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Reaction of hydrogen atoms with diethyldisulfide and ethylmethyldisulfide
Author(s) -
Ekwenchi M. M.,
Safarik I.,
Strausz O. P.
Publication year - 1981
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.550130905
Subject(s) - chemistry , radical , reaction rate constant , kinetics , hydrogen , chain reaction , entropy of activation , medicinal chemistry , photochemistry , organic chemistry , physics , quantum mechanics
H atoms react with C 2 H 5 SSC 2 H 5 to give C 2 H 5 SH as the sole retrievable product with ϕ = 2.32 at 25°C and 2.84 at 145°C. The primary reaction is postulated to be H + C 2 H 5 SSC 2 H 5 ← C 2 H 5 SH + C 2 H 5 S with k 1 = (4.73 ± 0.64) × 10 13 exp [−(1710 ± 69)/ RT ] cm 3 /mol·s relative to the rate constant of the H + C 2 H 4 ← C 2 H 5 reaction. The high value of the entropy of activation suggests the presence of partial hydrogen bonding in diethyldisulfide which is broken in the transition state. Ethylmethyldisulfide reacts similarly: H + C 2 H 5 SSCH 3 ← C 2 H 5 SH + CH 3 S or CH 3 SH + C 2 H 5 S. The thiyl radicals propagate a chain of radical exchange reactions forming the symmetrical disulfides with exposure‐time‐dependent quantum yields. The overall kinetics conform to a 16‐step mechanism from which the rate constants of the elementary reactions could be established by computer modeling. Thiyl radicals react considerably more slowly with disulfides than H atoms.