Unexpected formation of N'-phenyl-thiophosphorohydrazidic acid O,S-dimethyl ester from acephate: chemical, biotechnical and computational study.

By the nucleophilic attack of phenylhydrazine on acephate in aqueous medium, a stable product N'-phenyl-thiophosphorohydrazidic acid O,S-dimethyl ester (1) was obtained and characterized by elemental, spectral and thermal analysis. Thermodynamic parameters, Ea, ΔH°, ΔS° and ΔG°, have found to be 62.15, -67.95, -0.068 and -20.05 kJ mol according to the Coats-Redfern equation. Analysis of interaction of 1 with BSA protein was done by using the UV-Vis and FTIR spectroscopic methods. The observed binding constants was 1.12 (±0.09) × 10 M. The biological effect of 1 was checked on different plant growth-promoting (PGPR) strains such as Rhizobium leguminosarum, Pseudomonas fluorescens, Arthrobacter citreus, Bacillus brevis and Salmonella typhimurium and compared with parent molecule acephate where 1 has shown less toxicity against PGPRs as compared to acephate. The experimental results for geometric parameters and values of peak position in IR spectra have found to match excellently with the computational studies performed by GAMESS software package. Theoretically, twelve new analogs of 1 were prepared and their comparative reactivity (HOMO-LUMO energy) and biodecomposition (on the basis of polarizability) is discussed.