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Aqueous solutions of HONO (ranging from 0.010M to 0.057M) and NO2 (ranging from 0.025M to 0.035M) were each photolyzed with nm ultraviolet (UV) light. In the presence of benzene scavenger, DH radical intermediate was indicated by formation of p-nitrosophenol (PNP). Ultraviolet/visible (UV/vis) absorption spectra of photolyzed aqueous HONO/benzene solutions showed the presence of PNP by its characteristic absorption at 298 nm. UV/vis absorption spectra of photolyzed aqueous NO -benzene solutions showed no evidence of PNP formation. Other compounds such as scavengers were toluene, benzoic acid, and terephthalic acid. UV/vis spectra of photolyzed aqueous HOND/scavenger solutions showed an Int n e road peak in the 295-310 nm range, Indicating that the scavenger was hydroxylated by OH, formed from HONO photolytic dissociation, and subsequently nitrostated by reaction with excess HONO. Hydrugen peroxide, a known OH producer, was photolyzed in the presence of benzene to verify the proposed OH-scavenging sequence under varying pH condItions. UV/vis spectra showed evidence of hydrocybenzene formation upon photolysis. The thermal decomposition of HONO was studied and a kinetic order with respect to HONO, of 0.5+-0.5 was determined. Quantitative data concerning the photochem cal de omposition of HONO was too inconsistent to make reasonable comparisons to thermal decomposition data.



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