1,3-Dinitrobenzene – hydroxide ion interactions. Equilibrium constants for σ-complex formation in the dimethylformamide–water solvent system

1981 ◽  
Vol 59 (22) ◽  
pp. 3168-3176 ◽  
Author(s):  
Erwin Buncel ◽  
Allen W. Zabel
Keyword(s):  
Equilibrium Constants ◽  
Solvent System ◽  
Medium Composition ◽  
Hydroxide Ion ◽  
Interacting Species ◽  
Ion Interactions ◽  
Water Solvent ◽  
Constant Measurement ◽  
Uv Visible ◽  
Solvent Isotope

The results of a uv–visible spectroscopic study of the interaction of 1,3-dinitrobenzene (DNB) with hydroxide ion in aqueous dimethylformamide (DMF) media are reported. Formation of several spectral species has been discerned, depending on factors such as the relative concentrations of the reactants, the time scale of the experiments, and the medium composition. The principal interaction is formation of the 1-hydroxy-2,4-dinitrocyclohexadienate anion. The molar absorptivities of this σ-complex, and the equilibrium constants (Ke) for its formation, have been determined as a function of medium composition. Values of Ke increase from 7.5 M−1 to 3 × 105M−1 as the DMF content of the medium is changed from 57.4 to 95.8 mol% DMF. A solvent isotope effect, Ke(D2O)/Ke(H2O), of ca. 0.4 has been observed. Structural and medium effects in this and related systems are evaluated. Correlations between log Ke and H− are examined using the stoichiometric as well as the calculated free hydroxide ion concentrations. Attention is drawn to an important condition for equilibrium constant measurement in systems where one of the interacting species contributes significantly to the overall basicity, or to another property of the medium.

Meisenheimer Complex Formation Between 1,3,5-Trinitrobenzene and Hydroxide Ion. Equilibrium Constants for the Dimethylformamide–Water Solvent System

1972 ◽  
Vol 50 (11) ◽  
pp. 1729-1733 ◽  
Author(s):  
E. A. Symons ◽  
E. Buncel
Keyword(s):  
Complex Formation ◽  
Aqueous Medium ◽  
Equilibrium Constant ◽  
Equilibrium Constants ◽  
Solvent System ◽  
Medium Composition ◽  
Hydroxide Ion ◽  
Spectrophotometric Methods ◽  
Water Solvent ◽  
Sigma Complex

Sigma-complex formation between 1,3,5-trinitrobenzene (TNB) and hydroxide ion has been studied quantitatively as a function of medium composition for part of the dimethylformamide (DMF)–water solvent system by spectrophotometric methods. Only a 1:1 complex is detected under the conditions of measurement, with [TNB] ≥ [OH−]. The equilibrium constant (Keq) for complex formation in 22 mol % DMF has the value 3 × 10−3 l mol−1, compared with 3 l mol−1 in purely aqueous medium. Further increases in Kcq occur as the DMF content of the medium is raised; in 50 mol % DMF Keq ≈ 105, but reliable Keq values could not be obtained in this region of medium composition. The increase in Keq with increasing DMF content is interpreted largely on the basis of hydroxide ion desolvation.

scholarly journals Standardisation Study of Kwatha Curnas

2004 ◽  
Vol 1 (5) ◽  
pp. 251-255
Author(s):  
M. K. Santosh ◽  
D. Shaila ◽  
I. Sanjeeva Rao
Keyword(s):  
High Performance ◽  
Solvent System ◽  
High Performance Liquid Chromatographic ◽  
Organic Analysis ◽  
Hplc Fingerprint ◽  
Visible Spectrophotometry ◽  
Water Solvent ◽  
Mother And Child ◽  
Uv Visible ◽  
Ethanol Extracts

The present paper deals with the standardization of kwatha curnas such as dhanyapanchak kwatha curna, guduchyadigana kwatha curna and stanyajanankashaya curna. These are the important Ayurvedic formulations used for peri-natal care of mother and child health. Standardization of kwatha curnas were achieved by physico-chemical analysis, qualitative inorganic and organic analysis, thin layer chromatography (TLC), UV- visible spectrophotometry and high performance liquid chromatographic (HPLC) fingerprint studies. TLC study of kwatha curnas was carried out in Ethyl acetate: Methanol: Water solvent system. Ethanol extracts of kwatha curnas were used for UV- visible spectrophotometry and qualitative HPLC fingerprint study.

Conversion of glucose into furans in the presence of AlCl3 in an ethanol–water solvent system

2012 ◽  
Vol 116 ◽  
pp. 190-194 ◽  
Author(s):  
Yu Yang ◽  
Changwei Hu ◽  
Mahdi M. Abu-Omar
Keyword(s):  
Solvent System ◽  
Water Solvent

Effect of Cellulose Coating on Properties of Cotton Fabric

2016 ◽  
Vol 860 ◽  
pp. 81-84
Author(s):  
Bandu Madhukar Kale ◽  
Jakub Wiener ◽  
Jiri Militky ◽  
Hafiz Shahzad Maqsood
Keyword(s):  
Tensile Strength ◽  
Cotton Fabric ◽  
Solvent System ◽  
Dissolving Pulp ◽  
Cotton Fibers ◽  
Cellulose Solution ◽  
Dyeing Properties ◽  
Sem Micrographs ◽  
Coated Substrate ◽  
Water Solvent

Cellulose solution was used for coating and it was prepared by dissolving pulp cellulose in Urea-Thiourea-NaOH-Water solvent system. Reactive Red 240 dye was used for dyeing the coated as well as control cotton fabric. The effect of cellulose coating on the dyeing properties of cotton fabric was studied by measuring K/S values of the coated substrate at various concentrations of cellulose and dye. K/S value decreased after coating cellulose on the surface of cotton fabric. The lightness of cotton fabric increased after cellulose coating. SEM micrographs revealed that coated cellulose was attached to cotton fibers. Tensile strength increased after cellulose coating.

Shape selective solvothermal synthesis of SnS: Role of ethylenediamine–water solvent system

2006 ◽  
Vol 129 (1-3) ◽  
pp. 265-269 ◽  
Author(s):  
S.K. Panda ◽  
S. Gorai ◽  
S. Chaudhuri
Keyword(s):  
Solvothermal Synthesis ◽  
Solvent System ◽  
Water Solvent ◽  
Shape Selective

Development and Validation of UV-Visible Spectrophotometric method for the Estimation of Curcumin and Tetrahydrocurcumin in Simulated Intestinal Fluid

2021 ◽  
pp. 2971-2975
Author(s):  
Jai Bharti Sharma ◽  
Sherry Sherry ◽  
Shailendra Bhatt ◽  
Vipin Saini ◽  
Manish Kumar
Keyword(s):  
Drug Release ◽  
Spectrophotometric Method ◽  
Tween 80 ◽  
Solvent System ◽  
Intestinal Fluid ◽  
Simulated Intestinal Fluid ◽  
Validation Parameters ◽  
Administration Method ◽  
Uv Visible ◽  
Development And Validation

Background: Due to solubility issues of curcumin and tetrahydrocurcumin, there is a need for the development of a UV-Visible spectrophotometric method that can estimate the drug release precisely and accurately. The addition of surfactant in the dissolution medium in low concentration achieved bio-comparable surface activity and can be used to estimate the drug release from formulations by avoiding sink conditions. Objective: The purpose of the present investigation was to develop a simple and précise UV-Visible spectrophotometric method for the determination of curcumin and tetrahydrocurcumin after oral administration. Method: A UV-Visible spectrophotometric method was developed using an appropriate solvent system for the estimation of curcumin and tetrahydrocurcumin. The solvent system having simulated intestinal fluid and particular concentration of surfactant was selected and further validated according to guidelines of the international conference on harmonization (ICH), the analytical parameter like linearity, precision and accuracy, etc. were studied. Results: Simulated intestinal fluid pH 7.4 with tween 80 at 1 % concentration satisfied all the conditions relative to peak quality at the stated wavelength for curcumin and intestinal fluid pH 7.4 with tween 80 at 0.5% concentration satisfied all the conditions relative to Peak quality at the stated wavelength for tetrahydrocurcumin. The developed methods were found within the range of all the validation parameters. Conclusion: The proposed method was found to be very simple and precise and can be used for routine quantitative analysis of curcumin and tetrahydrocurcumin.

Free-base corroles: determination of deprotonation constants in non-aqueous media

2007 ◽  
Vol 11 (04) ◽  
pp. 269-276 ◽  
Author(s):  
Jing Shen ◽  
Zhongping Ou ◽  
Jianguo Shao ◽  
Michał Gałęzowski ◽  
Daniel T. Gryko ◽  
...  
Keyword(s):  
Equilibrium Constants ◽  
Aqueous Media ◽  
Free Base ◽  
Organic Base ◽  
Experimental Conditions ◽  
Spectral Changes ◽  
Base Analysis ◽  
Uv Visible ◽  
The Given

A series of free-base corroles with different electron-donating or electron-withdrawing substituents were reacted with piperidine, 4-aminopyridine, 2-methylimidazole, 2-aminopyridine or pyridine in PhCN and the UV-visible spectral changes monitored during conversion of ( Cor ) H 3 to [( Cor ) H 2]- as a function of the concentration and strength of the added organic base. Analysis of the UV-visible spectral changes as a function of the added base concentration enabled calculation of equilibrium constants ( logK ) for deprotonation of each corrole under the given experimental conditions. Relationships are examined between the experimentally measured logK values and previously published spectroscopic and structural properties of the compounds.

scholarly journals Pyrolyzing Renewable Sugar and Taurine on the Surface of Multi-Walled Carbon Nanotubes as Heterogeneous Catalysts for Hydroxymethylfurfural Production

Catalysts ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 517 ◽  
Author(s):  
Huiping Ji ◽  
Jie Fu ◽  
Tianfu Wang
Keyword(s):  
Carbon Nanotubes ◽  
Heterogeneous Catalysts ◽  
Metal Salt ◽  
Textural Properties ◽  
Solvent System ◽  
Hydrothermal Stability ◽  
Transportation Fuels ◽  
Water Solvent ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

Conversion of biorenewable feedstocks into transportation fuels or chemicals likely necessitates the development of novel heterogeneous catalysts with good hydrothermal stability, due to the nature of highly oxygenated biomass compounds and the prevalence of water as a processing solvent. The use of carbon-based materials, derived from sugars as catalyst precursors, can achieve hydrothermal stability while simultaneously realizing the goal of sustainability. In this work, the simultaneous pyrolysis of glucose and taurine in the presence of multi-walled carbon nanotubes (MWCNTs), to obtain versatile solid acids, has been demonstrated. Structural and textural properties of the catalysts have been characterized by TEM, TGA, and XPS. Additionally, solid state nuclear magnetic resonance (ssNMR) spectroscopy has been exploited to elucidate the chemical nature of carbon species deposited on the surface of MWCNTs. Al(OTf)3, a model Lewis acidic metal salt, has been successfully supported on sulfonic groups tethered to MWCNTs. This catalyst has been tested for C6 sugar dehydration for the production of HMF in a tetrahydrofuran (THF)/water solvent system with good recyclability.

scholarly journals DEVELOPMENT AND VALIDATION OF UV-VISIBLE SPECTROPHOTOMETRIC METHOD FOR DETERMINATION OF DULOXETINE

2019 ◽  
pp. 27-31
Author(s):  
LIPSA SAMAL ◽  
AMARESH PRUSTY
Keyword(s):  
Spectrophotometric Method ◽  
Spectroscopic Method ◽  
Solvent System ◽  
Spectrophotometric Analysis ◽  
Thiophene Derivative ◽  
Experimental Conditions ◽  
Relative Standard ◽  
Uv Visible ◽  
Development And Validation

Objective: The aim of the present work was to develop and validate a simple UV spectroscopic method for the determination of duloxetine, which is a thiophene derivative and a selective neurotransmitter reuptake inhibitor for serotonin, norepinephrine, and to lesser degree dopamine. Methods: The UV Spectrophotometric analysis was performed using Shimadzu UV-1800 and Shimadzu UV-1700 spectrophotometer by using solvent system acetonitrile and water in the ratio of 8:2. Detection was performed at a wavelength of 290 nm. Method validation was carried out according to ICH Q2R1 guidelines by taking the parameters linearity, accuracy, precision, ruggedness, and robustness, LOD and LOQ. Results: The UV Spectrophotometric method was found linear in the range of 10-50 μg/ml. The method was rugged and robust with % relative standard deviation less than 2. The extraction recoveries were found to be higher than 99% in all experimental conditions. Conclusion: Based upon the performance characteristics, the proposed method was found accurate, precise and rapid and suitable for the determination of Duloxetine for routine analysis.

Phosphato complexes of cobalt(III). IV. Hydrolysis in basic solution

1968 ◽  
Vol 21 (7) ◽  
pp. 1733 ◽  
Author(s):  
SF Lincoln ◽  
DR Stranks
Keyword(s):  
Isotope Effects ◽  
Base Hydrolysis ◽  
Basic Solution ◽  
Tracer Technique ◽  
Hydroxide Ion ◽  
Solvent Water ◽  
Coordination Spheres ◽  
Solvent Isotope ◽  
Hydrolysis Of ◽  
Solvent Isotope Effects

The rates of hydrolysis of phosphato complexes of cobalt(111) in sodium hydroxide concentrations ranging from 0.02M to 0.37M, and at several ionic strengths, have been measured with a tracer technique. Bidentate phosphato complexes exhibit the same rates of hydrolysis as the corresponding monodentate complexes, due to a rapid conversion of the bidentate into the monodentate form. The general rate law for base hydrolysis of all the phosphato complexes is: d[PO34]/dt = {kH2O + kOH[OH-]}[complex] At 60� and at unit ionic strength, the rate constants for the complexes cis-[Co(NH3)4OH.PO4]-, cis-[Co en2OH.PO4]-, and [Co(NH3)5PO4] respectively are: 103kH2O (min-l) 85.0, 2.0, <1; and 103kOH (1. mole-1 min-l) 42.7, 12.0, 69.5. Mechanistic conclusions have been based on the measured enthalpies and entropies of activation and deuterium solvent isotope effects. For all complexes, kH2O is identified with an aquation mechanism involving synchronous interchange of the phosphate and solvent water between the first and second coordination spheres of the complexes. In the case of the tetrammine and bis(ethylenediamine) complexes, kOH is identified with a process involving synchronous interchange of phosphate and hydroxide ion between the first and second coordination spheres of the complexes. In the case of the pentammine complex, an SN2CB mechanism is considered to be more probable. A comparison with the base hydrolysis of halogen complexes of cobalt(111) is presented.

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