1 research outputs found
Can Carbamates Undergo Radical Oxidation in the Soil Environment? A Case Study on Carbaryl and Carbofuran
Radical oxidation of carbamate insecticides,
namely carbaryl and
carbofuran, was investigated with spectroscopic (electron paramagnetic
resonance [EPR] and UV–vis) and theoretical (density functional
theory [DFT] and ab initio orbital-optimized spin-component scaled
MP2 [OO-SCS-MP2]) methods. The two carbamates were subjected to reaction
with <sup>•</sup>OH, persistent DPPH<sup>•</sup> and
galvinoxyl radical, as well as indigenous radicals of humic acids.
The influence of fulvic acids on carbamate oxidation was also tested.
The results obtained with EPR and UV–vis spectroscopy indicate
that carbamates can undergo direct reactions with various radical
species, oxidizing themselves into radicals in the process. Hence,
they are prone to participate in the prolongation step of the radical
chain reactions occurring in the soil environment. Theoretical calculations
revealed that from the thermodynamic point of view hydrogen atom transfer
is the preferred mechanism in the reactions of the two carbamates
with the radicals. The activity of carbofuran was determined experimentally
(using pseudo-first-order kinetics) and theoretically to be noticeably
higher in comparison with carbaryl and comparable with gallic acid.
The findings of this study suggest that the radicals present in soil
can play an important role in natural remediation mechanisms of carbamates