Molecular formulae

A molecular formula simply counts the numbers of each sort of atom present in the molecule, but tells you nothing about the way they are joined together. For example, the molecular formula of butane is C₄H₁₀ , and the molecular formula of ethanol is C₂H₆O .

Molecular formulae are very rarely used in organic chemistry, because they do not give useful information about the bonding in the molecule. About the only place where you might come across them is in equations for the combustion of simple hydrocarbons, for example:

In cases like this, the bonding in the organic molecule isn't important.