Iranian Journal of Chemistry and Chemical Engineering
Volume:19 Issue: 2, Nov-Dec 2000

NaBrO combined with NHCL is found to be an efficient reagent for the transformation of sulfides in to sulfoxides in aqueous acetonitrile and under mild conditions

 A PVC-based membrane containing cerium phosphate was developed. Unlikethe cerium phsophate itself that acts as a cation exchanger, the membrane exhibitedanion-exchange properties. Therefore, the utility of this compound as a sensory element fordetection of molybdate ions was pursued. The response of molybdate selective electrodebased on this membrane was perfectly linear in the concentration range 1. 98خ10-5 to 10-1M. Characteristics of this electrode such as electric resistance, stability and membranepreconditioning process, and regeneration of its sensitivity are reported.

Abstract: Silver tetrafluoroborate complex of 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(diphenylphosphinoylmethoxy)calix[4]arene (L) has been synthe-sized by reaction of silver tetrafluoroborate and L in dichloromethane at roomtemperature. The complex formed has a 1:1 metal/ligand ratio. 1H and 31P NMRdata support an encapsulated structure of the complex in which silver ion islocated inside the hydrophilic cavity of the ligand.

 The solvent extraction of rare earth metal ions from nitrate solu-tions by 5,11,17,23-tetra-tert-butyl-25,27-bis(diethylcarbamoylmethoxy)-26,28-dihydroxycalix[4]arene (L) in 1,2-dichloroethane has been investigated. The analy-sis of the extraction equilibrium obtained from a mixture of La3+, Eu3+, Er3+ andY 3+ revealed that the extracted species have a 1:1 metal/ligand ratio. Theintra-group separation efficiencies of the ligand have been evaluated in a compe-titive extraction and transport of 11 rare earth metal ions (La3+, Pr3+, Nd3+,Sm3+, Eu3+, Gd3+, Dy3+, Ho3+, Er3+, Yb3+ and Y 3+). The transport experimenthas been performed through a supported liquid membrane containing the ligandin o-nitrophenyl hexyl ether (NPHE). The distribution ratio and the flux of theions generally increases as the atomic radii decrease.

Birdged bithiazoles (5.5 - ethylene - 4.4 - bithiazoles) are synthesized as a good chelating agent

The complexation reaction between iodine and 1,10-Diaza-18-Crown-6(DA18C6) has been studied in acetonitrile by spectrophotometric, biamperometric andI+. I3-] formation of [(CH3CN)n indicative of the results are The techniques. conductometricfrom iodine and acetonitrile, and the formation of DA18C6 I+.I- from DA18C6 and]. The formation constant of the latter reaction has been calculated from I+I3- [(CH3CN)nthe absorbance-mole ratio data, using the nonlinear least square program "KINFIT". The IRspectra of acetonitrile-acetonitrile iodine complex and DA18C6-DA18C6 iodine complex arecompared and the effect of complexation on absorption bands are discussed.

 Coal with low ash content has an important role in the coal andsteel industry. There are different methods to measure the ash content. Theconventional method which is used in most coal mines of Iran, is to burn thecoal and measure the remaining ash. A new method has been recently developedat Nuclear Research Center (NRC) of Iran, which works on the basis of theabsorption of the dual energy g-ray by coal. In this paper we present the resultsobtained from coal mine "Zirab, Central Alborz, Iran" to which we have appliedthis method, and compared the results with those obtained by the conventionalmethod. In addition, the chemical components of the coal samples from six layersof this mine was obtained by X-ray fluorescence (XRF). We have found that forSiO2, Al2O3, TiO2, Na2O and K2O there exists a linear relationship betweenthese components and the ash content, but such a relationship was not obtainedfor Fe2O3, CaO, SO3 and MgO.

Supercritical carbon dioxide (SC-CO2) was used as solvent to synthesizeoleyl oleate as an analog of Jojoba oil from oleic acid and oleyl alcohol with highconversion (100%) of the acid into ester in a short time of 100 min. Utilizing a lowcost solid catalyst, p-toluenesulfonic acid monohydrate (PTSA), the esterificationreaction was performed, without any prior preparation step, in a flow mode, at apressure of 147 bar and a temperature of 60C. This method seems industrially suitablefor the production of oleyl oleate. The solubility of a mixture of oleyl alcohol and oleicacid in SC-CO2 were also measured to calculate the alcohol to acid ratio and theesterification yield.

A method for the degradation of pyrrolidine in water is described. The method relaies on the photocatalytic degradation of pyrrolidine to CO2 and NH3 by UV irradiation and using titanium dixide semiconductor as a photocatalyst. Compared with direct photolysis, the semiconductor catalytic photolysis gave consistently higher degradation yields for pyrrolidine in water. The effects of variable parameters such as pH, amount of semiconductor and time of photolysis on degradation of pyrrolidine were investigated. An optimal volue of pH=9, amount of semiconductor, 4 mmol.L-1 and time of UV irradiation, 25 min. was found. Amount of pyrrolidine was measured spectrophotometrically at l = 480 nm using 1,2-naphtoquinone-4-sulphonate as a selective reagent. The concentration of ammonia produced during the reaction was monitored spectrophotometrically at l=410 nm by Nessler''s reagent

FT-IR and FT-Raman spectra of hirudin have been recorded from the native solid hirudin. The conformation of the molecule has been discussed on the basis of IR and Raman data. It has been concluded that hirudin molecule has a mixed a-helix and random coil conformation.

The effects of solvent، temperature، time، weight percent of catalyst on the rate and mechanism of cyclization of natural rubber (NR) was studied in toluene and xylene solutions having tin tetra chloride catalyst (SnCl4). Iodometric titration show، with 8% SnCl4 (based on polymer weight) cyclization occurs، leaving 27. 4% of the total unsaturation. Infrared spectra of cyclized NR show decreased absorption intensity at 840 and 780 cm-1 which are characteristic bands of the linear polymer and the appearance of absorption and at 890 cm-1 as cycles were formed. By using this chemical modification، NR is transformed into a resinous thermoplastic، hard، non rubbery cyclized material with much less unsaturation than the original rubber، which ou7ld find commercial applications as adhesives، printing inks، industrial and ship paints.