Studies with polyfunctionally substituted heteroaromatics: 2-Phenyl-4-p-tolylhydrazono-2-oxazoline-5-one as a precursor for the synthesis of substituted 1,2,4-triazoles and pyridines

2-Phenyl-4-p-tolylhydrazono-2-oxazoline-5-one ( 3 ) was rearranged by the action of phenols and naphthols into 1,2,4-triazole-5-carboxylic esters ( 5 ) that were rearranged further on reflux in AcOH-ZnCl₂ into triazolyl ketones ( 7 ). Rearrangement of 3 into 1,2,4-triazole derivatives could also be effected by the action of heterocyclic amines and 1-naphthylamine. © John Wiley & Sons, Inc.     

Spectrophotometric determination and kinetic studies of condensation of aromatic aldehydes with 1,3-dimethylbarbituric acid

The condensation reaction of 1,3-dimethylbarbituric acid with aromatic aldehydes in ethanol has been investigated spectrophotometrically at 25–35°C. The reaction follows overall second-order kinetics, first-order each in reactant. From the dependence of the rate constants on temperature, activation parameters have been calculated. The rate of condensation increases with the presence of electron donating groups on the aromatic ring of the aldehyde. The rate-determining step involves dehydration of the aldol intermediate. The reaction was found to be catalyzed by HCl solutions. Based on this reaction, determination of 10 aromatic aldehydes in a concentration range of 0.13–70.25 μg/ml is proposed. The method was applied for determination of barbituric and 1,3-dimethylbarbituric acids also.     

Spectrophotometric Determination and Kinetic Studies of Condensation of Aromatic Aldehydes with 7,9‐Dioxo‐6,10‐dioxaspiro[4.5]decane

The condensation reaction rates of 7,9‐dioxo‐6,10‐dioxaspiro[4.5]decane with aromatic aldehydes in chloroform in the presence of piperidine has been investigated spectrophotometrically at 25–50 °C. The reaction follows overall second order kinetics, first order in each of the reactants and zero order with respect to piperidine. The rate of condensation increases with the presence of electron withdrawing groups on the aromatic ring of the aldehyde. From the dependence of the rate constants on temperature, activation parameters have been calculated. Plot of ΔH# versus ΔS# for the reaction gave a good straight line with an isokinetic temperature of 367.55 K. Based on this reaction, determination often aromatic aldehydes in a concentration range of 2.65–69.2 μg/mL is proposed.     

Isotope ratio monitoring gas chromatography/Mass spectrometry of D/H by high temperature conversion isotope ratio mass spectrometry

Of all the elements, hydrogen has the largest naturally occurring variations in the ratio of its stable isotopes (D/H). It is for this reason that there has been a strong desire to add hydrogen to the list of elements amenable to isotope ratio monitoring gas chromatography/mass spectrometry (irm-GC/MS). In irm-GC/MS the sample is entrained in helium as the carrier gas, which is also ionized and separated in the isotope ratio mass spectrometer (IRMS). Because of the low abundance of deuterium in nature, precise and accurate on-line monitoring of D/H ratios with an IRMS requires that low energy helium ions be kept out of the m/z 3 collector, which requires the use of an energy filter. A clean mass 3 (HD(+.)) signal which is independent of a large helium load in the electron impact ion source is essential in order to reach the sensitivity required for D/H analysis of capillary GC peaks. A new IRMS system, the DELTA(plus)XL(trade mark), has been designed for high precision, high accuracy measurements of transient signals of hydrogen gas. It incorporates a retardation lens integrated into the m/z 3 Faraday cup collector. Following GC separation, the hydrogen bound in organic compounds must be quantitatively converted into H(2) gas prior to analysis in the IRMS. Quantitative conversion is achieved by high temperature conversion (TC) at temperatures >1400 degrees C. Measurements of D/H ratios of individual organic compounds in complicated natural mixtures can now be made to a precision of 2 per thousand (delta notation) or, better, with typical sample amounts of approximately 200 ng per compound. Initial applications have focused on compounds of interest to petroleum research (biomarkers and natural gas components), food and flavor control (vanillin and ethanol), and metabolic studies (fatty acids and steroids). Copyright 1999 John Wiley & Sons, Ltd.     

Three-phase upward flow in a vertical pipe

In this paper we develop an approach to design a three-phase, gas–solid–liquid flow system that transports pneumatically scarified solid particles, including sticky ones, through a vertical pipe. The proposed system permits the introduction and maintenance of a liquid film that coats the pipe’s inner wall and acts as a lubricant that ensures sticky particles continue to move upward without permanently adhering to the pipe wall. The system’s operating conditions fall within the boundaries of the annular dispersed region on a typical flow pattern map of vertical flow of a gas–liquid mixture. High gas superficial velocities combined with low liquid superficial velocities characterize such a region. A combination of a modified one-dimensional, two-fluid annular dispersed flow model and a one-dimensional pneumatic conveying model is shown to describe this transport process satisfactorily. Solution of the combined models produces all the necessary design parameters including power requirements and superficial velocities of the two-fluid media needed to transport a given amount of solid particles. Results of model calculations are compared with rare three-phase flow data obtained prior to the development of the present model, by an independent experimental team that used the physical conditions of the present approach. Reasonable agreement justifies the use of the combined model for engineering design purposes.     

Extended-ion approximation and pressure shifts inF-band energies

Pressure variation of maximumF-band absorption energies in the halides of lithium, sodium and potassium has been investigated employing the extended-ion approximation for the calculation of theF-electron energy eigenvalues and using values of local compressibility in the neighbourhood of theF-centres which include the effect of vacancy and pressure. The results obtained agree with the experimental results.