PHARM 201 – Final Questions and Verified Answers, 100% Guarantee
An object is chiral if: - - no plane of symmetry
- cannot be superimposed on its mirror image
- at least one asymmetric atom (ex. carbon)
A molecule is chiral if: - It contains chiral carbon centers.
chiral atoms need to attach to ___ different atoms - 4
A carbon atom with 3 different heteroatoms attached to it cannot be chiral because: -
When the mirror image is flipped 180 degrees, it ends up being the same molecule (can be
superimposed).
Apart from carbon, these other 3 asymmetric molecules can be chiral: - N, P, S
pro-chiral drug - a drug with non-chiral centers that can be transformed into chiral centers
(ex. by addition of atoms to molecule).
Carbons that contain double bonds are usually not: - chiral
(fewer than 4 groups, lone pair constantly switching)
Stereoisomers - Compounds possessing the same molecular formula, but differ only in the
configuration of at least 1 chiral center.
Two types of stereoisomers - 1. Enantiomers
2. Diastereomers
,Enantiomers - Two compounds that are non-superimposable mirror images of one
another.
Enantiomers must contain at least one chiral center as part of their structure.
(non-superimposable = more than 3 different groups = chiral)
In enantiomers, the stereocenters become: - flipped (ex. dashed line hydrogen instead of
solid line hydrogen)
The chemical and physical properties of enantiomers are: - identical.
Enantiomers differ solely in: - The direction in which they rotate plane polarized light.
+ isomer (dextrorotary) - The enantiomer that rotates plane polarized light clockwise (to
the right).
- isomer (laevorotary) - The enantiomer that rotates plane polarized light
counterclockwise (to the left).
(Both + and - isomers do not provide information about activity -> only direction of light.
Cannot determine + or - just by looking at structure.)
D/L configuration - Look at the highest numbered chiral carbon.
-OH on right = D-sugars, -OH on left = L-sugars.
Mainly used for amino acids and sugars.
There is no direct relationship between (+)(-) designation and either: - D/L designation or
R/S designation.
,A complete stereochemical designation requires both: - (+)(-), as well as D/L or R/S.
The atom with the lowest priority is rotated ____________ from the viewer. Most of the time,
this group will be: - away, hydrogen
S is (clockwise/counterclockwise), whereas R is (clockwise/counterclockwise). -
counterclockwise, clockwise
(based on priorities)
Atoms ordered, based on priorities: - I (highest atomic number)
Br
Cl
S
P
F
O
N
C
H (lowest atomic number)
What is the rule in assigning priorities with double bonds? - A double-bonded carbon will
take priority over a single bonded carbon. (double bonds are duplicated, meaning two carbons
count instead of one).
Triple bonds have an even stronger priority.
Swap rule - If the hydrogen is in the front instead of the back, assign priorities like you
normally would then switch the R with the S, or vice versa.
, Enantiomers differ in their abilities to bind to: - Protein receptors, DNA, enzymes,
transport proteins.
Ex. an S enantiomer could be more potent than the R enantiomer.
Unlike (+)/(-) configurations where it doesn't matter
Group 1 enantiomers - Have **identical potency and pharmacological action** at the
target binding site. VERY RARE!
Group 2 enantiomers - Enantiomers with similar activity, but different *potency*. Very
common. (potency as a result of ability to bind).
Group 3 enantiomers - Enantiomers that exert *different* pharmacological effects.
Somewhat common.
ex. one could cause desirable effect, while the other could cause toxic effects.
Group 4 enantiomers - One enantiomer is active, while the other enantiomer is inactive.
Somewhat uncommon.
A + or - designation indicates that the molecule can: - *rotate* polarized light.
If a molecule has the + designation, then its enantiomer must have the: - - designation.
Enantiomers are always opposite in the direction they rotate polarized light. However, both R
and S can be either + or - (as long as the enantiomer is opposite).
Diastereomers - Compounds with the same molecular formula, but differ in the
configuration of at least TWO chiral centers. One chiral center must remain the same, while the
other chiral center must have the opposite direction. (unlike enantiomers, where the opposite
chiral center is always different).
An object is chiral if: - - no plane of symmetry
- cannot be superimposed on its mirror image
- at least one asymmetric atom (ex. carbon)
A molecule is chiral if: - It contains chiral carbon centers.
chiral atoms need to attach to ___ different atoms - 4
A carbon atom with 3 different heteroatoms attached to it cannot be chiral because: -
When the mirror image is flipped 180 degrees, it ends up being the same molecule (can be
superimposed).
Apart from carbon, these other 3 asymmetric molecules can be chiral: - N, P, S
pro-chiral drug - a drug with non-chiral centers that can be transformed into chiral centers
(ex. by addition of atoms to molecule).
Carbons that contain double bonds are usually not: - chiral
(fewer than 4 groups, lone pair constantly switching)
Stereoisomers - Compounds possessing the same molecular formula, but differ only in the
configuration of at least 1 chiral center.
Two types of stereoisomers - 1. Enantiomers
2. Diastereomers
,Enantiomers - Two compounds that are non-superimposable mirror images of one
another.
Enantiomers must contain at least one chiral center as part of their structure.
(non-superimposable = more than 3 different groups = chiral)
In enantiomers, the stereocenters become: - flipped (ex. dashed line hydrogen instead of
solid line hydrogen)
The chemical and physical properties of enantiomers are: - identical.
Enantiomers differ solely in: - The direction in which they rotate plane polarized light.
+ isomer (dextrorotary) - The enantiomer that rotates plane polarized light clockwise (to
the right).
- isomer (laevorotary) - The enantiomer that rotates plane polarized light
counterclockwise (to the left).
(Both + and - isomers do not provide information about activity -> only direction of light.
Cannot determine + or - just by looking at structure.)
D/L configuration - Look at the highest numbered chiral carbon.
-OH on right = D-sugars, -OH on left = L-sugars.
Mainly used for amino acids and sugars.
There is no direct relationship between (+)(-) designation and either: - D/L designation or
R/S designation.
,A complete stereochemical designation requires both: - (+)(-), as well as D/L or R/S.
The atom with the lowest priority is rotated ____________ from the viewer. Most of the time,
this group will be: - away, hydrogen
S is (clockwise/counterclockwise), whereas R is (clockwise/counterclockwise). -
counterclockwise, clockwise
(based on priorities)
Atoms ordered, based on priorities: - I (highest atomic number)
Br
Cl
S
P
F
O
N
C
H (lowest atomic number)
What is the rule in assigning priorities with double bonds? - A double-bonded carbon will
take priority over a single bonded carbon. (double bonds are duplicated, meaning two carbons
count instead of one).
Triple bonds have an even stronger priority.
Swap rule - If the hydrogen is in the front instead of the back, assign priorities like you
normally would then switch the R with the S, or vice versa.
, Enantiomers differ in their abilities to bind to: - Protein receptors, DNA, enzymes,
transport proteins.
Ex. an S enantiomer could be more potent than the R enantiomer.
Unlike (+)/(-) configurations where it doesn't matter
Group 1 enantiomers - Have **identical potency and pharmacological action** at the
target binding site. VERY RARE!
Group 2 enantiomers - Enantiomers with similar activity, but different *potency*. Very
common. (potency as a result of ability to bind).
Group 3 enantiomers - Enantiomers that exert *different* pharmacological effects.
Somewhat common.
ex. one could cause desirable effect, while the other could cause toxic effects.
Group 4 enantiomers - One enantiomer is active, while the other enantiomer is inactive.
Somewhat uncommon.
A + or - designation indicates that the molecule can: - *rotate* polarized light.
If a molecule has the + designation, then its enantiomer must have the: - - designation.
Enantiomers are always opposite in the direction they rotate polarized light. However, both R
and S can be either + or - (as long as the enantiomer is opposite).
Diastereomers - Compounds with the same molecular formula, but differ in the
configuration of at least TWO chiral centers. One chiral center must remain the same, while the
other chiral center must have the opposite direction. (unlike enantiomers, where the opposite
chiral center is always different).
