40 Questions
What is the system of naming enantiomers with the prefixes R or S called?
The Cahn-Ingold-Prelog system
How are priorities assigned to the atoms directly bonded to the stereogenic center?
In order of decreasing atomic number
What is the purpose of assigning priorities to the atoms bonded to the stereogenic center?
To distinguish between enantiomers
What is the lowest priority group in many molecules?
H
How are priorities assigned to two identical atoms bonded to the stereogenic center?
Based on the atomic number of the atoms bonded to these atoms
What is the purpose of the IUPAC name in the Cahn-Ingold-Prelog system?
To provide a base name for the enantiomer
What is the direction of the circle tracing to assign R to a stereogenic center?
Clockwise
How many stereoisomers are possible for a compound with two stereogenic centers?
4
What is the term used to describe a molecule with two stereogenic centers that may or may not be chiral?
Diastereomers
What is the formula to calculate the maximum number of stereoisomers for a compound with n stereogenic centers?
2^n
What is the result of tracing the circle in a counterclockwise direction when assigning R or S to a stereogenic center?
The isomer is named S
How many stereoisomers are possible for a compound with one stereogenic center?
2
What is the order of priority of groups in 2-butanol?
–OH (1), –CH2CH3 (2), –CH3 (3), and –H (4)
According to Rule 3, what is the order of priority among isotopes of hydrogen?
In order of decreasing mass number
How is a multiply bonded atom treated in assigning priority?
As an equivalent number of singly bonded atoms
What is the first step in assigning R or S to a stereogenic center?
Assigning priorities from 1 to 4 to each group
What is the purpose of rotating the remaining three groups in assigning R or S?
To place the lowest priority group in the down position
What is the Fischer projection used for in stereogenic centers?
To display enantiomers
What is the property of a meso compound?
It is optically inactive
What is the characteristic of a molecule with a plane of symmetry?
It cannot be optically active
What is the relationship between VII and VIII?
VII is superimposable on VIII
Why is VII not optically active?
It is a meso compound
What is the characteristic of a molecule with stereogenic centers?
It can be optically active or inactive
Why can we recognize a meso structure on sight?
Because one half of the molecule is the mirror image of the other half
What is the relationship between structures I and II?
They are diastereomers
What is the characteristic of structure III compared to I and II?
It is not superimposable on either I or II
What is the relationship between structures III and IV?
They are enantiomers
What is the characteristic of compound IV?
It is a diastereomer of both I and II
How many stereoisomeric forms does 2,3-dichlorobutane exist in?
Four
What is the result of finding the mirror image of structure III?
It is not superimposable on III
A molecule with stereogenic centers is always chiral.
False
A meso compound can exist in two enantiomeric forms.
False
A molecule with a plane of symmetry is always optically active.
False
VII and VIII are enantiomers of each other.
False
A molecule with stereogenic centers is always optically active.
False
A meso compound has a plane of symmetry.
True
VII is a chiral molecule.
False
A molecule with a plane of symmetry is always chiral.
False
VIII is a diastereomer of VII.
False
A molecule with stereogenic centers can exist in multiple stereoisomers.
True
Learn how to identify and label stereogenic centers with R or S notation, and understand the Cahn-Ingold-Prelog system for naming enantiomers. This quiz covers the prioritization of groups bonded to the stereogenic center and how to assign R or S prefixes. Test your knowledge of organic chemistry and stereoisomerism!
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