VOLUME 13, NO3, SEPT 1991

VISCOMETRIC AND LIGHT-SCATTERING-STUDIES OF POLY(VINYL PYRROLIDONE) .1.

Poly(vinyl pyrrolidone) (PVP) K-30 sample was subjected to fractionation using ethanol-petroleum ether system as solvent and non solvent, eight fractions were obtained and studied having molecular weight in the range 1.17 x 10(4) to 9.30 x 10(4). The corresponding limiting viscosity numbers of the various fractions were determined and the data relating to the methanolic system conform with the theory. A relation between intrinsic viscosity and weight average molecular weight is derived. The second virial coefficient A2 for different fractions were calculated showing increase with decrease in molecular weight. Although this increase is not very pronounce. It was also concluded that methanol is as good solvent as water for PVP light scattering study.read more

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NOOR AHMAD ,BASHIR AHMED ,ALI KHAN BHETTANI ,

HEATS OF ADSORPTION OF CHROMATOGRAPHIC SILICA-GEL

The structural system of chromatographic silica gel, as investigated by adsorption techniques and electron microscopy is highly porous having 63% porosity and composed of large irregular grains, arrange in disorderly manner, constituting the voids. Treatment at high temperature shrinks the materials on the expense of bound water. Most of the surface area and pore volume lie in the micropores. Organic vapours such as acetone, methyl alcohol, methyl ethyl ketones and methyl acetate were adsorbed on the gel between 0-37-degrees-C under vacuum. The data were taken on Cahn electrobalance- 1000. Isosteric heats of adsorption at number of temperatures and coverages were determined by applying Clausius Clapeyron equation. It is interpreted in terms of activation energies which suggests two types of adsorption processes.read more

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M AFZAL ,H AHMAD ,M kHAN ,

SPECTRAL PROPERTIES OF AZO-COMPOUNDS 5-(4-SUBSTITUTED PHENYLAZO)BARBITURIC ACID

Synthesis of new 5-(54-substituted phenylazo) barbituric acid compounds was described. The spectral properties and the analytical data were used for assigning their structures. The pK values are interpreted based on the electronic characters of the substituents. Better correlation analyses are given.read more

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EKRAM A KHALIL ,MAMDOUH S MASOUD ,

ONE-STEP SYNTHESIS OF 4-HYDROXYCARBOSTYRILS .6.

4-Hydroxycarbostyril, 4-hydroxy-1-substituted-carbostyrils, 4-hydroxy-6-methylcarbostyril, benzol(f) and benzo(h)-4-hydroxycarbostyrils have been synthesized by one step, simple, short, and effective method. H-1-NMR and IR spectroscopic data are given.read more

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EL HOSSAIN ALI MOHAMED ,

SYNTHESIS OF 6-METHOXYMETHYLMORPHINOL

An allyl ether of 14-hydroxycodeinone (2) was investigated as an intermediate for the preparation of analogues of (10) or (11) of cyclohexenodihydrocodeinones (9). The reactions involve an aromatising degredation of 14-hydroxycodeinone through the methine base (4) to yield 6-methoxymethylmorphinol (6, R = Me) with the elimination of the side chain, a process not reported with any 14-substituted codeinone.read more

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M U VALHARI ,M U MEMON ,F C NACHNANI ,M Y kHAN ,A U RAHMAN ,

MULTINUCLEAR NMR-STUDY OF 1-FLUORO-2,4-DINITROBENZENE

A multinuclear H-1, F-19, C-13, N-14 and O-17 NMR chemical shift study of 1-Fluoro-2,4-Dinitrobenzene has been carried out in detail. The detail H-1 chemical shift study gives 9.061, 8.897, 8.033 ppm for H3, H5 and H6 protons respectively while the F-19 chemical shift is -107.876 ppm with respect to CFCl3 and - 60.606 ppm with respect to C6F6 as an external standard in the neat liquid at 32-degrees-C. The F-19 signal is a septet. C-13 spectrum is analyzed on the basis of C-13 spin-lattice relaxation time T1 and proton chemical shifts. Only the C5 signal is singlet and the other are doublets. The chemical shifts are 159.2, 137.3, 131.3, 144.1, 122.5 and 120.6 ppm for C1 to C6 respectively at 32-degrees-C with respect to TMS as an internal standard. The N-14 chemical shifts is -16.6 ppm (w.r.t. NO3- of NH4NO3 used as an external standard) and -18.1 ppm (w.r.t. CH3NO2 as an external standard). The O-17 Chemical shifts w.r.t. H2O as the external standard is 607.6 ppm at 95-degrees-C.read more

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M A R ABID ,A W K KHANZADA ,

SYNTHESIS OF FLUORESCENT N-ACYL-PARA-AMINOPHENOLS

Various N-acyl-p-aminophenol derivatives were synthesised by introducing cinnamyl, p-methoxy cinnamyl, (o- methoxycarbonyl)-o-coumaryl, o-coumaryl, m-coumaryl and ferulyl groups into p-aminophenol. N,N dicyclohexyl-carbodiimide was used as the condensing agent.read more

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HAHBUB ALAM ,RIZWAN MAHMOOD ,M HAFEEZ KHAN ,HAIDER ALI ,

C-13 CHEMICAL-SHIFTS IN HEXAMETHYLDISILAZANE IN VARIOUS NONAROMATIC SOLVENTS AND EFFECT OF VANDERWAALS INTERACTION ON THESE SHIFTS

C-13 CHEMICAL-SHIFTS IN HEXAMETHYLDISILAZANE IN VARIOUS NONAROMATIC SOLVENTS AND EFFECT OF VANDERWAALS INTERACTION ON THESE SHIFTSread more

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M A R ABID ,A W K KHANZADA ,

SYNERGIC EXTRACTION OF LEAD WITH 2-THENOYLTRIFLUOROACETONE AND TRIBENZYLAMINE BY ATOMIC-ABSORPTION SPECTROPHOTOMETRY

Synergic extraction studies of lead with HTTA-TBA in chloroform is carried out employing atomic absorption spectrometry. Quantitative extraction is observed at pH 3.0, ionic strength 0.1M(H+, ClO4) with an equimolar concentration of 0.5M for both extractants. The stoichiometry of the adducts and reaction mechanism have been suggested at different pH conditions. Equilibrium constants (log K2,0 and log K2,1) are found to be -7.27 and -4.12 respectively and the stability constant (log-beta-2,1) is 3.15 at pH 3.read more

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N KHALID ,M N CHEEMA ,M MUFAZZAL SAEED ,I H QURESHI ,

KINETIC SOLVENT EFFECT ON HYDROLYSIS OF ETHYLCHLOROFORMATE IN BINARY AQUEOUS MIXTURES

The kinetics of the neutral hydrolysis of ethylchloroformate have been studied in water-acetonitrile and in water- tetrahydrofuran mixtures in the temperature range of 30-50-degrees-C. The hydrolysis reaction follows a first-order rate law. The rates of the hydrolysis showed maxima at 0.9 and at 0.92 water mole fraction in water-acetonitrile and in water- tetrahydrofuran mixtures, respectively. The activation parameters DELTA-H# and DELTA-S# showed minima at nearly the same solvent composition range. The significance of these results from the viewpoint of the changing of solvent structure in such mixture is discussed.read more

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EL HUSSEINY M DIEFALLAH ,MAHMOUD A MOUSA ,M M ABDEL BADEI ,MERVATA A ASSEM ,