Stereoisomers

Isomers

Different compounds that have the same molecular formula but differ in chemical and physical properties.

Structural isomers

Compounds with the same molecular formula but different structural formulae.

Carbon-chain isomerism

The difference between isomers is the length of the carbon chain.

Positional isomerism

Isomers have the same functional group in different locations on the carbon skeleton.

Functional-group isomerism

Isomers are members of different homologous series with different functional groups.

Stereoisomers

Compounds with the same structural formula but atoms arranged differently in space.

Chiral centre

A carbon atom with four different groups attached, leading to optical isomerism.

Enantiomers

Optical isomers that are non-superimposable mirror images of each other.

Racemic mixture

An equimolar mixture of enantiomers with no net effect on plane-polarised light.

Optical isomerism

Occurs when four different groups are attached to the same carbon atom.

Geometric isomers

Also known as cis-trans isomers, caused by the presence of a functional group that restricts rotation.

Cis isomer

Isomers where groups are on the same side of the double bond.

Trans isomer

Isomers where groups are on opposite sides of the double bond.

Conformational isomerism

Different spatial orientation of atoms in a molecule created by rotation of sigma bonds.

Newman projection

A way to visualize conformational isomerism in molecules.

Sigma bond

A bond formed by the head-on overlap of atomic orbitals.

Meso form

An isomer with a plane of symmetry that is not optically active.

Biochemical reactions

Most are stereospecific and occur with only one of the two enantiomers.

Thalidomide

A drug with one enantiomer that is a cure for morning sickness and another causing birth defects.

Partial mirror images

Molecules with more than one asymmetric carbon atom that result in distinct optical activities.