Hydration of tri-n-hexyl amine hydrochloride,tri-n-octyl amine hydrochloride,tri-n-decyl amine hydrochloride and tri-n-dodecyl amine hydrochloride benzene solutions

Isopiestic equilibrations of THxA·HCl, TOA·HCl, TDA·HCl and TLA·HCl benzene solutions have been made in the concentration range from 0·02 to 0·13 mole/kg at different water activities and 25°C. The mean hydration number of the chloride ion at unit water activity was found to be 1·024±0·015 for the systems investigated. To determine the effect of water activity on the amine salt activity the results were treated on the basis of the Gibbs-Duhem equation and a simple linear relation obtained between salt and water activities. IR spectrophotometric measurements were performed to identify the nature of the hydrated species.     

The stability constant of Pd-EDTA

The literature value of the stability constant of the palladium-ethylenediaminetetra-acetate complex (log K(Pd-EDTA) = 18.5), is open to question. From replacement experiments with thorium a value log K(Pd-EDTA) = 26.4 has been found. This value is in better agreement with experimental facts from protonation studies at low pH and with the fact that excess of EDTA can be back-titrated in presence of Pd-EDTA at pH 1-2 with ions such as Bi(3+), Tl(3+) and Th(4+). Some preliminary results are given for ternary complex formation between Pd(2+), EDTA and Cl(-).     

Highly efficient oxidative amidation of aldehydes with amine hydrochloride salts

A mild and efficient copper-catalyzed oxidative amidation of aldehydes was developed using amine HCl salts and tert-butyl hydroperoxide as an oxidant.     

The thermal stability of triprolidine hydrochloride and its mixtures with cyclodextrin and glucose

Triprolidine hydrochloride (C₁₉H₂₂N₂·HCl·H₂O) (TPH) is a well-known antihistamine drug which is reported as being photosensitive. The thermal stabilities of TPH and of 1:1 molar and 1:1 mass ratio physical mixtures of TPH with β-cyclodextrin (BCD) and with glucose have been examined using DSC, TG and TG-FTIR, complemented by X-ray powder diffraction (XRD) and infrared spectroscopic (IR) studies. Thermal studies of the solid TPH/BCD mixtures indicated that interaction between the components occurs and it is possible that the TPH molecule may be least partially accommodated in the cavity of the BCD host molecule. XRD results support this indication of inclusion. The results of molecular modelling suggest that TPH is most likely to be accommodated in the BCD cavity as a neutral triprolidine molecule with the toluene portion of the molecule preferentially included in the cavity. The results obtained illustrate the general stability of TPH. The study has also shown TPH to be compatible with both glucose and BCD, which are potential excipients both in solid and liquid dosage forms. The presence of these excipients in dosage forms will thus not adversely affect the stability and the therapeutic efficacy of TPH. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of amine on the tribological properties and hydrolytic stability of borate ester additives

Research on Chemical Intermediates - The effect of amine on the tribological properties and hydrolytic stability of borate ester additives was examined by adding different kinds and quantities of...     

The effect of hindered amine light stabilizers on the photooxidative stability of high-density polyethylene

The photoprotective effectiveness of various polymeric and nonpolymeric hindered amine light stabilizers (HALS) was determined by exposing samples of high-density polyethylene (HDPE) containing these additives to ultraviolet (UV) light and measuring the resultant oxygen uptake characteristics. Values of the initial quantum yield for oxygen uptake calculated for these formulations indicate that the higher molecular weight HALS compounds are less effective photostabilizers than the nonpolymeric HALS, and this is partly attributable to their decreased mobility in the polymer matrix. It was further found that the addition of an ultraviolet absorber (UVA) to a formulation containing a polymeric HALS compound enhances its photostability, although this phenomenon may be partly due to synergism between the UVA and the antioxidant, the latter having been added as part of the base stabilization. The antagonism which exists between certain sulfur-containing antioxidants and HALS compounds was also investigated and it was found that the lower molecular weight sulfur-containing antioxidants exhibit the greatest degree of antagonism. The results confirm that the mobility in the polymer matrix of the stabilizer system can serve as an explanation of its effectiveness. The article provides evidence that the technique of oxygen uptake monitoring is a sensitive and rapid method of assessment of polymer photostability in the presence of stabilizer systems.     

One-pot synthesis of aryl oxime analogues from methyl arenes using NBS and hydroxyl amine hydrochloride

The one-pot synthesis of aryl oximes is reported by the reaction of methyl arenes with NBS using hydroxyl amine hydrochloride. The direct conversion of methyl group into oxime group has been achieved under mild reaction conditions in the presence of sensitive functional groups including chloro, bromo, cyano, hydroxy, fluoro, dioxaborolane, esters, and trifluoro methyl substituents with excellent yields. The simple experimental procedure and easy purification make this protocol advantageous.     

Edge excitation red shift and energy migration in quinine bisulphate dication

Photoinduced excited state dynamical processes in quinine sulphate dication (QSD) have been studied over a wide range of solute concentrations using steady state and nanosecond time-resolved fluorescence spectroscopic techniques. The edge excitation red shift (EERS) of emission maximum, emission wavelength dependence of fluorescence lifetimes and the time dependence of emission maximum are known to occur due to the solvent relaxation process. With increase in solute concentration, the emission spectrum shifts towards the lower frequencies accompanied with decrease in fluorescence intensity, however, absorption spectrum remains unchanged. A decrease in EERS, fluorescence lifetimes, time dependent fluorescence Stokes shift (TDFSS), fluorescence polarization and the solvent relaxation time (τ_r) is observed with the increase in solute concentration. The process of energy migration among the QSD ions along with solvent relaxation has been found responsible for the above experimental findings.     

Disproportionation-combination rate constant ratios for haloalkyl radicals: Evidence for heterogeneous disproportionation

Disproportionation-combination rate constant ratios, k_d/k_c, have been determined for R + RCH₂CHCl and for the auto disproportionation-combination of RCH₂CHCl radicals, R = CF₃, C₂F₅, and C₃F₇. The k_d/k_c for R = CF₃ and to a lesser degree for R = C₂F₅ and C₃F₇ were very sensitive to the surface/volume ratio of the reaction vessel suggesting a heterogeneous component for disproportionation.     

Derivation of rate constant ratios for consecutive second‐order irreversible reactions

The determination of rate constants for consecutive irreversible reactions is a difficult and time‐consuming problem, especially when the research extends up to many subsequent products. Thus, the derivation of proper mathematical expressions would greatly facilitate the determination of these rate constants when only the rate constant of the first consecutive reaction is known. Many authors have dealt with this problem in the past but the issue is still of interest to the scientific community judging from recent publications. This paper aims at extending our knowledge of mathematical expressions for rate constant ratios of consecutive reactions to more than three reactions, as is the situation now, and offering a simple graphical estimation of the rate constant ratios exploiting the maxima of each intermediate product. Furthermore, the method extends to the derivation of a generic formula for the estimation of the rate constant ratios based on this graphical approach. This approach for the estimation of rate constant ratios based on mathematical expressions and graphical estimations was validated against experimental data found in the literature.     

An approximate theory of the ozone isotopic effects: rate constant ratios and pressure dependence

The isotopic effects in ozone recombination reactions at low pressures are studied using an approximate theory which yields simple analytic expressions for the individual rate constant ratios, observed under "unscrambled" conditions. It is shown that the rate constant ratio between the two competing channels XYZ-->X+YZ and XYZ-->XY+Z is mainly determined by the difference of the zero-point energies of diatomic molecules YZ and XY and by the efficiency of the deactivation of the newly formed excited ozone molecules, whereas the mass-independent fractionation depends on a "nonstatistical" symmetry factor eta and the collisional deactivation efficiency. Formulas for the pressure effects on the enrichment and on the rate constant ratios are obtained, and the calculated results are compared with experiments and more exact calculations. In all cases, ratios of isotope rates and the pressure dependence of enrichments, the agreement is good. While the initial focus was on isotope effects in the formation of O(3), predictions are made for isotope effects on ratios of rate constants in other reactions such as O+CO-->CO(2), O+NO-->NO(2), and O+SO-->SO(2).     

Thermal stability of new complexes bearing both acrylate and aliphatic amine as ligands

This paper reports the investigation of the thermal stability of a series of new complexes with mixed ligands of the type [M(en)(C₃H₃O₂)₂]·nH₂O ((1) M=Ni, n=2; (2) M=Cu, n=0; (3) M=Zn, n=2; en=ethylenediamine and (C₃H₃O₂)=acrylate anion). The thermal behaviour steps were investigated in a nitrogen flow. The thermal transformations are complex processes according to TG and DTA curves including dehydration, ethylenediamine elimination as well as acrylate thermolysis. The final products of decomposition are the most stable metal oxides except for complex (2) that generates metallic copper.     

Chelate compound stability constant calculations on metal diketonate complexes

Acetylacetone (CH₃COCH₂COCH₃ or Hacac) may give up a proton and chelate with a metal ion through the two oxygen atoms. The stability constant for the neutral complex (given as log β_Σ) in aqueous solution can be calculated using the electrostatic relation log βΣ = N_AV_c²e²/(2.3RT?/d) when cations in S states are involved. Larger values that reflect exchange related electron correlation as well as electrostatic contributions to cohesive energy are obtained using transition metal ions. Separate values for the two energies are determined (see the text for definitions of the symbols).     

Supramolecular hexagonal network based on a tritopic amine hydrochloride and a cucurbit[5]uril analogue

Research on Chemical Intermediates - A planar tritopic 120° ammonium salt—1,3,5-tri(4-aminophenyl)benzene hydrochloride—was synthesized. Each of the three protonated amine moieties...     

Complex fluorescence decay of quinine bisulphate in aqueous sulphuric acid solution

Fluorescence of quinine bisulphate is shown to be two-component. In 1.0 N H₂SO₄ solution the major component has a decay time ≈20 ns, but there is a minor component with decay time ≈2 ns with a different fluorescence spectrum. It is recommended that the compound not be used as a standard for decay-time measurements.     

Stabilizing selenium nanoparticles with chymotrypsin: The effect of pH and nanoparticle-enzyme concentration ratios on the stability of nanocomplexes

Conditions of the formation of soluble chymotrypsin complexes with selenium nanoparticles are studied. It is established that the aggregative stability of the nanocomplexes is determined by their conditions of preparation, depending also on the medium pH and ratio of selenium: chymotrypsin concentration. It is shown that chymotrypsin has a “protective” effect due to its hydrophobic adsorption on the surface of selenium nanoparticles and hence the hydrophilization of their surfaces due to ionized groups of the protein.