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EC number: 233-113-0 | CAS number: 10035-10-6
Phototransformation in air
Administrative data
Link to relevant study record(s)
Description of key information
HBr undergoes photolysis via a series of mechanisms to form hydrogen and bromine in air.
Key value for chemical safety assessment
Additional information
Falconer and Sunder (1968) showed that the photolysis reaction of HBr could progress via one or more of the following reaction schemes:
[1] HBr +hν → HBr*
[2] HBr* + M → HBr + M
[3] HBr* → H(2S) + (Br(2P3/2)
[4] [HBr + HBr]c+hν → [HBr…H…Br]c
[5] [HBr…H…Br]c→ HBr + HBr
[6] [HBr…H…Br]c→ H2+ 2[Br]c
[7] [HBr…H…Br]c→ HBr + H+ [Br]c
[8] H + H + M → H2+ M
[9] H + HBr → H2+ [Br]c
[13] [Br2+ HBr]c+hν → [HBr…H…Br]c
[14] [HBr…H…Br]c→ Br2+ HBr
[15] [HBr…H…Br]c→ H + Br2+ [Br]c
[16] H + Br2→ HBr + Br
Dotted lines indicate complexes and the subscript c indicates caged or matrix restrained species.
Baumfalk R, et al (1997) measured kinetic energies the dissociation reaction and obtained values of 1.36 ± n0.06 eV (Br) and 0.90 ± 0.05 eV (Br*) which were in good agreement with the calculated values of 1.35 eV and 0.89 eV obtained using the following equation:
hν(243.1nm) –D0(HBr) =Ekin(H) +Ekin(Br) +Eint(Br)
WhereD0is the dissociation energy of the HBr molecule andEkinandEintthe kinetic and internal energy of the fragment atoms.
The H atom photofragmented with zero kinetic energy after the photo-dissociation
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