Question 1

Which statements about stereoisomers are true? (Sec. 6.7, 6.8)
I. enantiomers and diastereomers have the same physical properties.
II. 50/50 mixtures of R and S enantiomers are called racemic mixtures.
III. meso isomers rotate the plane of plane polarized light.
IV. dextrorotatory compounds rotate plane polarized light to the right.

Accepted Answer

Statement II is true, stating that racemic mixtures are made up of a 50/50 mix of R and S enantiomers. Statement IV is also true, stating that dextrorotatory compounds (compounds that rotate plane polarized light to the right) are a type of stereoisomer. Statement I is false, as enantiomers and diastereomers have different physical properties (such as boiling point and specific rotation). Statement III is also false, as meso isomers do not rotate plane polarized light, despite being a type of stereoisomer.

Question 2

The specific rotation of dextrorotatory tartaric acid is +12.7 degrees. A mixture of dextrorotatory and levorotatory tartaric acid has a specific rotation of +6.35 degrees. What is the optical purity of the mixture?

Accepted Answer

The optical purity is calculated as the observed rotation divided by the rotation of the pure enantiomer, times 100. Here, +6.35 / +12.7 * 100 = 50%. This means the mixture is 50% optically pure, indicating an equal mixture of dextrorotatory and levorotatory forms.

Question 3

What is the relationship between these two structures?

Accepted Answer

The answer of What is the relationship between these two...

Question 4

What is the relationship between these two structures?
HINT: Build the molecular models and compare!

Accepted Answer

The answer of What is the relationship between these two...

Question 5

What is the relationship between these two structures?

Accepted Answer

The answer of What is the relationship between these two...

Question 6

What is the relationship between these two structures?

Accepted Answer

The answer of What is the relationship between these two...

Question 7

The priority order for the following groups are (highest = 1),

Accepted Answer

The answer of The priority order for the following groups...

Question 8

The priority order for the following groups is (highest = 1),

Accepted Answer

The answer of The priority order for the following groups...

Question 9

Which statement about enantiomers is false?

Accepted Answer

Enantiomers are mirror images of each other but cannot be superimposed, meaning they do not have the same three-dimensional orientation. This distinguishes them from being identical in spatial arrangement.

Question 10

Which are meso compounds?

Accepted Answer

Meso compounds are those that have chiral centers but are achiral as a whole. In the given structures, only I and III have chiral centers and exhibit internal symmetry, making them meso compounds. Therefore, the correct answer is option C) I and III.

Question 11

Which are meso compounds?

Accepted Answer

Compound II and III are meso compounds because they have a plane of symmetry that divides the molecule into two identical halves. Compound I is not a meso compound because it does not have a plane of symmetry. Compound IV is also not a meso compound because it does not have identical halves even though it has a plane of symmetry.

Question 12

How many stereoisomers are possible for Prilosec?

Accepted Answer

The answer of How many stereoisomers are possible for Prilosec?

...

Question 13

Which are meso compounds?

Accepted Answer

Meso compounds are stereoisomers that have an internal plane of symmetry, making them optically inactive even though they possess chiral centers. 
I and III have internal planes of symmetry, making them meso compounds. II and IV do not have internal planes of symmetry and therefore are not meso compounds.

Question 14

The structure of the S,S enantiomer of 2,3-butanediol is,

Accepted Answer

The answer of The structure of the S,S enantiomer of...

Question 15

Tuftsin (named after Tufts University) has important functions in the human immune system. It binds to stereospecific receptors at the surface of macrophages and leukocytes, stimulating their bactericidal and tumoricidal activity. All stereocenters in this molecule have S-configurations. How many stereoisomers of tuftsin exist, which do not have the correct stereochemistry for receptor-binding?

Accepted Answer

The answer of Tuftsin (named after Tufts University) has important...

Question 16

The following structure is the _____________ configuration.

Accepted Answer

The answer of The following structure is the _____________ configuration.
...

Question 17

How many pairs of enantiomers are possible for cholesterol?

Accepted Answer

The answer of How many pairs of enantiomers are possible...

Question 18

Which compound is a meso compound?

Accepted Answer

The answer of Which compound is a meso compound?

...

Question 19

The following structure is the _____________ configuration.

Accepted Answer

The answer of The following structure is the _____________ configuration.
...

Question 20

How many pairs of enantiomers are possible for cortisone acetate?

Accepted Answer

Cortisone acetate has 4 chiral centers, therefore it has 2^4 = 16 possible stereoisomers. However, since it is a racemic mixture of enantiomers, there are only half as many unique enantiomeric pairs, which is 16/2 = 8. Each pair consists of two enantiomers (mirror images), so the total number of enantiomers is 8 x 2 = 16.

Quiz 6: Chirality: the Handedness of Molecules

The specific rotation of dextrorotatory tartaric acid is +12.7 degrees. A mixture of dextrorotatory and levorotatory tartaric acid has a specific rotation of +6.35 degrees. What is the optical purity of the mixture?

What is the relationship between these two structures?

What is the relationship between these two structures? HINT: Build the molecular models and compare!

What is the relationship between these two structures?

What is the relationship between these two structures?

The priority order for the following groups are (highest = 1),

The priority order for the following groups is (highest = 1),

Which statement about enantiomers is false?

Which are meso compounds?

Which are meso compounds?

How many stereoisomers are possible for Prilosec?

Which are meso compounds?

The structure of the S,S enantiomer of 2,3-butanediol is,

The following structure is the _____________ configuration.

How many pairs of enantiomers are possible for cholesterol?

Which compound is a meso compound?

The following structure is the _____________ configuration.

How many pairs of enantiomers are possible for cortisone acetate?