Lecture 13 - Isomerism Flashcards
what is isomerism?
molecules which have the same molecular formula but different arrangement of their atoms in space
Describe structural isomers
different compounds with different physical and chemical properties
what are the 4 types of structural isomerism?
- chain
- position
- functional
- tautomerism
what is tautomerism?
movement of bonds and a proton usually involving a double bond in a molecule - molecules which readily converted in a chemical reaction where hydrogen is transferred from one part of the molecule to another
Describe geometric isomerism
E/Z isomerism - different arrangement in space
cis = two alkyl groups on the same side of the double bond
trans = two alkyl groups on different sides of the double bond
Describe optical isomers
can rotate plane polarised light in opposite directions due to chiral centre
Describe optical isomerism in a molecule with more than one chiral centre
may or may not show optical activity depending on whether they are non-superimposable mirror images
what is a meso compound?
a compound which contains a chiral component but is not chiral overall
what are Fischer projections?
flat drawings that represent a 3D molecule commonly used to represent sugars, the carbon chain is always vertical
what is an enantiomer?
a pair on non superimposable molecules - one will rotate left, one right
what is a racemic mixture?
a 50:50 mixture of the two enantiomers of a compound , has no optical activity
what are diastereomers?
- stereo isomers that are not mirror images of each other , they differ at one carbon called an epimer
- they have 2 or more chiral centres where at least one differ
what is the importance of enantiomers in biology?
proteins/enzymes and receptors are made up of L-amino acids which have a chiral environment
