CHEM219 Principles of Organic
Chemistry
(Module 1 – 8)
Final Exam Review
(Questions & Solutions)
2025
1
, I. Foundations of Structure (Bonding and Isomerism)
1. Which type of isomerism arises from differences in the connectivity of
atoms in a molecule?
A. Constitutional isomerism
B. Stereoisomerism
C. Geometric isomerism
D. Optical isomerism
ANS: A
Rationale: Constitutional isomers (or structural isomers) have the
same molecular formula but differ in the connectivity of atoms.
Stereoisomers, by contrast, have the same connectivity but differ in
spatial orientation.
2. An sp²-hybridized atom in an organic molecule typically exhibits
which geometry?
A. Tetrahedral
B. Trigonal planar
C. Linear
D. Bent
ANS: B
Rationale: sp² hybridization leads to three hybrid orbitals arranged in
a trigonal planar geometry with approximately 120° bond angles.
3. The cis and trans descriptors are used to describe which type of
isomerism?
A. Constitutional isomerism
B. Optical isomerism
C. Geometric isomerism
D. Conformational isomerism
ANS: C
Rationale: “Cis” and “trans” describe geometric isomers that differ
2
, based on the relative positions of substituents around a double bond or
in cyclic structures, where free rotation is restricted.
4. For a molecule to exhibit optical activity, it must have:
A. At least one stereocenter and no internal plane of symmetry
B. Only one stereocenter regardless of symmetry
C. Multiple Double bonds
D. A cis configuration only
ANS: A
Rationale: Optical activity requires chirality—a condition achieved by
having at least one chiral (stereogenic) center and lacking an internal
plane of symmetry. Meso compounds, even with stereocenters, are
optically inactive due to symmetry.
5. Resonance stabilization in benzene is critical because it:
A. Increases the reactivity of benzene
B. Distributes electron density evenly around the ring, lowering
reactivity compared to typical alkenes
C. Causes benzene to be easily ionized
D. Makes benzene nonaromatic
ANS: B
Rationale: Benzene's resonance involves the delocalization of π
electrons over the ring, which stabilizes the structure and renders it less
reactive toward addition reactions compared to typical isolated double
bonds.
---
II. Hydrocarbons
6. Which of the following compounds is classified as a saturated
hydrocarbon?
A. Ethene
B. Ethyne
C. Ethane
3
Chemistry
(Module 1 – 8)
Final Exam Review
(Questions & Solutions)
2025
1
, I. Foundations of Structure (Bonding and Isomerism)
1. Which type of isomerism arises from differences in the connectivity of
atoms in a molecule?
A. Constitutional isomerism
B. Stereoisomerism
C. Geometric isomerism
D. Optical isomerism
ANS: A
Rationale: Constitutional isomers (or structural isomers) have the
same molecular formula but differ in the connectivity of atoms.
Stereoisomers, by contrast, have the same connectivity but differ in
spatial orientation.
2. An sp²-hybridized atom in an organic molecule typically exhibits
which geometry?
A. Tetrahedral
B. Trigonal planar
C. Linear
D. Bent
ANS: B
Rationale: sp² hybridization leads to three hybrid orbitals arranged in
a trigonal planar geometry with approximately 120° bond angles.
3. The cis and trans descriptors are used to describe which type of
isomerism?
A. Constitutional isomerism
B. Optical isomerism
C. Geometric isomerism
D. Conformational isomerism
ANS: C
Rationale: “Cis” and “trans” describe geometric isomers that differ
2
, based on the relative positions of substituents around a double bond or
in cyclic structures, where free rotation is restricted.
4. For a molecule to exhibit optical activity, it must have:
A. At least one stereocenter and no internal plane of symmetry
B. Only one stereocenter regardless of symmetry
C. Multiple Double bonds
D. A cis configuration only
ANS: A
Rationale: Optical activity requires chirality—a condition achieved by
having at least one chiral (stereogenic) center and lacking an internal
plane of symmetry. Meso compounds, even with stereocenters, are
optically inactive due to symmetry.
5. Resonance stabilization in benzene is critical because it:
A. Increases the reactivity of benzene
B. Distributes electron density evenly around the ring, lowering
reactivity compared to typical alkenes
C. Causes benzene to be easily ionized
D. Makes benzene nonaromatic
ANS: B
Rationale: Benzene's resonance involves the delocalization of π
electrons over the ring, which stabilizes the structure and renders it less
reactive toward addition reactions compared to typical isolated double
bonds.
---
II. Hydrocarbons
6. Which of the following compounds is classified as a saturated
hydrocarbon?
A. Ethene
B. Ethyne
C. Ethane
3
