Formulas and Structural Isomerism

General Formula - An algebraic formula that can describe any member of a family of compounds.

Empirical Formula - The simplest ratio of each element in a compound (cancel the numbers down if possible)

Molecular Formula - The actual of atoms of each element in a molecule.

Structural Formula - Shows the atoms carbon by carbon, with the attatched hydrogens and functional groups.

Displayed Formula - Shows all the atoms are arranged and all the bonds between them.

In structural isomers the atoms are connected in different ways. But they still have the same molecular formula. There are three types of structural isomers:

Chain isomers - Chain isomers have different arrangements of the carbon skeleton. Some are straight chains and others branched in different ways.

Positional Isomers - Positional isomers have the same skeleton and the same atoms or groups of atoms attatched. The difference is that the atom or group of atoms is attached to a different atom.

Functional Group Isomers - Functional group isomers have the same atoms arranged into different functional groups.

Attoms can rotate as much as they like around single C-C bonds. Remember this when you work out structural isomers - sometimes what looks like an isomer isn't.