organic chemistry
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| organic chemistry | |
|---|---|
| Name | Organic Chemistry |
| Caption | The benzene ring, a fundamental structure in many organic compounds. |
| Subdisciplines | Medicinal chemistry, polymer chemistry, organometallic chemistry |
| Key people | Friedrich Wöhler, August Kekulé, Robert Burns Woodward |
| Related fields | Biochemistry, materials science, pharmacology |
organic chemistry is the scientific study of the structure, properties, composition, reactions, and preparation of carbon-containing compounds. This vast field encompasses not only hydrocarbons but also compounds with any number of other elements, including hydrogen, oxygen, nitrogen, halogens, phosphorus, silicon, and sulfur. The unique ability of carbon to catenate, forming stable chains and rings with itself, is the foundational reason for the immense diversity of organic molecules, which range from simple gases like methane to complex macromolecules such as DNA and proteins.
Overview
The modern definition of the discipline, primarily focusing on compounds of carbon, was solidified in the 19th century, overcoming the vitalist theory that organic substances required a "life force." A pivotal moment was the synthesis of urea from inorganic precursors by Friedrich Wöhler in 1828. The field is central to understanding the molecular basis of life processes studied in biochemistry and is the engine behind the development of new materials, pharmaceuticals, and agrochemicals. Major industrial applications are managed by global entities like BASF, Dow Chemical Company, and Pfizer.
Fundamental concepts
Core principles include the concept of the functional group, a specific grouping of atoms that dictates a molecule's characteristic chemical reactions. The systematic naming of compounds is governed by the IUPAC nomenclature system. Isomerism, where molecules share the same molecular formula but differ in structure or spatial arrangement, is a critical concept, with forms including structural isomers and stereoisomers like those studied in the Cahn–Ingold–Prelog system. The analysis of organic compounds relies heavily on spectroscopic techniques such as NMR and mass spectrometry.
Structure and bonding
The bonding in organic molecules is primarily covalent, with carbon typically forming four bonds. Hybridization concepts (sp³, sp², sp) explain the geometries around carbon atoms, from the tetrahedral shape of methane to the trigonal planar arrangement in ethylene. Resonance theory, famously applied by August Kekulé to benzene, describes the delocalization of electrons in certain structures. The three-dimensional arrangement of atoms, or stereochemistry, has profound implications in biology and pharmacology, as evidenced by the differing effects of enantiomers like thalidomide.
Organic compounds and functional groups
Organic compounds are classified based on their functional groups. Major classes include alkanes, alkenes, alkynes, arenes like benzene, alcohols, aldehydes, ketones, carboxylic acids, esters, amines, and amides. Each class undergoes characteristic reactions; for example, carboxylic acids react with alcohols to form esters in a Fischer esterification. Complex natural products, such as penicillin isolated by Alexander Fleming and morphine, are built from combinations of these groups.
Organic reactions and mechanisms
Organic reactions are studied through their mechanisms—the step-by-step pathways by which reactants are transformed into products. Major reaction types include substitution reactions (S<sub>N</sub>1 and S<sub>N</sub>2), elimination reactions (E1cB and E2), and addition reactions, such as the Diels–Alder reaction. The work of physical organic chemists like Christopher Kelk Ingold was instrumental in elucidating these mechanisms. Reactions often involve reactive intermediates like carbocations, carbanions, and free radicals.
Applications and importance
The applications of this field are ubiquitous and critical to modern society. It is the foundation of the petroleum industry, where crude oil is refined into fuels and feedstocks. In medicinal chemistry, it enables the design and synthesis of drugs, from aspirin to complex agents like those developed by Merck & Co. and GlaxoSmithKline. It drives advancements in polymer chemistry, yielding materials like polyethylene, nylon, and Kevlar. Furthermore, it is essential in developing agrochemicals, dyes, flavors, and fragrances, impacting sectors from agriculture to cosmetics.