Photochemical Behaviour of Carbamates Structurally Related to Herbicides in Aqueous Media: Nucleophilic Solvent Trapping versus Radical Reactions

Monica Passananti,Flavio Cermola,Maria Rosaria Iesce,Marina Dellagreca,Fabio Temussi,Rosalia Sferruzza,Lucio Previtera

doi:10.1155/2014/864361

Abstract

Irradiation ofN-arylO-aryl carbamates has been carried out in H2O/CH3CN (1 : 1 v/v) solutions atλ>290 nm. When chlorine is on theN-aryl ring, halogen-substituted products are found. These photoproducts derive from the trapping of the intermediate radical cation by water and, even, by acetonitrile leading to phenols andN-arylacetamides (photo-Ritter products), respectively. UnsubstitutedN-aryl carbamates slowly undergo photo-Fries reaction.

Highlights

Interaction of light with matter is one of the most important processes responsible for abiotic transformations of a xenobiotic in the environment, mainly in surface water [1,2,3]
When chlorine is on the N-aryl ring, halogen-substituted products are found. These photoproducts derive from the trapping of the intermediate radical cation by water and, even, by acetonitrile leading to phenols and N-arylacetamides, respectively
We studied the photochemical reactivity of two carbamate herbicides, chlorpropham, and phenisopham (Scheme 1) [14]

Summary

Introduction

Interaction of light with matter is one of the most important processes responsible for abiotic transformations of a xenobiotic in the environment, mainly in surface water [1,2,3]. Carbamate function is present in a wide number of biologically active compounds. Carbamate pesticides are an important group which are widely used through the world [9]. Carbamates exhibit absorption of radiation present in sunlight (>290 nm), and this requires the understanding of their photochemical behaviour [10]. The most general photochemical event, mainly observed in O-aryl derivatives, leads to rearranged products, via photoFries reaction and/or fragmentation [10, 11]. Less frequent is this type of photorearrangement in N-aryl carbamates [12, 13]. We studied the photochemical reactivity of two carbamate herbicides, chlorpropham, and phenisopham (Scheme 1) [14]

Methods

Results

Conclusion