شیمی و مهندسی شیمی ایران
سال:1379 | دوره:19 | شماره:2-1 |تعداد مقالات:13

NaBrO3 combined with NH4Cl is found to be an efficient reagent for the transformation of sulfides into sulfoxides in aqueous acetonitrile and under mild conditions.

A PVC-based membrane containing cerium phosphate was developed. Unlike the cerium phsophate itself that acts as a cation exchanger the membrane exhibited anion-exchange properties. Therefore, the utility of this compound as a sensory element for detection of molybdate ions was pursued The response of molybdate selective electrode based on this membrane was perfectly linear in the concentration range 1.98x10-5 to 10-1 M. Characteristics of this electrode such as electric resistance, stability and membrane preconditioning process, and regeneration of its sensitivity are reported.

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

The solvent extraction of rare earth metal ions from nitrate solutions by 5 11, 17, 23-tetra-tert-butyl-25, 27-bis(diethylcarbamoylmethoxy)-26, 28-dihydroxycalix[4]arene (L) in I,2-dichloroethane has been investigated The analysis of the extraction equilibrium obtained from a mixture of La3+, Eu3+ Er3+ and Y 3+ revealed that the extracted species have a 1:1 metal/ligand ratio. The intra-group separation efficiencies of the ligand have been evaluated in a competitive extraction and transport of II rare earth metal ions (La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Dy3+, Ho3+, Er3+, Yb3+ and Y3+. The transport experiment has been performed through a supported liquid membrane containing the ligand in o-nitrophenyl hexyl ether (NPHE). The distribution ratio and the flux of the ions generally increase as the atomic radii decrease.

Bridged bithiazoles (5,5'-ethylene-4,4'-bithiazoles) are synthesized as a good chelating agent.

The complexation reaction between iodine and I,10-Diaza-18-Crown-6 (DA18C6) has been studied in acetonitrile by spectrophotometric, biamperometric and conductometric techniques. The results are indicative of the formation of [(CH3CN)n I+.I-3(-)] from iodine and acetonitrile, and the formation of DA18C6 I+.I- from DA18C6 and [(CH3CN) nI+.I-3] The formation constant of the latter reaction has been calculated from the absorbance-mole ratio data, using the nonlinear least square program "KINFIT". The IR spectra of acetonitrile-acetonitrile iodine complex and DA18C6-DA18C6 iodine complex are compared and the effect of complexation on absorption bands is discussed.

Supercritical carbon dioxide (SC-CO2) was used as solvent to synthesize oleyl oleate as an analog of Jojoba oil from oleic acid and oleyl alcohol with high conversion (100%) of the acid into ester in a short time of 100 min. Utilizing a low cost solid catalyst, p-toluenesulfonic acid monohydrate (PTSA), the esterification reaction was performed, without any prior preparation step, in a flow mode, at a pressure of 147 bar and a temperature of 60 degreesC. This method seems industrially suitable for the production of oleyl oleate. The solubility of a mixture of oleyl alcohol and oleic acid in SC-CO2 were also measured to calculate the alcohol to acid ratio and the esterification 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 dioxide 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 value 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 I,2-naphthoquinone-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 mired alpha -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 band 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 could find commercial applications as adhesives, printing inks, industrial and ship paints.