Thermometric Titrimetry Research Articles

Détermination des paramètres thermodynamiques de transfert eau/ n-octanol de barbituriques : application aux relations quantitatives

Thermometric titrimetry allows the determination of the three thermodynamic parameters of transfer ( ΔG 0 T , ΔH 0 T , and ΔS 0 T ) from water to n-octanol for barbiturates. The transfer is entropy driven when the substituents are saturated; when one is unsaturated, this entropy effect is less marked. For phenobarbital, enthalpy and entropy effects are cooperative. Quantitative structure—activity relationships analyzed with these data show no improvement when transfer enthalpy or entropy is used instead of transfer free energy (log P).

ChemInform Abstract: Applications of Catalytic Thermometric Titrimetry to Studies of Molecular Structure and Reactivity. Part 2. Condensation and Rearrangement Reactions of Carbonyl Compounds.

AbstractAliphatic and aromatic carbonyl compounds such as cyclobutanone, ‐pentanone, ‐hexanone, acetone, and benzil and some binary mixtures of these compounds are used as indicator reagents in the catalytic thermometric titration of benzoic acid with KOH in propanol.

Advanced undergraduate experiments in thermoanalytical chemistry

Experiments are described that are suitable for final year undergraduates that involve simple equipment and standard laboratory techniques that illustrate the applications of thermal analysis and thermometric titrimetry in inorganic chemistry.

Applications of catalytic thermometric titrimetry to studies of molecular structure and reactivity. Part 2. Condensation and rearrangement reactions of carbonyl compounds

Aliphatic and aromatic carbonyl compounds and some binary mixtures of these compounds are used as indicator reagents in the catalytic thermometric titration of benzoic acid with potassium hydroxide in propan-1-ol. Comparison of titration curves obtained in blank titrations and in titrations of benzoic acid are used to evaluate the relative reactivities of the carbonyl compounds when they undergo inter- and intra-molecular condensation and rearrangement reactions, and to investigate reaction processes with the binary mixtures. Consideration of the relative reactivities is used to establish relationships between reactivity and molecular environment of the carbonyl group.

A thermometric titration study of the interaction of Co 2+ with metallochromic indicators

A thermometric titrimetry study of the interaction in aqueous solution of Co 2+ with xylenol orange, eriochrome black T and catechol violet at a specified pH, has revealed in each case a linear reaction heat/[Co 2+] relationship, thereby suggesting the potential of metallochromic indicators for the determination of macro trace levels of cobalt in water. The relevant complexation enthalpies are rationalized in terms of a combination of ligand steric effect, cobalt-ligand bond energies and chelate effect.

Complexes of nickel(II) withS-carboxyalkyl-L-cysteines in aqueous medium. Determination of enthalpies by thermometric titrimetry

Molar heats for the reaction of nickel(II) with sulphur-containing amino acids,S-carboxymethyl-L-cysteine andS-carboxyethyl-L-cysteine, have been determined by thermometric titrimetry. The data refer to aqueous solutions at 25°C andI=2.0m. From these enthalpies and equilibrium constants, the corresponding entropies have been calculated. The present thermodynamic data are complementary to previous spectrophotometric data in explaining the structures of the complexes. In particular, the importance of solute-solvent external factors in determining different stabilities for successive steps of complex-formation is stressed.

Determination of ascorbic acid in multivitamin tablets by thermometric titrimetry with cerium(IV)

Cerium(IV) sulphate in aqueous sulphuric acid has been used as a titrant for the thermometric determination of ascorbic acid. The method has been applied to the analysis of vitamin tablets containing between 10 and 30 mg of ascorbic acid per tablet, and has been shown to be free from interference from tablet excipients.Comparative analyses of two types of multivitamin tablet have been carried out using this method, two HPLC methods and visual titrimetry [cerium(IV) ammonium sulphate]. The precisions of the thermometric method and the HPLC methods are similar and acceptable. The presence of vanillin has been identified as a cause of positive bias in the visual method.The thermometric method is inexpensive to set up and operate, relatively rapid and comparable in performance to other thermal methods for the determination of ascorbic acid.

A thermometric titration study of the interaction of Al3+, Co2+, Ni2+ and Zr4+ with xylenol orange

A thermometric titrimetry study of the interaction in aqueous solution of A13+, Co2+, Ni2+ and Zr4+ with xylenol orange has revealed in each case a linear reaction heat/[Mn+] relationship at a specified pH, thereby suggesting the potential of metallochromic indicators for the analytical determination of these metals in water. The effect of pH on the reaction heat is investigated and is interpreted in terms of the ability of these metal cations to complex with the known xylenol orange species existing at the various pH studied. An interference study, involving transition and non-transition metal ions, is also reported and the interference effect, as measured by the deviation ofQ′/Q from unity (Q′ andQ are the relevant reaction heats in the presence and absence of interfering ion), is partially explained in terms of the coordination numbers, relative sizes and crystal field stabilization energies of the cations studied and the known behaviour of xylenol orange in aqueous solution.

A rapid method for the determination of some antihypertensive and antipyretic drugs by thermometric titrimetry

A simple and rapid method is described for the direct thermometric determination of milligram amounts of methyl dopa, propranolol hydrochloride, 1-phenyl-3-methylpyrazolone (MPP) and 2,3-dimethyl-1-phenylpyrazol-5-one (phenazone) in the presence of excipients. The compounds are reacted with N'-bromosuccinimide and the heat of reaction is used to determine the end-point of the titration. The time required is approximately 2 min, and the accuracy is analytically acceptable.

Determination of sulfide in natural waters by thermometric titrimetry

The thermometric titration of sulfide with permanganate in alkaline solution has been investigated as a potential analytical method for the determination of sulfide in natural waters. The molar enthalpy of the corresponding complex calorimetric reaction has been determined as 1010 ±36 kJ mol − and the interference effect of a variety of anionic and heavy metal cationic species has been investigated. The analytical potential of the proposed thermoanalytical method has been further tested by application to sulfide determination in a sewage sample and comparison made with sulfide assay of the same sample by differential pulse polarography.

Evaluation of the reactivity of vinyl monomers by catalytic thermometric titrimetry

Evaluation of the reactivity of vinyl monomers by catalytic thermometric titrimetry

Potentiometric and thermometric determination of mercaptopyrimidines

Potentiometric and Thermometric Determination of Mercaptopyrimidines Potentiometric and thermometric methods for the determination of several 2- and 6-mercaptopyrimidines are described. Mercapto groups can be titrated as acids in water or in dimethylformamide media. The use of acetic acid as solvent allows titration of the basic pyrimidine nucleus. Thermometric titrimetry is also a valuable procedure for the titration of mercapto groups, either directly with sodium hydroxide or by back-titration with hydrochloric acid after addition of excess of alkali. About 10–25 mg of sample can be determined with an error better than 1%.

Use of catalytic thermometric titrimetry to investigate the interaction of dipolar aprotic solvents with water

The interaction between water and the dipolar aprotic solvents dimethyl sulfoxide (Me/sub 2/SO), dimethylformamide (DMF), and hexamethylphosphoramide (HMPA) is investigated by a kinetic procedure in which catalytic thermometric titrimetry, with acrylonitrile as the thermometric indicator, is used to determine reaction rates. The interaction is measured by determining the influence of the solvents on the inhibiting effect of water on the base-catalyzed polymerization and cyanoethylation reactions occurring at the end point of the titration. The reactivity of the water is reduced by hydrogen bonding with the solvents, and discontinuities in the relationship between solvent-water molar ratio and end-point reaction rate confirm that association complexes are formed corresponding to molar ratios of 1:1 and 2:1, 1:1 and 2:1, and 1:1 for Me/sub 2/SO, DMF, and HMPA, respectively. 20 references, 4 figures.

Borate-polyol complexes in aqueous solution Determination of enthalpies by thermometric titrimetry

Enthalpies for the reaction of borate with 1,2-ethanediol, 1,2-propanediol, 1,2,3-propanetriol and d-mannitol have been determined by thermometric titrimetry. From these enthalpies and equilibrium constants taken from the literature, corresponding entropies have been calculated. The data refer to aqueous solutions at 25 degrees and I = 1.0M (NaNO(3)). The results indicate reasons for the differences in the stabilities of the complexes.

Determination of some 1,4-benzodiazepines and their tablet formulations by a catalymetric thermometric method

1,4-Benzodiazepines of pharmaceutical importance, alone and in tablet formulations, are determined in non-aqueous solution by catalymetric thermometric titrimetry using perchloric acid in acetic acid as the titrant and also as catalyst for the acetylation of diacetone alcohol by acetic anhydride, which serves as the thermometric indicator reaction. Direct titration of halide acid salts is possible without addition of mercury(II) acetate, and excipients do not interfere. Using 0.01 M acid, sample sizes down to 0.17 mg are titrated. Coefficients of variation for four replicate determinations are mostly in the range 0.2–2.0% with the 0.1 M titrant, but are higher when the 0.01 M titrant is used.

Applications of kinetic methods in non-aqueous catalytic thermometric titrimetry. Part I. Evaluation of acetylation, α-methylstyrene and acrylonitrile indicator systems

Kinetic methods, based on the measurement of the rates of reaction of reagent systems originally developed as thermometric indicators, may be used as a method to determine perchloric acid, potassium hydroxide and quinoline in microgram amounts. The reaction rate is measured by the initial slope of the temperature-time graph recorded when the sample compound is added to the reagent mixture. Perchloric acid is determined using both acetylation and α-methylstyrene indicator systems, and potassium hydroxide is determined with the acrylonitrile reagent. Quinoline is determined on mixtures of quinoline and an excess of perchloric acid using the acetylation indicator reaction. The rate of the acrylonitrile reaction is influenced significantly by the presence of dimethyl sulphoxide, which is used to increase the sensitivity of the method. In the α-methylstyrene reaction, the induction time before the reaction commences is also used to measure the catalyst concentration.

Coupling of thermometric titrimetry and constant-current coulometry: Study and applications

Two systems involving the coupling of thermometric and coulometry are presented. In the first assembly, the two electrodes were in the same compartment. Bromocoulometry was used to test the possibilities of this coupling in the sequential titration of a vitamin C+ aspirin mixture about (10−4M) and the determination of enthalpy changes. In a second coupling system, the anodic and cathodic compartments were separated by a sintered-glass disc of porosity 3. The conditions for obtaining an electrochemical cell which is also a good calorimeter are discussed. Examples of applications are given, such as analytical measurements, the study of an electrochemically catalysed reaction and of the thermal effects of electrode reactions.

Ionic polymerisation as a means of end-point indication in non-aqueous thermometric titrimetry. Part XII. Acetals and cyclic ethers as end-point indicators in the titration of organic bases

Dimethoxymethane, 1,3,5-trioxane, 1,3-dioxolane and alicyclic ethers with three-to seven-membered rings were evaluated as thermometric end-point indicators in the non-aqueous titration of weak organic bases including some basic drugs, in the free form and as hydrochlorides, phosphate and tartrate, with perchloric acid in acetic acid.

Determination simultanee de l'enthalpie, de l'enthalpie libre via le coefficient de partage et de l'entropie de transfert eau/ n-octanol de l'ephedrine par titrimetrie thermometrique

Thermometric titrimetry allows the simultaneous determination of the three thermodynamic parameters of transfer (Δ G 0 T, Δ H 0 T and Δ S 0 T) of ephedrine from water to n-octanol. Principle, methods, results and discussion are given.

Investigation of the use of thermometric titrimetry for the determination of acidic substances in wine

The use of thermometric titrimetry in the determination of acidic substances in red wine is described. The titration curve obtained in the thermometric titration of red wine with strong base presents two inflections. The stoichiometry corresponding to the first inflection presents good agreement with the so-called “total acidity” of wine, and is proposed for its determination. The second inflection is related to the content of phenolic substances in red wine.