B) Geometrical isomerism
C) Structural isomerism
D) Optical isomerism (unless meso)
3. For 3-methylpent-2-ene, if the two higher priority groups (CH3 on C2 and CH2CH3 on C3) are on opposite sides, what is the configuration?
A) E
B) Z
C) cis
D) trans
4. For 3-methylpent-2-ene, if the two higher priority groups (CH3 on C2 and CH2CH3 on C3) are on the same side, what is the configuration?
A) E
B) Z
C) cis
D) trans
5. Consider 3-methylpent-2-ene. The substituents on C2 are CH3 and H. The substituents on C3 are CH3 and CH2CH3. What is the priority order on C2 and C3 respectively?
A) CH3 > H and CH2CH3 > CH3
B) CH3 > H and CH3 > CH2CH3
C) H > CH3 and CH2CH3 > CH3
D) H > CH3 and CH3 > CH2CH3
6. Geometrical isomers have different:
A) Molecular formulas
B) Connectivity of atoms
C) Physical properties
D) Number of pi bonds
7. What is the priority of -CH2CH3 compared to -CH3 according to Cahn-Ingold-Prelog rules?
A) -CH3 has higher priority.
B) -CH2CH3 has higher priority.
C) They have equal priority.
D) Priority depends on the other substituent.
8. Which of the following is a correct application of the E/Z nomenclature?
A) E-1-butene
B) Z-2-methylbut-2-ene
C) E-2-chloropropene
D) Z-1,2-dibromoethene
9. What is the product of the reduction of an alkyne with sodium in liquid ammonia (dissolving metal reduction)?
A) Cis alkene
B) Trans alkene
C) Alkane
D) E/Z mixture
10. Consider the reaction of an alkyne with H2 in the presence of Lindlar's catalyst. What type of alkene is formed and what is its configuration?
A) Trans alkene, E configuration
B) Cis alkene, Z configuration
C) Trans alkene, Z configuration
D) Cis alkene, E configuration
11. Why are trans isomers generally more stable than cis isomers?
A) Trans isomers have less steric hindrance.
B) Cis isomers have more dipole-dipole interactions.
C) Trans isomers are more polar.
D) Cis isomers have better packing in solid state.
12. The stability of geometrical isomers is generally such that:
A) Cis isomers are more stable than trans isomers.
B) Trans isomers are more stable than cis isomers.
C) Stability is always equal.
D) It depends entirely on the solvent.
13. In the E/Z system, if the two higher priority groups are on the same side of the double bond, the configuration is:
A) E
B) Z
C) cis
D) trans
14. In the E/Z system, if the two higher priority groups are on opposite sides of the double bond, the configuration is:
A) E
B) Z
C) cis
D) trans
15. Which of the following molecules cannot exhibit geometrical isomerism?
A) 1-phenylpropene
B) 2-phenylpropene
C) 1,1-diphenylethene
D) 1,2-diphenylethene
16. The Cahn-Ingold-Prelog priority rules state that if the atoms directly attached to the points of comparison are the same, one moves to the next atoms until a point of difference is found. This is known as:
A) Atomic number comparison
B) Sequential comparison of atoms
C) Isotopic comparison
D) Lone pair comparison
17. Geometrical isomerism requires restricted rotation. Which of the following exhibits restricted rotation?
A) Ethane
B) Ethene
C) Methane
D) Acetylene
18. What is the priority of -SH compared to -OH using Cahn-Ingold-Prelog rules?
A) -OH has higher priority.
B) -SH has higher priority.
C) They have equal priority.
D) Priority depends on the molecule.
19. Consider 1,2-dimethylcyclopentane. This molecule exhibits geometrical isomerism. What are the possible configurations?
A) Only cis
B) Only trans
C) Both cis and trans
D) Neither cis nor trans
20. Geometrical isomerism in cyclic compounds occurs when substituents are on:
A) Adjacent carbon atoms in the ring
B) The same carbon atom in the ring
C) A double bond within the ring
D) The same side of the ring plane
21. If a molecule can exist as cis and trans isomers, these isomers are also known as:
A) Constitutional isomers
B) Enantiomers
C) Diastereomers
D) Tautomers
22. Apply E/Z nomenclature to 3-methylpent-2-ene. What is the configuration?
A) E
B) Z
C) cis
D) trans
23. Apply E/Z nomenclature to 2-bromobut-2-ene. What is the configuration?
A) E
B) Z
C) cis
D) trans
24. Which of the following is correctly named using cis-trans nomenclature?
A) 1-bromo-1-chloropropene
B) 2-bromobut-2-ene
C) 1,2-dibromoethene
D) 3-methylpent-2-ene
25. Why do trans isomers often have higher melting points than cis isomers?
A) They are more polar.
B) They pack more efficiently into a crystal lattice.
C) They have stronger intermolecular forces.
D) They have lower molecular weight.
26. Which geometrical isomer generally has a higher melting point?
A) The cis isomer
B) The trans isomer
C) Both have similar melting points
D) It depends on the substituents
27. What is the primary difference in physical properties between cis and trans isomers?
A) Boiling point
B) Melting point
C) Solubility
D) All of the above
28. Consider 1-bromo-2-chlorocyclopentene. Which isomers can exist?
A) Only cis isomers
B) Only trans isomers
C) Both cis and trans isomers
D) Neither cis nor trans isomers
29. The E/Z nomenclature is essential when cis-trans nomenclature is ambiguous. When does ambiguity arise in cis-trans nomenclature?
A) When there are only two different substituents on the double bond.
B) When there are identical groups on one of the double bond carbons.
C) When there are three or more different substituents on at least one of the double bond carbons.
D) When the molecule is cyclic.
30. For a molecule like 2-methyl-2-butene (CH3-C(CH3)=CH-CH3), can it exhibit geometrical isomerism?
A) Yes, due to the methyl groups.
B) No, because one carbon of the double bond has two identical methyl groups.
C) Yes, due to the ethyl group.
D) No, because it is an alkene.
31. In the E/Z system, what is the priority of Br compared to Cl?
A) Br has higher priority than Cl.
B) Cl has higher priority than Br.
C) They have equal priority.
D) Priority depends on the other substituent.
32. What is the priority order of the following groups according to Cahn-Ingold-Prelog rules: -OH, -CH3, -NH2, -F?
A) -OH > -NH2 > -CH3 > -F
B) -F > -OH > -NH2 > -CH3
C) -F > -OH > -CH3 > -NH2
D) -F > -NH2 > -OH > -CH3
33. Consider the molecule CH3-CH=C(Br)-Cl. What is the configuration of this molecule?
A) It cannot exhibit geometrical isomerism.
B) It can be either E or Z.
C) It is always E.
D) It is always Z.
34. Can cyclopropane exhibit geometrical isomerism?
A) Yes, due to rotation around C-C single bonds.
B) No, it is a rigid ring structure.
C) Yes, if substituted with different groups.
D) No, it lacks a double bond.
35. Which factor makes geometrical isomers different from each other?
A) Connectivity of atoms
B) Spatial arrangement of atoms
C) Number of atoms
D) Types of functional groups
36. Geometrical isomerism is also known as:
A) Stereoisomerism
B) Enantiomerism
C) Diastereomerism
D) Cis-trans isomerism
37. What is the relationship between cis-2-butene and trans-2-butene?
A) Constitutional isomers
B) Enantiomers
C) Diastereomers (specifically, geometrical isomers)
D) Identical compounds
38. Which of the following pairs are geometrical isomers?
A) 1-Butene and 2-Butene
B) cis-2-Butene and trans-2-Butene
C) 1-Butyne and 2-Butyne
D) Butane and Isobutane
39. When is the cis-trans nomenclature system preferred over the E/Z system?
A) When there are more than two different substituents on the double bond.
B) When there are identical groups on one of the double bond carbons.
C) When there are only two different substituents on each carbon of the double bond.
D) When dealing with cyclic compounds.
40. For 1-bromo-1-chloropropene, if Br and H are on the same side, and Cl and CH3 are on the same side, what is the configuration?
A) E
B) Z
C) cis
D) trans
41. For 1-bromo-1-chloropropene, if Br and CH3 are on the same side, and Cl and H are on the same side, what is the configuration?
A) E
B) Z
C) cis
D) trans
42. Consider 1-bromo-1-chloropropene. How would you determine the priority of the groups on the double bond carbons?
A) Assign priority based on alphabetical order.
B) Assign priority based on the Cahn-Ingold-Prelog rules, starting with atomic number.
C) Assign priority based on the number of carbon atoms.
D) Assign priority based on which group is listed first in the name.
43. In the E/Z nomenclature, 'E' (from German 'entgegen') indicates that the higher priority groups are on:
A) The same side of the double bond
B) Opposite sides of the double bond
C) Adjacent positions
D) The same plane
44. In the E/Z nomenclature, 'Z' (from German 'zusammen') indicates that the higher priority groups are on:
A) Opposite sides of the double bond
B) The same side of the double bond
C) The same side of the ring
D) Opposite sides of the ring
45. The E/Z nomenclature system is based on the priority of substituents determined by:
A) Their atomic mass
B) Their atomic number (Cahn-Ingold-Prelog rules)
C) Their size
D) Their position relative to the double bond
46. Which of the following molecules can exhibit geometrical isomerism?
A) Ethene (CH2=CH2)
B) Propene (CH3-CH=CH2)
C) 1,1-Dichloroethene (CCl2=CH2)
D) 1,2-Dichloroethene (CHCl=CHCl)
47. In the cis-trans nomenclature system, 'trans' refers to isomers where similar groups are on:
A) The same side of the double bond
B) Opposite sides of the double bond
C) Adjacent carbon atoms
D) The same plane
48. In the cis-trans nomenclature system, 'cis' refers to isomers where similar groups are on:
A) Opposite sides of the double bond
B) The same side of the double bond
C) The same side of a chiral center
D) Opposite sides of a chiral center
49. Which type of isomerism arises due to restricted rotation around a double bond?
A) Optical isomerism
B) Positional isomerism
C) Geometrical isomerism
D) Tautomerism
50. What is the fundamental requirement for a molecule to exhibit geometrical isomerism around a double bond?
A) At least one atom attached to each carbon of the double bond must be identical.
B) Both carbon atoms of the double bond must be attached to two different groups.
C) The molecule must contain a chiral center.
D) The double bond must be part of an aromatic ring.
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