Reactivity of neonicotinoid insecticides with carbonate radicals

MARÍA LAURA DELL'ARCIPRETE; JUAN M. SOLER; LUCAS SANTOS-JUANES; ANTONIO ARQUES; DANIEL MÁRTIRE; JORGE FURLONG; MONICA C.GONZALEZ

WATER RESEARCH

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2012 vol. 46 p. 3479 - 3489

0043-1354

The reaction of three chloronicotinoid insecticides, namely Imidacloprid (IMD), Thiacloprid (THIA) and Acetamiprid (ACT), with carbonate radicals (CO3•-) was investigated. The second order rate constants (4 ± 1)×106, (2.8 ± 0.5)×105, and (1.5 ± 1)×105 M-1s-1 were determined for IMD, THIA and ACT, respectively. The absorption spectra of the organic intermediates formed after CO3•- attack to IMD is in line with those reported for alpha-aminoalkyl radicals. A reaction mechanism involving an initial charge transfer from the amidine nitrogen of the insecticides to CO3•- is proposed and further supported by the identified reaction products. The pyridine moiety of the insecticides remains unaffected until nicotinic acid is formed. CO3•- radical reactivity towards IMD, ACT, and THIA is low compared to that of HO• radicals, excited triplet states, and 1O2, and is therefore little effective in depleting neonicotinoid insecticides.