unimolecularadj.
Chemistry.
a. [ < French unimoléculaire (J. H. Van 't Hoff Études Dynam. Chim. (1884) 8).] In chemical kinetics: having or pertaining to a molecularity of one; involving the fragmentation or internal transformation of a single molecule in the rate-determining step of a reaction (rather than the collision of a pair of molecules); in quot. 1901, first-order (see order n. 4d). Cf. monomolecular adj. 2.
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the world > matter > chemistry > physical chemistry > chemical kinetics > [adjective] > molecularity > involving single molecule
unimolecular1901
the world > matter > chemistry > chemical reactions or processes > [adjective] > of or relating to molecularity > of one
unimolecular1946
1901 Jrnl. Chem. Soc. 80 ii. 647 The reaction between ferric salts and metallic iodides is unimolecular for the iron salt and bimolecular for the iodide.
1946 Nature 20 July 94/1 Those bimolecular and unimolecular substitutions in which a nucleophilic reagent displaces halogen as halide ion from an alkyl halide.
1972 R. A. Jackson Mechanism i. 5 Unimolecular reactions occur as a result of reorganization of the bonds within a molecule, with or without rupture into fragments.
1978 P. W. Atkins Physical Chem. xxvi. 863 Most reactions can be broken down into a sequence of steps that involve either a unimolecular reaction, in which a single molecule shakes itself apart or into a new configuration, or a bimolecular reaction.
b. = monomolecular adj. 3.
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the world > matter > chemistry > physical chemistry > chemical kinetics > [adjective] > molecularity
polymolecular1896
unimolecular1925
1925 Proc. Royal Soc. A. 109 303 Unimolecular films are thus to be anticipated in those cases in which the surface of the adsorbate is not very active, e.g., on diamond.
1942 S. Brunauer Adsorption of Gases I. i. i. 6 When a surface can take up only one layer of adsorbed gas the adsorption is called unimolecular. [Note] I. Langmuir [proposing the concept in 1917] used the term monomolecular. However since this is a term of mixed Greek and Latin derivation the use of the term unimolecular is preferable.
1978 K. J. Laidler Physical Chem. with Biol. Applic. xi. 462 Ammonia molecules are rather strongly attached to such a surface, which may become completely covered by a unimolecular layer.
Derivatives
unimoˈlecularly adv.
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the world > matter > chemistry > physical chemistry > chemical kinetics > [adverb]
unimolecularly1901
1901 Jrnl. Chem. Soc. 80 ii. 647 Strontium and calcium iodides act unimolecularly.
1935 Jrnl. Chem. Physics 3 112 Suppose we have a non-linear molecule of n atoms decomposing unimolecularly.
1974 G. B. Gill & M. R. Willis Pericyclic Reactions vi. 203 Both 2,5-dihydrofuran and 1,4-cyclohexadiene are decomposed unimolecularly into hydrogen and respectively furan and benzene.
This entry has not yet been fully updated (first published 1986; most recently modified version published online June 2019).
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adj.1901