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Kinetics of the iodine atom catalyzed gas phase geometrical isomerization of diiodoethylene. Rotation about a single bond
Author(s) -
Golden David M.,
Furuyama Shozo,
Benson Sidney W.
Publication year - 1969
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.550010107
Subject(s) - chemistry , isomerization , reaction rate constant , enthalpy , activation energy , iodine , atom (system on chip) , catalysis , adduct , arrhenius equation , single bond , kinetics , gas phase , thermodynamics , group (periodic table) , organic chemistry , physics , quantum mechanics , computer science , embedded system
The spectrophotometric determination of the rate of iodine atom catalyzed geometrical isomerization of diiodoethylene in the gas phase from 502.8 to 609.1°K leads to a rate constant for the bimolecular reaction between I and trans ‐diiodoethylene of log k t−c ( M −1 sec −1 ) = 8.85 ± 0.12 − (11.01 ± 0.30)/θ. Estimates of the entropy and enthalpy change for the addition of I atoms to trans ‐diiodoethylene (process a.b) lead to log K a.b ( M −1 ) = −2.99 − 4.0/θ, and thus to log k c (sec −1 ) = log k t−c – log K a b = 11.8 −7.0/θ for the rate constant for rotation about the single bond in the adduct radical. The theory for calculation of the rotation rate constant is presented and it is shown that while the exact value depends on the barrier height, a value of 6.8 kcal/mole for this quantity leads to log k (sec −1 ) = 11.8 −6.7/θ. The activation energy points to a better value of the group contribution to heat of formation of the group C ‐(I) 2 (H)(C) than one based on bond additivity.