Crystalline Substances Research Articles

Catastrophe theory and thermodynamic instability to predict congruent melting temperature of crystals

Melting temperature (Tm) is a crucial physical property of solids and plays an important role in the characterization of materials. Therefore, the capacity to predict Tm is a relevant issue for solid state sciences. This investigation aims i) to provide a theoretical basis for the link between catastrophe theory and thermodynamic instability; ii) to estimate Tm through the notion of “degenerate critical temperature” (Td), related to (Pd,Vd,Td), where KT → 0 and the Gibbs function shows a non-Morse behaviour; iii) to compare predictions of (Pm,Tm) with observations for three crystalline pure substances that undergo congruent melting and exhibit different bonding and stability ranges: NaCl (halite), SiO2,st (stishovite), and MgSiO3 (perovskite). The P-T locus of KT = 0 associated with melting is identified using the maximum values of Td and ΔH/ΔV at a given pressure. We observed an average absolute discrepancy ranging between 0.2 % (halite) and 5.8 % (stishovite), and an agreement between theoretical and experimental T(P)melting-points from better than 1 to approximately 14 %.

Unveiling the anticancer potential: Exploring 4-fluoro benzoic acid and piperazine through spectroscopic, X-ray diffraction, DFT and molecular docking analysis

The crystalline substance formed from piperazine and 4-fluorobenzoic acid (PZ-PFBA) was successfully synthesized. This synthesis involved the transfer of protons between the selected acid and base, resulting in the formation of distinct crystalline salt. The SCXRD analysis conforms the salt crystallized in a monoclinic crystal system with a P 21/c space group and lattice parameters are a = 13.0688(14) Å, b = 8.2686(8) Å, and c = 8.2552(9) Å. Hirshfeld surface analysis, a technique for quantifying molecular interactions, was employed to investigate the prepared crystalline salt. Additionally, the salt was subjected to further examination using FT-IR, 1H NMR, 13C NMR, and SCXRD studies. The crystalline salt has major and established biological actions that inhibit the human lung cancer cell line A549. In vitro, and Insilico anticancer tests show that PZ-PFBA has better efficacy against the human cervical cancer cell line (HeLa) and in bioinformatics analysis. PZ-PFBA demonstrated more efficacy in reducing pathogenic strains compared to its parent reactants.

Mechanisms of drug release from a melt-milled, poorly soluble drug substance

Increasing the dissolution kinetics of low aqueous soluble drugs is one of the main priorities in drug formulation. New strategies must be developed, which should consider the two main dissolution mechanisms: surface reaction and diffusion.One promising tool is the so-called solid crystal suspension, a solid dispersion consisting of purely crystalline substances. In this concept, reducing the drug particle size and embedding the particles in a hydrophilic excipient increases the dissolution kinetics. Therefore, a solid crystal suspension containing submicron drug particles was produced via a modified stirred media milling process. A geometrical phase-field approach was used to model the dissolution behavior of the drug particles.A carrier material, xylitol, and the model drug substance, griseofulvin, were ground in a pearl mill. The in-vitro dissolution profile of the product was modeled to gain a deep physical understanding of the dissolution process. The used numerical tool has the potential to be a valuable approach for predicting the dissolution behavior of newly developed formulation strategies.

Construction of two-dimensional heterojunctions based on metal-free semiconductor materials and Covalent Organic Frameworks for exceptional solar energy catalysis

Covalent organic frameworks (COFs) are newly developed crystalline substances that are garnering growing interest because of their ultra-high porosity, crystalline nature, and easy modified architecture, showing promise in the field of photocatalysis. However, it is difficult for pure COFs materials to achieve excellent photocatalytic hydrogen production due to their severe carrier recombination problems. To mitigate this crucial issue, establishing heterojunction is deemed an effective approach. Nonetheless, many of the metal-containing materials that have been used to construct heterojunctions with COFs own a number of drawbacks, including small specific surface area and rare active sites (for inorganic semiconductor materials), wider bandgaps and higher preparation costs (for MOFs). Therefore, it is necessary to choose metal-free materials that are easy to prepare. Red phosphorus (RP), as a semiconductor material without metal components, with suitable bandgap, moderate redox potential, relatively minimal toxicity, is affordable and readily available. Herein, a range of RP/TpPa-1-COF (RP/TP1C) composites have been successfully prepared through solvothermal method. The two-dimensional structure of the two materials causes strong interactions between the materials, and the construction of heterojunctions effectively inhibits the recombination of photogenic charge carrier. As a consequence, the 9% RP/TP1C composite, with the optimal photocatalytic ability, achieves a photocatalytic H2 evolution rate of 6.93 mmol g−1 h−1, demonstrating a 10.19-fold increase compared to that of bare RP and a 4.08-fold improvement over that of pure TP1C. This article offers a novel and innovative method for the advancement of efficient COFs-based photocatalysts.

Unveiling the Nature of Chemical Bonds in Real Space.

Recent advent of diverse chemical entities necessitates a re-evaluation of chemical bond concepts, underscoring the importance of experimental evidence. Our prior study introduced a general methodology, termed Core Differential Fourier Synthesis (CDFS), for mapping the distribution of valence electron density (VED) in crystalline substances within real space. In this study, we directly compare the VED distributions obtained through CDFS with those derived from high-accuracy theoretical calculation using long-range corrected density functional theory, which quantitatively reproduces accurate orbital energies. This comparison serves to demonstrate the precision of the CDFS in replicating complex details. The VED patterns observed experimentally exhibited detailed structures and phases of wave functions indicative of sp3 hybrid orbitals, closely aligning with theoretical predictions. This alignment underscores the utility of our approach in gathering quantum chemical data experimentally, a crucial step for discussing the chemical properties, such as reaction mechanisms.

Influence of Na2CO3 on the activation degree and microstructure of coal gasification coarse slag

ABSTRACT Silicon in coal gasification coarse slag (CGCS) accounts for more than 40%. CGCS can be developed into an inorganic silicon source to improve its utilization value. Alkali activation can increase extraction rate of silicon. In this study, the influence of Na2CO3 on the activation degree and microstructure of CGCS was investigated. The activation mechanism was discussed based on IR, XRD, SEM, and EDS data. The results showed that the dosage of Na2CO3 was positively correlated with SiO2/Al2O3 in CGCS, which is generally 0.8 ~ 1.3 times of CGCS. The activation temperature of CGCS was 800°C ~ 850°C. A small amount of residual carbon could slightly reduce the activation temperature. The alkali activation process involved depolymerizing the polymer structure into an oligomer, whereby the crystalline structure was transformed into an amorphous structure. Moreover, Q4 structure in CGCS could be more easily activated than Q3 or Q2 structure. The activation reaction was carried out under gas-liquid-solid three-phase conditions. The diffusion effect of CO2 gas could be fully utilized in the activation process to ensure the melting of heteroatoms and the formation of defects, which prevented the emergence of crystalline substances. This research provides a solid theoretical foundation for low-cost and high-quality extraction of silicon from CGCS.

Study of mesomorphic, thermal and optical properties of 4-pentylbenzoic acid (5BA) and 4-n-alkyl-4́-cyanobiphenyl (nCB; n = 5, 6) supramolecular hydrogen bonded mesogenic complexes

Within the scope of this study, the process of producing and analyzing a liquid crystalline substance (supramolecular hydrogen-bonded mesogen) is presented. The formation of this mesogen involves the use of two chemicals, namely 4-pentylbenzoic acid (5BA) and 4-n-alkyl-4́-cyanobiphenyl (nCB; n = 5, 6). Equimolar (1:1) 5BA/5CB and 5BA/6CB binary combination samples have been organized by using one at a time mixing 5CB and 6CB liquid crystal chemical substances with 5BA. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) are employed for the examination of phase transitions, and liquid crystalline phase texture properties of the produced mesogens. The phase transformation sequence that occurred during heating and cooling is Crystal (Cr) ↔ Smectic A (SmA) ↔ Nematic (N) ↔ Isotropic (I) with the 1st order or weakly 1st order transition. The nematic range value observed for 5BA/6CB is considerably smaller than the nematic range value observed for 5BA/5CB, but the thermal mesophase range value for both is approximately the same. Fourier-transform infrared (FTIR) evaluation of 5BA, 5CB, and their hydrogen-bonded combos (5BA/nCB; n = 5, 6) confirmed attribute peaks. The X-ray diffraction (XRD) study revealed that the produced mesogens possess a crystalline structure. In addition, UV–Vis experiments demonstrated that the increase in alkyl chain length in the combination resulted in a decrease in absorbance and wavelength values, while leading to an increase in absorbency and band gap energy values. These results propose workable purposes for the synthesized substances in liquid crystal displays and other optoelectronic devices. Overall, the findings display the feasibility and viability of these novel hydrogen-bonded liquid crystalline mesogens in various technological applications.

A comprehensive bibliometric review and analysis on the evolution of nanotube-based hydrogen storage materials via DFT simulations

Abstract Hydrogen’s promise as a clean energy carrier is tempered by the challenges of efficient storage and safety concerns. While it offers an alternative to finite fossil fuel resources, current hydrogen storage methods, like cryo-compression and liquefaction, are often economically impractical. To tackle these issues, researchers are turning to nanotube materials (NTMs), crystalline substances with unique attributes ideal for hydrogen storage. Structural adaptability - NTMs can be precisely engineered for optimized hydrogen adsorption. These materials boast significant porosity, providing ample room for hydrogen molecules. NTMs offer a large surface area, enhancing their hydrogen adsorption capacity. NTMs employ weak van der Waals forces for hydrogen adsorption, enabling easy release via heat or pressure. Efforts are underway to enhance NTMs’ surface area and hydrogen uptake capabilities, along with a focus on mechanisms like the hydrogen spill-over for achieving high-density storage. NTMs go beyond storage; they can act as proton exchange membranes and fuel cell electrodes, making them versatile components in hydrogen-based energy systems. One strategy for improving NTM hydrogen storage involves introducing dopants or defects. Transition metals, due to their ability to attract and store hydrogen molecules in NTMs, are commonly explored. However, this addition may reduce the material’s gravimetric density, a critical practical consideration. In summary, research into NTMs and their potential for hydrogen storage via density functional theory is ongoing. This work explores strategies to enhance hydrogen storage, especially through transition metal doped NTMs. While these metals can improve hydrogen adsorption, the trade- offs in gravimetric density must be carefully weighed. Overall, this research contributes to the broader goal of harnessing hydrogen’s potential as a clean energy carrier, addressing the world’s growing energy needs.

Pressure studies of rod-like liquid crystals – experimental facts and theoretical deficiencies

ABSTRACT In the years 1990–2015, many liquid crystalline (LC) substances were studied under elevated pressure. The main aims of studies were to determine the P vs. T phase diagrams, the equation of state V(P,T) for isotropic and LC phases, measuring the dynamical properties of molecules (mainly the flip-flop motions) and analysing them at the isobaric, isothermal and isochoric conditions. The observed phenomena were discussed using existing theoretical models of LC state or – in the absence of them – models adopted from the field of glass-forming liquids. In the present review, the attention will be paid to a comparative data analysis for two rings compounds with the strongly polar terminal group (CN or NCS) at one site and the n-alkyl or n-alkoxy group at the other. Such molecules may well mimic the rod-like molecules commonly used in theoretical models of LC state.

Large-cage occupation and quantum dynamics of hydrogen molecules in sII clathrate hydrates.

Hydrogen clathrate hydrates are ice-like crystalline substances in which hydrogen molecules are trapped inside polyhedral cages formed by the water molecules. Small cages can host only a single H2 molecule, while each large cage can be occupied by up to four H2 molecules. Here, we present a neutron scattering study on the structure of the sII hydrogen clathrate hydrate and on the low-temperature dynamics of the hydrogen molecules trapped in its large cages, as a function of the gas content in the samples. We observe spectral features at low energy transfer (between 1 and 3meV), and we show that they can be successfully assigned to the rattling motion of a single hydrogen molecule occupying a large water cage. These inelastic bands remarkably lose their intensity with increasing the hydrogen filling, consistently with the fact that the probability of single occupation (as opposed to multiple occupation) increases as the hydrogen content in the sample gets lower. The spectral intensity of the H2 rattling bands is studied as a function of the momentum transfer for partially emptied samples and compared with three distinct quantum models for a single H2 molecule in a large cage: (i) the exact solution of the Schrödinger equation for a well-assessed semiempirical force field, (ii) a particle trapped in a rigid sphere, and (iii) an isotropic three-dimensional harmonic oscillator. The first model provides good agreement between calculations and experimental data, while the last two only reproduce their qualitative trend. Finally, the radial wavefunctions of the three aforementioned models, as well as their potential surfaces, are presented and discussed.

SCATTERING OF ELECTROMAGNETIC WAVES ON FLAT GRID TWO-PERIODIC STRUCTURES

Context. One of the scientific hypotheses for the creation of nonreciprocal optical metasurfaces is based on the use of a wave channel in which rays of the direct and reverse diffraction scenarios are realized on two-periodic flat structures with nonlinear elements. Such processes in the nanometer wavelength range of electronic devices require precise calculations of the interaction of waves and microstructures of devices. It is also important to describe the behavior of antenna devices in mobile communications. Expanding the wavelength range of stable communication is achieved by using prefractal structures in antenna devices in combination with periodic structuring. Similar modeling problems arise when electromagnetic waves penetrate materials with a crystalline structure (radio transparency).
 Objective. To test this hypothesis, it is necessary to carry out mathematical modeling of the process of scattering of electromagnetic waves by metasurfaces under conditions of excitation of several diffraction orders. It is known that among two-periodic flat lattices of different structures there are five types that fill the plane. These are the Bravais grilles. The problem of scattering of an incident monochromatic TE polarized wave on a metal screen with recesses in two-periodic structures filled with silicon was considered.
 Method. The paper builds mathematical models for the study of spatial-amplitude spectra of metasurfaces on Brave lattices and gives some results of their numerical study. The condition for determining the diffraction orders propagating over the grating is proposed. Scattered field amplitudes are from the solution of the boundary value problem for the Helmholtz equation in the COMSOL Multiphysics 5.4 package. Similar problem formulations are possible when studying the penetration of an electromagnetic field into a crystalline substance.
 Results. Obtained relations for diffraction orders of electromagnetic waves scattered by a diffraction grating. The existence of wavelengths incident on a two-periodic lattice for which there is no reflected wave is shown for different shapes (rectangular, square, hexagonal) of periodic elements in the center of which a depression filled with silicon was made. Distributions of reflection coefficients for different geometric sizes of colored elements and recesses are given. The characteristics of the electric field at resonant modes in the form of modulus isolines show the nature of the interaction of the field over the periodic lattice and the scatterersdepressions. At the resonant wavelengths of the incident waves, standing waves appear in the scatterers.
 Conclusions. A mathematical model of the set of diffraction orders propagating from a square and hexagonal lattice into halfspace is proposed z >= 0. It has been shown that flat periodic lattice with square or hexagonal periodicity elements and resonant scatterers in the form of cylindrical recesses filled with silicon can produce a non-mirrored scattered field in metal. The response of the lattices to changes in the wavelength of the incident field by the structure of diffraction orders of the scattered field and high sensitivity to the rotation of the incident plane were revealed. The two-periodic lattices have prospects for creating anti-reflective surfaces of various devices. Two-periodic lattices have prospects for creating anti-reflective surfaces for various devices, laser or sensor electronic devices, antennas in mobile communication elements, and radio transparency elements. They have more advanced manufacturing technologies in relation to spatial crystal structures.

Oznaczanie 1,2-dihydroksybenzenu w powietrzu na stanowiskach pracy metodą chromatografii gazowej z detekcją płomieniowo-jonizacyjną

1,2-Dihydroxybenzene is a colorless crystalline substance with a characteristic odor that turns brown when exposed to air and light. It is used in industry as an antioxidant. Worker exposure to 1,2-dihydroxybenzene can occur during the production, processing and use of the chemical, through inhalation, dermal and gastrointestinal routes. The aim of the study was to develop a method for the determination of 1,2-dihydroxybenzene to assess occupational exposure within 1/10–2 of the proposed MAC value (10 mg/m3 ). The method involves the collection of 1,2-dihydroxybenzene in a system consisting of a glass fiber filter and a tube containing two layers of XAD-7 sorbent, extraction with a solution of N,N-dimethylformamide in methanol, and chromatographic analysis of the resulting solution. The method allows the determination of 1,2-dihydroxybenzene in air in the concentration range from 1.0 to 20.0 mg/m3 . The method has been validated in accordance with PN-EN 482. The scope of the article includes health and environmental health and safety issues being the subject of research in health sciences and environmental engineering.

Characteristic and mechanism of efficient phosphate removal by Portland cement/slag powder/coal ash-hydrate (PC/SP/CA-H)

The excessive presence of phosphate in water leads to eutrophication, prompting us to develop a novel material named PC/SP/CA-H (Portland cement/slag powder/coal ash-hydrate). The experimental data accorded with the pseudo-second-order kinetics and Langmuir model, suggesting that chemical interactions predominated in the adsorption process. Within 4 hours, PC/SP/CA-H rapidly removed phosphate at a rate of 65%, which exceeded 90% after 12 hours with a material dosage of 30 g/L and a phosphate concentration of 30 mg/L. The maximum phosphate adsorption capacity of PC/SP/CA-H was 8.84 mg/g. The material exhibited effective phosphate removal capabilities across a wide pH range of 3.0–11.0. It demonstrated remarkable selectivity to phosphate in the presence of competitive anions, such as CO32-, HCO3-, NO3-, SO42-, and Cl-. Characterization analyses including SEM, BET, XRD, XRF, FTIR, and XPS were conducted to investigate the performance of PC/SP/CA-H and mechanisms of phosphate removal. The findings indicated that phosphate replaced hydroxyl groups on the material to form inner-sphere complexes through ligand exchange. Besides, phosphate was adsorbed onto the positively charged material via electrostatic attraction with protonated hydroxyl groups (-OH2+). It also reacted with metal cations (Ca2+) released by the material to form insoluble crystalline substances (Ca-P) through surface precipitation. This material holds promising prospects for efficiently removing phosphate from water or wastewater, while simultaneously enhancing the resource utilization of coal ash and slag powder.

Features of chemical elements migration in natural waters and their deposition in the form of neocrystallisations in living organisms (physico-chemical modeling with animal testing)

Relevance. An original modeling method is presented, which allows obtaining qualitatively new results in practice of ecological-geochemical and biomedical research. Aim. To obtain new data on the forms of element migration in the conditions of animal and human organism parameters by means of physicochemical modeling (PC "Selector") with verification of calculated data with the results obtained for real natural objects and animal organisms. Objects. Samples of natural waters and tissues of wild animals. Methods. Computer modeling (PC "Selector"); inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7700x spectrometer) – 55 elements; atomic emission spectrometry (AES, spectrometer iCAP 7600 Duo) –- 5 macrocations; ion chromatography (IC, ion-liquid chromatograph LC-20) – 6 anions; inductively coupled plasma mass spectrometry (ICP-MS, mass spectrometer NexION 300D; scanning electron microscopes Hitachi S-3400N with Bruker X@Flash 5010 energy dispersive spectrometer. Results. By means of modeling, the authors have determined the qualitative and quantitative composition of the system "solution – crystalline substance". They took into account environmental conditions and physiological parameters of animal and human organism. Natural drinking water, gastric juice, mixture of drinking water and gastric juice were used as a solution, and crystalline substance was used as newly formed mineral phases in equilibrium with the solution. The work allowed establishing that the complexes assumed in the model experiment can be the cause of appearance of nanomineral phases of chemical elements in separate tissues of a living organism.

Isolation and Characterization of Antimicrobial Constituent(s) from the Stem of Cissus populnea Guill. & Perr.

Cissus populnea Guill. & Perr. (Vitaceae) is used in traditional medicine to treat microbial infections, venereal diseases and infertility, among others. The aim of this research is to isolate and characterize the antimicrobial constituent(s) from the stem of C. populnea. The n-butanol fraction of C. populnea, being most active, was subjected to silica gel column chromatography, which led to the isolation of white solid and white crystalline substances coded compounds C1 and C4C5, respectively. Spectral analysis (1D and 2D-NMR) of the isolated compounds and comparison with the literature data indicated C1 to be Bis-(2-ethyloctyl)-phthalate and C4C5 to be a mixture of stigmasterol and β-sitosterol; C4C5 exhibited a zone of inhibition ranging from 24 to 29 mm against the test organisms with Candida albicans being the most sensitive organism while Trichophyton rubrum was the least sensitive organism. Of the standard drugs, ciprofloxacin had 27–37 mm while fluconazole and fulcin exhibited zones of inhibition ranging from 34 mm to 29–32 mm, respectively. The MIC and MBC/MFC values for C4C5 ranges from 12.5 to 25.0 µg/cm3 and 25.0 to 50.0 µg/cm3 against methicillin-resistant Staphylococcus aureus, Staphylococcus. aureus, Escherichia coli, Candida albicans, Trichophyton rubrum and Trichophyton mentagrophyte, respectively. In conclusion, Bis-(-(2-ethyloctyl)-phthalate) and a mixture of stigmasterol and β-sitosterol were identified for the first time from the stem of C. populnea.

Hierarchical topological analysis of crystal structures: the skeletal net concept.

Topological analysis of crystal structures faces the problem of the `correct' or the `best' assignment of bonds to atoms, which is often ambiguous. A hierarchical scheme is used where any crystal structure is described as a set of topological representations, each of which corresponds to a particular assignment of bonds encoded by a periodic net. In this set, two limiting nets are distinguished, complete and skeletal, which contain, respectively, all possible bonds and the minimal number of bonds required to keep the structure periodicity. Special attention is paid to the skeletal net since it describes the connectivity of a crystal structure in the simplest way, thus enabling one to find unobvious relations between crystalline substances of different composition and architecture. The tools for the automated hierarchical topological analysis have been implemented in the program package ToposPro. Examples, which illustrate the advantages of such analysis, are considered for a number of classes of crystalline substances: elements, intermetallics, ionic and coordination compounds, and molecular crystals. General provisions of the application of the skeletal net concept are also discussed.

REACTION OF 1-ANTIPYRYL-4-AROYL-5-METHOXYCARBONYL-1H-PYRROLE-2,3-DIONES WITH ARYLAMINES

In this work, we investigated the reaction of 1-antipyryl-4-aroyl-5-methoxycarbonyl-1H-pyrrole-2,3-diones with aromatic amines, which resulted in the production of 1-antipyryl-5-arylamino-4-aroyl-3-hydroxy-5-methoxycarbonyl-1H-pyrrol-2-ones. The reactivity of previously synthesized antipyryl-substituted monocyclic 1H-pyrrole-2,3-diones was studied using the example of reactions with NH-mononucleophilic reagents such as aniline, p-toluidine and 1-naphthylamine. The studied 1-antipyryl-4-aroyl-5-methoxycarbonyl-1H-pyrrole-2,3-diones are generated by boiling 1-antipyryl-4-aroyl-3-hydroxy-5-chloro -1,5-dihydro-1H-pyrrol-2-ones in an absolute toluene environment for 20-30 min, followed by distillation of part of the solvent and hydrogen chloride. Arylamines were added to the resulting concentrated hot solution in a 1:1 ratio. The resulting adduct is a light yellow crystalline substance. Apparently, the reaction of 1-antipyryl-4-aroyl-5-methoxycarbonyl-1H-pyrrole-2,3-diones with aromatic amines occurs through a nucleophilic attack by the amino group at the most electron-deficient position of the pyrrole ring. For all synthesized compounds, physical properties are given, such as solubility, melting points. The elemental composition was determined, and the structure of the molecules is established using NMR and IR spectroscopy. The 1H NMR spectra of solutions of the obtained compounds contain two singlets of the protons of the methyl groups of the antipyryl fragment in the region of 2.17-2.18 ppm. and 3.17-3.19 ppm, singlet of protons of the methoxycarbonyl group in the region of 3.69-3.71 ppm, singlet of protons of the amino group in the region of 6.53-6.68 ppm (1H, NH). The IR spectra of the products contain stretching vibrations of the ketone group in the region of 1653-1658 cm-1, the ester carbonyl group in the region of 1716-1718 cm-1, as well as a signal in the region of 3375-3388 cm-1 (NH). The described interaction proceeds quickly and with high yields. The reaction is a convenient preparative method for the synthesis of 1-antipyryl-5-arylamino-4-aroyl-3-hydroxy-5-methoxycarbonyl-1H-pyrrol-2-ones, which are of interest for further study of various types of biological activities, such as antimicrobial, anti-inflammatory, analgesic and others.

REACTION OF O-PHENYLENEDIAMINE WITH EPICHLOROHYDRIN AND EVALUATION OF THE PRODUCT AS A RUBBER ANTIAGING AGENT

The epichlorohydrin - o-phenylenediamine reaction product has have obtained. With reverse titration the fact has been proven that the epoxy groups were completely used up to produce the adduct. The Shimadzu FTIR-8400S Fourier spectrometer was used to register the IR spectra. Through IR spectroscopy it was demonstrated that the resulting product is a secondary amine. Thus, epichlorohydrin epoxide groups react with the o-phenylenediamine amino groups. The product has been isolated in the form of a solid crystalline substance having the melting temperature range of 104-106 °С. The rubber mixes based on SKS-30ARKM-15 butadiene-styrene rubber containing sulfur, 2-mercaptobenzthiazole, diphenylguanidine, zinc white, industrial stearin, N-550 carbon black and rubber anti-aging agents at 6.6 mmol/100 g were also studied. The epichlorohydrin - o-phenylenediamine reaction product, N-isopropyl-N'-phenyl-p-phenylenediamine, and 2,2-methylene-bis(4-ethyl-6-tert-butylphenol) were used as the anti-aging agents. A rubber mix containing no anti-aging additives was studied. The rubber mixes have been prepared in LB 320 160/160 rollers, at 45-55 °C. The vulcanization properties of the rubber compounds were tested using Prescott Instruments Rheo-Line MDR rheometer at 160 °C. It was established that the studied adduct has virtually no effect on the vulcanization rate. High values of the difference between the maximum and minimum values of the torque of rubber with the adduct under study indicated a high degree of cross-linking of macromolecules. The mixture has been vulcanized in a 600-600 2E hydraulic vulcanization press at 160 ºC for 15 min. Studies of the properties of vulcanized rubber were carried out in accordance with the standards accepted for the rubber industry. High tensile stress values at given elongations for the rubber containing the product studied have also indicated a high degree of vulcanization. The use of the epichlorohydrin - o-phenylenediamine reaction product in the SKS-30ARKM-15 rubber based compounds has ensured high thermal aging resistance as well as dynamic fatigue resistance.

Identification of Cathine in Unknown White Crystalline Substance in Sri Lanka

The drug abuse in Sri Lanka is continuously grown fast and variety of new narcotic drugs comes to the market day by day. Cathine {(1S,2S)-2-amino-1-phenylpropan-1-ol} is a monoamine alkaloid found naturally in the shrub Catha edulis (Khat). It is a psychoactive drug of the phenethylamine and amphetamine chemical classes which act as a stimulant. The drug responsible for the CNS stimulating effect and it can be isolated from fresh khat leaves. Synthetic Cathinones and Cathine referred to as designer Drugs, Party drugs or club drugs. Cathine was detected recently in the Narcotic Laboratory of Government Analyst’s Department and this is the first report of finding Cathine in Sri Lanka. The white crystalline substance concealed in an envelope was delivered to the Narcotic Laboratory of Government Analyst’s Department of Sri Lanka for further analytical examination including qualitative and quantitative analysis. Preliminary colour test and secondary test including TLC, UVVisible spectroscopy, GC-MS, FTIR spectroscopy and Raman spectroscopy were performed for qualitative analysis. The results revealed that the unknown white crystalline substance contained Cathine Hydrochloride and it was found for the first time in Sri Lanka. Furthermore, GC with FID detector was carried out to find the quantification results and it revealed that the unknown substance contained nearly 23% of Cathine Hydrochloride in the sample. The tendency may be more common that most new designer drugs are prepared to circumvent existing legislation and becoming attractive to illicit drug cookers in the world.

HYDROGEN BONDING EFFECT ON OPTICAL PROPERTIES OF SUPRAMOLECULAR LIQUID CRYSTALS IN UV VISIBLE REGION

This study utilizes spectral analysis techniques and various computational methods to examine the impact of hydrogen bonding on the optical characteristics of supramolecular liquid crystals within the UV-visible spectrum.This investigation involves the computational method of spectral denoising for quantitative analysis of UV-visible spectra, and then spectral analysis is carried out for the measurement of the optical properties of supramolecular liquid crystals. Other computational methods, like the texture absorbance method, are also employed for colorimetric studies of compounds.The investigation will focus on supramolecular systems:p,n- alkoxy benzoic acid: Do-decyl hydroxybenzoate (nOBA:12HB), where n = 7, 8, and 9. The supramolecular system is formed via hydrogen bond development between the OH acceptor of the non-liquid crystalline substance Do-decyl hydroxyl benzoate (12HB) and the COOH donor of the liquid crystal p-n alkoxy benzoic acid. Here, optical properties: such as absorption coefficient, optical energy band gap, Urbach energy, and refractive index of supramolecular liquid crystals are measured for the denoised spectral data. The influence of hydrogen bonding and alkoxy chain length on the optical properties of liquid crystals has been deliberated upon. Further, the attempt at computation studies on the spectral data will yield important insights for subsequent investigations into UV-visible spectral data measurements.