Electrochemical reduction of the synthetic pyrethroid insecticides tralomethrin and tralocythrin at glassy carbon and mercury electrodes
Introduction
Tralomethrin and tralocythrin, Fig. 1a, are synthetic pyrethroid insecticides synthesised by bromination across the double bonds of the dihalovinyl substituent of the pyrethroids deltamethrin [1]and the (S)-α-(1R)-cis isomer of cypermethrin [2], Fig. 1b, respectively. The compounds are produced as a mixture of two stereoisomers as the bromination reaction introduces a further chiral centre into deltamethrin (a single stereoisomer) and the cypermethrin stereoisomer.
In a previous publication [3]the reduction behaviour of a range of pyrethroids based upon esters of α-cyano-3-phenoxybenzyl alcohol was detailed. The initial reduction process led to cleavage of both the ester and the cyanide bond. In this paper we report the reduction behaviour of tralomethrin and tralocythrin in the non-aqueous solvents acetonitrile and methanol. Although these compounds are based on α-cyano-3-phenoxybenzyl alcohol, the initial reduction behaviours follow a different and specific reaction mechanism which is fully elucidated.
Section snippets
Pyrethroid compounds
Tralomethrin (93.8%), tralocythrin (94%) (Roussell Uclaf Australia Pty., Pennant Hills, N.S.W., Australia), cypermethrin (99.3%) (Shell Chemical Pty., Melbourne, Vic., Australia) and deltamethrin (99%) (CSIRO Division of Wool Technology, Belmont, Vic., Australia) were gifts of the organisations named and were used without further purification. The IUPAC names of the pyrethroid compounds used in this study are presented in Appendix A.
Instrumentation
Electrochemical, HPLC and mass spectrometric instrumentation,
Cyclic voltammetry
Reduction (Epred) and oxidation (Epox) peak potential data obtained for tralomethrin and tralocythrin are summarised in Table 1.
Discussion
The results of voltammetric and CPE experiments indicate that at both mercury and glassy carbon electrodes the overall reduction mechanism of tralomethrin and tralocythrin involves reductive debromination to give one mole of deltamethrin and cypermethrin, respectively, and two moles of bromide ion. The debromination reactions are independent of the proton donating ability of the solvent.
Under conditions of reductive CPE, despite the fact that very different potentials are employed, identical
Acknowledgements
Funding for this study was provided by the Australian Wool Research and Development Corporation through the award of postgraduate scholarship UDG002 to D.C.C. Mass spectra were obtained by Mr Gary Franklin of Deakin University. Much of the research was undertaken at La Trobe Univeristy when A.M.B. was Professor of Chemistry at that institution. The donation of pyrethroid standards by the organisations listed in the text is gratefully acknowledged.
References (20)
- Roussel Uclaf, Ger. Offen. Patent, 2 742 546,...
- Ciba-Geigy, Ger. Offen. Patent, 2 805 226,...
- et al.
J. Electroanal. Chem.
(1997) - et al.
Anal. Chem.
(1996) - et al.
Electroanalysis
(1998) - et al.
Eisei Kagaku
(1990) - et al.
- P. Pouillen, A.M. Martre, P. Martinet, Bull. Soc. Chem. Fr., (1979) 387 Part...
- et al.
J. Assoc. Off. Anal. Chem.
(1993) - et al.
J. Org. Mass Spectrom.
(1993)
Cited by (9)
Pesticides determination in foods and natural waters using solid amalgam-based electrodes: Challenges and trends
2020, TalantaCitation Excerpt :The first is a rapid step involving the adsorption of bipyridinium on the working electrode and the transfer of an electron, forming an intermediate radical, which is subsequently reversibly reduced to a species with a greater degree of reduction, forming a neutral molecule, as shown in Table S2 in the Supplementary Data [36,66]. Pyrethroids are reversibly reduced at cathodic potential values; the reaction mechanism will depend on the substituents, which can promote a shift to a less negative potential value and a change in the reversibility of the redox process [67]. Cypermethrin, deltamethrin, fenpropathrin, fenvalerate, bifenthrin, permethrin, λ-cyhalothrin, and cyfluthrin are the pyrethroids most evaluated on mercury-based surfaces, due to reduction of carbonyl groups, which can occur in the pH range from 2 to 12, involving the exchange of two electrons.
Screen-printed acetylcholinesterase-based biosensors for inhibitive determination of permethrin
2012, Science of the Total EnvironmentCitation Excerpt :Many analytical methods have been described in the literature for the determination of permethrin, most of them related to chromatographic (Chocholous et al., 2008; de Souza Pinheiro and de Andrade, 2009; Du et al., 2010; Vazquez et al., 2008; Vonderheide et al., 2009) and spectrophotometric techniques (Butte and Kemper, 1999; Kazemipour et al., 2002). The analysis of similar insecticide species has also been performed by electroanalytical methods (Coomber et al., 1998a, 1998b; Manisankar et al., 2009, 2008, 2005; Oudou et al., 2001) but, to the authors' knowledge, few of them describe the successful determination of permethrin using this kind of method. In the work described by Thriveni and Sreedhar (2004), the determination of the insecticide was carried out using a hanging mercury drop electrode (HDME).
Electroreductive Remediation of Halogenated Environmental Pollutants
2016, Chemical ReviewsElectrochemical dehalogenation of organic pollutants
2014, Journal of the Mexican Chemical SocietyVoltammetric nanosensor for cyfluthrin based on graphene and poly (3-methyl) thiophene
2014, Analytical and Bioanalytical ElectrochemistryElectrode reactions and electroanalysis of organomercury compounds
2010, Russian Chemical Reviews
- 1
Present address: Department of Chemistry, Monash University, Clayton, Victoria 3168, Australia.