Stereochemistry
and Isomerism
Exam
Instructions:
Time Allowed: 2 hours
Materials Allowed: Calculator, periodic table, and formula sheet.
Answer all questions. Ensure all work is shown for problem-solving sections.
Section 1: Multiple Choice Questions (20 points)
1. Which of the following statements about enantiomers is true?
a) They are identical in all physical properties.
b) They are mirror images of each other and cannot be superimposed.
c) They have identical boiling points and melting points.
d) They have different chemical reactivities with achiral reagents.
Answer: b) They are mirror images of each other and cannot be superimposed.
2. What is the maximum number of stereoisomers possible for a molecule with
3 chiral centers?
a) 4
b) 6
c) 8
d) 16
Answer: d) 16
3. Which of the following molecules is achiral?
a) 2,3-Butanediol
, b) 2-Butene
c) 3-Chloropentane
d) Lactic acid
Answer: b) 2-Butene
4. How do you denote the configuration of a molecule with a double bond in
the E/Z system?
a) By using R/S notation
b) By comparing the priority of groups on each carbon of the double bond
c) By identifying the mirror image relationship
d) By analyzing the molecular weight
Answer: b) By comparing the priority of groups on each carbon of the double
bond
5. Which of the following best describes a meso compound?
a) A compound with no chiral centers
b) A compound with multiple chiral centers but is superimposable on its mirror
image
c) A compound that rotates plane-polarized light to the right
d) A compound with only one chiral center
Answer: b) A compound with multiple chiral centers but is superimposable on
its mirror image
Section 2: Short Answer Questions (30 points)
1. Define chirality and give an example of a chiral molecule.
Answer: Chirality refers to the property of a molecule that makes it non-
superimposable on its mirror image, like a pair of human hands. A common
example of a chiral molecule is 2-butanol, where the central carbon atom is
bonded to four different groups.
2. Explain the difference between enantiomers and diastereomers with
examples.
Answer: Enantiomers are a type of stereoisomer that are non-superimposable
mirror images of each other, such as (R)- and (S)-lactic acid. Diastereomers are
stereoisomers that are not mirror images of each other and differ in
configuration at one or more chiral centers, such as (2S,3S)- and (2S,3R)-butane-
2,3-diol.
and Isomerism
Exam
Instructions:
Time Allowed: 2 hours
Materials Allowed: Calculator, periodic table, and formula sheet.
Answer all questions. Ensure all work is shown for problem-solving sections.
Section 1: Multiple Choice Questions (20 points)
1. Which of the following statements about enantiomers is true?
a) They are identical in all physical properties.
b) They are mirror images of each other and cannot be superimposed.
c) They have identical boiling points and melting points.
d) They have different chemical reactivities with achiral reagents.
Answer: b) They are mirror images of each other and cannot be superimposed.
2. What is the maximum number of stereoisomers possible for a molecule with
3 chiral centers?
a) 4
b) 6
c) 8
d) 16
Answer: d) 16
3. Which of the following molecules is achiral?
a) 2,3-Butanediol
, b) 2-Butene
c) 3-Chloropentane
d) Lactic acid
Answer: b) 2-Butene
4. How do you denote the configuration of a molecule with a double bond in
the E/Z system?
a) By using R/S notation
b) By comparing the priority of groups on each carbon of the double bond
c) By identifying the mirror image relationship
d) By analyzing the molecular weight
Answer: b) By comparing the priority of groups on each carbon of the double
bond
5. Which of the following best describes a meso compound?
a) A compound with no chiral centers
b) A compound with multiple chiral centers but is superimposable on its mirror
image
c) A compound that rotates plane-polarized light to the right
d) A compound with only one chiral center
Answer: b) A compound with multiple chiral centers but is superimposable on
its mirror image
Section 2: Short Answer Questions (30 points)
1. Define chirality and give an example of a chiral molecule.
Answer: Chirality refers to the property of a molecule that makes it non-
superimposable on its mirror image, like a pair of human hands. A common
example of a chiral molecule is 2-butanol, where the central carbon atom is
bonded to four different groups.
2. Explain the difference between enantiomers and diastereomers with
examples.
Answer: Enantiomers are a type of stereoisomer that are non-superimposable
mirror images of each other, such as (R)- and (S)-lactic acid. Diastereomers are
stereoisomers that are not mirror images of each other and differ in
configuration at one or more chiral centers, such as (2S,3S)- and (2S,3R)-butane-
2,3-diol.
