Phosphinsubstituierte Chelatliganden, XX [1] Darstellung und diastereoselektive Komplexierung von chiralen Phosphinothioformamiden, Ph2P(X)C(S)NHCHMePh (X = 2 e- , O, S) / Phosphine-Substituted Chelate Ligands, XX [1] Synthesis and Diastereoselective Complexation of Chiral Phosphinothioformamides, Ph2P(X)C(S)NHCHMePh (X = 2e-, O, S)

1986 ◽  
Vol 41 (9) ◽  
pp. 1142-1150 ◽  
Keyword(s):  
Free Energy ◽  
Solid State ◽  
Chelate Complexes ◽  
Metal Centre ◽  
First Order ◽  
First Order Kinetics ◽  
Free Energy Of Activation ◽  
Optical Induction ◽  
Optically Pure ◽  
High Stereoselectivity

Abstract The am bidentate chiral phosphinothioform am ides (-)-S- and (+)-R-Ph2P(X)C(S)NHCHMePh with X = 2e- (1a). O (1b), S (1c) were obtained from optically pure S- and R -l-phenylethylamine via the isothiocyanate interm ediates. Coordination of (-)-la to CpM(CO)3Cl(M = Mo, W) and ClMn(CO)5 in methanol proceeds with high stereoselectivity forming the P.S-chelate complexes (+)-2a (Mo), (+)-3a (W) and (-)-4a (Mn) which maintain their configuration in solid state. In solution, how ever, the primary diastereom ers 2aA and 3aA epimerize to 2aB and 3aB with inverted configuration at the metal centre. The equilibrial ratio of B /A ≥ 1 (40 °C) indicates only a slight optical induction. The epimerization rate was determined by polarimetry and follow s a formal first-order kinetics with an average free energy of activation ΔḠ* = 92 ± 5 kJ - mol-1 at 20-40 °C. The N .S-chelates (-)-2b, (-)-3b derived from the P-oxide (-)-lb are configurationally stable up to 80 °C suggesting both a kinetic and thermodynamic preference of the A diastereomer. The enantiomeric complexes (-)-2a, (-)-3a, (+)-2b, (+)-3b obtained from Rconfigurated (+)-la, b display mirror-symmetrical CD plots. In contrast to -1a, b, the P-sulfide 1c does not show any selectivity during coordination to the S.S-chelates 2c and 3c.

Ring-Opening Polymerization of ε-Caprolactone Using Novel Tin(II) Alkoxide Initiators

2008 ◽  
Vol 55-57 ◽  
pp. 757-760 ◽  
Author(s):  
A. Kleawkla ◽  
Robert Molloy ◽  
W. Naksata ◽  
Winita Punyodom
Keyword(s):  
Solid State ◽  
Rate Constants ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Zero Order ◽  
Molecular Aggregation ◽  
First Order ◽  
First Order Kinetics ◽  
Zero Order Kinetics ◽  
Kinetics Of

Two novel tin(II) alkoxides, namely: tin(II) hexoxide, Sn(OC6H13)2, and tin(II) octoxide, Sn(OC8H17)2, have been synthesized for use as coordination-insertion initiators in the bulk ring-opening polymerization of ε-caprolactone. The kinetics of the polymerization reactions were studied at 140 °C by dilatometry. It was found that both alkoxides were slow to dissolve in the ε-caprolactone monomer due to their molecular aggregation in the solid state. As a result, the slow solubilization of the initiators gave rise to deviations from the expected first-order kinetics. Instead, the kinetic results adhered more closely to zero-order kinetics with apparent zero-order rate constants k0 of 6.58 x 10-2 and 4.63 x 10-2 mol l-1 min-1 for the hexoxide and octoxide respectively

scholarly journals A Fast, Inexpensive, and Safe Method for Residue Analysis of Meptyldinocap in Different Fruits by Liquid Chromatography/Tandem Mass Spectrometry

2010 ◽  
Vol 93 (6) ◽  
pp. 1957-1964 ◽  
Author(s):  
Kaushik Banerjee ◽  
Soma Dasgupta ◽  
Manjusha R Jadhav ◽  
Dattatraya G Naik ◽  
Axel Patrick Ligon ◽  
...  
Keyword(s):  
Ethyl Acetate ◽  
Residue Analysis ◽  
First Order ◽  
First Order Kinetics ◽  
Free Energy Of Activation ◽  
Subsequent Hydrolysis ◽  
Liquid Chromatography Tandem Mass ◽  
Rate Kinetics ◽  
Entropy Of Activation ◽  
Hydrolysis Of

Abstract An analytical method is reported for residue analysis of the fungicide meptyldinocap in different fruit matrixes that involves extraction with ethyl acetate, hydrolysis of the residues with ethanolamine, and determination by LC/MS/MS. The method involves extraction of 10 g sample with 10 mL ethyl acetate; evaporation of the ethyl acetate phase to dryness, and subsequent hydrolysis of the residues to 4,6-dinitro-2-(1-methylheptyl) phenol on reaction with 1 ethanolamine. The pH of this hydrolyzed product was neutralized with formic acid and analyzed by LC/MS/MS. The hydrolysis reaction followed pseudo-first-order kinetics, and the reaction product was spectroscopically confirmed as 2-(1-methylheptyl)-4,6-dinitrophenol. The method offered >80 recoveries at an LOQ of 10 ng/g for grape and mango, 25 ng/g for pomegranate with intralaboratory Horwitz ratio <0.5, and measurement uncertainties <10 at LOQ levels. Considering first-order rate kinetics, activation energy, enthalpy of activation, and entropy of activation varied as solvent > mango > grape > pomegranate. Free energy of activation at 298 K was higher than at 280 K and was similar for solvent and three matrixes at both temperatures.

scholarly journals Solid-State Stability Profiling of Ramipril to Optimize Its Quality Efficiency and Safety

Pharmaceutics ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1600
Author(s):  
Katarzyna Regulska ◽  
Joanna Musiał ◽  
Beata J. Stanisz
Keyword(s):  
Solid State ◽  
Hydroxypropyl Methylcellulose ◽  
Stress Conditions ◽  
Pure Substance ◽  
Air Humidity ◽  
First Order ◽  
First Order Kinetics ◽  
Relative Air Humidity ◽  
Solid State Stability ◽  
Comprehensive Study

High global expenditure on out-of-label-date drugs, along with safety concerns associated with the accumulation of degradation impurities, justify the need for stability profiling. In this article, a comprehensive study on the solid-state stability of ramipril (RAM) was performed via isothermal methods under stress conditions. A validated stability-indicating HPLC protocol was used. The effects of various factors on the rate of RAM degradation were investigated, including: temperature, relative air humidity (RH), excipients (talc, starch, methylcellulose and hydroxypropyl methylcellulose), mode of tablet storage, and immediate packaging. The degradation impurities were also identified by HPLC–MS. It was found that RAM was unstable, and temperature accelerated its degradation. RAM was also vulnerable to RH changes, suggesting that it must be protected from moisture. The reaction followed first-order kinetics. The studied excipients stabilized RAM as a pure substance. The tableting process deteriorated its stability, explaining the need for appropriate immediate packaging. RAM in the form of tablets must be stored in blisters, and it cannot be crushed into two halves. The degradation impurities were ramiprilat and the diketopiperazine derivative.

scholarly journals Evaluation of Plants and Weeds Extract on the Corrosion Inhibition of Mild Steel in Sulphuric Acid

2011 ◽  
Vol 8 (s1) ◽  
pp. S488-S494 ◽  
Author(s):  
Abida Begum
Keyword(s):  
Free Energy ◽  
Mild Steel ◽  
Sulphuric Acid ◽  
Steel Surface ◽  
Inhibition Efficiency ◽  
Adsorption Process ◽  
First Order ◽  
First Order Kinetics ◽  
Maximum Value ◽  
Kinetic Treatment

Experiments were performed in order to determine the inhibitive effects of extracts of plants and weeds namelyParthenium hysterophorus, Dathura stromonium, Azadirachta indica, Helianthus annuusleaves extract for mild steel in sulphuric acid by using weight loss and thermometric technique. Results demonstrated that, all the experimental inhibitors show an adsorption on steel surface according to Langmuir’s isotherm. The inhibition efficiency increased with increase in the concentration of all tested inhibitors to attain a maximum value at 1.0%. Free energy values for adsorption process show that the process is spontaneous. The kinetic treatment of the results shows first order kinetics.

The Influence of Sodium Benzoate on the Alkaline Hydrolysis of Fuchsin: Inhibition Study

2021 ◽  
Vol 46 (1) ◽  
Author(s):  
D. F Latona ◽  
A.E Akinola
Keyword(s):  
Alkaline Hydrolysis ◽  
Sodium Benzoate ◽  
Activation Parameters ◽  
First Order ◽  
First Order Kinetics ◽  
Free Energy Of Activation ◽  
Hydrolytic Reaction ◽  
Presence And Absence ◽  
Gibb’S Free Energy ◽  
Hydrolysis Of

Kinetics of alkaline hydrolysis of Fuchsin in the absence and presence of sodium benzoate was investigated at 546.5 nm by pseudo first order kinetics. The reaction was found to be first order each in [Fuchsin] and [NaOH] in the presence and absence of sodium benzoate. Double reciprocal plot indicates the presence of an intermediate complex in the course of the reaction. Activation parameters were obtained from Erying’s equation as ΔH# 24.70 kJmol-1, ΔS# -0.193 kJK-1mol-1 and ΔG# 82.21 kJ mol-1 in the absence of sodium benzoate and ΔH# 27.59 kJmol-1, ΔS# -0.185 kJ K-1mol-1 and ΔG# 82.72 kJ mol-1in the presence of sodium benzoate. Sodium benzoate plays an inhibitory role in the hydrolysis reaction. The values of the change in Gibb’s free energy of activation shows same mechanism for the hydrolytic reaction in the presence and absence of sodium benzoate. A plausible mechanism is proposed. Keywords: Sodium benzoate, Fuchsin, NaOH, rate law, mechanism

Photo-catalytic degradation of gaseous pollutants in paper mills of southern China

TAPPI Journal ◽  
2018 ◽  
Vol 17 (03) ◽  
pp. 167-178 ◽  
Author(s):  
Xin Tong ◽  
Jiao Li ◽  
Jun Ma ◽  
Xiaoquan Chen ◽  
Wenhao Shen
Keyword(s):  
Degradation Rate ◽  
Southern China ◽  
Catalytic Degradation ◽  
Pulp And Paper ◽  
Gaseous Pollutants ◽  
Pulp And Paper Mills ◽  
Paper Mills ◽  
Initial Concentration ◽  
First Order ◽  
First Order Kinetics

Studies were undertaken to evaluate gaseous pollutants in workplace air within pulp and paper mills and to consider the effectiveness of photo-catalytic treatment of this air. Ambient air at 30 sampling sites in five pulp and paper mills of southern China were sampled and analyzed. The results revealed that formaldehyde and various benzene-based molecules were the main gaseous pollutants at these five mills. A photo-catalytic reactor system with titanium dioxide (TiO2) was developed and evaluated for degradation of formaldehyde, benzene and their mixtures. The experimental results demonstrated that both formaldehyde and benzene in their pure forms could be completely photo-catalytic degraded, though the degradation of benzene was much more difficult than that for formaldehyde. Study of the photo-catalytic degradation kinetics revealed that the degradation rate of formaldehyde increased with initial concentration fitting a first-order kinetics reaction. In contrast, the degradation rate of benzene had no relationship with initial concentration and degradation did not conform to first-order kinetics. The photo-catalytic degradation of formaldehyde-benzene mixtures indicated that formaldehyde behaved differently than when treated in its pure form. The degradation time was two times longer and the kinetics did not reflect a first-order reaction. The degradation of benzene was similar in both pure form and when mixed with formaldehyde.

Kinetic of oxidation of methyl orange by vanadium(V) under conditions VO2+ and decavanadates coexist: Catalysis by Triton X-100 micellar medium

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Methyl Orange ◽  
Solution Ph ◽  
Vanadium Concentration ◽  
Limiting Behavior ◽  
First Order ◽  
First Order Kinetics ◽  
Ph Range ◽  
Kinetic Pattern ◽  
Triton X ◽  
Kinetics Of

The kinetics of oxidation of methyl orange by vanadium(V) {V(V)} has been investigated in the pH range 2.3-3.79. In this pH range V(V) exists both in the form of decavanadates and VO2+. The kinetic results are distinctly different from the results obtained for the same reaction in highly acidic solution (pH < 1) where V(V) exists only in the form of VO2+. The reaction obeys first order kinetics with respect to methyl orange but the rate has very little dependence on total vanadium concentration. The reaction is accelerated by H+ ion but the dependence of rate on [H+] is less than that corresponding to first order dependence. The equilibrium between decavanadates and VO2+ explains the different kinetic pattern observed in this pH range. The reaction is markedly accelerated by Triton X-100 micelles. The rate-[surfactant] profile shows a limiting behavior indicative of a unimolecular pathway in the micellar pseudophase.

Viscosity of Dimethyl Sulfoxide + 1,4 Dimethylbenzene System

2008 ◽  
Vol 59 (1) ◽  
pp. 45-48
Author(s):  
Oana Ciocirlan ◽  
Olga Iulian
Keyword(s):  
Free Energy ◽  
Dimethyl Sulfoxide ◽  
Atmospheric Pressure ◽  
Entire Range ◽  
Polynomial Equation ◽  
Energy Of Activation ◽  
Excess Gibbs Free Energy ◽  
Experimental Measurements ◽  
Gibbs Energy Of Activation ◽  
Free Energy Of Activation

This paper reports the viscosities measurements for the binary system dimethyl sulfoxide + 1,4-dimethylbenzene over the entire range of mole fraction at 298.15, 303.15, 313.15 and 323.15 K and atmospheric pressure. The experimental viscosities were correlated with the equations of Grunberg-Nissan, Katti-Chaudhri, Hind, Soliman and McAllister; the adjustable binary parameters have been obtained. The excess Gibbs energy of activation of viscous flow (G*E) has been calculated from the experimental measurements and the results were fitted to Redlich-Kister polynomial equation. The obtained negative excess Gibbs free energy of activation and negative Grunberg-Nissan interaction parameter are discussed in structural and interactional terms.

Biodegradation rates of aromatic contaminants in biofilm reactors

1995 ◽  
Vol 31 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Jean-Pierre Arcangeli ◽  
Erik Arvin
Keyword(s):  
Aromatic Hydrocarbons ◽  
Competitive Inhibition ◽  
Removal Rate ◽  
First Order ◽  
Biofilm Reactors ◽  
First Order Kinetics ◽  
Reducing Conditions ◽  
Low Concentrations ◽  
Degradation Rates ◽  
Order Surface

This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/l concentration range. The biodegradation rates of the following compounds were investigated in biofilm systems: aromatic hydrocarbons, phenol, methylphenols, chlorophenols, nitrophenol, chlorobenzenes and aromatic nitrogen-, sulphur- or oxygen-containing heterocyclic compounds (NSO-compounds). Furthermore, a comparison with degradation rates observed for easily degradable organics is also presented. At concentrations below 20-100 μg/l the degradation of the aromatic compounds was typically controlled by first order kinetics. The first-order surface removal rate constants were surprisingly similar, ranging from 2 to 4 m/d. It appears that NSO-compounds inhibit the degradation of aromatic hydrocarbons, even at very low concentrations of NSO-compounds. Under nitrate-reducing conditions, toluene was easily biodegraded. The xylenes and ethylbenzene were degraded cometabolically if toluene was used as a primary carbon source; their removal was influenced by competitive inhibition with toluene. These interaction phenomena are discussed in this paper and a kinetic model taking into account cometabolism and competitive inhibition is proposed.

In-vitro Kinetic Hydrolysis Study of Metronidazole Derivatives with Carvacrol and Eugenol Using Validated RP-HPLC Method

2020 ◽  
Vol 16 ◽  
Author(s):  
M. Alarjah
Keyword(s):  
Half Life ◽  
Hplc Method ◽  
Hydrolysis Rate ◽  
First Order ◽  
First Order Kinetics ◽  
Rp Hplc ◽  
Pharmacokinetic Properties ◽  
Pseudo First Order ◽  
Kinetic Hydrolysis

Background: Prodrugs principle is widely used to improve the pharmacological and pharmacokinetic properties of some active drugs. Much effort was made to develop metronidazole prodrugs to enhance antibacterial activity and or to improve pharmacokinetic properties of the molecule or to lower the adverse effects of metronidazole. Objective: In this work, the pharmacokinetic properties of some of monoterpenes and eugenol pro metronidazole molecules that were developed earlier were evaluated in-vitro. The kinetic hydrolysis rate constants and half-life time estimation of the new metronidazole derivatives were calculated using the validated RP-HPLC method. Method: Chromatographic analysis was done using Zorbbax Eclipse eXtra Dense Bonding (XDB)-C18 column of dimensions (250 mm, 4.6 mm, 5 μm), at ambient column temperature. The mobile phase was a mixture of sodium dihydrogen phosphate buffer of pH 4.5 and methanol in gradient elution, at 1ml/min flow rate. The method was fully validated according to the International Council for Harmonization (ICH) guidelines. The hydrolysis process carried out in an acidic buffer pH 1.2 and in an alkaline buffer pH 7.4 in a thermostatic bath at 37ºC. Results: The results followed pseudo-first-order kinetics. All metronidazole prodrugs were stable in the acidic pH, while they were hydrolysed in the alkaline buffer within a few hours (6-8 hr). The rate constant and half-life values were calculated, and their values were found to be 0.082- 0.117 hr-1 and 5.9- 8.5 hr., respectively. Conclusion: The developed method was accurate, sensitive, and selective for the prodrugs. For most of the prodrugs, the hydrolysis followed pseudo-first-order kinetics; the method might be utilised to conduct an in-vivo study for the metronidazole derivatives with monoterpenes and eugenol.

Sign in / Sign up

Export Citation Format

Share Document