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2‐Methyl‐1,3‐disulfoimidazolium polyoxometalate hybrid catalytic systems as equivalent safer alternatives to concentrated sulfuric acid in nitration of aromatic compounds
Author(s) -
Saikia Susmita,
Borah Ruli
Publication year - 2019
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.5146
Subject(s) - polyoxometalate , chemistry , ionic liquid , sulfuric acid , catalysis , salt (chemistry) , nitration , inorganic chemistry , aqueous solution , chloride , keggin structure , ionic bonding , organic chemistry , ion
Ionic liquid‐derived polyoxometalate salts [mdsim] 3 [PM 12 O 40 ] (where M = W and Mo) of two heteropolyacids H 3 PW 12 O 40 . n H 2 O and H 3 PMo 12 O 40 .nH 2 O 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 ─SO 3 H group of these polyoxometalate salts were studied for the nitration of aromatic compounds with 69% HNO 3 at normal temperature and 80°C without use of any external concentrated sulfuric acid. These strongly acidic polyoxometalates display good recyclability and efficient reusability.