Chemistry 3719 Chapter 7
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Is chloroethane chiral or achiral?
Achiral (neither C atom has 4 different groups attached)
How many stereoisomers of 2-bromo-3-chloropentane are possible?
4 (2 chiral centers; 2n
How are the compounds (1S,2R)-2-methylcyclohexanol and (1S,2S)-2-methylcyclohexanol related? Are they enantiomers or diastereomers?
What is a meso compound?
A molecule containing chiral centers but which is achiral due to an internal plane of symmetry
Name the following molecule, including stereocenters
How many stereoisomers of the following molecule are possible?
4 (there are only 2 chiral centers)
Define absolute configuration
The actual 3-dimensional arrangement of atoms about a chiral center
Why is sp3 N usually not chiral?
N undergoes the process of pyramidal inversion
Give the following molecule a complete IUPAC name (including stereocenters):
How many chiral centers does the following molecule possess?
Why are enantiomers difficult to separate?
They have the same physical properties, e.g. melting point, boiling point, and retention factor in chromatography
What is the optical rotation observed for (2R,3S)-butane-2,3-diol?
Rotation will be 0 since the molecule is meso (internal plane of symmetry)
If the specific optical rotation observed for (+)-2-butanol is +13.5o, what is the expected specific rotation of its enantiomer?
-13.5o since enantiomers have equal, but opposite, rotations
Is it possible to physically separate diastereomers?
Yes; the will have different physical properties such as boiling point and chromatographic retention factors
Label the stereocenters in the following molecule as having either the R
How many possible stereoisomers are there for a molecule with 4 stereocenters?
16 (2n = 24)
What is the expected optical rotation of trans-2-butene?
Zero; planar alkenes do not typically exhibit asymmetry
How many stereoisomers would epoxidation of trans-2-pentene produce?
addition leads to two of the possible 4 stereo isomers (stereochemistry of double bond is carried through since addition is concerted):
How many different stereiosomers are possible for 2,3-dibromobutane?
3; two of the expected 4 isomers will be meso
and therefore equivalent:
How many stereoisomers are possible for 2-bromo-3-methylbutane?
2; only one chiral center:
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