Question 1

Two enantiomers typically have the same biological activity.

Accepted Answer

Enantiomers are mirror images of each other and, therefore, have the same physical and chemical properties, except for their interaction with plane-polarized light. However, they can have different biological activities because they can interact differently with chiral molecules in the body, such as enzymes, receptors, and transporters. This phenomenon is known as enantiomeric or optical isomerism, and it is important in pharmacology and drug design because one enantiomer can be beneficial while the other can be harmful or ineffective.

Question 2

The compound 3, 6-diethyl-6-methyl-3-decanethiol is a chiral molecule with more than one chirality center.

Accepted Answer

The compound name given is contradictory and incorrectly structured, making it impossible to accurately determine its chirality or the number of chirality centers.

Question 3

Which statement concerning stereochemistry is incorrect?

Accepted Answer

Enantiomers are non-superimposable mirror image isomers, not superimposable mirror image isomers.

Question 4

Any molecule with one chirality center is a chiral compound.

Accepted Answer

A chiral center is an atom in a molecule that is attached to four different groups. If a molecule contains one chiral center, it means that there are two possible mirror image structures that cannot be superimposed on each other, making the molecule chiral.

Question 5

Hexane (CH₃CH₂CH₂CH₂CH₂CH₃)has a mirror image, but it does not have an enantiomer.

Accepted Answer

Hexane is a straight-chain alkane without any chiral centers, meaning it cannot have an enantiomer, which requires the presence of chirality for a molecule to have a non-superimposable mirror image.

Question 6

Recent rulings by the Food and Drug Administration have encouraged the development of so-called racemic switches, the patenting and marketing of a single enantiomer that was originally sold as a racemic mixture.

Accepted Answer

Recent rulings by the FDA have indeed encouraged the development of racemic switches, as reported by various news outlets such as Chemical & Engineering News and Science Daily.

Question 7

The specific rotation of pure cholesterol was measured to be -32. Based on this information, which statement concerning cholesterol is NOT true?

Accepted Answer

A substance with a specific rotation value of -32 is levorotatory, meaning it rotates plane polarized light in a counterclockwise direction. This indicates that cholesterol is a chiral compound, meaning it has a non-superimposable mirror image. However, if it is optically inactive, it means that it does not rotate plane polarized light, which is contradictory to the given information. Therefore, option B is the incorrect statement.

Question 8

cis-2-butene and trans-2-butene are enantiomers.

Accepted Answer

cis-2-butene and trans-2-butene are not enantiomers because they are not mirror images of each other. They are diastereomers, since they have different physical and chemical properties. Enantiomers have the same physical and chemical properties, except for the direction in which they rotate plane-polarized light.

Question 9

Another term in common use for a chirality center is an asymmetric carbon.

Accepted Answer

This statement is true. A chirality center is a carbon atom bonded to four different groups, resulting in non-superimposable mirror images. Another term commonly used for this is an asymmetric carbon.

Question 10

The Fischer projection shown on the right properly represents the three-dimensional compound shown on the left.

Accepted Answer

The Fischer projection accurately represents the stereochemistry of a compound.

Question 11

The molecule below is achiral.

Accepted Answer

The molecule does not have a chiral center and is therefore achiral.

Question 12

Enantiomers are mirror images that are not superimposable.

Accepted Answer

Enantiomers are stereoisomers that are non-superimposable mirror images of each other, meaning that they have the same chemical and physical properties but differ in their three-dimensional structure.

Question 13

The Fischer projection shown on the right properly represents the ball and stick model of the compound shown on the left.

Accepted Answer

The answer of The Fischer projection shown on the right...

Question 14

Any molecule with two chirality centers is an achiral compound.

Accepted Answer

A molecule with two chirality centers can have different arrangements of atoms around those centers, resulting in stereoisomers that are not superimposable on their mirror images. Therefore, a molecule with two chirality centers is chiral, not achiral.

Question 15

Propranol, shown below, is a chiral compound that exists as a pair of enantiomers. One enantiomer is used to treat irregular heartbeats, and the other enantiomer is used as a contraceptive. Identify the chirality center(s)in Propranol.

Accepted Answer

The answer of Propranol, shown below, is a chiral compound...

Question 16

A carbonyl carbon is a common example of a chirality center.

Accepted Answer

A carbonyl carbon is not a chirality center because it is double-bonded to an oxygen, leaving only three distinct groups attached, whereas a chirality center requires a carbon atom to be attached to four different groups.

Question 17

Which property of enantiomers is not identical?

Accepted Answer

Enantiomers have identical physical properties including melting point, boiling point, and solubility. However, they differ in their ability to rotate plane polarized light, known as their specific rotation.

Question 18

Propranol, shown below, is a chiral compound that exists as a pair of enantiomers. One enantiomer is used to treat irregular heartbeats, and the other enantiomer is used as a contraceptive. Identify the chirality center(s)in Propranol.

Accepted Answer

The answer of Propranol, shown below, is a chiral compound...

Question 19

Carbohydrates, lipids, proteins, and nucleic acids are all chiral biomolecules. What does the term chiral indicate about a molecule?

Accepted Answer

The term chiral indicates that the molecule has a mirror image, and that the molecule and its mirror image are not identical.

Question 20

The amino acid alanine found in the proteins of the body has a melting point of 297 °C and a specific rotation of +8.5. The enantiomer of alanine would have a melting point of -297 °C and a specific rotation of -8.5.

Accepted Answer

The statement is incorrect. The enantiomer of alanine would have the same melting point and specific rotation as the original alanine, but the direction of optical rotation (clockwise or counterclockwise) would be reversed.

Quiz 15: The Three-Dimensional Shape of Molecules

Two enantiomers typically have the same biological activity.

The compound 3, 6-diethyl-6-methyl-3-decanethiol is a chiral molecule with more than one chirality center.

Which statement concerning stereochemistry is incorrect?

Any molecule with one chirality center is a chiral compound.

Hexane (CH₃CH₂CH₂CH₂CH₂CH₃)has a mirror image, but it does not have an enantiomer.

Recent rulings by the Food and Drug Administration have encouraged the development of so-called racemic switches, the patenting and marketing of a single enantiomer that was originally sold as a racemic mixture.

The specific rotation of pure cholesterol was measured to be -32. Based on this information, which statement concerning cholesterol is NOT true?

cis-2-butene and trans-2-butene are enantiomers.

Another term in common use for a chirality center is an asymmetric carbon.

The Fischer projection shown on the right properly represents the three-dimensional compound shown on the left.

The molecule below is achiral.

Enantiomers are mirror images that are not superimposable.

The Fischer projection shown on the right properly represents the ball and stick model of the compound shown on the left.

Any molecule with two chirality centers is an achiral compound.

Propranol, shown below, is a chiral compound that exists as a pair of enantiomers. One enantiomer is used to treat irregular heartbeats, and the other enantiomer is used as a contraceptive. Identify the chirality center(s) in Propranol.

A carbonyl carbon is a common example of a chirality center.

Which property of enantiomers is not identical?

Propranol, shown below, is a chiral compound that exists as a pair of enantiomers. One enantiomer is used to treat irregular heartbeats, and the other enantiomer is used as a contraceptive. Identify the chirality center(s) in Propranol.

Carbohydrates, lipids, proteins, and nucleic acids are all chiral biomolecules. What does the term chiral indicate about a molecule?

The amino acid alanine found in the proteins of the body has a melting point of 297 °C and a specific rotation of +8.5. The enantiomer of alanine would have a melting point of -297 °C and a specific rotation of -8.5.

Quiz 15: The Three-Dimensional Shape of Molecules

Two enantiomers typically have the same biological activity.

The compound 3, 6-diethyl-6-methyl-3-decanethiol is a chiral molecule with more than one chirality center.

Which statement concerning stereochemistry is incorrect?

Any molecule with one chirality center is a chiral compound.

Hexane (CH3CH2CH2CH2CH2CH3)has a mirror image, but it does not have an enantiomer.

Recent rulings by the Food and Drug Administration have encouraged the development of so-called racemic switches, the patenting and marketing of a single enantiomer that was originally sold as a racemic mixture.

The specific rotation of pure cholesterol was measured to be -32. Based on this information, which statement concerning cholesterol is NOT true?

cis-2-butene and trans-2-butene are enantiomers.

Another term in common use for a chirality center is an asymmetric carbon.

The Fischer projection shown on the right properly represents the three-dimensional compound shown on the left.

The molecule below is achiral.

Enantiomers are mirror images that are not superimposable.

The Fischer projection shown on the right properly represents the ball and stick model of the compound shown on the left.

Any molecule with two chirality centers is an achiral compound.

Propranol, shown below, is a chiral compound that exists as a pair of enantiomers. One enantiomer is used to treat irregular heartbeats, and the other enantiomer is used as a contraceptive. Identify the chirality center(s) in Propranol.

A carbonyl carbon is a common example of a chirality center.

Which property of enantiomers is not identical?

Propranol, shown below, is a chiral compound that exists as a pair of enantiomers. One enantiomer is used to treat irregular heartbeats, and the other enantiomer is used as a contraceptive. Identify the chirality center(s) in Propranol.

Carbohydrates, lipids, proteins, and nucleic acids are all chiral biomolecules. What does the term chiral indicate about a molecule?

The amino acid alanine found in the proteins of the body has a melting point of 297 °C and a specific rotation of +8.5. The enantiomer of alanine would have a melting point of -297 °C and a specific rotation of -8.5.

Hexane (CH₃CH₂CH₂CH₂CH₂CH₃)has a mirror image, but it does not have an enantiomer.