Isomerism Flashcards
Learn everything about Isomerism
What are the main two types of Isomers?
Structural and Stereoisomers
What are the 3 types of structural isomers?
Positional, Functional Group, and Chain
What is structural isomerism?
When isomers have the same molecular formula, but a different structural formula
What is positional isomerism?
The functional group is attached to the main chain at different points.
What is functional group isomerism?
When the isomers have different functional groups
What is chain isomerism?
The hydrocarbon chain is arranged differently
What is stereoisomerism?
Isomers that have the same structural formula but different spatial arrangements
What are the 2 types of stereoisomers?
E-Z isomerism and optical isomerism
What is E-Z Isomerism?
It occurs when there is restricted rotation about the C=C double bond. Each carbon in the double bond must have two different groups attached
What is optical isomerism?
Occurs when a molecule has a chiral centre, so the carbon atom is asymmetric, leading to non-superimposable mirror images (enantiomers)
What are 2 properties of enantiomers?
They rotate plane polarised light in opposite directions.
They have identical physical and chemical properties except in chiral envionments
What is a chiral carbon?
A carbon bonded to four different groups
How do you differentiate between enantiomers?
Pass polarised light through two solutions of the same conc, each containing a different optical isomer of the same substance. One solution will rotate the light through a specific angle clockwise. This is the (+) isomer. The other will rotate the light by the same angle anticlockwise. This is the (-) isomer.
What is a racemate?
A mixture of equal amounts of two optical isomers of a chiral compound. It is optically inactive
What does optically inactive mean?
Compounds that lack the ability to rotate plane polarised light
What are 3 solutions when you have a racemate, but you only want one of the isomers, and what are the disadvantages if there are any?
Separate the two isomers - difficult and expensive, as optical isomers have similar properties
Sell mixture as a drug - This is wasteful as half of it is inactive
Design an alternative synthesis of the drug that makes on the required isomer
What are Cahn-Ingold-Prelog (CIP) priority rules?
They are the rules that determine whether an isomer is an E isomer or Z isomer
How do you determine whether an isomer is an E isomer or a Z isomer?
E - entgegen: The high priority groups on either side of the C=C bond are opposite each other
Z - zusammen: The high priority groups on either side of the C=C bond are next to each other
