How to name CARBOXYLIC ACIDS and write their formulas

Note: There’s a summary table at the end of this page.

Overview

Organic: Contains carbon

Hydrocarbons: Organic compounds made from hydrogen and carbon only

Homologous series: A series of compounds with the same functional group and similar chemical properties

Functional group: A part of a compound that indicates what homologous series it is a part of.

Eg. This is butanoic acid with the functional group highlighted

General formula

General formula for carboxylic acids: C_nH_2nO₂

Each homologous series has its own general formula.

To use the general formula, replace n in the general formula with the number of C (carbon) atoms.
eg. A carboxylic acid compound with 3 carbon atoms:

C_nH_2nO₂
= C₍₃₎H₂₍₃₎O₂
= C₃H₆O₂

How to name Carboxylic acids

Every carboxylic acid has the format of “alkanoic acid”. Depending on the number of carbons, you just change the “alk” part:

1 – meth
2 – eth
3 – prop
4 – but
5 – pent
6 – hex

eg. A carboxylic acid compound with 2 carbon atoms: ethanoic acid

Here’s a trick I use to remember how each compounds starts:
(1) Monkeys (2) Eat (3) Peanut (4) Butter
5 & 6 are easy enough to remember because they are the same as shapes (pentagon, hexagon)

Displayed / structural formula

Important:

H (Hydrogen) has 1 bond
C (Carbon) has 4 bonds
O (Oxygen) has 2 bonds
(This will help you draw the structure)

Steps:

1. Draw a chain with the correct number of C’s (carbons).
2. Add an -OH at the end of the chain.
3. Add a double bond O (=O) on the same carbon.
4. Complete the molecule by adding H’s (hydrogens) around the C’s (carbons) to make each carbon have 4 bonds. REMEMBER TO COUNT THE DOUBLE BOND.
5. Ensure that the lines are drawn in and that each letter has the correct number of bonds.
6. You can check that the number of each element matches the formula.

Summary

Have any questions about this topic? Leave a comment below and I’ll get back to you 🙂