Monatshefte fu ¨r Chemie 138, 449–452 (2007) DOI 10.1007/s00706-007-0593-6 Printed in The Netherlands Nitration of Aromatic Compounds Catalyzed by Divanadium-Substituted Molybdophosphoric Acid, H 5 [PMo 10 V 2 O 40 ] Majid M. Heravi 1; , Khadijeh Bakhtiari 1 , Tina Benmorad 1 , Fatemeh F. Bamoharram 2 , Hossein A. Oskooie 1 , and Maryam H. Tehrani 1 1 Department of Chemistry, School of Sciences, Azzahra University, Vanak, Tehran, Iran 2 Department of Chemistry, School of Sciences, Islamic Azad University Mashhad-Branch, Mashhad, Iran Received November 14, 2006; accepted (revised) November 23, 2006; published online March 16, 2007 # Springer-Verlag 2007 Summary. The nitration of aromatic compounds was carried out in the presence of divanadium-substituted molyb- dophosphoric acid, H 5 PMo 10 V 2 O 40 , as catalyst and a mixture of nitric acid and acetic anhydride as nitrating agent. In the presence of this heteropolyacid the ortho- and para-nitro com- pounds were obtained in good to excellent yields under mild reaction conditions. Keywords. Catalyst; Heteropolyacid; Aromatic substitution; Nitration; H 5 PMo 10 V 2 O 40 . Introduction The nitronium ion is usually the nitrating agent in electrophilic aromatic nitration. The nitronium ion is formed in situ from nitric acid, alkyl nitrate, acyl nitrates (XONO 2 , X ¼ H, RC(O)), in which it is bound to an oxygen atom [1]. On the other hand, nitration of aromatic substrates is a widely studied reaction of great industrial sig- nificance as many nitro-aromatics are extensively uti- lized and act as chemical feedstock for a wide range of useful material such as dyes, pharmaceuticals, perfumes, and plastics. Aromatic nitration is quite notorious for its unfriendly nature towards the en- vironment. The use of large quantities of nitric and sulfuric acids, corrosiveness, and potential danger of explosion, low regioselectivity, and oxidative degra- dation of by-products are the disadvantages of this reaction [2]. Zeolite-based solid acid catalysts such as ZSM-5 [3], X [4], Y [3–5], and  [3, 5, 6] have been used for nitration of various activated as well as deactivated substrates [3, 4, 6–8]. A variety of other solid acids such as silica gel [9], clay supported metal nitrates [10–12], modified and sulfated zirconia [13], and vapor phase nitration of benzene by dilute nitric acid in the presence of het- eropolyacid partially neutralized by Cs or Tl ions [14] have also been applied for nitration of aromatic compounds. Heteropoly acids, HPAs, catalyze a wide variety of reactions in homogeneous or heterogeneous (liquid– solid, gas–solid, or liquid–liquid biphasic) systems, offering strong options for more efficient and clean- er processing compared to conventional mineral acids [15–18]. Catalysts based on heteropolyacids as Brønsted acids have many advantages over liquid acid catalysts. They are non-corrosive and environ- mentally benign, presenting fewer disposal problems. Solid heteropolyacids have attracted much attention in organic synthesis owing to easy work-up proce- dures, easy filtration, and minimization of cost and waste generation due to reuse and recycling of the catalysts [19]. Being stronger acids, heteropolyacids will have significantly higher catalytic activity than conventional catalysts such as mineral acids, mixed-  Corresponding author. E-mail: mmh1331@yahoo.com