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racemic, a. Chem.|rəˈsɛmɪk, rəˈsiːmɪk|
[f. as prec., ad. F. (acide) racémique (printed racenique) (J. L. Gay-Lussac Cours de Chimie (1828) xxiv. 23).]
a. Derived from grapes or grape-juice.
racemic acid, an acid existing in certain tartars, isomeric with tartaric acid, but differing from it in several respects, esp. in its optical properties. (Discovered by Kestner in 1822, and also called paratartaric acid.) racemic camphor, a product of the oxidation of borneol. racemic ethers, the acid racemates of ethyl and methyl (Watts 1868).
1835Rec. Gen. Sci. II. 97 The term racemic acid given by the French is preferable. 1838T. Thomson Chem. Org. Bodies 66 The term racemic acid, given it by M. Gay-Lussac in 1828. 1857W. A. Miller Elem. Chem. III. 333 The ordinary salts of racemic acid occur in symmetrical crystals. 1876tr. Schützenberger's Ferment. 7 It might be thought that..it resulted, like racemic acid, from the union of two active but opposed molecules. 1894Morley & Muir Watts' Dict. Chem. I. 672/2 The ‘racemic’ camphor, bromo-camphor, and camphoric acid were also prepared by mixture.
b. Composed of dextro- and lævorotatory isomers of a compound in equal molecular proportions, and therefore optically inactive.
1892Jrnl. Chem. Soc. LXII. ii. 822 The fact that the racemic modification of gulolactone cannot be obtained by crystallisation from water is of general interest, but not without analogy. 1894G. M'Gowan tr. Bernthsen's Text-bk. Org. Chem. (ed. 2) 39 Optically inactive modifications, which result like racemic acid from the conjunction of two active components, are termed ‘racemic’ modifications. 1926H. G. Rule tr. J. Schmidt's Text-bk. Org. Chem. 37 In a few instances it is possible, by allowing a solution of the racemic mixture to crystallise under certain conditions, to obtain the two enantiomorphs depositing individually. 1947Endeavour VI. 97/2 Pasteur not only showed that the effect on polarized light was due to asymmetry of molecular architecture, but devised methods of resolving racemic mixtures. 1964N. G. Clark Mod. Org. Chem. iii. 34 The racemic modification of a substance is sometimes said to be ‘externally compensated’ because its optical inactivity is due to the balancing of two equal and opposite rotations which do not occur within the same molecule. 1971Sci. Amer. May 6/1 L-Leucine has a bitter taste, D-leucine has a sweet taste and the racemic mixture (both) is tasteless.
Hence † ˈracemism, the state of existing in a racemic form; † ˈracemoid a. = racemic a. b.
1896Proc. Chem. Soc. 23 Apr. 97 The ethereal salts..were examined for racemoid compounds, but the quantity found was not sufficient to account for the low activity. 1897Jrnl. Chem. Soc. LXXI. 990 Notwithstanding these marked differences, which may be accepted as conclusive evidence of racemism, this modification of the inactive acid has the same melting point as the active compound. 1902Proc. Chem. Soc. XVIII. 198 Amygdalic acid is racemoid with respect to its asymmetric carbon atom. 1904Science 5 Aug. 178/2 In the cases of some double nuclei (as the camphor group) racemism appears to be impossible, owing to the peculiar molecular structure. |