Organic Functional Groups Overview

Overview

This lecture covers the most common organic functional groups, their structures, how to identify them, and basic naming conventions.

Alkanes, Alkenes, and Alkynes

• Alkanes are hydrocarbons with only single carbon-carbon bonds (suffix: -ane, e.g., pentane has five carbons).
• Alkenes have at least one carbon-carbon double bond (suffix: -ene, e.g., 2-butene).
• Alkynes contain at least one carbon-carbon triple bond (suffix: -yne, e.g., 2-butyne).

Cyclic and Aromatic Compounds

• Cycloalkanes are ring-shaped alkanes with only single bonds (e.g., cyclopentane, cyclohexane).
• Aromatics have rings with alternating double bonds; benzene is the simplest aromatic ring.

Halides, Ethers, and Alcohols

• Alkyl halides (haloalkanes) have a halogen (F, Cl, Br, I) attached to a carbon chain (general formula: R-X).
• Ethers have an oxygen between two carbon groups (R-O-R’), such as dimethyl ether.
• Alcohols have a hydroxyl group (-OH) attached to a carbon (suffix: -ol, e.g., 1-butanol).

Carbonyl Compounds: Ketones and Aldehydes

• Ketones have a carbonyl group (C=O) between two carbons (suffix: -one, e.g., 2-pentanone).
• Aldehydes have a carbonyl group at the end of the carbon chain (suffix: -al, e.g., hexanal).

Carboxylic Acids, Esters, and Derivatives

• Carboxylic acids have a carboxyl group (-COOH, suffix: -oic acid, e.g., hexanoic acid).
• Esters have a carbonyl next to an oxygen attached to another carbon group (suffix: -oate, e.g., methyl ethanoate).
• Acid anhydrides have two acyl groups joined by an oxygen (e.g., acetic anhydride).
• Acid chlorides have an acyl group attached to a halide (e.g., acetyl chloride).

Nitrogen, Sulfur, and Special Functional Groups

• Amines have an amino group (-NH2, e.g., methylamine).
• Amides have a carbonyl group attached to an amino group (e.g., butanamide).
• Nitriles have a carbon triple-bonded to nitrogen (-C≡N, e.g., ethanenitrile).
• Thiols have a sulfhydryl group (-SH, e.g., methylthiol).
• Thioethers and thioesters substitute sulfur for oxygen in ethers/esters (e.g., thioester).
• Enols have adjacent alkene and alcohol groups.
• Enamines have adjacent alkene and amine groups.
• Imines have a carbon double-bonded to a nitrogen atom (C=N).

Peroxides, Peroxy Acids, and Nitro Groups

• Peroxides have two oxygens connected by a single bond (e.g., organic peroxide).
• Peroxy acids combine carboxylic acid and peroxide groups.
• Nitro groups contain -NO2 attached to a carbon.

Miscellaneous Organic Species

• Carbocation: carbon with a positive charge.
• Carbanion: carbon with a negative charge.
• Radical: molecule with an odd number of electrons.
• Carbene: neutral carbon species with two substituents and two lone electrons.

Key Terms & Definitions

• Functional Group — specific atom/group of atoms responsible for characteristic reactions of a molecule.
• Hydrocarbon — molecule made only of carbon and hydrogen.
• Alkane — saturated hydrocarbon with only single bonds.
• Alkene — hydrocarbon with at least one double bond.
• Alkyne — hydrocarbon with at least one triple bond.
• Aromatic Ring — ring with alternating double bonds (e.g., benzene).
• Alcohol — compound with an -OH group.
• Ketone — compound with a carbonyl group between carbons.
• Aldehyde — compound with a carbonyl group at chain end.
• Carboxylic Acid — compound with a -COOH group.
• Ester — compound with a -COOR group.
• Amine — compound with an -NH2 group.
• Amide — compound with -CONH2 group.
• Nitrile — compound with -C≡N group.
• Thiols/Thio- — sulfur analogs of oxygen-based groups.
• Peroxide — two oxygens single-bonded together.
• Nitro Group — -NO2 group attached to a carbon.

Action Items / Next Steps

• Review the names, structures, and examples of each functional group for quiz/exam preparation.