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Pyrolytic production of Se ( 3 P ) from carbon diselenide. II. Rate of CSe 2 decay
Author(s) -
Belford R. L.,
Marquart J. R.,
Fraenkel H. A.,
Cross A. J.,
Lenhardt T. M.,
Wei G. J.
Publication year - 1979
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550111009
Subject(s) - chemistry , analytical chemistry (journal) , arrhenius equation , reaction rate constant , activation energy , atmospheric temperature range , kinetic energy , absorbance , pyrolytic carbon , argon , kinetics , pyrolysis , thermodynamics , physics , organic chemistry , chromatography , quantum mechanics
Pyrolytic decay of carbon diselenide was monitored by ultraviolet absorption spectroscopy in reflected shock waves in the temperature range of 1600–2600°K. The temperature dependence of the absorption coefficient of CSe 2 at 2308 Å was determined and was used to provide kinetic information along with a deconvolution procedure which accounted for and removed systematic distortions of the fast time‐resolved absorbance profile. For temperatures of 1600–2600°K and argon densities of 1.5–7.0 × 10 −5 mol/cm 3 dilute (1.0–9.0 × 10 −9 mol/cm 3 ) CSe 2 pyrolyzed with measured first‐order decay rates in the range of log 10 k 1 (sec −1 ) = 3.0−5.7; at midrange (2100°K and 4.3 × 10 −5 mol/cm 3 in Ar) k 1 ≈ 3 × 10 4 sec −1 . The decay probably occurs via a unimolecular low‐pressure process, first order in both CSe 2 and Ar, for which k 2 ± 10 9 cm 3 /mol·sec at 2100°K. The deconvoluted data yield Arrhenius activation energies of 53.2 kcal/mol under second‐order treatment, but the activation energy is less reliable than the general magnitude of the rate constant. A comparison of CSe 2 with other molecules which are isoelectronic in their valence shells (CO 2 , CS 2 , OCS, and N 2 O) is made.