Formulas, functional groups and the naming of organic compounds — common mistakes

Be careful with classifying amines! Unlike alcohols, the classification depends on bonds to the nitrogen atom itself, not the adjacent carbon. A common mistake is to classify CH₃CH₂NH₂ as a primary amine (correct) but then misclassify (CH₃)₂CHNH₂ as a secondary amine (it's still primary, as the N is only bonded to one carbon group).

A displayed formula shows every atom and every bond individually. A structural formula is a condensed version that shows how atoms are grouped, for example, CH₃CH₂OH, which is less cluttered than drawing out all the C-H and O-H bonds.

There is a priority order for functional groups in IUPAC nomenclature. For A-Level, the general trend is: Carboxylic acids > Esters > Aldehydes > Ketones > Alcohols > Amines > Alkenes/Alkynes. The highest priority group determines the suffix, and all others are named as prefixes (e.g., 'hydroxy-' for an –OH group if a –COOH is present).

Skeletal formulae are quick to draw and easy to read once you are familiar with them. They de-clutter the image, allowing you to focus on the carbon backbone and the functional groups, which are the most important parts for understanding the molecule's shape and reactivity.

'Butan-1-ol' is the specific name of a molecule. 'Primary alcohol' is a classification. Butan-1-ol is an example of a primary alcohol because the carbon atom attached to the -OH group is bonded to only one other carbon atom.