Chapter 25 (Nomenclature) Flashcards
Define Structural Isomerism
Same molecular formula but different structure (atoms arranges differently along molecule).
What are the three types of structural isomerism?
Chain, Positional, Functional Group
Define Functional Group Isomerism
Compounds with the same molecula formula but atoms arranged to give different functional groups so in different homologous series.
Define Chain Isomerism
Alkyl groups move along carbon chain.
Define Positional Isomerism
Functional group moves along the chain so different number for functional group
e.g. in primary and secondary alcohols propane-1-ol propan-2-ol
Define Stereoisomerism
Compounds have the same molecular and structural formula but atoms have a different arrangement in space.
What are the two types of stereoisomerism?
Geometric and Optical
Why are geometric isomers created?
Restricted rotation about a C=C bond and two components around the bond are different.
Why do E-Z isomers have different properties?
E isomers can pack more tightly together so have higher melting points.
Define a chiral carbon?
4 different groups attached to a carbon so it is asymmetrical.
Define Optical Isomerism
When chiral carbons which have the same molecular and structural formula have non-superimposable mirror images.
What shape does a chiral carbon have?
Tetrahedral (109.5º)
What are 3D non-superimposable mirror images called?
Enantiomers
What are the two differences between enantiomers?
- They interact differently with plane polarised light by rotating it in opposite directions but by the same amount. This is know as being optically active.
- They react differently with other asymmetrical molecules such as enzymes and proteins.
Define Optically Active
When enantiomers rotate plane polarised light in the opposite direction by the same amount.
