2‐Methyl‐1,3‐disulfoimidazolium polyoxometalate hybrid catalytic systems as equivalent safer alternatives to concentrated sulfuric acid in nitration of aromatic compounds

Abstract

Ionic liquid‐derived polyoxometalate salts [mdsim]3[PM12O40] (where M = W and Mo) of two heteropolyacids H3PW12O40.nH2O and H3PMo12O40.nH2O were synthesized using 2‐methyl‐1,3‐disulfoimidazolium chloride ([mdsim][Cl]) ionic liquid and the corresponding heteropolyacids. Three equivalents of [mdsim][Cl] were treated with the respective Keggin‐structured heteropolyacids (one equivalent) in aqueous medium at room temperature to afford the water‐stable ionic polyoxometalates as acidic solids. They were completely characterized using spectroscopic and other analytical techniques including thermal analysis and Hammett acidity studies. The inherent Brønsted acidic properties of ─SO3H group of these polyoxometalate salts were studied for the nitration of aromatic compounds with 69% HNO3 at normal temperature and 80°C without use of any external concentrated sulfuric acid. These strongly acidic polyoxometalates display good recyclability and efficient reusability.

Study of the catalytic activity of methylene-bridged dicationic –SO3H-functionalized imidazolium phosphomolybdate hybrids for the one-pot sequential synthesis of 3-substituted indoles

“…The connecting alkyl spacer groups between the imidazole rings as well as the methyl groups at the 2 position of the imidazole showed C–H rocking (1350–1392 cm −1 ) along with C–H bending (1450–1470 cm −1 ) bands in the respective IR spectra of the IL-POMs. 66…”

Equilibrium Solubility and Solvent Effect Study of 3-Nitrosalicylic Acid in Different Monosolvents Covering Temperatures from 278.15 to 323.15 K

“…It is a useful synthetic intermediate for 3-aminosalicylate or 3-aminosalicylamide products, which are of wide interest and relevance for agrochemical and pharmaceutical products. − In spite of the key significance of 3-nitrosalicylic acid, although much attention has been paid to its applications, only few studies have been carried out on the thermodynamics of 3-nitrosalicylic acid dissolved in various solvent systems. 3-Nitrosalicylic acid is usually obtained from nitration of salicylic acid using nitric and sulfuric acid mixtures. − However, the byproduct, 5-nitrosalicylic acid, is also formed simultaneously during nitration. Obviously, the presence of 5-nitrosalicylic acid as an impurity has an impact on 3-nitrosalicylic acid properties and hampers its further applications in diverse fields.…”