Question 1

Which of the following statements best describes constitutional isomers?

Accepted Answer

They have the same molecular formula but different connectivity of atoms.

Question 2

Which type of isomerism is responsible for the difference between cis- and trans-2-butene?

Accepted Answer

Geometric (cis-trans) isomerism due to restricted rotation around a double bond

Question 3

Which of the following compounds cannot exhibit cis-trans isomerism?

Accepted Answer

1,1-dichloroethene

Question 4

What is the maximum number of stereoisomers possible for a molecule with $$n$$ chiral centers?

Accepted Answer

$$2^n$$

Question 5

Which of the following statements about enantiomers is TRUE?

Accepted Answer

Enantiomers have identical physical and chemical properties in achiral environments.

Question 6

A chiral center is defined as:

Accepted Answer

An atom attached to four different groups.

Question 7

Which of the following molecules is achiral?

Accepted Answer

1,2-dichlorocyclohexane (cis isomer)

Question 8

Which of the following best describes a meso compound?

Accepted Answer

A compound with a plane of symmetry and is optically inactive despite having chiral centers.

Question 9

Which of the following is TRUE regarding the E/Z system of nomenclature for alkenes?

Accepted Answer

The Z isomer has the higher priority groups on the same side of the double bond.

Question 10

A sample of (S)-2-bromobutane has an observed specific rotation of $$+9.2^	ext{o}$$, while the pure enantiomer has a specific rotation of $$+23.1^	ext{o}. $$What is the enantiomeric excess of the sample?

Accepted Answer

$$40\%$$

Question 11

Which of the following statements about diastereomers is correct?

Accepted Answer

Diastereomers are stereoisomers that are not enantiomers.

Question 12

Which of the following is a consequence of amine inversion?

Accepted Answer

Amines with a lone pair cannot be separated into enantiomers due to rapid inversion.

Question 13

Which of the following is NOT a method for separating enantiomers?

Accepted Answer

Distillation based on boiling point differences

Question 14

Which of the following statements about optical activity is TRUE?

Accepted Answer

A chiral compound rotates plane-polarized light.

Question 15

Which of the following is a real-world example of enantiomers having different physiological effects?

Accepted Answer

Methamphetamine in Vicks Vapor Inhaler vs. illicit methamphetamine

Question 16

Which of the following statements is TRUE regarding the relationship between chiral centers and optical activity?

Accepted Answer

Compounds with a plane of symmetry and chiral centers (meso compounds) are optically inactive.

Question 17

Which of the following best describes a stereocenter?

Accepted Answer

An atom at which the interchange of two groups produces a stereoisomer.

Question 18

Which of the following is TRUE about the physical properties of cis and trans isomers?

Accepted Answer

Cis and trans isomers have different physical properties due to their spatial arrangement.

Question 19

Which of the following is the correct formula for calculating enantiomeric excess ($$ee$$)?

Accepted Answer

$$ee = \frac{	ext{observed specific rotation}}{	ext{specific rotation of pure enantiomer}} 	imes 100\%$$

Isomers: The Arrangement of Atoms in Space (Organic Chemistry Chapter 4 Study Notes)

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