Melting Point Data Research Articles

Measurement of ascorbic acid samples’ optical rotation via an improvised polarimeter for purity assessment

Abstract The polarization of light finds practical application in physics and chemistry through the optical activity phenomenon, where polarimeters play a crucial role. This research builds on the improvised polarimeter designed by Kvittingen and Sjursnes [1], implemented with relevant modifications, to measure optical rotations of over-the-counter ascorbic acid samples. The study aims to assess the purity of two brands of ascorbic acid through polarimetry, comparing the calculated specific rotation with the literature values and supplementing the characterization with melting point determination. The constructed polarimeter, assembled using Lego bricks, provides an affordable alternative for educational purposes, addressing the challenges observed in the accessibility of commercial polarimeters for classroom demonstrations. The methodology encompasses pre-experiment steps involving polarimeter construction, the experiment utilizing polarimetry and complementary melting point determination, and post-experiment analysis to determine specific rotation from the measured optical rotations. Results indicate that Brand X exhibited specific rotations close to theoretical values, inferring high purity. Conversely, Brand Y shows significant deviations, suggesting potential impurities. These conclusions are supported by melting point data. The comprehensive approach combining polarimetry and melting point determination enhances the reliability of purity assessments, showcasing the effectiveness of the improvised polarimeter in practical applications.

Integrating Data Mining and Natural Language Processing to Construct a Melting Point Database for Organometallic Compounds.

As semiconductor devices are miniaturized, the importance of atomic layer deposition (ALD) technology is growing. When designing ALD precursors, it is important to consider the melting point, because the precursors should have melting points lower than the process temperature. However, obtaining melting point data is challenging due to experimental sensitivity and high computational costs. As a result, a comprehensive and well-organized database for the melting point of the OMCs has not been fully reported yet. Therefore, in this study, we constructed a database of melting points for 1,845 OMCs, including 58 metal and 6 metalloid elements. The database contains CAS numbers, molecular formulas, and structural information and was constructed through automatic extraction and systematic curation. The melting point information was extracted using two methods: 1) 1,434 materials from 11 chemical vendor databases and 2) 411 materials identified through natural language processing (NLP) techniques with an accuracy of 86.3%, based on 2,096 scientific papers published over the past 29 years. In our database, the OMCs contain up to around 250 atoms and have melting points that range from -170 to 1610 °C. The main source is the Chemsrc database, accounting for 607 materials (32.9%), and Fe is the most common central metal or metalloid element (15.0%), followed by Si (11.6%) and B (6.7%). To validate the utilization of the constructed database, a multimodal neural network model was developed integrating graph-based and feature-based information as descriptors to predict the melting points of the OMCs but moderate performance. We believe the current approach reduces the time and cost associated with hand-operated data collection and processing, contributing to effective screening of potentially promising ALD precursors and providing crucial information for the advancement of the semiconductor industry.

Exploring the Potential of Novel 4-Thiazolidinone Derivatives as Dual Anti-inflammatory and Antioxidant Agents: Synthesis, Pharmacological Activity and Docking Analysis

A series of 4-thiazolidinone was synthesized and characterized by means of TLC, melting point, and spectral data like IR, 1H NMR, and Mass spectra. The anti-inflammatory activity of the synthesized compounds was determined via in vivo studies. The antioxidant properties of the synthesized compounds were determined by carrageenan-induced rat paw edema model. The synthesized compounds (A1-A14) showed significant anti-inflammatory and antioxidant activities. The most promising results for both antioxidant and antiinflammatory activity were exhibited by compound A8 which may emerge as a potent anti-inflammatory agent with potential free radical scavenging activity. Molecular docking studies were carried out to determine the interaction of compounds into the active site of COX-2 inhibitor (PDB ID: 3LN1), which suggested compound A8 to have the best docking score by showing interactions with ASP483 and LYS478.

Synthesis, characterization, volatility, and thermal stability of fluorinated copper(II) aminoalkoxide complexes as potential vapour deposition precursors

The sodium aminoalkoxides Na[OCR(CF3)CH2NMeR′] {R = H, R′ = Me (1a); R = R′ = Me (1b); R = CF3, R′ = Me (1c); R = Me, R′ = Et (1d); R = CF3, R′ = Et (1e)} were synthesized by reaction of the corresponding fluorinated epoxide {OCH2CR(CF3); R = H (A), Me (B), CF3 (C)} with a secondary amine (HNMe2 or HNMeEt), followed by deprotonation with sodium hydride. Compounds 1a–e were isolated as white powders and characterized by combustion elemental analysis and NMR spectroscopy. Epoxides A and C are commercially available, while epoxide B was prepared by in situ deprotonation and alkylation of A. Reactions of 1a–e with copper(II) chloride in THF afforded [Cu{OCR(CF3)CH2NMeR′}2] {R = H, R′ = Me (2a); R = R′ = Me (2b); R = CF3, R′ = Me (2c); R = Me, R′ = Et (2d); R = CF3, R′ = Et (2e)}; compounds 2b and 2c have previously been reported but not structurally characterized, while 2a, 2d, and 2e are new to this report. All copper(II) compounds were characterized by combustion elemental analysis and single crystal X-ray crystallography. The physical properties of 2a–e were also evaluated using thermogravimetric analysis, melting point, and sublimation (at 5 mTorr) data, with comparison to previously reported non-fluorinated [Cu{OCHMeCH2NMe2}2] (III; [Cu(dmap)2]).

Chiral resolution of RS-ofloxacin through a novel diastereomeric cocrystal formation with L-glutamic acid by evaporative crystallization and quantification with capillary electrophoresis

Chiral drugs often exhibit significant differences in pharmacological activity between their enantiomers, highlighting the importance of effective chiral separation to enhance therapeutic efficacy and safety. Despite advances in this field, efficient methods for enantiomer separation remain a critical demand, especially for drugs like RS-Ofloxacin (RS-OFX), a chiral fluoroquinolone antibiotic. For RS-OFX, the S-enantiomer exhibits significantly higher potency—approximately 8–128 times greater—than the racemic mixture. This highlights the need to accurately separate the enantiomers. This study presents a new cocrystallization-based method for the precise and economical chiral separation of RS-OFX using amino acids by utilizing the formation of diastereomeric cocrystals. L-Glutamic acid (L-Glu) was identified as an appropriate coformer during the screening of potential coformers; consequently, diastereomeric cocrystals of R-OFX:L-Glu and S-OFX:L-Glu were successfully obtained. Melting point data, Fourier-Transform Infrared Spectroscopy (FTIR), and Powder X-Ray Diffraction (PXRD) analyses all confirmed the existence of a new solid state, revealing significant modifications in the crystal structure indicative of cocrystal formation. Capillary electrophoresis (CE) was employed to quickly identify the most suitable solvent mixture for the separation of the diastereomeric pair. The diastereomeric cocrystals exhibited distinct solubility profiles in various solvent mixtures, allowing effective chiral separation through evaporative crystallization in methanol:chloroform (50:50, v/v) mixture, yielding 61.82% enantiomeric excess (ee) of the more active S-OFX:L-Glu. The results of this study suggest that the chiral resolution of racemic APIs through diastereomeric cocrystal formation with amino acids has the potential for scalability and adaptability in other APIs. This approach has the potential to be a valuable tool for the pharmaceutical industry in improving the efficiency of producing enantiopure pharmaceuticals.

CALPHAD-guided design and experimental study on a novel Al-Ti-Nb alloy

We have used a CALPHAD-guided design methodology to develop a novel lightweight Al-Ti-Nb alloy with nearly 50 vol% of in-situ formed trialuminide reinforcement. After compositional optimization, we selected Al87.5Ti6.25Nb6.25 (at%) as the experimental alloy composition and subjected it to a 24-hour homogenization heat-treatment at 475°C for attainment of equilibrium, guided by DSC and CALPHAD-derived melting point data. Phase and microstructure analysis revealed a microstructure with approximately 50 vol% of a FCC Al-rich matrix and 50 vol% of trialuminide phases for strengthening. The experimental onset melting point of the Al-rich matrix was determined to be 647°C, which significantly surpasses Al-Si based high-temperature alloys (577 ℃), showcasing the potential of this alloy as a high-temperature structural material. Nanoindentation tests demonstrated exceptional mechanical properties. The alloy was found to have a microhardness of 3350 MPa, which not only outperformed 7075 Al alloy, A390 Al-Si alloy, and commercially pure Ti but also exceeds the levels of Ti-6Al-4V alloy at nearly 28% lower density. This study's significance lies in its integration of CALPHAD predictions and meticulous microstructural investigation, offering an effective approach for the design and characterization of novel Al-based alloys.

Synthesis, Characterization and Antioxidant Evaluation of Tranexamic Acid-derived Benzimidazole, Azomethines, and Oxazolidine

This work includes the synthesis of heterocyclic compounds and azomethines starting from tranexamic acid. The benzimidazole C2 was prepared by mixing equal molar amounts of tranexamic acid with 4-methyl-o-phenylenediamine). Compounds C13-C18 were prepared by the reaction of tranexamic acid with the aromatic aldehydes. The oxazolidine (C19) was synthesized from the reaction of the compound C13 with hydroxyacetic acid. The synthesized compounds were identified by physical properties such as melting point, color change, and spectral data (Fourier transform infrared and mass). The effectiveness of the compounds C2, C13, C15, C17, and C19 was estimated as antioxidants outside the body (in vitro) and by three methods, namely, reducing power assay, scavenging of hydrogen peroxide, and phosphomolybdenum method.. KEYWORDS :Antioxidant, Azomethine, Benzimidazole, Oxazolidine, Tranexamic acid.

Research on even-odd effects of bio-based Nylon nF salts

Nylon nF is a type of bio-based Nylon, whose raw materials NH2-(CH2)n-NH2 and 2,5-furandicarboxylic acid (FDCA) are both prepared by biological methods. The Nylon nF salts (PAnF salts) are the monomer salts before the polymerization of Nylon nF, whose product quality has a significant impact on the properties of Nylon nF. In this study, Nylon nF salts of FDCA and seven NH2-(CH2)n-NH2 diamines were synthesized. The crystal structures and thermodynamic behaviors of these Nylon salts were determined and analyzed by single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), and thermogravimetric analysis-differential scanning calorimetry (TG-DSC). Based on the analysis of melting point and solubility data, it was found that there is a significant even–odd effect between Nylon nF salts (n = 4–10). Moreover, the lattice energy and solvation energy in methanol of these Nylon salts were calculated by Materials Studio (MS) and Gaussian, respectively. The results indicated that there was also an even–odd effect in the lattice energy of Nylon nF salts. It is speculated that these even–odd phenomena were related to the symmetry of the ligand diamines and the stacking mode of Nylon salts. The study of the even–odd effect is significant in predicting and designing the physicochemical properties of cocrystals.

Extended atom-based and bond-based group contribution descriptor and its application to melting point prediction of energetic compounds

17817 compounds were collected from the Bradley open melting point data set, including eight elements: C, H, O, N, F, S, Cl, Br, and I. An extended atom-based and bond-based group contribution descriptor was suggested to represent these compounds, which consists of a one-dimensional descriptor based on the molecular formula, a two-dimensional group contribution descriptor based on atoms and bonds, and a structural feature descriptor. Random forest (RF), Partial Least Squares (PLS), and Deep Learning (DL) methods were used to establish models to predict melting points, and the constructed models were evaluated by correlation coefficient (R), mean absolute error (MAE) and root-mean-square error (RMSE). Among them, the best results were obtained using the model constructed by Random forest: the results of out-of-bag (OOB) cross-validation of the training set are R = 0.8977/MAE = 29.57 °C/RMSE = 40.34 °C; the predicted results of the test set are R = 0.8982/MAE = 29.68 °C/RMSE = 40.63 °C. Compared with the results obtained using the subset of this data set in a literature, the results in this study are better than the corresponding results in the literature. The established model was also used to predict an external data set consisting of 74 compounds retrieved from another literature, and the obtained results are R = 0.8946 °C/MAE = 24.51 °C/RMSE = 34.19 °C, which were significantly better than the corresponding results in the literature. If the descriptor suggested in this study is combined with RDKit descriptor that contains charge and electronegativity information and so on, better results were achieved: the results of OOB cross-validation of the training set are R = 0.9013/MAE = 29.25 °C/RMSE = 39.76 °C; the results of the test set are R = 0.9017/MAE = 29.34 °C/RMSE = 40.07 °C.

Principled Decision-Making Workflow with Hierarchical Bayesian Models of High-Throughput Dose-Response Measurements.

We present a case study applying hierarchical Bayesian estimation on high-throughput protein melting-point data measured across the tree of life. We show that the model is able to impute reasonable melting temperatures even in the face of unreasonably noisy data. Additionally, we demonstrate how to use the variance in melting-temperature posterior-distribution estimates to enable principled decision-making in common high-throughput measurement tasks, and contrast the decision-making workflow against simple maximum-likelihood curve-fitting. We conclude with a discussion of the relative merits of each workflow.

Pre-assembly required: Nickel(II) complexes containing a Schiff-base ligand derived from tris(2-aminoethyl)amine and acetylacetone, salicylaldehyde, or ortho-vanillin

We have prepared and characterized seven new nickel(II) complexes that each incorporate tris(2-aminoethyl)amine (tren) and a deprotonated carbonyl-containing compound, both as two separate ligands and when condensed into a 1:1 Schiff-base ligand. We found the application of an existing literature procedure to be unsuccessful in procuring the Schiff-base variants without first assembling the ligand. IR, UV–VIS, magnetic susceptibility, elemental, and melting point data were obtained for the complexes prepared. Three of these compounds were also characterized through X-ray diffraction, and the resulting crystal structures are presented here for [Ni(acac)(tren)]BPh4 (1), [Ni(trensal)(OH2)]ClO4 (5), and [Ni(trenvan)]BPh4·H2O (7) ([acac]- = acetylacetonate ligand, [trensal]- = deprotonated 1:1 condensation product of tren and salicylaldehyde, [trenvan]- = deprotonated 1:1 condensation product of tren and ortho-vanillin). We also screened a selection of the complexes for biological activity. Two of the complexes, [Ni(trenacac)]BPh4 (4) and [Ni(trensal)]BPh4·½H2O (6) were found to fully inhibit the growth of the pathogenic yeast Candida albicans at the sub-micromolar concentration range ([trenacac]- = deprotonated 1:1 condensation product of tren and acetylacetone).

Design, Synthesis and Pharmacological Evaluation of New Thiazole Derivatives as Anthelmintic Agents

Pharmacological agents that kills parasites are essential drugs in some tropical countries. In this study, a series of 2-amino substituted 4-phenyl thiazole derivatives (4a-e) have been synthesized by the conventional method. The thiazole derivatives were synthesized by three steps. The obtained five derivatives were purified by recrystallization using methanol as a solvent or column chromatography. They were characterized by melting point, TLC, FTIR, 1H NMR and MASS spectral data. Compounds 4a-e were evaluated in silico by using different software’s (Lipinski’s Rule of 5, OSIRIS molecular property explorer, Molsoft molecular property explorer, and PASS & docking studies). These compounds were then evaluated for their possible anthelmintic activity against Indian adult earth worms (Pherituma postuma). All the compounds displayed significant anthelmintic activity. Compound 4c and 4e were more potent compounds when compared with the standard drug (mebendazole). Molecular docking studies guided and proved the biological activity against beta tubulin protein (1OJ0). In conclusions, these new molecules have promising potential as anthelmintic for treatment of parasites. 

Anti-inflammatory and ulcerogenic activity of newer phytoisolates of Swertia alata C.B. Clarke

The present study was intended to evaluate the in vitro (COX-1/COX-2) and in vivo anti-inflammatory and ulcerogenic activity of newer phytoconstituents isolated from the aerial parts of Swertia alata C.B. Clarke (Gentianaceae). For isolation of newer phytoconstituents, the ethanolic extract of aerial parts of S. alata was subjected to column chromatography using mixture of petroleum ether and chloroform in various concentrations, which yielded two phytoisolates characterised as nonacosyl triacontanoate (SA-3) and 8-O-glucpyranosyl-(2-acetyl)-1,3-dihydroxy-5-methoxy-xanthone (SA-9). Identification of compounds was based on melting point, UV, FTIR, 1H-NMR, 13C-NMR and mass spectrometric data. The isolates were screened for in vitro COX-1/COX-2 inhibitory activity, in vivo anti-inflammatory and ulcerogenic activity. Among the two compounds, SA-3 was found to be more effective than SA-9. The ulcerogenic study revealed significant gastric tolerance of SA-3 and SA-9 in comparison to indomethacin.

Design, Synthesis and Antimicrobial Evaluation of Novel 2-Thiobenzimidazole Derivatives: in silico and in vitro Approach

The development of potent antimicrobial agents is more essential due to resistance developed in microorganisms towards the existing drugs. The diversity in the biological retort profile of benzimidazole more attracted the attention to develop novel compounds to its various potential against microorganisms. In present work, designed molecular structures docked against DNA gyrase subunit B and lanosterol 14α-demethylase (LAD) proteins. Interestingly, most of the compounds revealed excellent docking scores and interactions compared with the co-crystal ligands KKK, 1YN of LAD proteins 3LD6, 5V5Z than DNA gyrase subunit B proteins 5L3J and 4P8O. Then, the molecular properties were predicted by the Swiss ADME tool, the compounds showed no violation in Lipinski’s rule and good synthetic accessibility. These compounds synthesized by stirring of 2-mercapto benzimidazole (1), epichlorohydrin (2) in the presence of sodium hydroxide gives 1-(1H-benzo[d]imidazole-2-ylthio)-3- chloropropan-2-ol (3), which upon refluxing with different substituted aliphatic and aromatic amines in methanol produces novel benzimidazole derivatives (4a-l). These compounds were characterized by their melting point, FT-IR, 1H NMR and Mass spectral data. The synthesized molecules screened for antibacterial and antifungal activity. The compound 4l exhibited excellent activity at MIC 0.4 μg/mL against C. albicans. Compounds 4c and 4e showed MIC at 3.12 μg/mL against E. coli and the compounds 4l and 4J exhibited MIC at 3.12 μg/mL against S. aureus. Docking studies and activity result reveals the novel benzimidazole compound 4l has excellent antifungal and antibacterial effect.

Synthesis and antitumor activity of podophyllotoxin derivatives

According to drug design flattening principle and using podophyllotoxin or 4'-demethylepipodophyllotoxin and aldehydes as starting material,a series of podophyllotoxin derivatives containing an imine structure with low toxicity were highly effective synthesized. Nine target compounds were successfully synthesized,and their structures were confirmed by ~1H-NMR,HR-ESI-MS and melting point data analysis. Using etoposide as positive control drug,nine target compounds were screened for cytotoxicity against He La cells in vitro by MTT method. The antitumor activity screening results showed that compound 6 b,6 d,6 e,6 f,6 g,6 i exhibited higher inhibitory rate against He La cells than those of control drug VP-16. It provides some practical reference value for the further development on the structure modification of podophyllotoxin and study on anti-tumor activity.

Synthesis of new 6-substituent 2-phenyl and 2-(furan-2-yl)-3-phenyl-quinoline-4-carboxylic acid derivatives

A synthesis of substituted quinolines has been achieved by the Doebner reaction which is a three component coupling of arylaldehyde, p-amino-acetophenone and phenyl pyruvic acid. The products of 2,3-diary-6-acetyl-quinoline-4-carboxylic acids were obtained by Claisen Schmidt condensation reaction with aldehydes in the presence of sodium hydroxide in order to give the corresponding α,β-unsaturated carbonyls. The substituted α,β-unsaturated carbonyls were condensed with urea, thiourea, hydrazine, phenyl hydrazine, semicarbazide hydrochloride and ethanolamine to synthesized 2-pyrimidinone, 2-pyrimidinethion, pyrazoline-1-phenyl, pyrazoline, pyrazoline-1-carboxamide and 1,4-oxazepines derivatives, respectively, with good yields. The purity and identities of products were elucidated through thin layer chromatography (TLC), melting point and spectroscopic data (IR, 1H NMR, 13C NMR and LC-Mass).

Molecular Similarity-Based Domain Applicability Metric Efficiently Identifies Out-of-Domain Compounds.

Domain applicability (DA) is a concept introduced to gauge the reliability of quantitative structure-activity relationship (QSAR) predictions. A leading DA metric is ensemble variance, which is defined as the variance of predictions by an ensemble of QSAR models. However, this metric fails to identify large prediction errors in melting point (MP) data, despite the availability of large training data sets. In this study, we examined the performance of this metric on MP data and found that, for most molecules, ensemble variance increased as their structural similarity to the training molecules decreased. However, the metric decreased for "out-of-domain" molecules, i.e., molecules with little to no structural similarity to the training compounds. This explains why ensemble variance fails to identify large prediction errors. In contrast, a new molecular similarity-based DA metric that considers the contributions of all training molecules in gauging the reliability of a prediction successfully identified predictions of MP data for which the errors were large. To validate our results, we used four additional data sets of diverse molecular properties. We divided each data set into a training set and a test set at a ratio of approximately 2:1, ensuring a small fraction of the test compounds are out of the training domain. We then trained random forest (RF) models on the training data and made RF predictions for the test set molecules. Results from these data sets confirm that the new DA metric significantly outperformed ensemble variance in identifying predictions for out-of-domain compounds. For within-domain compounds, the two metrics performed similarly, with ensemble variance marginally but consistently outperforming the new DA metric. The new DA metric, which does not rely on an ensemble of QSAR models, can be deployed with any machine-learning method, including deep neural networks.

The influence of solid state information and descriptor selection on statistical models of temperature dependent aqueous solubility

Predicting the equilibrium solubility of organic, crystalline materials at all relevant temperatures is crucial to the digital design of manufacturing unit operations in the chemical industries. The work reported in our current publication builds upon the limited number of recently published quantitative structure–property relationship studies which modelled the temperature dependence of aqueous solubility. One set of models was built to directly predict temperature dependent solubility, including for materials with no solubility data at any temperature. We propose that a modified cross-validation protocol is required to evaluate these models. Another set of models was built to predict the related enthalpy of solution term, which can be used to estimate solubility at one temperature based upon solubility data for the same material at another temperature. We investigated whether various kinds of solid state descriptors improved the models obtained with a variety of molecular descriptor combinations: lattice energies or 3D descriptors calculated from crystal structures or melting point data. We found that none of these greatly improved the best direct predictions of temperature dependent solubility or the related enthalpy of solution endpoint. This finding is surprising because the importance of the solid state contribution to both endpoints is clear. We suggest our findings may, in part, reflect limitations in the descriptors calculated from crystal structures and, more generally, the limited availability of polymorph specific data. We present curated temperature dependent solubility and enthalpy of solution datasets, integrated with molecular and crystal structures, for future investigations.

Moderan pristup organskoj sintezi upotrebom mikroreaktorskih sistema

Mikroreaktori poseduju brojne prednosti u odnosu na konvencionalne šaržne reaktore koji se koriste u hemijskoj industriji. Kontinualni režim rada, veliki odnos površine i zapremine, smanjena potrošnja polaznih materijala, poboljšana produktivnost, energetska efikasnost, čistija proizvodnja kao i jednostavan scale-up samo su neke od prednosti mikroreaktorskih sistema. U okviru rada ispitivana je sinteza 3-cijano-4,6-dimetil-2-piridona u mikroreaktoru, a dobijeni rezultati upoređeni su sa rezultatima iz šaržnog sistema. Proizvod sintetisan u mikroreaktorskom sistemu dobijen je u visokom prinosu i stepenu čistoće. U cilju ostvarenja što većeg prinosa, varirani su molski odnosi polaznih jedinjenja, kao i vreme zadržavanja u mikroreaktoru. Sintetisani piridon okarakterisan je temperaturama topljenja, UV-Vis, FT-IR i NMR podacima.

Aqueous Solubility of Organic Salts. Investigating Trends in a Systematic Series of 51 Crystalline Salt Forms of Methylephedrine

A data set consisting of structures and aqueous solubility and melting point data for 51 salt forms of the phenylethylamine base methylephedrine is presented. Analysis showed correlation between solubility and melting point and between melting point of the salt and melting point of the parent acid, but no correlation of salt solubility with solubility of the parent acid. Identification of associations was aided by examining chemically sensible subgroups of the data set, and this approach highlighted significantly different relationships between solubility and melting point for these subgroups. Thus, for example, the expected negative correlation between solubility and melting point was found for 24 anhydrous benzoate salts, but a positive correlation observed for eight halide salts. Hydrated forms were anomalous. Packing analysis identified groups of structures that were isostructural with respect to cation packing. Correlation between solubility and melting point was found to be greatest within these iso...