In 1828, Friedrich Wöhler, a German chemist working in Berlin, accidentally synthesized urea — previously thought to be uniquely produced by living organisms — from the inorganic compound ammonium cyanate. The result, communicated in a letter to his teacher Jöns Jacob Berzelius, demolished the prevailing doctrine of vitalism, the belief that organic compounds required a vital force unique to living things to produce; Wöhler wrote: I must tell you that I can make urea without thereby needing to have kidneys, or anyhow, an animal, be it human or dog. Organic chemistry — the chemistry of carbon — became, after Wöhler, a unified discipline connected to the rest of chemistry rather than a separate science of the living, and functional groups — small, recurring atomic arrangements that confer characteristic chemistry on a carbon skeleton — became the organizing principle that made the field's millions of compounds tractable.
Carbon is the unique foundation of organic chemistry because of its bonding versatility: four valence electrons, the ability to form long chains and rings, equal facility forming single, double, and triple bonds, and a self-bonding ability that lets it construct frameworks of arbitrary size. Most chemistry of carbon-rich molecules is conducted by substituents on the carbon skeleton — the functional groups. The hydroxyl (−OH) of alcohols and phenols is polar, hydrogen-bonds, and oxidizes to aldehydes, ketones, and carboxylic acids; the carbonyl (C=O) of aldehydes and ketones is highly reactive and underwrites much of synthetic organic chemistry; the carboxyl (-COOH) is acidic (pKa 4–5) and dimerizes in solution; the ester (R-COO-R') makes pleasant smells and is hydrolyzed by acid, base, or enzymes; the amino (−NH₂) is basic and polar; the amide (R-CO-NR'R'') links amino acids into proteins as the peptide bond and is unusually stable to hydrolysis; the phosphate (-OPO₃²⁻) builds the high-energy bonds in ATP and the backbone of DNA and RNA; sulfhydryl (-SH) and disulfide (-S-S-) bridges stabilize protein structure in cysteine residues; and the aromatic ring (benzene and its derivatives) gives the remarkable stability of delocalized π-electrons. The combinatorial power is what makes organic chemistry the most diverse branch of chemistry — about twenty functional groups, combined on carbon skeletons of essentially arbitrary length and shape, produce on the order of 10⁸ known compounds and an estimated 10⁶⁰ possible drug-sized molecules. Reaction mechanisms organize around functional-group transformations — nucleophilic substitution (S<sub>N</sub>1, S<sub>N</sub>2), elimination (E1, E2), addition to carbonyls, oxidation/reduction, condensation, cycloaddition — and retrosynthetic analysis (E. J. Corey, Nobel 1990) treats target molecules as products of disconnections at strategic functional groups, working backward to commercially available starting materials. The IUPAC nomenclature names organic compounds systematically by identifying the longest carbon chain, specifying functional groups by suffix and prefix, and numbering positions for substituents.
Pharmaceutical chemistry is the most economically consequential application of organic chemistry: over 80% of FDA-approved drugs are small organic molecules built around recognized functional-group scaffolds. Every commodity plastic (polyethylene, polypropylene, PET, nylon, polystyrene) is built by polymerization at specific functional groups, and materials science (liquid crystals, organic semiconductors in modern OLEDs, conductive polymers, photoresists for chip manufacturing) is functional-group chemistry at scale. Click chemistry (Sharpless, Bertozzi, Meldal — Nobel 2022) — a small set of selective, robust reactions that work in biological conditions — has transformed bioconjugation and pharmaceutical labeling, while AI-assisted synthesis planning (IBM's RXN, MIT's ASKCOS, several startups) suggests retrosynthetic disconnections from millions of literature examples and is increasingly capable of multi-step routes. The framework Wöhler accidentally inaugurated in 1828 is, two centuries later, the most diverse and economically consequential branch of chemistry.