MECHANISTIC INVESTIGATIONS CONCERNING THE AQUEOUS OZONOLYSIS OF BROMACIL

Bromacil ozonolysis was examined to determine the mechanism of product formation in an effort to optimize a chemical-microbial remediation s trategy for contaminated waters. Two debrominated products, 3-sec-buty l-5-acetyl-5-hydroxyhydantoin (II) (24%) and 3-sec-butylparabanic acid (III) (56%), and a dibromohydrin, 3-sec-butyl-5,5-dibromo-6-methyl-6- hydro (IV) (20%), were formed. The latter compound, arising from HOBr addition to bromacil, reverted back to starting material, causing the treated solution to remain somewhat phytotoxic. Mass balance studies p rovided evidence for parallel reaction pathways as opposed to a series pathway where II gives rise to III. Addition of hydrogen peroxide sli ghtly decreased the rate of bromacil degradation while the addition of tert-butyl alcohol (t-BuOH), a hydroxy radical scavenger, increased t he degradation rate, strongly suggesting that the mechanism does not i nvolve hydroxy radicals but direct ozone attack at the double bond. A much lower yield of IV, 6%, relative to the control was observed with H2O2, whereas a slightly higher yield, 23%, was found with t-BuOH.