Kinetics, mechanism, and tautomerism in ametryn acid hydrolysis: From molecular structure to environmental impacts.

The excessive use of pesticides and the demand for environmentally friendly compounds have driven the focus to detailed studies of the environmental destination of these compounds. Degradation by hydrolysis of pesticides, when released into the soil, can result in the formation of metabolites with potentially adverse effects on the environment. Moving in this direction, we investigated the mechanism of acid hydrolysis of the herbicide ametryn (AMT) and predicted the toxicities of metabolites through experimental and theoretical approaches. The formation of ionized hydroxyatrazine (HA) occurs with the release of the SCH3- group and the addition of H3O+ to the triazine ring. The tautomerization reactions privileged the conversion of AMT into HA. Furthermore, the ionized HA is stabilized by an intramolecular reaction that provides the molecule in two tautomeric states. Experimentally, the hydrolysis of AMT was obtained under acidic conditions and at room temperature with HA as the main product. HA was isolated in a solid state through its crystallization as organic counterions. The mechanism of conversion of AMT to HA and the experimental investigation of the reaction kinetics allowed us to determine the dissociation of CH3SH as the rate-controlling step in the degradation process that culminates in a half-life between 7 and 24 months under typical acid soil conditions of the Brazilian Midwest - region with strong agricultural and livestock vocation. The keto and hydroxy metabolites showed substantial thermodynamic stability and a decrease in toxicity compared to AMT. We hope that this comprehensive study will support the understanding of the degradation of s-triazine-based pesticides.

Structural insights into the biological activity of a thioxopyrimidine derivative.

Bacterial resistance to the main widespread antibiotics, such as those based on quinolones, is a concern of the scientific community, leading to the search for new classes of molecules that can be used as an alternative. Here, we investigate the crystalline and chemical characteristics of a thioxopyrimide to understand its demonstrated biological activity and to identify which portion of the molecule can be used as a framework to develop new antibiotics. For this purpose, structural studies of ethyl 4-methyl-2-phenyl-6-thioxo-1,6-dihydro-5-pyrimidinecarboxylate were carried out aided by Hirshfeld surface analysis, as well as theoretical calculations on frontier molecular orbitals, molecular electrostatic potential, and conformational stability, in addition to docking studies targeting topoisomerase IV. The docking results show a reasonable accommodation of the molecule at the topoisomerase IV binding site and interact mainly by hydrogen bonds between the thioxopyrimidine portion with Glu198, Thr292, and Gly225, aided by hydrophobic interactions involving the rest of the molecule. These results suggest a relationship between the antibacterial activity shown mainly with the 4-thioxopyrimidine portion, leading to the investigation of new compounds that use this scaffold.

Synthesis, characterization, and computational study of a new heteroaryl chalcone.

This work presents the synthesis of the chalcone (E)-3-(2,6-difluorophenyl)-1-(furan-2-yl)-prop-2-en-1-one molecule through the equimolar reaction between 1-(furan-2-yl)-ethenone and 2,6-difluorobenzaldehyde. The crystallographic characterization and the extensive theoretical study regarding electronic properties were obtained. The supramolecular arrangement was described by X-ray diffraction and Hirshfeld surfaces. Optimized geometrical structure was obtained by density functional theory, and the electronic study for differences between the solid and gas phases was carried out with M062-X at 6-311++G(2d,2p) basis set. Natural bond orbital, frontier molecular orbitals (HOMO-LUMO), and molecular electrostatic potential map were determined to elucidate the information related to the charge transfer in the molecule. The theoretical and experimental vibrational spectra were plotted, which included the IR intensities, the calculated and experimental vibrational frequencies, and the assigned vibrational modes for the main groups of DTP.

Structural comparison of five new halogenated dihydroquinoline-4(1H)-ones.

Compounds with dihydroquinoline-4(1H)-one nuclei have been reported in the literature for being important in the development of medicines due to their broad spectrum of activities. In this way, the structural knowledge of this class becomes relevant for obtaining new materials with desired biological properties. This study presents the structural elucidation of five halogenated dihydroquinolines, as well as the discussion about the effect on the molecular conformation of the type and position of halogen atom on aromatic rings. Compounds I and IV differ in halogen substitution on 2-phenyl ring, while compounds III and V differ in halogen substitution on the benzylidene ring. Moreover, compound II has a para-substituted 2-phenyl ring in their molecular structure. The crystal packing of all five molecules is mainly ruled by C-H⋯O and C-H···halogen interactions that form dimers and chains. The shift in position and the kind of the halogen in ring C shows a starring role in the conformation of the studied compounds, and the packaging of these compounds is more susceptible to variations when the halogen position changes.

A Comprehensive Topological Analysis on a New Bromine-Chalcone with Potential Nonlinear Optical Properties.

The application of organic crystals on nonlinear optical (NLO) materials has been increasing in recent years, and compounds like chalcones are interesting due to their significant third-order nonlinear properties. Hereof, we describe the synthesis, molecular structure, supramolecular arrangement, and theoretical calculations for a bromine-chalcone 3-(4-bromophenyl)-1-[3-(2-oxo-2-phenylethoxy)phenyl]-propenone (BC), which crystallized into noncentrosymmetric space group Pc. Also, a comprehensive topological analysis performed by QTAIM highlights the observed halogen bonds on solid state. In addition, the thermal stability was studied in temperatures smaller than 800 °C showing BC crystal as potential optical devices at temperatures up to 250 °C. Finally, the NLO properties indicate a photonic application based on strong third-order nonlinear response.

Analysis of two novel 1-4 quinolinone structures with bromine and nitrobenzyl ligands.

The scientific community has shown particular interest in the study of quinolinones-a class of bicyclic organic compounds. An example of these compounds are the 4-quinolinones, considered to be very useful building blocks, since they can adapt their molecular structures with different ligands for applications in various fields such as pharmacy, medicine, physics and engineering. The compounds (E)-3-(benzylidene)-2-(3-nitrophenyl)-2,3-dihydro-1-(phenylsulfonyl)-quinolin-4-(1H)-one (NFQ) and (E)-3-(benzylidene)-2-(4-bromophenyl)-2,3-dihydro-1-(phenylsulfonyl) quinolin-4-(1H)-one (BFQ) were synthesized and characterized by infrared spectroscopy, 1H and 13C NMR, and melting point. NFQ crystallized in the orthorhombic Pbca space group while BFQ appears in the monoclinic P21/n space group. X-ray diffraction was used to evaluate their crystallographic structures, and Hirshfeld surface evaluates the intermolecular interactions, supramolecular arrangement and packaging. Theoretical vibrational assignments and calculated electronic properties also demonstrate acceptable agreement between experimental and theoretical results.

Conformation analysis of a novel fluorinated chalcone.

Chalcones are an important class of natural compounds that exhibit numerous biological activities. In this paper, we report the synthesis and characterization of new fluorinated chalcone (FCH). The molecular geometry was determined by means of single crystal X-ray diffraction, and density functional theory (DFT) at B3LYP, M06-2X functionals and MP2 method, with the 6-311++G(d,p) basis set, was applied to optimize the ground state geometry and to study the molecular conformational stability. The molecular electrostatic potential (MEP) was also investigated at the same level of theory in order to identify and quantify the possible reactive sites. The FCH crystallizes in the centrossymmetric space group [Formula: see text] with two independent conformers (α and ß) in the asymmetric unit cell. The α conformer is arranged in planar layer whereas the ß creates a layer of non-classical dimer along c axis, that differ from α in about 11° in the orientation of phenyl groups. The stabilization of the ß conformer is achieved by C-H···π arrangement. The small energy difference between the conformers (0.086 kcal mol-1) and the absence of activation energy indicates that the conversion between them can takes place at room temperature and the ß isomer is stable only in solid state. The FCH most electrophilic site occurs on the oxygen atom from the carboxyl group with absolute MEP value of about -52 kcal mol-1 whereas the MEP value calculated for F site is about -23 kcal mol-1.