The degradation of diflubenzuron and its chief metabolites in soils. Part II: Fate of 4‐chlorophenylurea

Abstract

The fate of 4‐chlorophenylurea in soils was studied with two preparations: one labelled with 14C in the phenyl ring and the other in the carbonyl group. The initial dose of 1 mg kg−1 decreased to 50% in about 5 weeks in aerobic sandy clay and in about 16 weeks in anaerobic hydrosoil. Soil treatment with each of the preparations resulted in the release of [14C]carbon dioxide, pointing to decarbonylation and ring opening. The fraction of non‐extractable (soil‐bound) radioactivity increased during incubation. Quantities of ring‐14C‐labelled and carbonyl‐14C‐labelled bound residues differed strongly in the aerobic soil but only slightly in the anaerobic hydrosoil. It is assumed that two sorts of bound residues are formed from 4‐chlorophenylurea: one is fairly stable and might consist of bound 4‐chloroaniline or its transformation products, whereas the other is presumed to be a degradable derivative of 4‐chlorophenylurea.

An In Vitro Spectroscopic Analysis to Determine the Chemical Composition of the Precipitate Formed by Mixing Sodium Hypochlorite and Chlorhexidine

“…While the toxin PCA is not produced, a different para-substituted molecule, chlorophenylurea, and a related molecule with an aliphatic linker still attached, is produced. While there are no toxicology data on these compounds, literature on related compounds suggests there could be toxicity issues, and chlorophenylurea may be metabolized to PCA (24,25). Accordingly, formation of the precipitate should still be avoided by using an intermediate flush in order to prevent occluding of dentinal tubules and compromised seal of the obturated root canal.…”

Microbial breakdown of halogenated aromatic pesticides and related compounds

“…Diflubenzuron (1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea) was hydrolysed in soil to 4-chlorophenylurea and 2,6-difluorobenzoate [314]. 4-Chlorophenylurea was presumably converted to 4-chloroaniline and bound to soil [315], while 2,6-difluorobenzoate mineralized to CO 2 [225]. The formation of halogenated anilines by hydrolysis of halogenated acylanilides, phenylcarbamates, and phenylureas is exemplified with the herbicides propanil, linuron and chlorpropham in Fig.…”

Detection of <i>Para</i>-Chloroaniline Resulting from the Interaction between Sodium Hypochlorite and Chlorhexidine Analyzed by Mass Spectrometry

“…Although, there are similar studies in the literature reporting the presence of PCA as the final product of the reaction in the precipitate formed with the mixture of CHX and NaOCl [19] [20] (2010) did not detect PCA in the reaction mixture analyzed by nuclear magnetic resonance (NMR), although they proposed the partial formation of PCA [5]. Nowicki and Sem (2011) analyzed the same mixture [31] and reported the presence of derivatives of benzene (p-chlorophenyl urea and chlorophenyl guanidine), which can be transformed into PCA [32] [33] [34]. On the other hand, the analysis by nuclear magnetic resonance spectroscopy and infrared spectroscopy of the precipitate formed after mixing NaOCl and QMix 2 did not reveal free PCA [35].…”