Stereoisomerism and Chirality Flashcards
What is the study of molecules as three-dimensional objects?
Stereochemistry
Define:
Mirror Image
The reflection of an object in a mirror
Can your reflection be superposed (placed on top of) the original ‘you’ in such a way that every detail of the reflection corresponds exactly to the original?
No.
You and your reflection are different objects. You cannot exactly superpose one on the other
# Define: Chiral
Objects that are not superposable on their mirror image. (from the Greek, cheir, hand). An object that has “handedness”
Define:
achiral
When an object and its mirror image are superposable. It lacks chirality.
What is a plane of symmetry?
An imaginary plane passing through an object or a molecule dividing it such that one half is the reflection of the other half.
What is a center of symmetry?
A point so situated that identical components of the object or molecule are located equidistant and on opposite sides from the point along any axis passing through that point.
True of False:
Because it has a center of symmetry, cyclobutane is identical to its mirror image and is achiral.
True
An object that lacks both a center of symmetry and a plan of symmetry are ____?
- Achiral
- Chiral
Chiral
How are stereoisomers different than constitutional isomers?
Constitutional isomers have the same molecular formula but a different connectivity of atoms in their molecules.
Stereoisomers have the same molecular formula and the same connectivity but with different orientations of their atoms in space
define:
Stereoisomer
Stereoisomers have the same molecular formula and the same connectivity but with different orientations of their atoms in space
Define:
Configurational Isomers
Configurational Isomers are isomers that differ by the configuration of substituents on an atom
Are these molecules constitutional isomers or configurational isomers?
Configurational isomers
What is the most specific term to describe the central carbon in this molecule?
- enantiomer
- chiral center
- stereocenter
- diasteriomer
Chiral center
a tetrahedral atom, most commonly carbon, bonded to four different groups. It lacks the two key symmetry elements and is chiral.
What is the difference between chiral/achiral and enantiomer?
Chiral and achiral refer to objects, while the term enantiomer refers to the relationship between a pair of objects
This is the definition for what concept?
A carbon atom with four different groups bonded to it
Chiral center
which definition is more broad?
Chiral center or Stereocenter
Stereocenter
Define:
Stereocenter
A stereocenter is an atom about which exchange of two groups produces a stereoisomer
Define:
enantiomer
When isomers are chiral, are they enantiomers or diastereomers?
Enantiomers
Define:
diastereomers
How many different groups is the central carbon bonded to?
4
Cl, CH3, CH2CH3, and H
Are these enantiomers of each other?
Yes
What is the difference between configurational isomers and conformational isomers?
Configurational isomers require the breaking of bonds while conformational isomers occur through rotations along single bonds
Enantiomers or diastereomers?
Diastereomers, because they are not mirror images of each other
Enantiomers or Diastereomers?
Enantiomers. They are mirror images and not superposable
Does this molecule have a chiral center? Is the molecule chiral?
This molecule does not have a chiral center, but it is chiral. It is an atropisomer
Define atropisomer
Define absolute configuration
What is the R,S System?
What is the 1st priority rule in the R,S System of naming chiral centers?
What is the 2nd priority rule in the R,S System of naming chiral centers?
What is the 3rd priority rule in the R,S System of naming chiral centers?
What is the 4th priority rule in the R,S System of naming chiral centers?
Assign priorities to the groups
Assign priorities to the groups
How do you assign R or S configuration to a chiral center?
Is the chiral center R or S?
S
Is the chiral center R or S?
R
Is the chiral center R or S?
R
True or false
More double bonds lead to more possible stereoisomers
True
How many stereoisomers are possible in a molecule with 3 chiral centers?
- we use the rule of 2n = # of stereocenters
in this case, 23 = 8
What is the formula to determine stereocenters from the number of chiral centers?
2n
Name this molecule
2,3,4-Trihydroxybutanal
How many stereoisomers are possible for this molecule?
It contains 2 chiral centers. 22 = 4
this molecule can have 4 stereocenters
Name this molecule
3-chloro-2-butanol
How many stereoisomers are there in 2,3-Dihydroxybutanedioic acid (Tartaric acid)?
- One meso compound and one pair of enantiomers.
Define Meso compound
A mesa compound contains two or more chiral centers but is achiral. To be a meso compound, a molecule must also have chiral isomers
What are three examples of achiral solvent environments?
H2O, CH3CH2OH, CH2Cl2
Define Fischer projection
How can you quickly tell if there is an enantiomer of a molecule with only one chiral center?
How can you quickly tell if there is an enantiomer of a molecule with more than one chiral center?
How can you quickly recognize a diastereomer?
Define optically active
Define resolution
