Unit 4: Organic Chemistry
- Structural isomerism: Compounds with the same molecular formula but different structural formulae.
- E-Z isomerism: A type of geometric isomerism (a.k.a cis-trans) which depends on the priorities of the groups attached to the carbon atoms of the double bond. The priority is equal to the sum of the atomic numbers attached. Z isomers have the two higher priority on the same side, E isomers have the two higher priority groups on opposite sides.
A cringey way to remember which way round E/Z isomers are: "Zee meanz on zee zame zide".
- Optical isomerism: compounds that do not have a plane of symmetry, and thus show optical isomerism, such isomers are known as enantiomers. Enantiomers are isomers that are non-superimposable on their mirror image. Optical isomerism arises as a result of a chiral centre in a molecule. A chrial centre in a molecule is part of a molecule which causes it to have two enantiomers. The most common cause of chirality is when a C atom has four different groups attached. This C atom will be the chiral centre of the molecule.
Enantiomers have idential chemical and physical properties (solubility and boiling point) and differ in two tays: they rotate the plane of polarisation of plane polarised light in different ways, and they have different biochemical properties (have a google of the Thalidomide disaster for some context on this fascinating characteristic of enantiomers).