Premium
A kinetic study of the chemistry of the SO 2 ( 3 B 1 ) reactions with cis ‐ and trans ‐2‐butene
Author(s) -
Demerjian Kenneth L.,
Calvert Jack G.,
Thorsell David L.
Publication year - 1974
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.550060606
Subject(s) - chemistry , 2 butene , isomerization , photochemistry , reaction rate constant , olefin fiber , quenching (fluorescence) , butene , quantum yield , kinetics , fluorescence , organic chemistry , catalysis , ethylene , physics , quantum mechanics
The chemical reactions of SO 2 ( 3 B 1 ) molecules with cis ‐ and trans ‐2‐butene have been studied in gaseous mixtures at 25°C by excitation of SO 2 within the SO 2 ( 3 B 1 ) → SO 2 (+, 1 A 1 ) ‘forbidden’ band using 3500–4100‐Å light. The initial quatum yields of olefin isomerization were determined as a function of the [SO 2 ]/[2‐butene] ratio and added gases, He and O 2 . The kinetic treatment of these data suggests that there is formed in the SO 2 ( 3 B 1 ) quenching step with either cis ‐ or trans ‐2‐butene, some common intermediate, probably a triplet addition complex between SO‐ and olefin. It decomposes very rapidly to form the 2‐butene isomers in the ratio [ trans ‐2‐butene]/[ cis ‐2‐butene] = 1.8. In another series of experiments SO 2 was excited using a 3630 ± 1‐Å laser pulse of short duration, and the SO 2 ( 3 B 1 ) quenching rate constants with the 2‐butenes were determined from the SO 2 ( 3 B 1 ) lifetime measurements. The rate constants at 21°C are (1.29 ± 0.18) × 10 11 and (1.22 ± 0.15) × 10 11 l/mole·sec with cis ‐2‐butene and trans ‐2‐butene, respectively, as the quencher molecule. Within the experimental error these quenching constants equal those derived from the quantum yield data. Thus the rate‐determining step in the isomerization reaction is suggested to be the quenching reaction, presumably the formation of the triplet SO 2 ‐2‐butene addition complex. In a third series of experiments using light scattering measurements, it was found that the aerosol formation probably originates largely from SO 3 and H 2 SO 4 mist formed following the reaction SO 2 ( 3 B 1 ) + SO 2 → SO 3 + SO( 3 Σ − ). Aerosol formation from photochemically excited SO 2 ‐olefin interaction is probably unimportant in these systems and must be unimportant in the atmosphere.