20 multiple-choice questions about Structural Isomers and Stereoisomers in Organic Chemistry, each with five alternatives (A–E). At the end, you'll find a detailed answer key with extended explanations.
-- Ads --
Structural Isomers and Stereoisomers — Multiple Choice Questions
1. What are structural isomers?
A) Compounds with the same physical properties but different atoms
B) Compounds with the same molecular formula but different connectivity
C) Compounds with identical names
D) Compounds with the same boiling points
E) Different compounds with the same structure
2. Which of the following is an example of structural isomerism?
A) Cis-trans isomerism
B) Optical isomerism
C) Chain isomerism
D) Enantiomerism
E) Diastereomerism
3. Which of these is NOT a type of structural isomerism?
A) Chain isomerism
B) Positional isomerism
C) Functional group isomerism
D) Geometrical isomerism
E) Ring-chain isomerism
4. What are stereoisomers?
A) Molecules with the same molecular formula and same connectivity but different spatial arrangement
B) Molecules with different functional groups
C) Molecules that are superimposable
D) Molecules with different molecular weights
E) Molecules with the same boiling point
5. Which of the following pairs are examples of stereoisomers?
A) Butane and isobutane
B) Ethanol and dimethyl ether
C) cis-but-2-ene and trans-but-2-ene
D) Propanol and butanol
E) Ethene and ethyne
6. What type of isomerism is exhibited by 1-butanol and 2-butanol?
A) Chain isomerism
B) Positional isomerism
C) Optical isomerism
D) Tautomerism
E) Geometrical isomerism
7. Which of the following is TRUE about enantiomers?
A) They are superimposable
B) They have different molecular formulas
C) They are a type of structural isomer
D) They rotate plane-polarized light in opposite directions
E) They cannot exist in organic compounds
8. Which of the following is an example of a functional group isomer?
A) Butane and 2-methylpropane
B) Ethanol and dimethyl ether
C) cis-but-2-ene and trans-but-2-ene
D) 1-chloropropane and 2-chloropropane
E) Lactic acid and acetic acid
9. What is the relationship between 2-butanol and 2-methylpropanol?
A) They are the same compound
B) Functional group isomers
C) Chain isomers
D) Optical isomers
E) Stereoisomers
10. What is required for a molecule to show optical isomerism?
A) Double bond
B) Chiral center
C) Aromatic ring
D) Alkene group
E) Lone pair on nitrogen
11. Which condition is necessary for cis-trans isomerism?
A) Presence of triple bonds
B) Tetrahedral geometry
C) At least one chiral carbon
D) Restricted rotation around a double bond
E) Ionic bonding
12. What kind of isomerism is shown by glucose and fructose?
A) Chain isomerism
B) Functional group isomerism
C) Geometrical isomerism
D) Tautomerism
E) Positional isomerism
13. Which pair represents chain isomers?
A) Ethanol and methoxyethane
B) Pentane and 2-methylbutane
C) cis-but-2-ene and trans-but-2-ene
D) Butanol and butanoic acid
E) Acetone and propanal
14. Which of the following isomers are mirror images but not superimposable?
A) Diastereomers
B) Geometrical isomers
C) Enantiomers
D) Positional isomers
E) Functional isomers
15. Which of these is not a stereoisomer?
A) cis-2-butene
B) trans-2-butene
C) 2-methylpentane
D) R-2-butanol
E) S-2-butanol
16. What is a meso compound?
A) A compound with a chiral center that is optically active
B) A compound with an internal plane of symmetry and optically inactive
C) A compound that has no stereocenters
D) A compound that has both cis and trans isomers
E) A type of positional isomer
17. Which pair of compounds are positional isomers?
A) Ethanol and dimethyl ether
B) 1-propanol and 2-propanol
C) cis-but-2-ene and trans-but-2-ene
D) Butane and pentane
E) Propene and propyne
18. Which characteristic distinguishes enantiomers from diastereomers?
A) Enantiomers are mirror images, diastereomers are not
B) Enantiomers have different molecular formulas
C) Enantiomers cannot exist in organic molecules
D) Diastereomers rotate light equally
E) Diastereomers are always superimposable
19. Which compound would exhibit cis-trans isomerism?
A) CH₃–CH₂–CH₃
B) CH₃–CH=CH–CH₃
C) CH₄
D) CH₃–C≡C–CH₃
E) CH₃–CH₂–CH₂–OH
20. Which of the following correctly describes the number of stereoisomers possible for a molecule with 2 chiral centers (no symmetry)?
A) 2
B) 3
C) 4
D) 6
E) 8
- Questions about Straight-Chain Alkanes (Organic Chemistry)
- Questions about Branched Alkanes in Organic Chemistry
- Questions about Alkenes and Alkynes (Organic Chemistry)
✅ Answer Key with Extended Explanations
1. B – Structural isomers have the same molecular formula but different connectivity of atoms.
2. C – Chain isomerism is a form of structural isomerism involving different carbon chain arrangements.
3. D – Geometrical isomerism is a type of stereoisomerism, not structural.
4. A – Stereoisomers have the same molecular formula and bond connections, but differ in spatial arrangement.
5. C – cis-but-2-ene and trans-but-2-ene are geometrical (stereo) isomers.
6. B – 1-butanol and 2-butanol differ in the position of the –OH group, showing positional isomerism.
7. D – Enantiomers rotate plane-polarized light in opposite directions and are non-superimposable mirror images.
8. B – Ethanol and dimethyl ether both have the formula C₂H₆O but different functional groups.
9. C – 2-butanol and 2-methylpropanol have the same molecular formula but different carbon chains.
10. B – A chiral center (typically a carbon with four different groups) is required for optical activity.
11. D – Restricted rotation around a double bond is needed for cis-trans isomerism.
12. B – Glucose (aldehyde) and fructose (ketone) are functional group isomers.
13. B – Pentane and 2-methylbutane differ in the structure of the carbon chain.
14. C – Enantiomers are mirror images and not superimposable.
15. C – 2-methylpentane is a structural isomer, not a stereoisomer.
16. B – A meso compound has chiral centers but is optically inactive due to internal symmetry.
17. B – 1-propanol and 2-propanol are positional isomers of the hydroxyl group.
18. A – Enantiomers are mirror images; diastereomers are not.
19. B – CH₃–CH=CH–CH₃ (but-2-ene) can exist as cis and trans isomers.
20. C – 2 chiral centers with no symmetry give 2² = 4 stereoisomers.
Dive into the groundbreaking science of neurotransmitters—your brain’s invisible architects—in Chemical Harmony: How Neurotransmitters Shape Our Lives (2025). This meticulously researched book reveals how serotonin, dopamine, GABA, and other brain chemicals silently orchestrate every aspect of your existence, from decision-making and relationships to mental health and emotional resilience.Click here to buy
Share Online!
