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100
What is a stereocenter (chiral center)?
An sp3 hybridized carbon attached to four different substituents.
100
What is R configuration
When the 4th priority substituent attached to a chiral carbon is behind the plane of the paper, and the other 3 substituents are arranged clockwise in regards to priority.
100
What is S configuration
When the 4th priority substituent attached to a chiral carbon is behind the plane of the paper, and the other 3 substituents are arranged counter-clockwise in regards to priority.
100
How many potential stereoisomers exist for a compound that has 3 stereocenters?
2^n = 2^3 = 8 stereoisomers
100
What is the difference between configuration and conformation?
Configuration: bonds between two atoms, unchanged unless at least one bond at the stereocenter is broken. Conformation: changes continuously at room temperature as a result of rotation about single bonds and flipping of rings in molecules.
200
What are enantiomers?
A pair of the same chiral compound, but with opposite R/S configurations. Creates a mirror image.
200
What are diastereomers?
A pair of the same chiral compound with at least 2 chiral centers, with a different R/S configuration, but not exactly the opposite configuration.
200
What are meso compounds?
A pair of the same chiral compound with at least 2 chiral centers, and opposite R/S configuration, but they are identical compounds.
200
Can a compound have stereocenters, but be achiral?
Yes, if it has an internal plane of symmetry. Includes meso compounds, but does not have to be meso.
200
List three rules assigning priorities to atoms bound to the stereocenter in order of importances.
1. Higher atomic number receives higher priority 2. Higher atomic mass takes priority 3. In case of ties, the next atom in the chain is used as a tiebreaker
300
What is inversion of stereochemistry?
This happens to the stereochemistry during an SN2 reaction.
300
What is a racemic mixture, and what is it's optical rotation?
A racemic mixture is an equimolar pair of enantiomers, has an optical rotation of zero.
300
What do enantiomers have in common and how do they differ?
Same: Boiling point, melting point, solubility, index of refraction Different: when they interact with other chiral substances, and when they interact plane polarized light (optical rotation)
300
What is an enantiomerically pure sample?
A sample of pure chiral compound uncontaminated by its enantiomer (enantiomeric excess of 100%).
300
What is the stereochemistry of the SN1 reaction products?
Racemization, caused by frontside and backside happening in equal amounts.
400
What is the stereochemistry required for an E2 reaction to occur?
The beta hydrogen and the leaving group must be in the same plane (anti periplanar).
400
In what conformation can the beta-hydrogen and the leaving group can be assumed to be anti periplanar in a cyclohexane ring?
When both are axial (trans-diaxial)
400
How does an elimination reaction at a stereocenter effect the stereochemistry?
Elimination reaction creates a carbon-carbon double bond (sp2 hybridization) and eliminates stereochemistry at the chiral center.
400
What is the stereoselective product created by the E1 reactions?
E1 reactions only produce trans products
400
What is the difference between alpha and beta hydrogens?
Alpha hydrogens are attached to the same carbon as the leaving group. Beta hydrogens are attached to the carbon one away from the carbon attached to leaving group.
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