Q: A sample of (S)-2-bromobutane has a specific rotation of $$+23.1. If a $$mixture of 2-bromobutane has an observed specific rotation of $$+9.2$$, what is the enantiomeric excess (ee) of the mixture?

$$ee = \frac{+9.2}{+23.1} \times 100\% = 40\%$$

Question 1

Which of the following statements best describes constitutional isomers?

Accepted Answer

They have the same molecular formula but differ in the way atoms are connected.

Question 2

Which of the following pairs are constitutional isomers?

Accepted Answer

C$$_2H$_5OH$ and CH_3$$OCH_3$

Question 3

Which type of isomerism is NOT possible for 2,3-dimethyl-2-butene?

Accepted Answer

cis-trans (geometric) isomerism

Question 4

A compound has the molecular formula C$$_4H$_{10}O. $$Which of the following pairs are constitutional isomers?

Accepted Answer

1-butanol and 2-butanol

Question 5

Which of the following statements about chiral molecules is correct?

Accepted Answer

A chiral molecule has a nonsuperimposable mirror image.

Question 6

Which of the following compounds is achiral?

Accepted Answer

meso-tartaric acid

Question 7

How many stereoisomers are possible for a compound with two chiral centers and no plane of symmetry?

Accepted Answer

$$2^2 = 4$

Question 8

Which of the following best describes a meso compound?

Accepted Answer

A compound with chiral centers that is achiral due to a plane of symmetry.

Question 9

Which of the following statements about enantiomers is FALSE?

Accepted Answer

Enantiomers can be separated by standard distillation.

Question 10

A sample of (S)-2-bromobutane has a specific rotation of $$+23.1. If a $$mixture of 2-bromobutane has an observed specific rotation of $$+9.2$$, what is the enantiomeric excess (ee) of the mixture?

Accepted Answer

$$ee = \frac{+9.2}{+23.1} 	imes 100\% = 40\%$$

Question 11

Which of the following is true regarding the E/Z system of nomenclature?

Accepted Answer

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

Question 12

Which of the following statements about diastereomers is correct?

Accepted Answer

Diastereomers are stereoisomers that are not mirror images.

Question 13

Which of the following best explains why a racemic mixture is optically inactive?

Accepted Answer

The optical rotations of the two enantiomers cancel each other out.

Question 14

Which of the following is a correct statement about the relationship between (R)-2-butanol and (S)-2-butanol?

Accepted Answer

They are enantiomers.

Question 15

A compound has two chiral centers and a plane of symmetry. How many stereoisomers does it have?

Accepted Answer

3

Question 16

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

Accepted Answer

Simple distillation

Question 17

Which of the following statements about the physiological properties of enantiomers is correct?

Accepted Answer

Enantiomers can have very different physiological effects in biological systems.

Question 18

Which of the following is true about a chiral center?

Accepted Answer

It is an atom attached to four different groups.

Question 19

Which of the following best describes the difference between conformational and configurational isomers?

Accepted Answer

Conformational isomers cannot be separated, while configurational isomers can be separated.

Question 20

Which of the following statements about the optical activity of meso compounds is correct?

Accepted Answer

Meso compounds are optically inactive due to an internal plane of symmetry.

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

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