Alcohols, Acids, Esters — study notes

Why does nail-varnish remover smell so sweet, almost fruity? That sharp fragrance is an ester — the product you get whenever a carboxylic acid meets an alcohol. It's the final link in a three-part organic chemistry chain that shows up again and again on the O-Level paper.

How the Three Families Connect

Alcohols carry an –OH group; carboxylic acids carry a –CO₂H group. Push an alcohol through oxidation and its –OH turns into –CO₂H, so it becomes a carboxylic acid. Combine that acid with a fresh alcohol under warm, acidic conditions and the two link up into an ester, releasing a small water molecule as they join — a reaction called esterification. Because the acid can, in principle, be pulled back apart from the alcohol again, chemists write this step with a double-headed arrow (⇌) rather than a single one.

The catalyst that drives esterification is concentrated sulfuric acid, alongside gentle heating — without both, the two molecules simply sit next to each other in solution and nothing links up. Naming the product follows a neat two-part pattern: take the alcohol's name and swap "-ol" for "-yl", then take the acid's name and swap "-ic acid" for "-ate". The alcohol-derived word is always said first.

Worked Example — Naming the Ester from Propan-1-ol and Methanoic Acid

1. Identify the alcohol and the acid: propan-1-ol supplies the "-yl" word; methanoic acid supplies the "-ate" word.
2. Convert the alcohol: propan-1-ol → drop "-ol", add "-yl" → propyl.
3. Convert the acid: methanoic acid → drop "-ic acid", add "-ate" → methanoate.
4. Join them, alcohol word first: the product is propyl methanoate, formed alongside a molecule of water.

That naming trick is only half the picture — the full lesson below walks through building the matching formula, works through several more acid-and-alcohol pairings, and includes an audio walkthrough plus a practice worksheet so you can drill the pattern until it's automatic.