Isomers

Question 1

Structural isomers

Answer 1

Have the same molecular formula but are connected differently

Question 2

Stereoisomers

Answer 2

Have the same connectivity and formula, but differ in their spatial arrangement

Two subgroups: Conformational and configurational isomers
Diastereomers and enantiomers

Question 3

Conformational vs. configurational isomers

Answer 3

Both are stereoisomers

Conformational isomers differ in rotation around single bonds

Configurational isomers can only change by breaking and remaking bonds

Question 4

Diastereomers vs. Enantiomers

Answer 4

Both are stereoisomers

Diastereomers are non-mirror image
-occur when there are differences at some, but not all, chiral centers
-Have different chemical propertires
-The optical activity of one diastereomer doesn’t say anything about the optical activity of another
-Include cis-trans isomers

Enantiomers are non-superimposable mirror images
-have the same physical and chemical properties
-Can make racemic mixtures, so knowing the optical activity of one enantiomer can tell you the optical activity of the other

Question 5

Meso compounds

Answer 5

Have a plane of symmetry, so they don’t rotate light regardless of whether or not they have chiral centers

Question 6

Relative vs. Absolute configurations

Answer 6

Relative configuration is in regards to another chiral molecule

Absolutely configuration is the exact spatial arrangement of the molecule (R&S)

Question 7

What is the equation for determining the number of stereoisomers a compound has?

Answer 7

2^n where n is the number of chiral centers

Question 8

Geometric isomers

Answer 8

Also known as configurational isomers

Differ in their orientation around a bond, ring, or other rigid structure

Ex: cis and trans (they have the same formula and connectivity, but they differ in the actual arrangement of the molecules around that same bond)