D. D. Agarwal

Epoxidation of olefins using cis-dioxomolybdenum complexes as catalysts

Abstract Cis-dioxomolybdenum complexes, having tetradentate and tridentate ligands, as catalyst with t-butylhydroperoxide gave epoxides from olefins in good yield. The catalysts, except MoO2(apac), have been found to withstand the oxidative conditions. The steric environment due to the ligand around the metal center plays a significant role in the epoxidation of substituted olefins, viz., isoprene and 1,2-dimethyl-1,4-cyclohexadiene and cis-and trans-2-hexene. The steric effect due to nonporphyrin ligands is much less than that observed with catalysts having porphyrin ligands.

Epoxidation of olefins catalysed by Fe(III) Schiff base complexes as catalyst

Abstract The epoxidation of olefins using tri- and tetradentate ligand-containing Fe( III ) complexes as catalyst and iodosylbenzene as oxidant have been studied. Cyclohexene gave cyclohexene oxide, cyclohexenol and cyclohexenone. At higher concentrations of catalyst, low yield but high selectivity of epoxide was observed. The yield of epoxide increases with increasing concentration of cyclohexene. The relative rates of epoxidation of cyclo-olefins exhibit the order norbornene > cyclooctene > cycloheptene > cyclohexene > cyclopentene. The addition of pyridine was found to increase the yield of epoxide. The addition of NaH 2 PO 4 and NaHCO 3 also increases the yield of the epoxide; the addition of cetyltrimethylammonium bromide completely inhibits the epoxidation, while addition of sodium lauryl sulphate slightly retards the yield of the epoxide. These studies point to a mechanism in which formation of oxoiron( V ) and oxoiron( IV ) cation radical takes place.

Oxidation of alkenes using the RuCl3/PhIO system

Abstract The RuCl3 catalysed epoxidation of olefins gave more than 10% of epoxide. Pyridine addition increased the yield and selectivity of the epoxide. Epoxidation of norbornene gave exo- and endo-epoxide. The effect of surfactants supports the involvement of carbocation intermediates. The epoxidation of cyclic olefins follows the reactivity order cyclo-octene > norbornene > cyclopentene > cycloheptene > cyclohexene. Spectral studies suggest that oxo ruthenium (V) is the active oxidizing species.

Epoxidation of olefins using a CrO3/TBHP system

Abstract The epoxidation of cyclohexene using CrO3/TBHP gave cyclohexene oxide, cyclohexenol and cyclohexenone in the ratio 3:1:40. The nature of the solvent affects the yield of the product. Pyridine, imidazole, NaH2PO4 and surfactants were found to have negative effects on the yield of epoxide while sodium bicarbonate increases the yield of the epoxide. The relative rate of epoxidation of cyclic olefins was norbornene > cycloheptene > cyclooctene > cyclopentene > cyclohexene.

Synthesis and characterization of some peroxo complexes of zirconium

Abstract The peroxo complexes of zirconium using bidentate, tridentate and tetradentate ligands have been synthesized and characterized. Oxidation studies showed that when Ph 3 P, cyclohexene and allylalcohol were involved, the peroxo complexes with the tetradentate ligand failed to oxidize Ph 3 P while the one with the bidentate ligand did. The peroxo complexes involving bidentate and tetradentate ligands gave peroxide when cyclohexene (the substrate) in the presence of tert-butyl hydroperoxide as oxidant was oxidized. The peroxo complexes with the bidentate ligand gave higher yields of peroxide compared with the tetradentate ligand complex. The peroxo complexes failed to oxidize stoichiometrically allylalcohol and cyclohexene. This shows that peroxo complexes containing the tetradentate moiety are more stable.

Thermodynamic behaviour and stability constants of 5-arylazo-2-methylthio-4-hydroxy-6-methylpyrimidine (AMHP) complexes

Abstract The thermodynamic behaviour and stability constants of 5-arylazo 2-methylthio-4-hydroxy-6-methyl-pyrimidine and its complexes with Fe 3+ , Cu 2+ , Ni 2+ , Fe 2+ , Co 2+ , UO 2+ 2 , Cd 2+ , Zn 2+ and Mn 2+ have been determined potentiometrically in 75% (v/v) methanol—water mixture at ionic strength 0.1 M NaClO 4 . The stability constants have been determined by the Bjerrum—Calvin titration technique as modified by Irving and Rossotti at 25, 30 and 35±0.1°C. The order of stability is Fe 3+ > UO 2+ 2 > Cu 2+ > Fe 2+ > Ni 2+ >Zn 2+ >Co 2+ > Mn 2+ . Thermodynamic functions have been calculated and show that the stability of the complexes decreases with increase in temperature and the complex formation is an enthalpy directed process.

Synthesis, characterization and catalytic behaviour of thorium peroxo complexes

Abstract Stable peroxo complexes of thorium are formed which are unreactive as stoichiometric reagents but active as catalysts in the presence of tert-butylhydroperoxide, resulting in the formation of cyclohexenone and cyclohexenol in substantial yields together with cyclohexene oxide. Competitive epoxidation of cyclo-olefins suggests that coordination of olefins to the metal centre does not take place.

Electrochemical investigations on nitro-substituted hydrazono compounds

The electrochemical reduction of 3-(N-nitro-N-phenylhydrazono)pentane-2,4-diones has been studied over a wide pH range at dropping mercury and glassy carbon electrodes. These compounds give two four-electron waves corresponding to the reduction of nitro and hydrazono groups, and one two-electron wave corresponding to the C–N reductive bond. On the basis of polarography, linear and cyclic sweep voltammetry, coulometry, IR, mass, and 1H NMR spectral studies, and product identification, a reaction mechanism is suggested to account for the reduction mechanism.

Rapid Tlc Separation of Some Closely Related Potential Antineoplastic Arylazothiazoles

Abstract A rapid thin layer chromatographic procedure that utilizes neutral solvent system for the separation of 24 closely related arylazothiazoles on silica gel adsorbent is reported.

Electrochemical oxidation of ethyl-2-arylhydrazono-3-phenylpropanoate-1,3-dione

In this paper, we report the electrochemical oxidation of ethyl-2-arylhydrazono-3-phenylpropanoate-1,3-dione, which, to our knowledge, is the first report of its kind. These compounds are very stable and are not hydrolysed by conventional reagents