IRANIAN JOURNAL OF CHEMISTRY AND CHEMICAL ENGINEERING
Year:1997 | Volume:16 | Issue:2|Papers Count:9

Nitration of phenol and various 4-substituted phenols with Cu(NO3)(2) . 3H(2)O, Cu(NO3)(2) . 3H(2)O/SiO2, Fe(NO3)(3) . 9H(2)O and Cr(NO3)(3). 9H(2)O in different anhydrous organic solvents are investigated High selectivity ratio of para vs ortho isomers has been observed Mono-and dinitro compounds from phenol and 4-substituted phenols by choosing the proper solvents and reaction conditions, are also obtained with high selectivity in excellent yields. Rate enhancement for mononitration of phenols in the presence of LiClO4 with Cu(NO3)(2). 3H(2)O is observed.

A spectrophotometric method was used to determine the acidity constant of 4"-carboxybenzo-24-crown-8 in 52% (w/w) ethanol-water mixture. The acid dissociation constant, K-a, was found to increase in the presence of Na+, K+, Rb+, Cs+ and Tl+ ions. The formation constants of the resulting 1:1 complexes between the carboxycrown and the metal ions used were evaluated from the observed changes of K-a value with varying concentration of cations and found to vary in the order Rb+>Cs+>Tl+>K+>Na+.

MNDO semi-empirical SCF MO calculations are used to study the pyramidal nitrogen atom inversion and configurational equilibria in the title compounds.

Rapid and highly efficient synthesis of 2- or 2,5-substituted 1,3,4-oxadiazoles by the condensation of aryl carboxylic acid hydrazides and orthoesters can be achieved under microwave irradiation using an unmodified commercial oven in unsealed vessels.

Substituted naphthofurans and naphthopyrans were constructed at high temperature from allyl or propargyl naphthyl ethers via Claisen rearrangement in moderate to good yields. Also, substituted (trimethylsilyl)naphthofurans were synthesized from the corresponding naphthofurans.

A simple, sensitive and rapid method for determination of trace amounts of nitrite ion in real samples is reported The reaction is initiated by adding known volumes of a nitrite ion solution of identified concentration to acidic solutions of thionine which causes decolorization of reagent with time. The absorbance changes is then monitored spectrophotometrically at lambda(max) = 602 nm at 25 degrees C. Calibration curve is linens in the range 0.005-1.500 mu g mL(-1) of nitrite ion. Many of cations and anions have no interfering effect but iodide, Mo(VI), W(VI) and S2O32- ions do interfere. The effect of interfering ions have been eliminated by the use of proper masking agents. This method was used to determine nitrite ion concentration in Karoon river water and foodstuffs such as susages.

A mixture of manganese, cobalt and lead para-amino benzoates supported on silica gel is used to catalyze oxidation of xylenes to toluic acids in presence of oxygen or air. Reactions are clean and catalysts can be recovered easily and reused.

Correlation of heat transfer coefficients for air flow through the regenerator constructed from randomly packed spheres is reported for the symmetric-balanced mode of operation. The experimental results have been correlated by the least square regression and the following correlation has been obtained: epsilon J(h) = 0.1783 Re-m(-0.2906) The present correlation has been compared with the heat transfer coefficient correlations in the literature.

Acrylamide was grafted in low density polyethylene during melt processing in the presence of a free radical initiator using a torque rheometer in a closed system. Effects of processing time, acrylamide and benzoyl peroxide concentrations were studied FTIR studies revealed that the degree of grafting increased by an increase in acrylamide concentration. Maximum grafting was obtained at 7 minutes processing time and 1% (wt/wt) peroxide. Increase in acrylamide concentration led to reduction in melt flow index and increase in apparent melt viscosity.