optical activity

Physical Chem.
the ability of a substance to rotate the plane of polarization of plane-polarized light.
[1875-80]

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Ability of a substance to rotate the plane of polarization of a beam of light passed through it, either as crystals or in solution.

Clockwise rotation as one faces the light source is "positive," or dextrorotary; counterclockwise rotation "negative," or levorotary. Louis Pasteur was the first to recognize that molecules with optical activity are stereoisomers (see isomerism). Optical isomers occur in pairs that are nonsuperimposable mirror images of one another. They have the same physical properties except for their effect on polarized light; in chemical properties they differ only in their interactions with other stereoisomers (see asymmetric synthesis).

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      the ability of a substance to rotate the plane of polarization of a beam of light that is passed through it. (In plane-polarized light, the vibrations of the electric field are confined to a single plane.) The intensity of optical activity is expressed in terms of a quantity, called specific rotation, defined by an equation that relates the angle through which the plane is rotated, the length of the light path through the sample, and the density of the sample (or its concentration if it is present in a solution). Because the specific rotation depends upon the temperature and upon the wavelength of the light, these quantities also must be specified. The rotation is assigned a positive value if it is clockwise with respect to an observer facing the light source, negative if counterclockwise. A substance with a positive specific rotation is described as dextrorotatory and denoted by the prefix d or (+); one with a negative specific rotation is levorotatory, designated by the prefix l or (-).

      Optical activity was first observed in quartz crystals in 1811 by a French physicist, François Arago (Arago, François). Another French physicist, Jean-Baptiste Biot (Biot, Jean-Baptiste), found in 1815 that liquid solutions of tartaric acid or of sugar are optically active, as are liquid or vaporous turpentine. Louis Pasteur was the first to recognize that optical activity arises from the dissymmetric arrangement of atoms in the crystalline structures or in individual molecules of certain compounds.

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Universalium. 2010.

Look at other dictionaries:

  • optical activity — n. (Chem.) the ability of a chemical compound to rotate the plane of plane polarized light. This is found only in chemicals whose molecular structure does not have a plane of symmetry, and is common in biochemical compounds. {optically active}… …   The Collaborative International Dictionary of English

  • optical activity — n ability of a chemical substance to rotate the plane of vibration of polarized light to the right or left * * * the property possessed by some substances of rotating the plane of polarization of polarized light. A compound that rotates the plane …   Medical dictionary

  • optical activity — n. the ability of certain substances to rotate the plane of polarization when transmitting polarized light …   English World dictionary

  • optical activity — optinis aktyvumas statusas T sritis Standartizacija ir metrologija apibrėžtis Medžiagos savybė sukti šviesos poliarizacijos plokštumą. atitikmenys: angl. optical activity vok. optische Aktivität, f rus. оптическая активность, f pranc. activité… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • optical activity — optinis aktyvumas statusas T sritis chemija apibrėžtis Medžiagos savybė sukti šviesos poliarizacijos plokštumą. atitikmenys: angl. optical activity rus. оптическая активность …   Chemijos terminų aiškinamasis žodynas

  • optical activity — optinis aktyvumas statusas T sritis fizika atitikmenys: angl. optical activity vok. optische Aktivität, f rus. оптическая активность, f pranc. activité optique, f …   Fizikos terminų žodynas

  • optical activity — noun a) a property caused by asymmetrical molecular or crystal structure that enables a compound or crystal to rotate the plane of incident polarized …   Wiktionary

  • optical activity — /ɒptɪkəl ækˈtɪvəti/ (say optikuhl ak tivuhtee) noun the rotation of the plane of vibration of polarised light as it travels through certain materials, used as a means of characterising substances in solution. Also, optical rotation …   Australian English dictionary

  • optical activity — noun : ability to rotate the plane of polarization of light compare optical rotation …   Useful english dictionary

  • optical activity — noun Date: 1877 ability of a chemical substance to rotate the plane of vibration of polarized light to the right or left …   New Collegiate Dictionary

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