Iranian Journal of Chemistry and Chemical Engineering
Volume:16 Issue: 2, Nov-Dec 1997

Nitration of phenol and various 4-substituted phenols withCu(NO3)2. 3H2O, Cu(NO3)2. 3H2O/SiO2, Fe(NO3)3. 9H2O and Cr(NO3)3. 9H2O in different anhydrous organic solvents are investigated. High selectivityratio of para vs ortho isomers has been observed. Mono- and dinitro compoundsfrom phenol and 4-substituted phenols by choosing the proper solvents andreaction conditions, are also obtained with high selectivity in excellent yields. Rateenhancement for mononitration of phenols in the presence of LiClO4 withCu(NO3)2. 3H2O is observed.

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

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

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

A simple, sensitive and rapid method for determination of traceamounts of nitrite ion in real samples is reported. The reaction is initiated byadding known volumes of a nitrite ion solution of identified concentration toacidic solutions of thionine which causes decolorization of reagent with time. Theabsorbance changes is then monitored spectrophotometrically at lmax = 602 nmat 25 ـC. Calibration curve is linear in the range 0. 005-1. 500 mg mL-1 of nitriteion. 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 elimi-nated by the use of proper masking agents. This method was used to determinenitrite ion concentration in Karoon river water and foodstuffs such as susages.

A mixture of manganese, cobalt and lead para-amino benzoatessupported on silica gel is used to catalyze oxidation of xylenes to toluic acids inpresence of oxygen or air. Reactions are clean and catalysts can be recoveredeasily and reused.

Correlation of heat transfer coefficients for air flow throughthe regenerator constructed from randomly packed spheres is reported forthe symmetric-balanced mode of operation. The experimental results havebeen correlated by the least square regression and the following correlationhas been obtained: eJh = 0.1783 Re-0.2906m The present correlation has been compared with the heat transfercoefficient correlations in the literature.

Acrylamide was grafted in low density polyethylene duringmelt processing in the presence of a free radical initiator using a torquerheometer in a closed system. Effects of processing time, acrylamide andbenzoyl peroxide concentrations were studied. FTIR studies revealed thatthe degree of grafting increased by an increase in acrylamide concen-tration. Maximum grafting was obtained at 7 minutes processing time and1% (wt/wt) peroxide. Increase in acrylamide concentration led to reduc-tion in melt flow index and increase in apparent melt viscosity.