configuration
In chemistry, the arrangement in space of the atoms in a molecule. It is especially important in organic chemistry (see organic compound), in which each carbon atom in a molecule can form from two to four covalent bonds (see bonding) with as many as four other atoms. A carbon atom with four single bonds, for example, lies at the centre of a tetrahedron, with one bond extending to each corner; if three or all four atoms bonded to the carbon are different, the structure that results has two different mirror-image (see optical activity; isomer) forms, similar to left- and right-handed gloves. Configuration issues also apply to some inorganic compounds. Until late in the 20th century, chemists struggled to determine the true three-dimensional form (absolute configuration) of a molecule experimentally, but modern optical and chemical methods have greatly simplified the task. The term electronic configuration refers to the number of electrons in the various shells of an atom, which defines its chemical reactivity and the type of bonding in which it participates.
configuration
configuration [kən‚fig·yə′rā·shən]
Configuration
(of molecules). In stereochemistry the configuration characterizes the spatial arrangement of atoms or groups of atoms in an asymmetric atom, in an asymmetrically substituted double bond, in a small (rigid) ring, and in the central atom of complex compounds.
The differences in configuration are determined by the existence of two types of stable stereoisomers: geometrical and optical isomers. Chemical and particularly physical methods of investigation are widely used in determining the configuration of molecules. Thus, using a special X-ray technique, it has been possible to demonstrate, for example, the spatial arrangement of substituents around asymmetric carbon atoms (designated by asterisks) in a molecule of tartaric acid—dextrorotatory (I) and levorotatory (II):
The configuration of a molecule does not alter with changes in its conformation, that is, the rotation of individual parts of a molecule relative to one another about single bonds. Sometimes (for example, in the chemistry and physical chemistry of macromolecular compounds), the term “configuration” is used in a broader sense to include the entire spatial model of a molecule.
V. M. POTAPOV
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