Elm 7 Drug Structures

Question 1

Q: What are stereoisomers?

Answer 1

A: Molecules that have the same sequence of atoms but differ in the 3D arrangement of bonds at one or more atoms.

Question 2

Q: What is a stereogenic center?

Answer 2

A: An atom that gives rise to stereoisomerism.

Question 3

Q: Define conformational isomerism.

Answer 3

A: A type of isomerism where stereoisomers can be interconverted solely by the rotation of bonds.

Question 4

Q: What is configurational isomerism?

Answer 4

A: Isomerism where stereoisomers cannot be interconverted by rotation of bonds, including optical isomerism and cis/trans isomerism.

Question 5

Q: Define enantiomers.

Answer 5

A: Also known as optical isomers, they are pairs of compounds that are mirror images of each other and rotate polarized light in opposite directions.

Question 6

Q: What is cis/trans isomerism?

Answer 6

A: Stereoisomerism where isomers differ in how groups are oriented either side of a double bond.

Question 7

Q: What does chiral mean?

Answer 7

A: Describes a molecule that cannot be superimposed on its mirror image.

Question 8

Q: What is a chiral center?

Answer 8

A: An atom, usually a carbon, that has four different groups attached to it, giving rise to chirality.

Question 9

Q: What is the Cahn-Ingold-Prelog (CIP) system?

Answer 9

A: A method for classifying the configuration of atoms at a chiral center, designating enantiomers as R or S.

Question 10

Q: What does the D/L system classify?

Answer 10

A: Stereoisomers of molecules based on their relationship to glyceraldehyde, mainly applicable to sugars and amino acids.

Question 11

Q: How does the +/- system classify enantiomers?

Answer 11

A: Based on the direction an optical isomer rotates polarized light: (+) clockwise and (-) counterclockwise.

Question 12

Q: Define diastereomers.

Answer 12

A: Stereoisomers that contain chiral centers but are not mirror images of each other.

Question 13

Q: What are optical isomers (enantiomers)?

Answer 13

A: Compounds that are non-superimposable mirror images of each other and rotate polarized light in opposite directions.

Question 14

Q: What does achirality mean?

Answer 14

A: Refers to molecules that do not have a chiral center, such as glycine.

Question 15

Q: What are conformational isomers?

Answer 15

A: Molecules that exist in different forms due to the rotation of bonds.

Question 16

Q: What are cis-trans isomers also known as?

Answer 16

A: Geometric isomers or E/Z isomers.

Question 17

Q: What is the significance of enantiomers in drug binding?

Answer 17

A: Optically active drugs will have one enantiomer that binds to the target tighter due to better fit with the receptor’s binding sites.

Question 18

Q: What is the concept of three-point binding?

Answer 18

A: It refers to the need for three points on a receptor to be blocked by three substituents of a molecule for maximum binding affinity. One isomer fits well, while the other does not.

Question 19

Q: What are the three systems for classifying enantiomeric pairs?

Answer 19

A: The +/-, D/L, and R/S (Cahn-Ingold-Prelog) systems.

Question 20

Q: How does the +/- system classify enantiomers?

Answer 20

A: Based on optical activity: (+) enantiomers rotate polarized light clockwise and (-) enantiomers rotate it counterclockwise.

Question 21

Q: What is the D/L system based on?

Answer 21

A: The relationship to glyceraldehyde, with D-enantiomers related to (+)-glyceraldehyde and L-enantiomers related to (-)-glyceraldehyde.

Question 22

Q: Why is the D/L system mainly used for sugars and amino acids?

Answer 22

A: It relies on an obvious structural relationship to glyceraldehyde, which is most applicable to these groups.

Question 23

Q: How does the Cahn-Ingold-Prelog (CIP) system classify enantiomers?

Answer 23

A: Enantiomers are classified as R (rectus) or S (sinister) based on the priority of substituents around a chiral center.

Question 24

Q: What is a chiral center?

Answer 24

A: An atom, usually carbon, with four different groups attached to it, leading to chirality.

Question 25

Q: What is the first step in the CIP system?

Answer 25

A: Identify the chiral center.

Question 26

Q: How do you prioritize substituents in the CIP system?

Answer 26

A: Based on atomic number, with higher atomic numbers given higher priority. Double/triple bonds are treated as multiple single bonds.

Question 27

Q: What should you do if two substituents have the same atomic number in the CIP system?

Answer 27

A: Look at the atoms bonded to them to determine priority.

Question 28

Q: What is the third step in the CIP system?

Answer 28

A: Rotate the molecule so the lowest priority group faces away (into the page).

Question 29

Q: How do you determine if an enantiomer is R or S in the CIP system?

Answer 29

A: If the order of substituents from highest to lowest priority goes clockwise, it is R. If it goes counterclockwise, it is S.

Question 30

Q: Give an example of a drug where only one enantiomer is effective.

Answer 30

A: Citalopram, where only (S)-citalopram is effective as an antidepressant.

Question 31

Q: What is the importance of enantiomer classification in pharmaceuticals?

Answer 31

A: The different enantiomers of a drug can have vastly different effects, with one often being more effective or having fewer side effects than the other.