Functional groups are groups of atoms with specific chemical properties that occur within organic molecules and are sometimes denoted as "R". Functional groups can "functionalize" a compound by enabling it to adopt different physical and chemical properties. Types of Advanced Functional Groups The table below summarizes some of the major functional groups in organic chemistry. Class of Organic Compounds Skeletal Structures of Compounds with Functional Groups in Red Names of Compounds Aromatic hydrocarbon Benzene Phenol Phenol (Hydroxybenzene) Aldehyde Ethanal (Acetaldehyde) Ketone Acetone Acid or acyl chloride Acetyl chloride Carboxylic acid Ethanoic acid (Acetic acid) Ester Ethyl acetate Amine Ethylamine Amide Acetamide Nitrile Acetonitrile Phosphate Methyl dihydrogen phosphate This text is adapted from Openstax, Chemistry 2e, Section 20.2: Alcohols and Ethers and Section 20.3: Aldehydes, Ketones, Carboxylic Acids, and Esters.