Org 1 Review - Stereochemistry

fibodica's version from 2016-04-21 22:05

Section 1

Question Answer
The definition of enantiomers is ______? Enantiomers: non superimposable on their mirror images
What's the difference between enantiomers and diastereomers? enantiomers are stereoisomers that are mirror images of each other. Diastereomers are stereoisomers that are not enantiomers.
cis-2-butene and trans-2-butene are what type of isomers?stereoisomers (diastereomers to be more precise)
Complete the sentence: A molecule that has an internal _______ cannot have enantiomers. If it has an internal mirror plane (plane of symmetry) it can't have enantiomers.
A molecule with one chiral center has 2 possible stereoisomers. In theory, a molecule with two chiral centers could have 4 possible stereoisomers, a molecule with three chiral centers 8 possible stereoisomers and so on. Why is it that some molecules have less than the theoretical maximum? It could be less than the theoretical maximum due to meso compounds.
What do we call a 1:1 mixture of two enantiomers? racemic mixture
When two compounds are related to each other by a "switch" of the orientation of a hydrogen and another substituent they are called _______. epimers
True or false: a molecule can have chiral centers and yet not be a chiral molecule. Explain. Molecules can have chiral centers and not be a chiral molecule if they have an internal mirror plane - e.g. meso compounds.
True or false: a molecule that is (R) will always rotate polarized light to the right (clockwise). False - there is no consistent relationship between R/S and the direction in which they rotate polarized light
Which class of stereoisomers have the same physical properties (boiling point, melting point, solubility)?enantiomers

Section 2

Question Answer
Which class of stereoisomers have different physical properties (boiling point, melting point, solubility)?diastereomers
What would be the relationship between the following compounds: 1) (1R, 2S) 2-methyl-1-cyclopentanol) and (1R, 2R) 2-methyl-1-cyclopentanol 2) (1R, 2R) 2-methyl-1-cyclopentanol and (1S, 2S) 2-methyl-1-cyclopentanol 3) (1S, 2S) 2-methyl-1-cyclopentanol and (1R, 2S)-2-methyl-1-cyclopentanol (1R, 2S) and (1R, 2R) will be diastereomers (1R, 2R) and (1S, 2S) will be enantiomers (1S, 2S) and (1R, 2S) will be diastereomers.
True or false: If you interchange the position of any two atoms on a chiral center you will invert the chirality of that center. True
True or false: if you interchange the position of any three atoms on a chiral center, the chirality of that center will remain the same. True. In essence, this depicts a bond rotation.
1,2-dimethylcyclohexane has two chiral centers, but only has 3 different stereoisomers. Why is this?Because cis-1,2-dimethylcyclohexane is a meso compound
Without having to draw anything, what will be the enantiomer of (3S,4S)-3,4-dimethylheptane?Enantiomer will be (3R, 4R)
Without having to draw anything, name a diastereomer of (3S,4S)-3,4-dimethylheptane?Diastereomer will be (3R, 4S) OR (3S, 4R)
A (+)-enantiomer rotates polarized light in a ____ direction and a (-)-enantiomer rotates plane-polarized light in a ____direction.(+)-enantiomers rotate polarized light clockwise, (-)-enantiomers rotate plane-polarized light counterclockwise
True or false: enantiomers have dfferent melting and boiling points, and different solubilitiesFalse, they have identical melting/boiling points, and identical solubilities (in achiral solvents)
What's the difference between "absolute stereochemistry" and "relative stereochemistry". Absolute stereochemistry refers to (R) or (S). Relative stereochemistry employs terms such as "trans", "cis", "anti", "syn". So (1R,2R)-1,2-dimethylcyclohexane and (1S, 2S)-1,2-dimethylcyclohexane have different absolute stereochemistry but similar relative stereochemistry (the methyl groups are trans in both molecules).
True or false: a molecule with a mirror plane will never have an enantiomer and will not rotate plane polarized light. True!
How do you distinguish a chiral carbon from a non-chiral carbon? Chiral carbons have 4 different substituents


Org 1 Review - Thermodynamics
Org 1 Review - Free Radicals
Org 1 Review - Reactions of Alcohols
Org 1 Review - Alkynes
Org 1 Review - Substitution and Elimination
Org 1 Review - Reactions of Double Bonds
Org 1 Review - Stereochemistry
Org 1 Review - Conformations
Org 1 Review - Structure and Bonding