Investigation of some factors influencing isomalathion formation in malathion products

Unequivocal Identification of Compounds Formed in the Photodegradation of Fenitrothion in Water/Methanol and Proposal of Selected Transformation Pathways

“…Isomerization ofBisfenitrothion: S-Methyl 0,0-Bis(3-methyl-4-nitro)phenyl Phosphate (XXV). Following the general procedure reported (Rengasamy and Parmar, 1988), a mixture of compound XXIV (0.040 g, 0.1 mmol) and silica gel (0.020 g, 60-200 µ ) in dry JV^V-dimethylformamide (2 mL) was heated under reflux until the reaction was complete (30 min, TLC monitoring).…”

“…Compounds were fully characterized by their spectral data (IR, , 13C, and 31P NMR, MS. the presence of silica gel [Scheme 1; cf. Rengasamy and Parmar (1988)], the different phosphorothioates were converted into their respective phosphates in nearly quantitative yields by treatment with dimethyldioxirane according to our previously reported procedure (Sanchez-Baeza et al, 1990). In these cases, the shift of approximately 70 ppm upfield in the 31P NMR spectra of the reaction products confirmed the conversion of the P=S into the corresponding P=0 moiety (Tebby, 1987).…”

Synthesis and 31P Chemical Shift Identification of Tripeptide Active Site Models That Represent Human Serum Acetylcholinesterase Covalently Modified at Serine by Certain Organophosphates

“…Oxons react with cholinesterases to afford O,O-dimethyl phosphorylated enzymes via ejection of the leaving group Z to give O,O-dimethyl phosphate inhibited ChE representing the major mechanism of action of phosphorothionate insecticides. Alternatively, O,O-dimethyl phosphorothionates 1 may isomerize to form phosphorothiolates (3) (Scheme 1), a process that occurs during the manufacture, storage, or environmental lifetime of the OP (8)(9)(10). Because a PdO bond is formed during the isomerization, phosphorothiolates (3) like oxons are more potent anticholinesterase agents than thionates (11).…”

Preparation, analysis and anticholinesterase properties of O,O-dimethyl phosphorothioate isomerides

“…The "isomerization" of alkoxy-thiophosphoryl to alkylthio-phosphoryl linkage is one such example of an impurity-forming reaction (eq 1; see Figure 1). This particular rearrangement may occur thermally (7,8), may occur photochemically (7,9), or may be induced chemically (10).…”

“…Lastly, alkylthio phosphorothioate compounds may be prone to "aging" (18,19). Despite this strong evidence, there have been few systematic studies (7,8) directed toward examining the "isomerization" products of phosphorothioates and related materials.…”