Organic Chapter 5
If (S)-glyceraldehyde has a specific rotation of -8.7°, what is the specific rotation of (R)-glyceraldehyde?
+8.7°
Optical Activity Trans
1,2 Optically Active 1,3 Optically Active 1,4 Optically Inactive
Optical Activity Cis
1,2 Optically Inactive 1,3 Optically Inactive 1,4 Optically Inactive
Which of the following terms best describes the pair of compounds shown: enantiomers, diastereomers, or the same compound?
enantiomers (tilt the one on the left down, shows mirror image)
Meso
has chiral carbons but is optically inactive
For each compound, determine whether the molecule has an internal mirror plane of symmetry. If the molecule does not have an internal mirror plane, determine whether the structure is chiral.
trans-1,2-dibromocyclobutane -No plane of symmetry -chiral
What are the absolute configurations of the indicated stereoisomer of 2-bromo-3-methylpentane?
(2R,3R)
Is this molecule chiral?
(2R,3S)-2,3-dibromobutane -meso -not optically active
Is this molecule chiral?
(2R,3S)-2-bromo-3-chlorobutane -chiral
Is this molecule chiral?
(R,R)-2,3-dibromobutane -chiral
Is this molecule chiral?
(±)-2,3-dibromo-2,3-dichlorobutane -not optically active
For each compound, determine whether the molecule has an internal mirror plane of symmetry. If the molecule does not have an internal mirror plane, determine whether the structure is chiral.
- Has a plane of symmetry
For each compound, determine whether the molecule has an internal mirror plane of symmetry. If the molecule does not have an internal mirror plane, determine whether the structure is chiral.
- No plane of symmetry. -chiral
(-)-Lactic acid has a specific rotation of -3.8°. What is the specific rotation of a solution containing 7.5 g of (-)-lactic acid and 2.5 g of (+)-lactic acid?
-1.9°
For each compound, determine whether the molecule has an internal mirror plane of symmetry. If the molecule does not have an internal mirror plane, determine whether the structure is chiral.
-Has a plane of symmetry.
Determine if there are any asymmetric carbon atoms. Then make the mirror image for each structure, and state whether they are a pair of enantiomers or just the same molecule.
-Has an asymmetric carbon -Mirror image is an enantiomer.
Determine if there are any asymmetric carbon atoms. Then make the mirror image for each structure, and state whether they are a pair of enantiomers or just the same molecule.
-Has an asymmetric carbon. -Mirror image is an enantiomer.
Determine if there are any asymmetric carbon atoms. Then make the mirror image for each structure, and state whether they are a pair of enantiomers or just the same molecule.
-No asymmetric carbons. -Mirror image is the same molecule
For each compound, determine whether the molecule has an internal mirror plane of symmetry. If the molecule does not have an internal mirror plane, determine whether the structure is chiral.
-No plane of symmetry. - chiral
For each compound, determine whether the molecule has an internal mirror plane of symmetry. If the molecule does not have an internal mirror plane, determine whether the structure is chiral.
1,2-dichloropropane -No plane of symmetry. -chiral
Determine if there are any asymmetric carbon atoms. Then make the mirror image for each structure, and state whether they are a pair of enantiomers or just the same molecule.
1-bromo-2-methylbutane -Has an asymmetric carbon. -Mirror image is an enantiomer.
Label each asymmetric carbon in the molecule below as having the R or S configuration.
2, S 3, S
Label each asymmetric carbon in the compound below as R or S.
2, S 4, R
How many asymmetric carbons are present in the compound below?
5
R Configuration
Clockwise
Same? Enantiomers? Diastereomers? Constitutional Isomers?
Constitutional Isomers
Optically Inactive
Contains a plane of symmetry
S Configuration
Counter-Clockwise
Same? Enantiomers? Diastereomers? Constitutional Isomers?
Diastereomers
Same? Enantiomers? Diastereomers? Constitutional Isomers?
Enantiomers
Same? Enantiomers? Diastereomers? Constitutional Isomers?
Enantiomers (Flip)
Classify the following pair of molecules as enantiomers or diastereomers.
Enantiomers: I and IV II and III Diastereomers: I and III III and IV II and IV I and II
Optically Active (Chiral)
No plane of symmetry
Is the molecule optically active?
Optically Active
Is the molecule optically active?
Optically Active (Cl opposite)
Is the molecule optically active?
Optically Active (trans, one Br up other Br down)
Is the molecule optically active?
Optically Inactive
Is the molecule optically active?
Optically Inactive (Cl both facing forward)
Is the molecule optically active?
Optically Inactive (cis, both Br up)
Is the molecule optically active?
Optically active
Assign the proper configurational label, R or S, to the chiral carbon in the molecule shown below.
S
Same? Enantiomers? Diastereomers? Constitutional Isomers?
Same
Draw all stereoisomers of 1-bromo-4-chlorocyclohexane.
This compound has a plane of symmetry so it's not chiral. It has only two geometrical isomers.
Draw all stereoisomers of 1-bromo-2-chlorocyclohexane.
This compound has two stereocenters, and there are 22 = 4 stereoisomers.
Draw all stereoisomers of 2,3,4-trihydroxybutanal
This compound has two stereocenters, and there are 22 = 4 stereoisomers.
Draw all stereoisomers of 2-bromo-4-chloropentane.
This compound has two stereocenters, and there are 22 = 4 stereoisomers.
Predict the specific rotation of the compound shown.
Zero; the compound is achiral.
Is the molecule shown below chiral or achiral?
achiral
Is the molecule shown below chiral or achiral?
chiral
Is this molecule chiral?
chiral
Determine if there are any asymmetric carbon atoms. Then make the mirror image for each structure, and state whether they are a pair of enantiomers or just the same molecule.
chlorocyclohexane -No asymmetric carbons. -Mirror image is the same molecule.
For each compound, determine whether the molecule has an internal mirror plane of symmetry. If the molecule does not have an internal mirror plane, determine whether the structure is chiral.
cis-1,2-dibromocyclobutane -Has a plane of symmetry.
Determine if there are any asymmetric carbon atoms. Then make the mirror image for each structure, and state whether they are a pair of enantiomers or just the same molecule.
cis-1,2-dichlorocyclobutane -Has an asymmetric carbon. -Mirror image is the same molecule.
Add either an H or OH group to complete the Fischer projection for D-fructose.
consider ther R or S to decide which side the OH goes on
What term describes the structural relationship between (2R,3R,4S)-2,3,4-trichloroheptane and (2S,3S,5R)-2,3,5-trichloroheptane?
constitutional isomers (the 5 and 4)
What could be theoretically separated by distillation or recrystallization.
diastereomers
Which of the following terms best describes the stereochemical relationship of the two compounds shown below in Fischer notation?
diastereomers
Is this molecule chiral?
meso not optically active
Is this molecule chiral?
meso-2,3-dibromo-2,3-dichlorobutane -not optically active -meso
For each compound, determine whether the molecule has an internal mirror plane of symmetry. If the molecule does not have an internal mirror plane, determine whether the structure is chiral.
methane -Has a plane of symmetry.
Is this molecule chiral?
not optically active meso
Choose the term that best describes the relationship between the two structures.
resonance structures (The only difference is in the location of π bonds.)
Choose the term that best describes the relationship between the two structures.
same (flip the molecule around)
Choose the term that best describes the relationship between the two structures.
skeletal isomers
Is the mirror image of the following molecule an enantiomer or is it superimposable with it?
superimposable
Which of the following terms best describes the pair of compounds shown: enantiomers, diastereomers, or the same compound?
the same compound
