Organic compounds are classified in several ways, mainly based on their structure and functional groups.
1. Classification based on Carbon Skeleton
- Acyclic (open-chain compounds):
Carbon atoms form straight or branched chains.
Examples: alkanes (CH₃–CH₃), alkenes, alkynes. - Cyclic (closed-chain compounds):
Carbon atoms form rings.- Homocyclic (carbocyclic): Ring contains only carbon atoms.
- Alicyclic: Non-aromatic rings (e.g., cyclohexane).
- Aromatic: Contain conjugated π-electrons and follow Huckel’s rule (e.g., benzene).
- Heterocyclic: Ring contains carbon and other atoms (O, N, S).
- Examples: furan (O), pyridine (N), thiophene (S).
- Homocyclic (carbocyclic): Ring contains only carbon atoms.
2. Classification based on Functional Groups
Functional groups are atoms or groups of atoms that determine chemical properties.
Some major classes:
- Hydrocarbons: Alkanes, alkenes, alkynes, aromatic hydrocarbons.
- Alcohols & Phenols: –OH group.
- Ethers: –O– linkage.
- Aldehydes & Ketones: –CHO, >C=O.
- Carboxylic Acids & Derivatives: –COOH, esters, amides.
- Amines: –NH₂ group.
- Halogen derivatives: –Cl, –Br, –I.
3. Classification based on Saturation
- Saturated compounds: Only single C–C bonds (alkanes).
- Unsaturated compounds: One or more double/triple bonds (alkenes, alkynes).
4. Classification based on Source
- Natural compounds: Obtained from plants, animals, or microbes (e.g., glucose, alkaloids, proteins).
- Synthetic compounds: Man-made in labs or industries (e.g., plastics, nylon, drugs).
In short:
Organic compounds are classified mainly by their carbon framework (acyclic, cyclic, aromatic, heterocyclic), by their functional groups (alcohols, acids, amines, etc.), and by saturation (saturated vs unsaturated).