Characteristics and Kinetics Study of Glycerolabietate from Glycerol and Abietic Acid from Rosin

Rosin is a natural resin from the coniferous tree sap, which separated from its oil content (terpenes). Rosin is brittle. Therefore modifications are needed to improve its mechanical properties. The main content of rosin is abietic acid which has a carboxylic group, so it can form an ester group when reacted with polyhydric alcohol (polyalcohol) such as glycerol. The research aimed to study the kinetics of the esterification reaction between the hydroxyl group in glycerol and the carboxylic group in abietic acid from rosin at various reaction temperatures and reactant compositions. This reaction is carried out in a three-neck flask at atmospheric pressure without a catalyst. The reaction temperatures used were 180˚C, 200˚C, and 220˚C, and the ratio of rosin and glycerol was 1:1, 1:3, and 1:5. The reaction kinetics calculations were analyzed with acid number data over the reaction time using three different models. The calculations showed that this reaction involves positioning a hydroxyl group on glycerol, which the primary and secondary hydroxyl groups contribute to forming a rosin ester (glycerolabietate). The rate of reaction constants of primary hydroxyl of glycerol and abietic acid were in the range 6.25x10-4 - 3.90x10-3 g/(mgeq.min), while reaction rate constants of secondary hydroxyl and abietic acid were in the range 1.06x10-5 - 1.15x10-4 g/(mgeq.min). FTIR analysis showed a change in the hydroxyl, carboxylate, and ester groups which were assigned by a shift of wavenumber and a difference of intensity at 3200-3570 cm-1, 1697.36 cm-1, and 1273.02 cm-1.

Structural Elucidation And Electrochemiluminescence On A 3D Cadmium (II) MOF With 5-C Topology

A novel cadmium (II) based MOF, [Cd(μ–ppza)]n (1) (H2ppza = 3–(pyridin–4–yl)–1H–pyrazole–5–carboxylic acid) was synthesized under solvothermal condition. The single-crystal X-ray diffraction reveals that the title MOF 1 exhibits a 3D structure bridged through the carboxylic group, which has a 5-c {46.64} topological structure. Furthermore, MOF 1 exhibits good electrochemiluminescence (ECL) behavior.

Spectrophotometric methods for the determination of lisinopril in medicines

Two simple, rapid and green spectrophotometric methods are described for the determination of lisinopril medicines. The determination is based on the reaction of the primary amino group of the lisinopril with ninhydrin in aqueous medium (Method I) and reaction on the carboxylic group of the lisinopril with copper (II) sulfate (Method II). For both methods, optimal spectrophotometric conditions were established. The linear relationship was found between absorbance at λmax and concentration of drug in the range 40–60 µg/mL (Method I) and 0.592–2.072 mg/mL (Method II). Regression analysis of Beer’s law plot at 400 nm yielded the regression equation, y = 7.4929x – 0.0545 (Method I) and at 730 nm y = 0.0443x – 0.0832 (Method II). High values of correlations coefficient (R2 = 0.9917 (Method I) and R2 = 0.999 (Method II)) and small values of intercept validated the linearity of calibration curve and obedience to Beer’s law. The LOD and LOQ values were calculated to be 6.91 µg/mL and 23.01 µg/mL respectively (Method I) and 0.11 mg/mL and 0.36 mg/mL respectively (Method II). Intra-day and inter-day accuracy and precision were in acceptable limits. The proposed methods were applied for the quantification of lisinopril in tablets pertaining to three commercial formulations. Analytical eco-scale for greenness assessment of the proposed spectrophotometric methods showed that both methods correspond to excellent green analysis.

Crystal structures of two alanylpiperidine analogues

The structure of ethyl 1-[N-(4-methylphenyl)-N-(methylsulfonyl)alanyl]piperidine-4-carboxylate, C19H28N2O5S, I, a compound of interest as activator of Ubiquitin C-terminal Hydrolase-L1 (UCH-L1), was determined by single-crystal X-ray diffraction (SCXRD) analysis. In order to find new activators, a derivative of compound I, namely, 1-[N-(4-methylphenyl)-N-(methylsulfonyl)alanyl]piperidine-4-carboxylic acid, C17H24N2O5S, II, was studied. The synthesis and crystal structure are also reported. Despite being analogues, different crystal packings are observed. Compound II bears a carboxylic group, which favors a strong hydrogen bond. A polymorph risk assessment was carried out to study interactions in compound II.

PROTOLYTIC EQUILIBRIUM OF TETRA- AND PENTANITROFLUORESCEINS IN A BINARY SOLVENT ACETONITRILE – DIMETHYL SULFOXIDE (MASS RATIO 96 : 4)

In this paper, the acid-base and tautomeric equilibria of four nitrofluorescein dyes, 2,4,5,7-tetranitrofluorescein, 2,4,5,7,4’-pentanitrofluorescein, 2,4,5,7,5’-pentanitrofluorescein, and 2,4,5,7-tetranitrofluorescein methyl ester, were studied. As reaction media, a binary solvent acetonitrile – dimethyl sulfoxide (96 : 4 by mass) was used. The acidity scale in this solvent was established previously. The indices of the dissociation constants of the dyes were determined using the spectrophotometric method. Interpreting the values ​​requires an understanding of the state of tautomeric equilibria. The behavior of these compounds differs significantly from that of other fluorescein dyes, e.g., halogen derivatives. In the case of the first three compounds, i.e., for dyes with a free carboxylic group, the lactonic structure is predominant not only for the neutral form, but even for the double-charged anion. The single-charged anionic form exists as an equilibrium mixture of a colored (and fluorescent) tautomer and an almost colorless lactone. The fourth compound with esterified carboxylic group exhibits extreme stability in its anionic form. Evaluation of the tautomerization constants made it possible to calculate the microscopic equilibrium constants of the stepwise dissociation of dye lactones, k1L and k2L. The consideration of the difference (pk2L – pk1L) allowed estimating the effective relative permittivity of the space between the ionizing groups basing on the Bjerrum – Kirkwood – Westheimer equation. Tautomerism of anions was discussed from the point of view of stabilization of symmetric structures.

Synthesis and Hypoglycemic Activity of the Derivatives of 4-(1,3-Thiazolidine-5-Ylidene)Pyrazole-3-Carbonic Acid and its Esters

A preparatively convenient method for synthesizing a series of new (pyrazole-4-yl)methylenethiazolidine structures fictionalized by the carboxylate or carboxylic group in the 3rd position of the pyrazole cycle and by the oxo- thio- or imine groups in the 3rd and 5th positions of the thiazolidine ring is discussed. The method is based on the condensation of 4-formylpyrazole-3-carbonic acids and their ethyl esters with a series of substituted thiazolidines: 1,3-thiazolidine-2,4-dione, 4-thioxo-1,3-thiazolidine-2-one, 2-thioxo-1,3-thiazolidine-4-one, and 2-imino-1,3-thiazolidine-4-one. As seen from the biochemical investigations results, a clear hypoglycemic activity has been registered for the compounds mentioned in this work. Five of ten products have ensured a prolonged effect embracing the entire duration of the experiment. 1-Methyl-4[(4-oxo-2-thioxo-1,3-thiazolidine-5-iliden)methyl]-1H-pyrazole-3-carbonic acid caused the deepest decrease in the glucose content (by 2.0 mmole/L or 30.4 %), while in the case of the reference medicine pioglitazone, it was only by 1.35 mmole/L (23.9 %). Some dependence between the compound structure and its pharmaceutical activity was also found. The most prolonged and steady hypoglycemic activity was registered for (pyrazole-4-il)methylethiazolidines with methyl group as a substitute in the 1st position and carboxylic group – in the 3rd position. The additional introduction of the methyl and carboxylate groups into the pyrazole scaffold results in a prolonged and more in-depth hypoglycemic effect leading to the 1.4 times lesser drop in glucose concentration as compared to that after administration of the reference medicine.

Separation of alkaloid and its analogs in HPLC using rosin-based polymer microspheres as stationary phases

Rosin-based polymer microspheres (RPMs) as stationary phases in HPLC were prepared using methyl acrylic acid as the functional monomer, ethylene glycol maleic rosinate acrylate as the cross-linker, and carboxylic group...