An addition of carbon nanostructures to cement paste is problematic due to the difficulties in obtaining homogenous mixtures. The paper reports on a more effective way of mixing carboxylated multi-walled carbon nanotubes (MWCNT-COOH) in cement pastes. The additional biological impact of the studied nanomodified cement was analyzed in the case of two moss species' vitality.
View Article and Find Full Text PDFWind is one of the most widely used renewable energy sources due to its cost-effectiveness, power requirements, operation, and performance. There are many challenges in wind turbines, such as wind fluctuation, pitch control, and generator speed control. When the wind speed exceeds its rated value, the pitch angle controller limits the generator output power to its rated value.
View Article and Find Full Text PDFA comparative structural study of two related donor-acceptor pyridine-based BF complexes, namely, 3-(dimethylamino)-1,1-difluoro-1H-pyrido[1,2-c][1,3,5,2]oxadiazaborinin-9-ium-1-uide, CHBFNO (1), and 3-{(1E,3E)-4-[4-(dimethylamino)phenyl]buta-1,3-dien-1-yl}-1,1-difluoro-1H-pyrido[1,2-c][1,3,5,2]oxadiazaborinin-9-ium-1-uide, CHBFNO (2), containing a dimethylamino group and either the shortest (in 1) or the longest (in 2) charge-transfer path known until now in this family of compounds, is presented. Single-crystal X-ray diffraction analysis supported by computational investigations shed more light on these systems, indicating, among other aspects, the predominance of C-H..
View Article and Find Full Text PDFThe development of efficient methods for facilitating N-C(O) bond activation in amides is an important objective in organic synthesis that permits the manipulation of the traditionally unreactive amide bonds. Herein, we report a comparative evaluation of a series of cyclic amides as activating groups in amide N-C(O) bond cross-coupling. Evaluation of -acyl-imides, -acyl-lactams, and -acyl-oxazolidinones bearing five- and six-membered rings using Pd(II)-NHC and Pd-phosphine systems reveals the relative reactivity order of N-activating groups in Suzuki-Miyaura cross-coupling.
View Article and Find Full Text PDFAminophosphonates are an important group of building blocks in medicinal and pharmaceutical chemistry. Novel representatives of this class of compounds containing nontypical side chains are still needed. The aza-Michael-type addition of amines to phosphonodehydroalanine derivatives provides a simple and effective approach for synthesizing '-substituted α,β-diaminoethylphosphonates and thus affords general access to aminophosphonates bearing structurally diverse side chains.
View Article and Find Full Text PDFAn application of the quantum chemical modeling allowed to investigate the nature of the field/inductive substituent effect (SE). For this purpose, series of X-tert-butyl···tert-butane (TTX) complexes (where X = NMe, NH, OH, OMe, Me, H, F, Cl, CF, CN, CHO, COMe, CONH, COOH, NO, NO) were studied. A starting distance between central carbon atoms in substituted and unsubstituted fragments of TTX, d, was the same as the distance C1-C4 in X-substituted bicyclo[2.
View Article and Find Full Text PDFThe influence of a solvent on the substituent effect (SE) in 1,4-disubstituted derivatives of benzene (BEN), cyclohexa-1,3-diene (CHD), and bicyclo[2.2.2]octane (BCO) is studied by the use of polarizable continuum model method.
View Article and Find Full Text PDFThe role of theory level in prediction of benzene magnetic indexes of aromaticity is analysed and compared with calculated nuclear magnetic shieldings of He used as NMR probe. Three closely related nucleus-independent chemical shift (NICS) based indexes were calculated for benzene at SCF-HF, MP2, and DFT levels of theory and the impact of basis set on these quantities was studied. The changes of benzene NICS(0), NICS(1), and NICS(1)zz parameters calculated using SCF-HF, MP2 and several density functionals were within 1 to 3 ppm.
View Article and Find Full Text PDFAn application of a charge of the substituent active region concept to 1-Y,4-X-disubstituted derivatives of bicyclo[2.2.2]octane (BCO) [where Y = NO, COOH, OH, and NH and X = NMe, NH, OH, OMe, Me, H, F, Cl, CF, CN, CHO, COMe, CONH, COOH, NO, and NO] provides a quantitative information on the inductive component of the substituent effect (SE).
View Article and Find Full Text PDFAn application of quantum chemical modeling allowed us to investigate a substituent effect on a σ and π electron structure of a ring and the nitro group in a series of meta- and para-X-substituted nitrobenzene derivatives (X = NMe, NHMe, NH, OH, OMe, Me, H, F, Cl, CF, CN, CHO, COMe, CONH, COOH, NO, and NO). The obtained pEDA and sEDA parameters (the π- and σ-electron structure characteristics of a given planar fragment of the system obtained by the summation of π- and σ-orbital occupancies, respectively) of the NO group and the benzene ring allowed us to reveal the impact of the substituents on their mutual relations as well as to analyze them from the viewpoint of substituent characteristics. The decisive factor for dependence of pEDA on sEDA of the ring is electronegativity of the atom linking the substituent with the ring; in subgroups an increase of sEDA is associated with a decrease of pEDA.
View Article and Find Full Text PDFDespite the immense growth in interest in difluoroborate dyes, the nature of the interactions of the boron atom within the N-BF2 -O kernel is not yet fully understood. Herein, a set of real-space bonding indicators is used to quantify the electronic characteristics of the dative N-B bond in difluoroborate derivatives. The atoms-in-molecules (AIM) partitioning scheme is complemented by the electron localizability indicator (ELI-D) approach, and both were applied to experimental and theoretical electron-density distributions (X-ray constrained wavefunction fitting vs.
View Article and Find Full Text PDFAbstract: A series of novel 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles were efficiently synthesized by cyclocondensation of the appropriate 3-(pyridyl)acrylohydrazides with triethyl orthoesters in the presence of glacial acetic acid. The products were identified by means of spectroscopic methods and their p ionization constants were determined. The influence of substituents on the basicity of the pyridine system has been discussed.
View Article and Find Full Text PDFActa Crystallogr Sect E Struct Rep Online
December 2014
The title salt, 2C3H8N(+)·C2O4 (2-), crystallized with six independent allyl-ammonium cations and three independent oxalate dianions in the asymmetric unit. One of the oxalate dianions is nearly planar [dihedral angle between CO2 planes = 1.91 (19)°], while the other two are twisted with angles of 11.
View Article and Find Full Text PDFActa Crystallogr Sect E Struct Rep Online
December 2014
In the title compound, the de-hydro-dipeptide (Boc-Phe-ΔAla-OiPr, C20H28N2O5), the mol-ecule has a trans conformation of the N-methyl-amide group. The geometry of the de-hydro-alanine moiety is to some extent different from those usually found in simple peptides, indicating conjugation between the H2C=C group and the peptide bond. The bond angles around de-hydro-alanine have unusually high values due to the steric hindrance, the same inter-action influencing the slight distortion from planarity of the de-hydro-alanine.
View Article and Find Full Text PDFActa Crystallogr Sect E Struct Rep Online
December 2014
The title compound, C11H17BrN2O5, is a de-hydro-amino acid with a C=C bond between the α- and β-C atoms. The amino acid residues are linked trans to each other and there are no strong intra-molecular hydrogen bonds. The torsion angles indicate a non-helical conformation of the mol-ecule.
View Article and Find Full Text PDFActa Crystallogr Sect E Struct Rep Online
November 2014
In the title hydrated mol-ecular salt, C4H12N(+)·C2HO4 (-)·0.5H2O, the O atom of the water mol-ecule lies on a crystallographic twofold axis. The dihedral angle between the CO2 and CO2H planes of the anion is 18.
View Article and Find Full Text PDFActa Crystallogr Sect E Struct Rep Online
September 2014
The asymmetric unit of the title compound, C2H8N(+)·C4H5O4 (-), consists of two allyl-ammonium cations and two hydrogen succinate anions (Z' = 2). One of the cations has a near-perfect syn-periplanar (cis) conformation with an N-C-C-C torsion angle of 0.4 (3)°, while the other is characterized by a gauche conformation and a torsion angle of 102.
View Article and Find Full Text PDFActa Crystallogr C Struct Chem
October 2014
The crystal structure of 9H-carbazole, C12H9N, (I), has been redetermined at low temperature for use as a reference structure in a comparative study with the structures of 1-nitro-9H-carbazole, C12H8N2O2, (II), and 9-nitrocarbazole, C12H8N2O2, (III). The molecule of (I) has crystallographically imposed mirror symmetry (Z' = 0.5).
View Article and Find Full Text PDFIn the title hydrated mol-ecular salt, C3H8N(+)·C2HO4 (-)·0.5H2O, the water O atom lies on a crystallographic twofold axis. The C=C-C-N torsion angle in the cation is 2.
View Article and Find Full Text PDFThe partitioning of space with Hirshfeld surfaces enables the analysis of fingerprint molecular interactions in crystalline environments. This study uses the decomposition of the crystal contact surface between pairs of interacting chemical species to derive an enrichment ratio. This quantity enables the analysis of the propensity of chemical species to form intermolecular interactions with themselves and other species.
View Article and Find Full Text PDFThe crystal and molecular structures of two para-substituted azobenzenes with π-electron-donating -NEt2 and π-electron-withdrawing -COOEt groups are reported, along with the effects of the substituents on the aromaticity of the benzene ring. The deformation of the aromatic ring around the -NEt2 group in N,N,N',N'-tetraethyl-4,4'-(diazenediyl)dianiline, C20H28N4, (I), may be caused by steric hindrance and the π-electron-donating effects of the amine group. In this structure, one of the amine N atoms demonstrates clear sp(2)-hybridization and the other is slightly shifted from the plane of the surrounding atoms.
View Article and Find Full Text PDFActa Crystallogr Sect E Struct Rep Online
October 2013
In the asymmetric part of the unit cell of the title compound, C16H14N2O4, there are two chemically equivalent but crystallographic independent half mol-ecules. The geometric centre of each complete mol-ecule lies on a crystallographic inversion centre. Both mol-ecules are almost planar [mean deviations of atoms in the two molecules are 0.
View Article and Find Full Text PDFStructures of selected 3,6-dihalogeno-N-alkyl carbazole derivatives were calculated at the B3LYP/6-311++G(3df,2pd) level of theory, and their (13) C nuclear magnetic resonance (NMR) isotropic shieldings were predicted using density functional theory (DFT). The model compounds contained 9H, N-methyl and N-ethyl derivatives. The relativistic effect of Br and I atoms on nuclear shieldings was modeled using the spin-orbit zeroth-order regular approximation (ZORA) method.
View Article and Find Full Text PDFThe central V(V) atom in the title mononuclear oxovanadium complex, [VO(C(23)H(20)N(2)O(4))(CH(3)OH)]·H(2)O, has a distorted octahedral coordination. Two N atoms and two O atoms of the Schiff base define the base of the bipyramid and two O atoms are in the apical positions, one from vanadyl and the second from methanol. Density functional theory (DFT) calculations were performed for the title complex and its ligand to compare their geometry in the solid and gas phases.
View Article and Find Full Text PDFThe title compound, C(15)H(11)N(3)O, (I), was obtained by the air oxidation of 3,5-diphenyl-4,5-dihydro-1,2,4-triazin-6(1H)-one. In the crystal structure, (I) forms centrosymmetric hydrogen-bonded dimers through pairs of N-H..
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