Substitution reactions of benzethonium chloride with ion associates of bromocresol green – quinine and bromophenol blue – quinine in dichloromethane

1991 ◽  
Vol 69 (6) ◽  
pp. 937-944 ◽  
Author(s):  
Alberto Hernandez Gainza ◽  
Roy Ikemefula Konyeaso
Keyword(s):  
Thermodynamic Parameters ◽  
Equilibrium Constants ◽  
Formation Constants ◽  
Bromocresol Green ◽  
Bromophenol Blue ◽  
Substitution Reactions ◽  
Dichloromethane Solution ◽  
Benzethonium Chloride ◽  
Quinine Hydrochloride ◽  
Ion Associate

An excess concentration of base quinine (Q) reacts with a sulphonphthalein diacidic dye XH2, (bromocresol green, BCGH2, or bromophenol blue, BPBH2) in dichloromethane solution to form an ion associate (X2−(QH+)2) of stoichiometry 1:2 (dye:amine). Benzethonium chloride (ClB) reacts with the 1:2 ion associate to form an ion associate (QH+,X2−,B+) and quinine hydrochloride ClQH+. This substitution reaction is a chemical equilibrium with formation constants of 1.50 ± 0.67, 1.61 ± 0.54, 1.07 ± 0.29, 1.04 ± 0.20, and 0.84 ± 0.26 for BCG and 1.86 ± 0.59, 1.47 ± 0.23, 1.40 ± 0.65, 1.13 ± 0.37, and 1.11 ± 0.27 for BPB at 283.16, 288.16, 293.16, 298.16, and 303.16 K respectively. The thermodynamic parameters determined by van't Hoff's equation are ΔH0 = −21.766 ± 7.482 kJ mol−1, ΔS0 = −73 ± 51 J mol−1 K−1, and ΔG0 = −1.134 ± 0.972 kJ mol−1for BCG and ΔH0 = −18.678 ± 7.482 kJ mol−1, ΔS0 = −61 ± 26 J mol−1 K−1, ΔG0 = −0.916 ± 0.401 kJ mol−1 for BPB (ΔG0 at 293.16 K; and ΔH0 and ΔS0 determined in the range 283–303 K). Key words: bromocresol green – quinine–benzethonium, ion associate mixture, bromophenol blue – quinine–benzethonium, equilibrium constants, thermodynamic parameters.

Associations of ajmaline and homatropine with bromocresol green and bromophenol blue in dichloromethane: thermodynamic and kinetic parameters

1987 ◽  
Vol 65 (6) ◽  
pp. 1279-1291 ◽  
Author(s):  
Alberto Hernández Gaínza
Keyword(s):  
Thermodynamic Parameters ◽  
Arrhenius Equation ◽  
Charge Transfer Complex ◽  
Ion Pairs ◽  
Bromocresol Green ◽  
Bromophenol Blue ◽  
Order Kinetic ◽  
Large Excess ◽  
First Order ◽  
Hoff Equation

Ajmaline (AJ) and homatropine (HM) react with bromocresol green (BCG) and bromophenol blue (BPB) in dichloromethane forming 1:1 and 1:2 ion pairs clearly in a chemical equilibrium. Thermodynamic parameters ΔG0, ΔH0, and ΔS0 are calculated using the Van't Hoff equation. In a large excess of HM a product P is formed from the 1:2 ion pair in a pseudo-first order kinetic process which fits Arrhenius' equation. The P product has been identified as a type of charge transfer complex. The thermodynamic parameters corresponding to the formation of the ion pairs BPB—(AJ)2, BCG—(AJ)2, BPB—(HM)2, and BCG—(HM)2 are, respectively: ΔG0 at 294 K, −26, −21, −26, and −19 kJ/mol; ΔH0, −63, −39, −63, and −61 kJ/mol; ΔS0, −125, −62, −125, and −138 J/K mol (ΔH0 and ΔS0 determined in a 288 to 313 K range). The values of the activation energy, Ea, for the reaction of HM (in large excess) with BCG and BPB are 58 and 91 kJ/mol.

scholarly journals Spectrophotometric Studies on the Reaction of Diaveridine with Some Sulfonphthalein Dyes Based on Ion-Pair/Ion-Associate Complexes Formation

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
A. L. El-Ansary ◽  
N. S. Abdel-Kader ◽  
A. M. Asran
Keyword(s):  
Spectral Characteristics ◽  
Pharmaceutical Preparations ◽  
Bromothymol Blue ◽  
Molar Absorptivity ◽  
Molecular Structures ◽  
Bromocresol Green ◽  
Bromophenol Blue ◽  
Bromocresol Purple ◽  
Donor And Acceptor ◽  
Ion Associate

The ion-associate complexes of diaveridine were prepared in a solution and studied spectrophotometrically. The bulky counter anions such as sulfonphthalein acidic dyes, namely, bromocresol green (I), bromophenol blue (II), bromothymol blue (III), bromocresol purple (IV), bromocresol blue (V), o-cresol red (VI), p-cresol blue (VII), and m-cresol purple (VIII) were used for ion-associate complexes formation. The optimal characteristics for the color formation and the stoichiometry of the reaction were evaluated. Spectral characteristics and stability constants of the formed ion associates are discussed in terms of nature of donor and acceptor molecular structures. The molar absorptivities and association constants for the colored complexes were evaluated using the Benesi-Hildbrand equation. Conformity to Beer’s law enabled the assay of dosage form of the drug. The molar absorptivity, specific absorptivity, Sandell sensitivity, correlation coefficient, and detection and quantification limits were also calculated. The methods were validated in terms of accuracy, specificity, precision, and linearity. Also, spectrophotometric determination of the drug in pure and pharmaceutical preparations was tested.

scholarly journals Spectrophotometric determination of dothiepin hydrochloride in pharmaceuticals through ion-pair complexation reaction

2012 ◽  
Vol 18 (2) ◽  
pp. 339-347 ◽  
Author(s):  
Sameer Abdulrahman ◽  
Kanakapura Basavaiah
Keyword(s):  
Ion Pair ◽  
Pure Form ◽  
Bromocresol Green ◽  
Bromophenol Blue ◽  
Complexation Reaction ◽  
Conditional Stability ◽  
Conditional Stability Constant ◽  
Accuracy And Precision ◽  
Significant Difference

Two simple, sensitive and extraction-free spectrophotometric methods are described for the determination of dothiepin hydrochloride (DOTH) both in pure form and in pharmaceutical tablets. The methods are based on ion-pair complex formation between dothiepin base (DOT) and two acidic dyes, namely, bromophenol blue (BPB) or bromocresol green (BCG) with absorption maximum at 425 nm for BPB method or 430 nm for BCG method. Beer?s law is obeyed over the concentration ranges of 1.0-15.0 and 1.0-17.5 ?g mL-1 DOT for BPB and BCG methods, respectively. The molar absorptivity values and Sandell?s sensitivity values are reported for both methods. The limits of detection (LOD) and quantification (LOQ) were calculated to be 0.18 and 0.53 ?g mL-1 for BPB method, and 0.17 and 0.50 ?g mL-1 for BCG method, respectively. The stoichiometry of the complex in either case was found to be 1: 1 and the conditional stability constant (KF) of the complexes has also been calculated. The proposed methods were applied successfully to the determination of DOTH in pure form and in its tablet form with good accuracy and precision. Statistical comparison of the results was performed using Student's t-test and variance ratio F-test at 95% confidence level and there was no significant difference between the official and proposed methods with regard to accuracy and precision. Further, the validity of the proposed methods was confirmed by recovery studies via standard addition technique.

Thermochromism of Metal Exchange Reaction between Zinc(II) and Mercury(II) Porphyrins

1995 ◽  
Vol 50 (4) ◽  
pp. 545-550 ◽  
Author(s):  
Masaaki Tabata ◽  
Masahiro Ide ◽  
Kentaro Kaneko
Keyword(s):  
Aqueous Solution ◽  
Exchange Reaction ◽  
Thermodynamic Parameters ◽  
Distribution Curve ◽  
Equilibrium Constants ◽  
Metal Exchange ◽  
Free Base ◽  
Temperature Range ◽  
Base Form ◽  
Metal Exchange Reaction

Thermochromism was observed for an aqueous solution containing zinc(II) and mercury( II) cations and N-p-nitrobenzyl-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin anion (NO2Bz(Htpps)4-) in the temperature range 10 to 70 °C. The equilibrium constants and the thermodynamic parameters of Zn(NO2Bztpps)3- and Hg(NO2Bztpps)3- have been determined spectrophotometrically to elucidate the thermochromism at 10, 15, 20, 25 and 30 °C in 0.1 mol dm-3 NaNO3. The protonation and metalation constants of NO2Bz(Htpps)4- are defined as K2 = [H2P][H+]-1[HP]-1, K3 = [H3P][H+]-1[H2P]-1 and KMP = [M P][H+][M2+]-1[HP]-1, where HP and MP denote the free base form of the prophyrin and the metalloporphyrins of zinc(II) and mercury(II), respectively. Charges of the prophyrin and metalloporphyrins are omitted for simplicity. The following values were found: logK2 = 7.75 ±0.02 (25 °C), ΔH°/kJmol-1 = -21.2±0.5 and ΔS°/Jmol-1K-1 = 77±1, logK3 = 2.55±0.02 (25 °C), ΔH°/kJmol-1 = -25±0.8 and ΔS°/Jmol-1K-1 = -35±3 and log KZnP = 0.63±0.03 (25 °C), ΔH°/kJmol-1 = 31.0±0.8 and ΔS°/Jmol-1K-1 = 116±3, logKHgP = 6.22±0.03 (25 °C), ΔH°/kJmol-1 = 4.5±0.7 and ΔS°/Jmol-1K-1 = 134±2. The distribution curve calculated from the thermodynamic parameters sufficiently agrees with the observed metal exchange reaction between the metalloporphyrins.

Kinetic and equilibrium studies of fluoride sorption onto surfactant-modified smectites

Clay Minerals ◽  
2012 ◽  
Vol 47 (4) ◽  
pp. 429-440 ◽  
Author(s):  
S. Gamoudi ◽  
N. Frini-Srasra ◽  
E. Srasra
Keyword(s):  
Aqueous Solution ◽  
Thermodynamic Parameters ◽  
Adsorption Kinetics ◽  
Equilibrium Constants ◽  
Second Order ◽  
Operating Conditions ◽  
Polluted Water ◽  
Isotherm Models ◽  
Fluoride Ions ◽  
Pseudo Second Order

AbstractThe use of organoclays as adsorbents in the remediation of polluted water has been the subject of many recent studies. In the present work, a Tunisian smectite modified with two cationic surfactants was used as an adsorbent to examine the adsorption kinetics, isotherms and thermodynamic parameters of fluoride ions from aqueous solution. Various pH values, initial concentrations and temperatures have been tested. Two simplified kinetic models, first-order and pseudo-second-order, were used to predict the adsorption rate constants. It was found that the adsorption kinetics of fluoride onto modified smectites at different operating conditions can best be described by the pseudo-second-order model. Adsorption isotherms and equilibrium adsorption capacities were determined by the fitting of the experimental data to well known isotherm models including those of Langmuir and Freundlich. The results showed that the Langmuir model appears to fit the adsorption better than the Freundlich adsorption model for the adsorption of fluoride ions onto modified smectites. The equilibrium constants were used to calculate thermodynamic parameters, such as the change of free energy, enthalpy and entropy. Results of this study demonstrated the effectiveness and feasibility of organoclays for the removal of fluoride ions from aqueous solution.

scholarly journals Spectrophotometric Determination of Gemifloxacin Mesylate, Moxifloxacin Hydrochloride, and Enrofloxacin in Pharmaceutical Formulations Using Acid Dyes

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Ayman A. Gouda ◽  
Alaa S. Amin ◽  
Ragaa El-Sheikh ◽  
Amira G. Yousef
Keyword(s):  
Pharmaceutical Formulations ◽  
Bromothymol Blue ◽  
Bromocresol Green ◽  
Bromophenol Blue ◽  
Bromocresol Purple ◽  
Acid Dyes ◽  
Spectrophotometric Methods ◽  
Significant Difference ◽  
Comparison Of The Results

Simple, rapid, and extractive spectrophotometric methods were developed for the determination of some fluoroquinolones antibiotics: gemifloxacin mesylate (GMF), moxifloxacin hydrochloride (MXF), and enrofloxacin (ENF) in pure forms and pharmaceutical formulations. These methods are based on the formation of ion-pair complexes between the basic drugs and acid dyes, namely, bromocresol green (BCG), bromocresol purple (BCP), bromophenol blue (BPB), bromothymol blue (BTB), and methyl orange (MO) in acidic buffer solutions. The formed complexes were extracted with chloroform and measured at 420, 408, 416, 415, and 422 nm for BCG, BCP, BPB, BTB, and MO, respectively, for GMF; at 410, 415, 416, and 420 nm for BCP, BTB, BPB, and MO, respectively, for MXF; and at 419 and 414 nm for BCG and BTB, respectively, in case of ENF. The analytical parameters and their effects are investigated. Beer’s law was obeyed in the ranges 1.0–30, 1.0–20, and 2.0–24 μg mL−1for GMF, MXF, and ENF, respectively. The proposed methods have been applied successfully for the analysis of the studied drugs in pure forms and pharmaceutical formulations. Statistical comparison of the results with the reference methods showed excellent agreement and indicated no significant difference in accuracy and precision.

Nuclear magnetic resonance studies of the solution chemistry of metal complexes. XIV. The aqueous chemistry of trimethyllead(IV) and its carboxylic acid complexes

1977 ◽  
Vol 55 (18) ◽  
pp. 3255-3260 ◽  
Author(s):  
T. L. Sayer ◽  
S. Backs ◽  
C. A. Evans ◽  
E. K. Millar ◽  
D. L. Rabenstein
Keyword(s):  
Carboxylic Acid ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Ph Dependence ◽  
Equilibrium Constants ◽  
Formation Constants ◽  
Solution Chemistry ◽  
Resonance Spectroscopy ◽  
Coupling Constant ◽  
Proton Coupling

The aqueous solution chemistry of the trimethyllead(IV) species and the trimethyllead(IV) complexes of six carboxylic acids of pKa values ranging from 2.75 to 4.95 has been investigated by proton magnetic resonance spectroscopy. Equilibrium constants for the reaction of (CH3)3Pb+ with hydroxide ion to form (CH3)3PbOH and ((CH3)3Pb)2OH+, and the formation constants of the carboxylic acid complexes were determined from the pH dependence of the chemical shift of the methyl protons of trimethyllead. The formation constants of the complexes increase as the pKa of the ligand increases. The lead-207-proton coupling constant was found to be insensitive to complexation.

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