Chlorine Compounds in the Stratosphere: HOCl, HOOCl, and ClOO

Abstract

Abstract Possible reactions leading to the formation and the loss of HOCl and HOOCl in the stratosphere are explored. Since such reactions must be exothermic, the heats of formation of the title com­pounds are discussed first. Values adopted are ΔHf 0(HOCl) = -22 ±3, ΔHf 0(ClOO) = 20.5 ± 0.4, ΔHf 0(HOOCl) = -17 kcal/mol. Several important reactions are then identified. The most significant reactions apepar to be HO2 + CIO → HOCl + O2 HOCl + hν → OH + Cl < 400nm OH + ClO + M → HOOCl + M HO2 + ClOO → OH + ClO. From estimates of the associated rate coefficients and photodissociation factors the steady state concentrations of HOCl and HOOCl are derived. Both are sufficiently low to exclude a significant influence upon the steady state concentrations of CIO and Cl.