JMS letters
[2] A. Navalon, A. Prieto, L. Araujo, J. L. Vilchez. Determination of
pyrimethanil and kresoxim-methyl in green groceries by headspace
solid-phase microextraction and gas chromatography-mass spec-
trometry. J. Chromatogr. A 2002, 975, 355.
[3] X. H. Sun, Y. F. Liu, Z. C. Tan, Y. Y. Di, H. F. Wang, M. H. Wang. Heat ca-
pacity and enthalpy of fusion of pyrimethanil laurate (C24H37N3O2).
J. Chem. Thermodyn. 2004, 36, 895.
[4] X. Yu, L. Pan, G. Ying, R. S. Kookana. Enhanced and irreversible
sorption of pesticide pyrimethanil by soil amended with biochars.
J. Environ. Sci. (China) 2010, 22, 615.
[5] H. Zhao, Y. K. Kim, L. Huang, C. L. Xiao. Resistance to thiabendazole
and baseline sensitivity to fludioxonil and pyrimethanil in Botrytis
cinerea populations from apple and pear in Washington State.
Postharvest. Biol. Tec. 2010, 56, 12.
analogous to that postulated for the formation of 6 (Fig. 2, right
hand). The formation of compound 2 (MW 177) may be also ratio-
nalized by a mechanism following photoionization of 7, in com-
petition with that postulated for the formation of 6 and
involving a ring aperture induced by the positive charge (Fig. 2,
right hand).
Structures B and C in Fig. 2 result from a water molecule
addition on ionized pyrimethanil followed by proton elimina-
tion. Compound 1, also characterized in GC-MS (see above),
results from elimination of the cyclohexa-2,4-dienone radical
from B, while the loss of the radical pyrimidine radical from C
leads to aniline; both compounds have been detected in a
previous study.[9] Isomeric forms of B and C have also been
considered; they are not displayed in Fig. 2 as they lead,
according to the mechanisms postulated above, to molecules
which are not detected.
Kinetics data show that 3 (eluted at 3.3 min) is among the first
compounds that are formed under irradiation. Cyclization of ion-
ized pyrimethanil followed by proton elimination leads to a free
radical, whose subsequent photoionization followed by hydride
addition leads to 3. The structure postulated for 3 is in good
agreement with the consecutive losses of CH3CN, CH4 and CN ob-
served under collisional activation of the ion 3H+. Kinetics data
(see Fig. 1) show that compound 5 seems to be produced from
3. Furthermore, given their very close retention times (3.30 min
for 3 vs 3.34 min for 5) and their difference of two mass units
(MW = 199 for 3 vs. MW = 197 min for 5), 5 was postulated to result
from dehydrogenation of 3 after photoionization of the latter
according to the mechanism depicted in Fig. 2.
[7] E. COMMISSION. Vol. 9, Journal officiel de l'Union Européenne, 2010.
[8] INERIS. Pyrimethanil
- N° CAS 53112-28-0. Normes de qualité
environementale 2011.
[9] E. A. Ana Aguera, A. Tejedor, A. Fernandez-Alba. Photocatalytic pilot
scale degradation study of pyrimethanil and its main degradation
products in waters by means of solid-phase extraction followed by
gaz and liquid chromatography with mass spectrometry detection.
Environ. Sci. Technol. 2000, 34, 1563.
[10] A. Vanni, F. Fontana. Photodegradation of Pyrimethanil induced by
iron(III) in aqueous solutions. J. Environ. Monit. 2003, 5, 635.
[11] L. Anfossi, P. Sales, A. Vanni. Degradation of anilinopyrimidine
fungicides photoinduced by iron(III)-polycarboxylate complexes.
Pest Manag. Sci. 2006, 62, 872.
[12] S. Navarro, J. Fenoll, N. Vela, E. Ruiz, G. Navarro. Photocatalytic
degradation of eight pesticides in leaching water by use of ZnO
under natural sunlight. J. Hazard. Mater. 2009, 172, 1303.
[13] J. Gomis, A. Arques, A. M. Amat, M. L. Marin, M. A. Miranda. A mechanis-
tic study on photocatalysis by thiapyrylium salts. Photodegradation of
dimethoate, alachlor and pyrimethanil under simulated sunlight.
Appl. Catal., B 2012, 123, 208.
[14] C. Sirtori, A. Zapata, S. Malato, A. Agueera. Formation of chlorinated
by-products during photo-Fenton degradation of pyrimethanil
under saline conditions. Influence on toxicity and biodegradability.
J. Hazard. Mater. 2012, 217, 217.
Conclusion
[15] M. Ashley. ROMIL technical report. Cambridge GB-CB5 9QT. www.
In conclusion, eight photo products were identified by HPLC-MS/
MS. Among them, compound 1 was the only one which was also
detected by GC-MS, with traces amounts of aniline. With the ex-
ception of compounds 1 and 7, the structures proposed for pho-
toproducts on the basis of mass spectra interpretation have not
been reported in previous studies.
[16] V. Feigenbrugel, S. Le Calve, P. Mirabel. Molar absorptivities of 2,4-D,
cymoxanil, fenpropidin, isoproturon and pyrimethanil in aqueous
solution in the near-UV. Spectrochim Acta A 2006, 63, 103.
[17] S. Coffinet, A. Rifai, C. Genty, Y. Souissi, S. Bourcier, M. Sablier, S.
Bouchonnet. Characterization of the photodegradation products of
metolachlor: structural elucidation, potential toxicity and persis-
tence. J. Mass Spectrom. 2012, 47, 1582.
[18] I. Oller, W. Gernjak, M. I. Maldonado, L. A. Perez-Estrada, J. A.
Sanchez-Perez, S. Malato. Solar photocatalytic degradation of some
hazardous water-soluble pesticides at pilot-plant scale. J. Hazard.
Mater. 2006, 138, 507.
[19] A. Vanni, F. Fontana, A. Cignetti, M. Gennari. Behaviour of
pyrimetranil in soil: Abiotic and biotic processes, Pesticide in air,
plant, soil & water system. Proceedings of the XII Symposium Pesticide
Chemistry, Piacenza, Italy, 4-6 June 2003 pp. 233-238.
[20] A. Vanni, L. Anfossi, A. Cignetti, A. Baglieri, M. Gennari. Degradation
of pyrimethanil in soil: Influence of light, oxygen, and microbial
activity. J. Environ. Sci. Health B 2006, 41, 67.
[21] T. Katagi. Photodegradation of pesticides on plant and soil surfaces.
Rev. Environ. Contam. Toxicol. 2004, 182, 1.
Yours,
AZIZ KINANI, AHMAD RIFAI, SOPHIE BOURCIER, FAROUK
JABER AND STÉPHANE BOUCHONNET
aLaboratoire des Mécanismes Réactionnels UMR-7651, Ecole
Polytechnique, 91128 Palaiseau Cedex, France
bLaboratoire d'Analyse des Pesticides et des Polluants Organiques -
Commission Libanaise de l'Energie Atomique - Centre National de
Recherches Scientifiques, Beirut, Lebanon
[22] NIST/EPA/NIH. NIST Mass Spectral Library. National Institute of
Standard and Technology. 2005, DC.
[23] D. O. J. S. Miller. Photolysis of polycyclic aromatic hydrocarbons in
water. Water Res. 2001, 35, 233.
[24] R. J. Hamilton. Blackie Academic and Professional. Thomson Science:
New york, 1998.
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