Hossein Razavi

Novel Catalytic Acetylation of Alcohols with Preyssler's Anion, [NaP5Wa30O110]14– 1

Sodium 30-tungstopentaphosphate, the so-called Preysslers anion with a formula of [NaP5W30O110]14– (I) catalyzes the acetylation of alcohols (CnH2n + 1OH, n = 2, 3, 4, 5) with acetic acid. High yield is obtained with I as pure acid or supported on silica. Both homogeneous and heterogeneous catalysts are discussed and compared. H14[NaP5W30O110], abbreviated as H14-P5, under homogeneous conditions, as well as supported on silica (heterogeneous conditions) is found to be an excellent catalyst. Our data indicate that, when the ammonium salt of I is employed as the catalyst, the yield increases as the alcohol carbon-chain is increased. This behavior is found to be quite general. The catalysts can be easily recovered and recycled with retention of their initial structure and activity.

Novel oxidation of aromatic aldehydes catalyzed by Preyssler's anion, [NaP5W30O110]14-

Preysslers anion, with formula [NaP5W30O110]14-, catalyzes the oxidation of aromatic aldehydes to related carboxylic acids by hydrogen peroxide as oxidizing agent, under microwave irradiation, or at 70 oC. Both homogeneous and heterogeneous Preysslers catalysts (as H14[NaP5W30O110 ]) were used and had their activity compared with those of some Keggin structures. Our data indicate that Sodium30-tungsto pentaphosphate, the so-called Preysslers anion, with high hydrolytic (pH=0-12) and thermal stability is the best catalyst with high yield and good selectivity. Under microwave irradiation, this polyanion supported on SiO2 was found to be an excellent catalyst for aldehydes with low loss factor in 1-2 min (the loss factor is a measure of the ability of the material to dissipate energy). The effects of various parameters, including catalyst type, nature of the substituent in the aldehyde and temperature, on the yield of the carboxylic acids were studied.

Useful chemical information obtained by use of common counterions as internal calibrants in X-ray photo-electron spectra of inorganic complex ions

Abstract It is shown that the accuracy and precision, and hence the value for bonding-structure studies, in relative binding energy measurements can be enhanced if a common counterion is employed. The differences in chemical shifts between the peaks for the atoms under consideration and for a common counterion in twenty-nine compounds are measured. This technique reduces charging effect errors, which otherwise often occur when non-conducting samples (e.g., salts) are measured relative to a traditional external calibrant. The improvements in accuracy and precision are demonstrated by using the cesium salt of twenty-nine heteropoly and isopoly anions in more than seventy-five different runs. Oxygen 1 s , tungsten 4 d , and molybdenum 3 d binding energies are measured relative to the cesium 3 d ionization potential. In this work the cesium counterion is assumed to be chemically invariant. For the relative binding energies that are studied, no dependence on the charge of the anion is observed. A linear relation seems to exist between the oxygen Is binding energies (measured relative to Cs) and the oxygen-to-tungsten ratio in five isopoly anions. This latter finding may serve as a useful aid in studies related to the synthesis of new compounds.

Study the effect of mechanical alloying parameters on synthesis of Cr{sub 2}Nb–Al{sub 2}O{sub 3} nanocomposite

Graphical abstract: - Highlights: • Cr{sub 2}Nb–Al{sub 2}O{sub 3} nanocomposite synthesized through MA. • Effect of BPR, rotating speed, milling time and PCA concentration investigated. • After annealing at 1100 °C crystalline phase were appeared. • Williamson–Hall analysis was used in order to study the grain size of nano composite. - Abstract: In this study, Cr{sub 2}Nb–20 vol.% Al{sub 2}O{sub 3} nanocomposite was prepared successfully by mechanochemical reaction between Al, Nb and Cr{sub 2}O{sub 3} powders. Amorphization of powder occurred during mechanical alloying because of high energy collisions between powders and steel balls in milling container which transfer high degree of energy to powders. Therefore, annealing was needed to form crystalline phases. The influence of different mechanical alloying parameters such as BPR, rotating speed, milling time and PCA concentration on synthesis of composite material were investigated. After mechanical alloying, the powder was encapsulated in quartz and then annealed at 1100 °C for 3 h. After annealing, 3 different phases were appeared (Cr{sub 2}Nb (cubic), Cr{sub 2}Nb (hexagonal) and α-Al{sub 2}O{sub 3}). The structural changes of powder particles during mechanical alloying were studied by X-ray diffractometry (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM)

Synthesis, molecular structure, and characterization of a new 3D-layered inorganic-organic hybrid material: [D/L-C{sub 6}H{sub 13}O{sub 2}N-H]{sub 3}[(PO{sub 4})W{sub 12}O{sub 36}].4.5H{sub 2}O

Abstract A new 3D-layered inorganic–organic hybrid [ d / l -C 6 H 13 O 2 N–H] 3 [(PO 4 )W 12 O 36 ]·4.5H 2 O ( 1 ), as racemic material in the solid phase, has been synthesized and fully characterized by elemental microanalysis, single crystal X-ray diffraction, and infrared, Raman, and proton nuclear magnetic resonance spectroscopes. The most unique structural feature of 1 is its three-dimensional inorganic infinite tunnel-like framework that results in weak van der Waals interactions along the a -axis. A weak interlayer interaction between the titled layers provides a desirable condition to explore its potential as a host in a host–guest complex. The racemization has been observed in the crystal structure with the centric space group ( P 2 1 / c ). The latter consists of α-[(PO 4 )W 12 O 36 ] 3− and [ d / l -C 6 H 13 O 2 N–H] + moieties with water molecules linked together by a complex network of hydrogen bond interactions.