A study is performed of tetra-4-carboxyphthalocyanine hydroxyaluminum. The thermal effects of the dissolution of crystalline phthalocyanine in aqueous solutions with different concentrations of KOH are determined via direct calorimetry at a temperature of 298.15 K. The thermal effects of stepwise dissociation AlOHРс(4-COOH)4 are calculated using the HEAT computer program. The enthalpies of combustion of the studied compound are determined with an IKA C6000 isoperibol calorimeter (bomb calorimetry) and used to calculate the standard enthalpies of formation of AlOHРс(4-COOH)4 along with products of its dissociation in aqueous solutions.

Cobalt–tetra-4-carboxyphthalocyanine complexes are synthesized. Direct calorimetry is used to determine heat effects of the dissolution of crystalline cobalt tetra-4-carboxymetallophthalocyanine in KOH aqueous solutions of various concentrations (0.002–0.02 mol/L) at 298.15 K. The standard enthalpies of formation of the compound are calculated using additive groups, based on group systematics with a Benson-type classification of fragments that considers the effect of the primary environment of atoms. Standard enthalpies of formation are calculated for products of the dissociation of tetra-4-carboxyphthalocyanine–cobalt complexes in an aqueous solution.

A complex of tetra-3-carboxyphthalocyanine with copper that is insoluble in water is obtained. Thermal effects from dissolving crystalline tetra-3-carboxymetalphthalocyanine in aqueous solutions of various KOH concentrations (from 0.002 to 0.02 mol/L) at 298.15 K are determined via direct calorimetry. Measurements are made in a calorimeter using an isothermal shell with automatic recording of the temperature and electrical calibration at T = (293.15–308.15) ± 0.01 K and P = 100.5 ± 0.7 kPa. Standard enthalpies of formation of the products of dissociation of the tetra-3-carboxyphthalocyanine complex with copper in aqueous solution are calculated. Thermal effects of stepwise dissociation are calculated using the HEAT computer program.

Potentiometry and calorimetry are used to study Ce3+–glycine–ethylenediaminedisuccinic acid and La3+–glycine–ethylenediaminedisuccinic acid systems in aqueous solutions at T = 298.15 K (KNO3). The formation of a mixed-ligand complex is revealed, and the thermodynamic characteristics (ΔrH, ΔrG, ΔrS) of the complexation reaction are determined.

5,10,15,20-tetrakis(1'-carboxymethylpyrid-4-yl)porphyrin tetrachloride (1) and 5,10,15,20-tetrakis(1'-carboxymethylpyrid-4-yl)porphyrin tetrabromide (2) were synthesized. Water-soluble tetrapyridylporphine derivatives are salts of halides with multicharged cations with a complex aromatic structure. Thermal effects of dissolution of crystalline tetrapyridylporphins (1) and (2) in water and in aqueous solutions of KOH at 298.15 K were determined by direct calorimetric method. The integral enthalpies of dissolution were measured on a variable temperature calorimeter with an isothermal shell that we designed. The reaction part of the calorimeter and all internal parts in contact with the solution are made of titanium alloy VT-1. The volume of the calorimetric cell was similar to 60 cm(3). The stability of the thermostating system during calorimetric measurements was maintained with an accuracy of 10(-3) K. The standard enthalpies of formation of compounds were calculated using the additive group method. This method takes into account the influence of the primary environment for atoms. The values of the standard enthalpy of tetrapyridylporphine formation and its dissociation products in an aqueous solution were obtained for the first time. They are key quantities in the thermochemistry of this compound, open up the possibility of conducting rigorous thermodynamic calculations in systems with tetrapyridylporphine. The differences in thermochemistry of porphyrins (1) and (2) related to different counter -ion (chloride or bromide) opens a possibility to use solution calorimetry for distinguishing between these ions, which can be useful in some industrial applications.

Recently, more and more drugs that are derivatives of oligopeptides have been introduced to the pharmaceutical market. The structural elements of these compounds are amino acids and dipeptides. When stabilizing functional groups are introduced into the peptide structure, as well as through the use of special delivery systems, oligopeptide derivatives can be used as innovative med-icines. The calorimetric method was used to determine the heat of interaction of glycyl-D-phenyl-alanine with solutions of nitric acid and potassium hydroxide at 298.15K and the values of the ionic strength of the solution 0.5, 0.75 and 1.0 in the presence of KNO3. Measurements were carried out on a calorimeter with an isothermal shell and automatic recording of the temperature-time curve. The unit was equipped with a reaction vessel with a volume of 60 cm(3). Calibration was performed by current at T = (293.15-308.15) +/- 0.01 K and P = 100.5 +/- 0.7 kPa. A thermistor KMT-14 was used as a temperature sensor. The temperature of the calorimetric cell was controlled in a thermostat equipped with a PID controller with an accuracy of 0.002 K. The temperature sensor of the ther-mostat was a platinum resistance thermometer. The calorimeter was calibrated by current. The volume of the calorimetric liquid is 42.83 ml. The enthalpy of stepwise dissociation of glycyl-D-phenylalanine at zero ionic strength was found by an equation with one individual parameter. Standard thermodynamic characteristics (Delta rH degrees, Delta rG degrees, Delta rS degrees) of acid-base interaction reactions in aqueous solutions of glycyl-D-phenylalanine are calculated. The effect of the background electro-lyte concentration on the dissociation heats of glycyl-D-phenylalanine is considered. Knowledge of the thermochemical characteristics of dipeptides is necessary for understanding and subsequent modeling of the process of protein biosynthesis occurring in biological systems. Data on the ther-modynamic characteristics of dipeptide solutions are needed in various fields where these com-pounds are used: pharmacology, medicine, food and cosmetic industries, for the development, jus-tification and optimization of technological processes involving these compounds and their com-plexes with metals.

The enthalpies of dissolution of crystalline glycyl-L-tyrosine in water and in aqueous potassium hydroxide at 298.15 К were determined by the direct calorimetric method. The measurements were performed on a calorimetric unit with automatic recording of the temperature–time curve. The standard enthalpies of combustion and formation of glycyl-L-tyrosine were calculated by the additive group method based on group systematics with classification of fragments of the type of Benson classification, with the effect of the initial environment for atoms included in calculation. The standard enthalpies of formation of dipeptide and the products of its dissociation in aqueous solution were calculated.

The heats of interaction between alanyl-phenylalanine and solutions of nitric acid and potassium hydroxide at 288.15 and 308.15 K and solution ionic strengths of 0.5, 0.75, and 1.0 are determined via calorimetry with KNO3. Standard thermodynamic characteristics (ΔrH°, ΔrG°, ΔrS°, Δ C_p^^∘ ) of the reactions of acid–base interaction in aqueous solutions of alanyl-phenylalanine. The effect temperature has on the heats of dissociation of alanyl-phenylalanine is considered along with the relationship between the thermodynamic characteristics of the dissociation of the dipeptide and the structure of this compound.

The thermal effects of acidic and basic dissociation of glycyl-D-phenylalanine dipeptide at a temperature of 298.15 K and ionic strengths of solution of 0.5, 0.75, and 1.0 M against the background of different supporting electrolytes were calculated from the results of direct calorimetric measurements performed on a calorimeter with an isothermal shell and automatic recording of the temperature–time curve. The influence of the nature of supporting electrolytes NaCl, NaClO 4 , NaNO 3 , KNO 3 , and LiNO 3 on the thermal effects of stepwise dissociation of the dipeptide is considered. The standard thermal effects of ionization of glycyl‑D‑phenylalanine in two steps were found by extrapolation to zero ionic strength. The standard changes in thermodynamic functions (enthalpy, entropy, and Gibbs energy) in the acidic and basic dissociation of g-lycyl-D-phenylalanine dipeptide were calculated.

The authors obtain complexes CuPc(4-S-C 6 H 4 -COOH) 4 and CuPc(4-O-C 6 H 4 -COOH) 4 that are insoluble in water. The standard enthalpies of formation of these compounds are calculated using additive groups based on group systematics with Benson-type classification of fragments, allowing for the influence of the atoms’ primary environment. Thermal effects of the dissolution of crystalline phthalocyanines in aqueous solutions of various KOH concentrations at a temperature of 298.15 K were determined via direct calorimetry. Thermal effects of the stepwise dissociation of CuPc(4-S-C 6 H 4 -COOH) 4 , CuPc(4-O-C 6 H 4 -COOH) 4 are calculated using the HEAT computer program. Standard enthalpies of formation are calculated for products of the dissociation of CuPc(4-S-C 6 H 4 -COOH) 4 and CuPc(4-O-C 6 H 4 -COOH) 4 in an aqueous solution.

Определены энтальпии растворения кристаллического глицил-L-тирозина в воде и в водных растворах гидроксида калия при 298.15 К прямым калориметрическим методом. Измерения проводили на калориметрической установке с автоматической записью кривой температура–время. Величины стандартных энтальпий сгорания и образования глицил-L-тирозина были рассчитаны по аддитивно групповому методу, основанному на групповой систематике с классификацией фрагментов типа классификации Бенсона, которая учитывает влияние первоначального окружения для атомов. Рассчитаны стандартные энтальпии образования дипептида и продуктов его диссоциации в водном растворе.

Complexes are obtained of tetra-4-carboxyphthalocyanines with copper and zinc that are insoluble in water. Standard enthalpies of formation of the compounds are calculated according to additive groups based on group systematics with a Benson-type classification of fragments that considers the influence of the primary environment of atoms. Thermal effects of the dissolution of crystalline tetra-4-carboxymetallo-phthalocyanines in aqueous solutions at different concentrations of KOH (0.002 to 0.02 mol/L) at 298.15 K are determined via direct calorimetry. The standard enthalpies of formation are calculated for products of the dissociation of complexes of tetra-4-carboxyphthalocyanines with copper and zinc in aqueous solutions.

Potentiometry and calorimetry are used to study the Ce 3+ –pyridoxine system in aqueous solution at T = 298.15 K (KNO 3 ). The enthalpies of formation are determined calorimetrically for a complex of pyridoxine and cerium(III) ions at a temperature of 298.15 K and an ionic strength of 0.2 (supporting electrolyte, KNO 3 ). Thermodynamic characteristics ∆ r H , ∆ r G , and ∆ r S of reactions of the formation of pyridoxine complexes with Ce 3+ ions of compositions CеL 2+ , CеОHL + , CeHL 3+ , and Cе(ОH) 2 L are calculated at different [metal] : [ligand] molar ratios.

Calorimetry is used to determine the heats of interaction between D,L-alanil–D,L-phenylalanine and solutions of nitric acid and potassium hydroxide at 298.15 K and ionic strengths of 0.5, 0.75, and 1.0 in solutions with KNO 3 . Standard thermodynamic characteristics (Δ r H °, Δ r G °, Δ r S °) are calculated for acid–base interaction in aqueous solutions of D,L-alanil–D,L-phenylalanine. The effect the concentration of background electrolyte has on the heats of dissociation of D,L-alanil–D,L-phenylalanine is considered. A comparative analysis is performed of the standard thermodynamic characteristics of the stepwise dissociation of L-phenylalanine and D,L-alanil–D,L-phenylalanine in light of modern ideas about the structure and physicochemical properties of these compounds and solutions of them.

Enthalpies of triglycine complexation are determined calorimetrically (HL ± ) with ions of neodymium(III), europium(III), gadolinium(III), and ytterbium(III) at a temperature of 298.15 K and an ionic strength of 0.1, using KNO 3 as the background electrolyte. The thermodynamic characteristics of the formation of complexes of the tripeptide and ions are calculated. Nd 3+ , Eu 3+ , Gd 3+ , and Yb 3+ composition LnL 2+ at different [metal] : [ligand] molar ratios in the 1.8–7.6 range of pH. Analysis of the resulting enthalpies of complexation confirms the preferred coordination of the central lanthanide ion through the carboxylic oxygen atom of triglycine, known from the literature.

Lornoxicam was chosen as the object of our research. It is a derivative of thienothiazine monocarboxylic acid amide. It plays the role of a nonsteroidal anti-inflammatory drug, a non-nar-cotic analgesic and an antipyretic. Lornoxicam is practically insoluble in water. The heat of disso-lution of crystalline lornoxicam in solutions of potassium hydroxide at 298.15 K was measured by direct calorimetric method. Measurements were carried out on a calorimeter with an isothermal shell and automatic recording of the temperature-time curve, in a reaction vessel with a volume of 60 cm3 and at T = 298.15 +/- 0.01 K and P = 100.5 +/- 0.7 kPa. The relative measurement error for the heat of dissolution of the standard substance was 0.1-0.3%. The operation of the calorimetric unit was tested according to the generally accepted calorimetric standard - the heat of dissolution of crystalline potassium chloride in water. The calculation of the equilibrium composition of the sys-tem, taking into account the processes of stepwise dissociation of lornoxicam and dissociation of water, was carried out according to the KEV program. The value of the standard enthalpy of lor-noxicam formation was calculated using an additive group method based on group systematics with a classification of fragments of the Benson classification type, which takes into account the influ-ence of the initial environment for atoms. The standard enthalpy of lornoxicam anion formation in an aqueous solution was determined using data on the heat of dissolution of lornoxicam in alkali solutions with a ratio of equivalents of at least 1:2. The standard enthalpy of lornoxicam formation and its dissociation products in an aqueous solution are calculated. The values of the standard enthalpy of lornoxicam formation and its dissociation products in an aqueous solution were ob-tained for the first time. They are key quantities in the thermochemistry of this compound, open up the possibility of conducting rigorous thermodynamic calculations in systems with lornoxicam.

Pyridoxine, as well as its derivatives, are the main forms of vitamin B6, which plays extremely important biological roles in living organisms. In our work, the enthalpies of dissolution of crystalline pyridoxine and pyridoxal-5'-phosphate in water and in aqueous solutions of KOH at 298.15 K were measured by a direct calorimetric method in a wide concentration range. The measurements were carried out on a calorimeter with an isothermal shell and automatic recording of the temperature-time curve. The values of the standard enthalpies of combustion and formation of pyridoxine and pyridoxal-5'-phosphate were calculated using the additive group method based on the group systematics with the classification of fragments like the Benson classification, which takes into account the effect of the primary environment for atoms. The standard enthalpies of formation of pyridoxine and pyridoxal-5'-phosphate and the products of their dissociation in an aqueous solution were calculated. (C) 2021 Elsevier B.V. All rights reserved.

Values of the standard enthalpies of formation D,L-alanyl-D,L-serine are calculated using additive groups approach based on group systematics with such classifications of fragments as the Benson classification, which considers the effect of the primary environment of atoms. The heat effects of the dissolution of crystalline D,L-alanyl-D,L-serine in water and in solutions of potassium hydroxide at 298.15 K are determined via direct calorimetry in a wide range of concentrations. The standard enthalpies of formation of the peptide and products of its dissociation in an aqueous solution are calculated.