S. K. Mukerjee

New photodegradation products of chlorpyrifos and their detection on glass, soil, and leaf surfaces

The organophosphate insecticide chlorpyrifos was irradiated under different photochemical conditions and the products characterized by gas chromatography, mass spectrometry, and NMR spectroscopy. Irradiation of chlorpyrifos in hexane yielded dechlorinated photoproducts and cleavage products. In methanol, besides these products, chlorpyrifos gave oxons. Several new photoproducts, the formation of which apparently occurs by the displacement of 5-chloro by a methoxy substituent in the pyridyl moiety. The possibility of formation of such products on glass, soil, and leaf surfaces under the influence of UV and solar simulated light have also been explored and many new products presumably formed due to simultaneous photo-dechlorination, oxidation and hydrolytic processes were detected. Photodegradation of chlorpyrifos was rapid on a soil surface but comparatively slow on glass and leaf surfaces.

Ferrxanthone, a 1,3,5,6-tetraoxygenated xanthone from Mesua ferrea

Abstract A new xanthone was isolated from the heartwood of Mesua ferrea and its structure determined by UV, IR, NMR and mass spectrometry as 1,3-dimethoxy-5,6-dihydroxyxanthone.

Photoreductive dehalogenation of 5-bromomethyl- 1,2,3,4,7,7-hexachloro-2-nor-bornene (bromodan) -a cyclodiene insecticide

Abstract Photoirradiation of bromodan in hexane and methanol gave mono and di-dehalogenated photoproducts by replacement of chlorine atoms from the double bond. Whereas on photolysis in triethylamine there was stereo-selective removal of syn-chlorine atom from the methanobridge carbon.

Photodecomposition of Isofenphos (O‐ethyl‐O(2‐isopropoxycarbonyl)‐phenyl)‐Isopropylphos‐Phoramidothioate)

Photodecomposition of the organophosphorus insecticide isofenphos (O‐ethyl‐O‐(2‐isopropoxy‐carbonyl)‐phenyl)‐N‐isopropylphosphoremidothioate) has been studied in solution, on glass and soil surfaces. Isofenphos underwent oxidation from P = S to the P = O group and deesterification on irradiation in hexane and methanol. Photoproducts were isolated and identified by spectroscopic methods.

Photolysis of propioconazole

The photodegradation of propioconazole was studied in solution (methanol and water) and as thin films (on glass and soil). Photolysis caused cleavage of the C1‐triazole bond liberating 1,2,4‐triazole as the major product. Other photo‐products recovered in 3–11% yields include pentane‐1,2‐diol,1‐[2‐(2,4‐dichlorophenyl)‐1,3‐dioxoIane‐2‐yl]‐methanoI, 1‐[2‐(2‐chlorophenyl)‐4‐propyl‐1,3‐dioxolane‐2‐yl‐methyl]‐1H‐1,2,4‐triazoleand 1‐[2‐(2,4‐dichlorophenyl)‐4‐propyl‐1,3‐dioxolane‐2‐yl‐methyl]‐1H,1,2‐diazidrine.

Superoxide mediated dehydrohalogenation of photodieldrin and photoaldrin

Abstract Photodieldrin and photoaldrin-two major metabolites of insecticides, dieldrin and aldrin readily undergo stereospecific dehydrohalogenation in the presence of superoxide (O − 2 ) under relatively mild conditions.

Superoxide mediated novel transformations of the insecticide 0,0‐diethyl‐0‐(3,5,6‐trichloro‐2‐pyridyl) phosphorothioate (chlorpyrifos)

Superoxide induced oxidative transformations of 0,0‐diethyl‐0‐(3,5,6‐trichloro‐2‐pyridyl) phosphorothioate affords three novel products which have been assigned the structures 2, 4 and 5. These products are likely formed by the replacement of the 5‐chloro substituent in the pyridyl moiety by hydroxyl, ethoxyl, and 0,0‐diethyl phosphoryl group respectively. Surprisingly, oxidative desulfuration of thion (P=S) to oxon (P=O) which is a common feature during oxidation with conventional reagents like metachloroperbenzoic acid and hydrogen peroxide, did not occur during reaction with superoxide.

Photochemical decomposition of tetrachlorovinphos

The photochemical degradation of tetrachlorovinphos in solvents and as a solid has been investigated. Photoproducts have been isolated and characterized by spectroscopic methods and comparison with authentic samples. The rate of phototransformation of this compound has also been studied.

Triethylamine induced photolysis of endosulphan

Photolysis of pure isomers of endosulphan in the presence of triethylamine gives products arising by the loss of a chlorine atom from the geminal bridge. The structures of these products have been established. The α‐isomer of endosulphan isomerised to s‐isomer on a leaf surface.

Photolytic decomposition of uc‐54229, a Proinsecticide of the Carbamate group

Phototransformation of UC‐54229 (1) [2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl‐N‐(trimethylamino acetyl)‐N‐methyl carbamate chloride] was studied under UV and visible light conditions. Photoirradiation of 1 with UV‐light resulted in the formation of five degradation products which on the basis of their mass and 1H Nmr spectral analysis were characterised as 2, 3, 4, 5 and 6. It was observed that under the influence of light, UC‐54229 was degraded to acetyl‐carbofuran which under similar conditions underwent further transformation to the actual toxicant carbofuran. The degradation products or impurities present in 100% water soluble powder formulation were identified as carbofuran phenol and triethylamine hydrochloride.