Question

why do we add an when naming organic compounds.
example is why do we write methanal and not methal

Answer 1

We donot write only meth- , prop- etc. to name a compound. We have to write its full name like methane(for one carbon atom), ethane(for two carbon atom), propane(for three carbon atoms), etc.

In case of methanal, [HCHO] also known as formaldehyde have an aldehydic functional group. To represent an aldehydic compound, suffix -al must be used which indicates that a carbonyl group attached to a hydrogen atom at the end of the carbon chain.