Naming Organic Compounds

Organic names are like addresses. They tell you the carbon chain length, the family (functional group), and where special parts are on the chain.

Carbon chain prefixes (1–4)

• 1 carbon: meth-
• 2 carbons: eth-
• 3 carbons: prop-
• 4 carbons: but-

Families (functional groups) and suffixes

• Alkanes (only single C–C bonds): suffix -ane, general formula $C_nH_{2n+2}$
• Alkenes (one C=C double bond): suffix -ene, general formula $C_nH_{2n}$
• Alcohols (–OH group): suffix -ol, general formula $C_nH_{2n+1}OH$
• Carboxylic acids (–COOH group): suffix -oic acid, general formula $C_nH_{2n+1}COOH$

Formulas you may see

• Displayed formula: shows every atom and bond.
• Structural formula: groups atoms, e.g. CH₃CH₂OH.

Steps to name unbranched molecules

1. Find the longest carbon chain (up to 4 here) → pick the prefix (meth-, eth-, prop-, but-).
2. Identify the family (functional group) → choose the suffix (e.g. -ane, -ene, -ol, -oic acid).
3. Number the chain from the end nearest the double bond or the functional group.
4. Give the position number before the part it belongs to: but-2-ene, propan-1-ol. Unbranched alkanes usually need no number.

Simple esters

Made from an alcohol and a carboxylic acid. Name = alcohol part (alkyl) + acid part (alkanoate). Example: ethanol + ethanoic acid → ethyl ethanoate.

Common mistakes

• For alkenes with 4 carbons, include the double-bond position (but-1-ene vs but-2-ene).
• Always number from the end closest to the C=C or the –OH/–COOH group.
• Do not mix up ethanol (-ol) with ethanoic acid (-oic acid).