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Basic Chemistry Concepts

Organic Chemistry

ultraviolet spectroscopy, aromaticity, nuclear magnetic resonance spectroscopy, carbon compounds, Infrared spectra

Deeper web pages:

>  Organic Formulas and Bonds

>  Classification and Nomenclature

>  Physical Properties of Organic Compounds

>  Chemical Reactions

Organic Chemistry, branch of chemistry in which carbon compounds and their reactions are studied. A wide variety of classes of substancesósuch as drugs, vitamins, plastics, natural and synthetic fibers, as well as carbohydrates, proteins, and fatsóconsist of organic molecules. Organic chemists determine the structures of organic molecules, study their various reactions, and develop procedures for the synthesis of organic compounds. Organic chemistry has had a profound effect on modern life: It has improved natural materials and it has synthesized natural and artificial materials that have, in turn, improved health, increased comfort, and added to the convenience of nearly every product manufactured today.

The advent of organic chemistry is often associated with the discovery in 1828 by the German chemist Friedrich Wohler that the inorganic, or mineral, substance called ammonium cyanate could be converted in the laboratory to urea, an organic substance found in the urine of many animals. Before this discovery, chemists thought that intervention by a so-called life force was necessary for the synthesis of organic substances. Wohler's experiment broke down the barrier between inorganic and organic substances. Modern chemists consider organic compounds to be those containing carbon and one or more other elements, most often hydrogen, oxygen, nitrogen, sulfur, or the halogens, but sometimes others as well.

Sources of Organic Compounds

Coal tar was once the only source of aromatic and some heterocyclic compounds. Petroleum was the source of aliphatic compounds that contain such substances as gasoline, kerosene, and lubricating oil. Natural gas supplied methane and ethane. These three categories of natural substances are still the major sources of organic compounds for most countries. When petroleum is not available, however, a chemical industry can be based on acetylene, which in turn can be synthesized from limestone and coal. During World War II, Germany was forced into just that position when it was cut off from reliable petroleum and natural-gas sources.

Table sugar from cane or beets is the most abundant pure chemical from a plant source. Other major substances derived from plants include carbohydrates such as starch and cellulose, alkaloids, caffeine, and amino acids. Animals feed on plants and other animals to synthesize amino acids, proteins, fats, and carbohydrates.

Determination of Structure

The use of chemical reactions to identify the structures of organic compounds has been replaced largely by instrumental methods since 1940. Infrared spectra are used to identify functional groups, and ultraviolet spectroscopy can distinguish aromaticity and certain kinds of unsaturation in a molecule. A nuclear magnetic resonance (nmr) spectrum gives the largest amount of information about the structure of a compound; infrared and ultraviolet spectra complement rather than duplicate such data. Proton resonance spectroscopy is sometimes used to determine the nature of the local environment of the hydrogen atoms in a molecule and it can often simultaneously supply the ratios of types of hydrogen. More recently, carbon-13 nuclear magnetic resonance spectroscopy has been used to derive complementary information to the proton data. Also, an X-ray spectrum may be necessary to determine three-dimensional aspects of structure in a complex organic molecule.

Contributors

Clapp, Leallyn B., M.A., Ph.D.

Professor Emeritus of Chemistry, Brown University.



Article key phrases:

ultraviolet spectroscopy, aromaticity, nuclear magnetic resonance spectroscopy, carbon compounds, Infrared spectra, heterocyclic compounds, halogens, functional groups, Coal tar, synthetic fibers, lubricating oil, acetylene, nmr, alkaloids, hydrogen atoms, Organic Chemistry, urea, kerosene, organic compounds, sulfur, beets, amino acids, methane, natural materials, caffeine, carbohydrates, chemical industry, hydrogen, starch, local environment, nitrogen, modern life, limestone, inorganic, profound effect, World War II, proteins, cane, oxygen, urine, fats, Natural gas, vitamins, gasoline, experiment, intervention, discovery, drugs, barrier, carbon, convenience, plastics, elements, plants, nature, laboratory, Germany, animals, procedures, countries, position, turn, product

 
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