New Dialkylamino Derivatives of Trivalent Phosphorus

Abstract

Recent developments in the chemistry of (R₂N)₂PH, (R₂N) (R'O)PH, (R₂N)₄P₄, and R₂NP(Cl)-P(Cl)NR₂ derivatives are discussed.     

Convolution operator and maximal function for the Dunkl transform

For a family of weight functionsh _K invariant under a finite reflection group onR ^d, analysis related to the Dunkl transform is carried out for the weightedL ^p spaces. Making use of the generalized translation operator and the weighted convolution, we study the summability of the inverse Dunkl transform, including as examples the Poisson integrals and the Bochner-Riesz means. We also define a maximal function and use it to prove the almost everywhere convergence. ST wishes to thank YX for the warm hospitality during his stay in Eugene. The work of YX was supported in part by the National Science Foundation under Grant DMS-0201669.     

Preparation and characterization of Co- and homopoly(phenylene etherimideketone)s

Poly(phenylene etherimdeketone)s were prepared by Friedel–Crafts acylation type polymerization using P₂O₅? CH₃SO₃H 1 : 10 (w/v) mixtures. Most of these polymers were semicrystalline. T_gS ranged from 203 to 236°C and crystalline melt temperatures were observed between 306 and 435°C. All of the polymers exhibited high thermal stability and good solvent resistance. © 1993 John Wiley & Sons, Inc.     

Theoretical study of a 1 : 1 complex between quinone and hydroquinone

The Variable Electronegativity Pariser–Parr–Pople method has been successfully applied to calculate the potential energy curve for the formation of a 1: 1 complex between quinone and hydroquinone. A consistent evaluation of core and electronic repulsion integrals is important to obtain a meaningful curve. A computationally simple procedure has been suggested for separating interactions due to electron exchange between the components from other intermolecular interactions. In agreement with experimental deductions the preferred configuration for the quinone-hydroquinone complex is found to be one in which the molecules are in parallel planes with their C—O bonds parallel. The equilibrium separation between the molecular planes is found to be 2.3 Å and the stabilization energy in this position is 1.2 eV. In this equilibrium position forces due to electron exchange constitute the major contributing factor to the stability of the complex.     

The heat kernel transform for the Heisenberg group

The heat kernel transform H_t is studied for the Heisenberg group in detail. The main result shows that the image of H_t is a direct sum of two weighted Bergman spaces, in contrast to the classical case of Rⁿ and compact symmetric spaces, and the weight functions are found to be (surprisingly) not non-negative.     

Extraction of indium,cadmium and thallium by dinonylnaphthalene sulfonic acid

The extraction of indium, cadmium and thallium by dinonylnaphthalene sulfonic acid (HD) from acid media has been studied. HD extracts the metal ion by an ion exchange mechanism. The nature of the species and the extent of aggregation has been evaluated. The effect of diluents on the extraction has also been studied and the results interpreted on the basis of aggregation of HD. A comparative study with solid ion exchangers has also been made.     

Molecular-orbital calculations on some mesoionic compounds

Molecular-orbital calculations have been performed on sydnone, sydnone imine, ψ-oxatriazole, and isosydnone rings and their positive ionized forms by the Pariser–Parr–Pople–Brown–Heffernan method. The importance of elaborate open-shell calculations and the effect of introducing nonneighbor core resonance integrals in this order of approximation are investigated. The available experimental data on closely related compounds are qualitatively in agreement with the calculated values. The computed charges and bond orders demonstrate that certain structural features are common to all five-membered mesoionic ring systems and in agreement with recent experimental findings.     

Bilayer tablets of atorvastatin calcium and nicotinic acid: formulation and evaluation

The objective of the study is to formulate bilayer tablets consisting of atorvastatin calcium (AT) as an immediate release layer and nicotinic acid (NA) as an extended release layer. The immediate release layer was prepared using super disintegrant croscarmellose sodium and extended release layer using hydroxypropylmethyl cellulose (HPMC K100M). Both the matrix and bilayer tablets were evaluated for hardness, friability, weight variation, thickness, and drug content uniformity and subjected to in vitro drug release studies. The amount of AT and NA released at different time intervals were estimated by HPLC method. The bilayer tablets showed no significant change either in physical appearance, drug content or in dissolution pattern after storing at 40 degrees C/75% relative humiding (RH) for 3 months. The release of the drug from the tablet was influenced by the polymer content and it was much evident from thermogravimetry/differential thermal analysis (TG/DTA) analysis. The results indicated that the bilayer tablets could be a potential dosage form for delivering AT and NA.     

Understanding the Impacts of AFEX™ Pretreatment and Densification on the Fast Pyrolysis of Corn Stover,Prairie Cord Grass,and Switchgrass

Lignocellulosic feedstocks corn stover, prairie cord grass, and switchgrass were subjected to ammonia fiber expansion (AFEX?) pretreatment and densified using extrusion pelleting and ComPAKco densification technique. The effects of AFEX? pretreatment and densification were studied on the fast pyrolysis product yields. Feedstocks were milled in a hammer mill using three different screen sizes (2, 4, and 8 mm) and were subjected to AFEX? pretreatment. The untreated and AFEX?-pretreated feedstocks were moisture adjusted at three levels (5, 10, and 15 % wb) and were extruded using a lab-scale single screw extruder. The barrel temperature of the extruder was maintained at 75, 100, and 125 °C. Durability of the extruded pellets made from AFEX?-pretreated corn stover, prairie cord grass, and switchgrass varied from 94.5 to 99.2, 94.3 to 98.7, and 90.1 to 97.5 %, respectively. Results of the thermogravimetric analysis showed the decrease in the decomposition temperature of the all the feedstocks after AFEX? pretreatment indicating the increase in thermal stability. Loose and densified feedstocks were subjected to fast pyrolysis in a lab-scale reactor, and the yields (bio-oil and bio-char) were measured. Bio-char obtained from the AFEX?-pretreated feedstocks exhibited increased bulk and particle density compared to the untreated feedstocks. The properties of the bio-oil were statistically similar for the untreated, AFEX?-pretreated, and AFEX?-pretreated densified feedstocks. Based on the bio-char and bio-oil yields, the AFEX?-pretreated feedstocks and the densified AFEX?-pretreated feedstocks (pellets and PAKs) exhibited similar behavior. Hence, it can be concluded that densifying the AFEX?-pretreated feedstocks could be a viable option in the biomass-processing depots to reduce the transportation costs and the logistical impediments without affecting the product yields.     

A kinetic and mechanistic study on the silver (I)-catalyzed oxidation of l-alanine by cerium (IV) in sulfuric acid medium

The kinetics and mechanism of Ag(I)-catalyzed oxidation of l-alanine by cerium (IV) in sulfuric acid media have been investigated by titrimetric technique of redox in the temperature range of 298–313 K. It is found that the reaction is of first order with respect to Ce(IV) and l-alanine, and it is of a positive fractional order with respect to Ag(I). It is found that the pseudo first order ([l-alanine] ? [Ce(IV)] ? [Ag(I)]) rate constant k′ increases with the increase of[H⁺]. The major oxidation product of alanine has been identified as acetaldehyde by an ¹H NMR and IR spectroscopy. Under the experimental conditions, the kinetically active species has been found to be Ce⁴⁺. Under nitrogen atmosphere, the reaction system can initiate the polymerization of acrylonitrile, indicating generation of free radicals. On the basis of the experimental results, a suitable mechanism has been proposed. The rate constants of the rate-determining step together with the activation parameters were evaluated.