38 Questions
When naming compounds containing multiple chiral atoms, what is the correct way to specify the configuration?
Give the configuration around each chiral atom in numerical order, separated by commas, all in parentheses at the start.
What is the correct configuration for the compound 2-bromo-3-chlorobutane?
(2S, 3S)-2-bromo-3-chlorobutane
What do the terms 'Z' and 'E' represent in geometric isomers?
Together and opposite in German
How do you determine the configuration of geometric isomers?
By looking at the highest priority group on both sides of the double bond
What is the correct notation for specifying the configuration of multiple chiral atoms?
(number, configuration) format
What is the purpose of specifying the configuration of chiral atoms in a compound?
To differentiate between isomers
What is stereochemistry?
The study of 3-dimensional properties and reactions of molecules
What are isomers?
Compounds with identical molecular formulas but different structural formulas
What are stereoisomers?
Compounds with the same connectivity, but different arrangement in space
What is optical isomerism?
A form of stereoisomerism in which molecules differ only in the spatial orientation of atoms
What is a chiral carbon atom?
A carbon with four different bonded groups
What is an enantiomer?
A type of stereoisomer that is a non-superimposable mirror image
When does a carbon atom become superimposable on its mirror image?
When it has two or more identical groups
How many chiral carbon atoms are in 2,4-dimethyl hexane?
2
What is the description of light that is vibrating in all possible planes?
Unpolarized
What is the physical property of an optically active compound?
Specific rotation
What is the formula for determining the maximum number of optical isomers?
2n
What is the characteristic of diastereomers?
They differ in all physical properties
What is the definition of epimers?
Diastereomers that are different at only one chiral center
What is the description of light that is oscillating in only one plane?
Plane polarized
What is the difference between enantiomers and diastereomers?
Enantiomers have opposite configurations at all chiral centers, while diastereomers have opposite configurations at some chiral centers
What is the unit of measurement for the length of the sample tube in specific rotation?
Decimeters
What is the characteristic of a meso compound?
It has more than one chiral center and is superimposable on its mirror image
What is the condition for a compound to be optically active?
It must be chiral in its overall structure
What is unique about the two structures on the right in the figure of tartaric acid?
They are identical
What type of isomerism can cyclic compounds exhibit?
Both geometric and enantiomerism
What is the characteristic of a cyclic compound with two dissimilar chiral carbon atoms?
It has two possible enantiomeric pairs
What is the example of a cyclic compound that exhibits enantiomerism and geometric isomerism?
1-bromo-2-chlorocyclopropane
What is the characteristic of a meso compound in a cyclic structure?
It has a plane of symmetry
What is the relationship between the two 'cis' enantiomers and the two 'trans' enantiomers in a cyclic compound?
They are diastereomers
What is the ratio of potency in raising blood pressure between L-epinephrine and D-epinephrine?
20:1
Which of the following statements is true about carvone?
It is an enantiomer responsible for spearmint odor
What is the purpose of a polarimeter?
To measure the optical activity of a chiral sample
What is the unit of measurement for specific rotation?
Degrees
What is the relationship between the specific rotation of enantiomers?
They are equal in magnitude but opposite in sign
Which of the following factors does the degree of rotation depend on?
All of the above
What is the formula to calculate specific rotation?
[α]D = observed rotation / (pathlength x concentration)
What is the specific rotation of (-)-lactic acid?
-3.82
Study Notes
Optical Activity and Stereochemistry
- Light can be described as a wave vibrating perpendicular to its direction of propagation, and can be unpolarized or plane polarized.
- Specific rotation is a physical property of an optically active compound, calculated by dividing the observed rotation by the length of the sample tube and the concentration of the sample.
- Stereoisomers with two chiral carbon atoms can have enantiomers and diastereomers.
Diastereomers
- Diastereomers are stereoisomers that are not mirror images of each other.
- They differ in all physical properties and can have opposite configurations at some, but not all, chiral centers.
Meso Compounds
- Meso compounds have two or more chiral centers and are optically inactive due to internal compensation.
- They have a plane of symmetry and can have identical substitution on both chiral centers.
Optical Isomerism in Cyclic Compounds
- Cyclic compounds can exhibit enantiomerism and geometric isomerism.
- A cyclic compound with two dissimilar chiral carbon atoms can have two enantiomeric pairs.
Stereochemistry
- Stereochemistry refers to the 3-dimensional properties and reactions of molecules.
- Isomers are compounds with identical molecular formulas but different structural formulas.
Optical Isomerism
- Optical isomerism occurs when molecules differ only in the spatial orientation of atoms, not in their arrangement.
Chiral Carbon Atoms, Enantiomers, and Racemic Mixtures
- A carbon with four different bonded groups is called a chiral carbon atom, chirality center, or stereocenter.
- A chiral carbon atom can exist in either of two three-dimensional arrangements that are non-superimposable mirror images (enantiomers).
Measurement of Optical Activity
- Optical activity can be measured using a polarimeter, which operates on the principle of rotating plane-polarized light.
- Specific rotation is defined as the observed rotation of an optically active compound in a cell with a 10 cm path using light from sodium metal vapor (589 nm).
Specification of Configuration
- When naming compounds containing multiple chiral atoms, the configuration around each chiral atom must be specified in numerical order, separated by commas, all in parentheses at the start.
- For geometric isomers, the configuration is determined by the priority of the groups attached to the double bond, with the highest priority group on the same side being termed Z (zusammen) and on opposite sides being termed E (entgegen).
This quiz covers the basics of stereochemistry, including the properties and reactions of molecules, isomers, and stereoisomers.
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