Noticeable characteristics of conventional and nonconventional hydrogen bonds in the binary systems of chalcogenoaldehyde and chalcogenocarboxylic acid derivatives.

Forty-eight stable structures of complexes formed between XCHZ and RCZOH (with X = H, F; R = H, F, Cl, Br, CH, NH; Z = O, S, Se, Te) were comprehensively investigated. It was found that the HZ-RZ complexes were more stable than the FZ-RZ ones, and their stability tendency decreased in the following order of Z: O > S > Se > Te. A predominant role of the electrostatic component was observed in XO-RO, while an outstanding contribution of the induction term was estimated in XS-RS, XSe-RSe, and XTe-RTe.

Vietnamese sixth graders' mathematical communication competency developed by teaching fraction topics using the 5E model.

The 5E, an exploratory instructional model with growing popularity in current learner-centered educational practices, aims to develop learners' competencies. The study aims to evaluate the effectiveness of teaching fractions using the 5E instructional model to develop students' mathematical communication competency (MCC). The researchers used mixed methods with data triangulation in a 38-student experiment group (EG) who learned with the 5E model and a 41-student control group (CG) using traditional learning approaches to clarify the impact of the 5E model on the development of MCC, academic performance and learning attitude among learners.

Profound importance of the conventional O-H⋯O hydrogen bond a considerable blue shift of the C-H bond in complexes of substituted carbonyls and carboxyls.

Using quantum chemical approaches, we investigated the conventional O-H⋯O and nonconventional C-H⋯O hydrogen bonds between carboxylic acids and aldehydes in 21 stable complexes. The strength of complexes is determined by the conventional O-H⋯O bond together with the nonconventional C-H⋯O hydrogen bond, in which the former one is 4-5 times as strong as the latter one. Proportional linear correlations of the interaction energy with both individual energies of the O-H⋯O and C-H⋯O hydrogen bonds are proposed.

Theoretical insights into the adsorption and gas sensing performance of Fe/Cu-adsorbed graphene.

The binding mechanism of gas molecules on material surfaces is essential for understanding adsorption and sensing performance. In the present study, we examine the interaction of some volatile organic compounds (VOCs), including HCHO, CHOH, and CHCOCH, on pristine graphene and its Fe/Cu-adsorbed surfaces using first-principles calculations. The results indicate that the adsorption of these molecules on graphene is regarded as physisorption, while chemisorption is observed for Fe/Cu attached surfaces.

Characteristics of nonconventional hydrogen bonds and stability of dimers of chalcogenoaldehyde derivatives: a noticeable role of oxygen compared to other chalcogens.

In this work, twenty-four stable dimers of RCHZ with R = H, F, Cl, Br, CH or NH and Z = O, S, Se or Te were determined. It was found that the stability of most dimers is primarily contributed by the electrostatic force, except for the dominant role of the induction term in those involving a Te atom, which has been rarely observed. Both electron-donating and -withdrawing groups in substituted formaldehyde cause an increase in the strength of nonconventional C-H⋯Z hydrogen bonds, as well as the dimers, in which the electron donating effect plays a more crucial role.

Revisiting conventional noncovalent interactions towards a complete understanding: from tetrel to pnicogen, chalcogen, and halogen bond.

Typical noncovalent interactions, including tetrel (TtB), pnicogen (PniB), chalcogen (ChalB), and halogen bonds (HalB), were systematically re-investigated by modeling the N⋯Z interactions (Z = Si, P, S, Cl) between NH - as a nucleophilic, and SiF, PF, SF and ClF - as electrophilic components, employing highly reliable methods. The characteristics of N⋯Z interactions when Z goes from Si to Cl, were examined through their changes in stability, vibrational spectroscopy, electron density, and natural orbital analyses. The binding energies of these complexes at CCSD(T)/CBS indicate that NH tends to hold tightly most with ClF (-34.

Synchronous rectal adenocarcinoma and intestinal mantle cell lymphoma: A case report.

Background: Mantle cell lymphoma (MCL) of the gastrointestinal tract is a rare malignancy, accounting for about 0.2% of malignant colorectal tumors. MCL synchronous with rectal adenocarcinoma is extremely rare.

Role of O-H⋯O/S conventional hydrogen bonds in considerable C -H blue-shift in the binary systems of acetaldehyde and thioacetaldehyde with substituted carboxylic and thiocarboxylic acids.

Stable binary complexes of RCZOH⋯CHCHZ (R = CH, H, F; Z = O, S) are due to contributions from the O-H⋯O/S and C -H⋯O/S hydrogen bonds. The strength of C /O-H⋯O is 1.5 to 2 times greater than that of the C /O-H⋯S bond.

Experimental and theoretical studies on the synthesis of 1,4,5-trisubstituted pyrrolidine-2,3-diones.

Substituted 4-acetyl-3-hydroxy-3-pyrroline-2-ones have been prepared via three-component reactions and the tautomerism of these 3-pyrroline-2-ones is due to the slight difference of energy, and the significantly large rate constant of transformation between two tautomers. 1,4,5-Trisubstituted pyrrolidine-2,3-dione derivatives were prepared from the above mentioned 2-pyrrolidinone derivatives and aliphatic amines, which exist in enamine form and are stabilized by an intramolecular hydrogen bond. A possible reaction mechanism between 3-pyrroline-2-one and aliphatic amine (CHNH) was proposed based on computational results and the main product is formed favorably following the PES via the lowest Δ pathway in both the gas-phase and an ethanol solvent model.

Importance of water and intramolecular interaction governs substantial blue shift of C -H stretching frequency in complexes between chalcogenoaldehydes and water.

Geometrical structure, stability and cooperativity, and contribution of hydrogen bonds to the stability of complexes between chalcogenoaldehydes and water were thoroughly investigated using quantum chemical methods. The stability of the complexes increases significantly when one or more HO molecules are added to the binary system, whereas it decreases sharply going from O to S, Se, or Te substitution. The O-H⋯O H-bond is twice as stable as C -H⋯O and O-H⋯S/Se/Te H-bonds.

Theoretical Aspects of Nonconventional Hydrogen Bonds in the Complexes of Aldehydes and Hydrogen Chalcogenides.

Hydrogen bonds (H-bonds) in the complexes between aldehydes and hydrogen chalcogenides, XCHO...

Indicuen, a new hopane from Hale growing in Vietnam.

One new hopane-type triterpene, indicuen (), along with eight known compounds () were isolated from the -hexane extract of the lichen Hale. The chemical structures of isolated compounds were identified by interpretation of their spectroscopic data (1D, 2D NMR and HRESIMS) combined with DFT-NMR chemical shift calculations and subsequent assignment of DP4+ probabilities and by comparison with the literature. Indicuen represents for a rare hopane bearing a 1-carboxyethyl substituent at C-21 in lichens.

SERS Chemical Enhancement of 2,4,5-Trichlorophenoxyacetic Acid Adsorbed on Silver Substrate.

Surface-enhanced Raman spectroscopy (SERS) was employed to gain an understanding of the chemical enhancement mechanism of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), an Agent Orange, adsorbed on a silver substrate surface. Experimental measurements were performed using a micro-Raman spectrophotometer with an excitation wavelength of 532 nm and successfully detected 2,4,5-T at a relatively low concentration of 0.4 nM.

Pandemic Risk Management for Public Health Care Schemes.

The coronavirus disease 2019 (COVID-19) caused by a novel coronavirus, severe acute respiratory syndrome coronavirus 2, has caused a large death, a range of serious health problems, and significant economic costs in many countries around the world. This study analyzes statistical characteristics of pandemic disasters using historical records since the Middle Ages. Compared to literature which studies the effect of the COVID- 19 pandemic on the financial market, this paper attempts to find two financial instruments in the financial market to hedge pandemic risks.

Nervione, a new benzofuran derivative from .

A new benzofuran derivative, nervione (), was isolated from (Blume) Schltr. (Orchidaceae). Eight previously reported compounds were also isolated: 5,7-dimethoxyflavone (2), 3,5,7-trimethoxyflavone (3), 7-methoxyflavone (4), 3,7-dimethoxy-5-hydroxyflavone (5), tetramethylscutellarein (4',5,6,7-tetramethoxyflavone) (6), 5,7-dimethoxy-4'-hydroxyflavone (7), rhamnetin (8), and 5,7-dihydroxy-3',4'-dimethoxyflavone (9).

A new 26-norlanostane from growing in Vietnam.

Chemical investigation on chloroform extract of led to the isolation of one new compound namely turgidol, together with five known triterpenoids, lupeol, lupenone, betulin, betulinic acid, and taraxerol. Their structures and stereochemistry have been determined by 1 D and 2 D NMR analysis, high resolution mass spectrometry, and compared with those in literatures. The relative configuration of turgidol was defined using DFT-NMR chemical shift calculations and subsequent DP4+ probability method.

Manilkzapotane, a novel dimeric alkylresorcinol derivative from the stem bark of .

A novel dimeric alkylresorcinol derivative, manilkzapotane (), along with seven known compounds, lupeol acetate (), lupeol (), arjunolic acid (), ergosterol peroxide (), taraxerol (), hederagonic acid (), and glochidiol () were isolated from the stem bark of . Their structures were determined on the basis of spectroscopic data. DFT-NMR chemical shift calculations and a modified probability (DP4+) method were applied to define the relative configuration of .

Rukamtenol, a new spiro compound isolated from Zoll. & Moritzi growing in Vietnam.

Chemical investigation of chloroform extract of Zoll. & Moritzi stems led to the isolation of one new compound namely rukamtenol together with four known compounds, viz., chaulmooric acid, flacourtin, 3,4,5-trimethoxyphenyl -D-glucopyranoside, and daucosterol.

Ricicomin A, a new alkaloid from the leaves of Linn.

From the leaves of Linn., one new alkaloid, named ricicomin A () together with three known ones, ricinine (), -demethylricinine () and 4-[2-formyl-5-(methoxymethyl)-1H-pyrrol-1-yl]butanoic acid () were justified by repeated chromatographic methods. Their structures were determined by comprehensive IR, HR-ESI-MS and NMR analyses.

In-Depth Investigation of a Donor-Acceptor Interaction on the Heavy-Group-14@Group-13-Diyls in Transition-Metal Tetrylone Complexes: Structure, Bonding, and Property.

Stabilization for tetrylone complexes, which carry ylidone(0) ligands [(CO)W-X (YCp*)] (X = Ge, Sn, Pb; Y = B-Tl), has become an active theoretical research because of their promising application. Structure, bonding, and quantum properties of the transition-metal donor-acceptor complexes were theoretically investigated at the level of theory BP86 with several types of basis sets including SVP, TZVPP, and TZ2P+. The optimized structures reveal that all ligands X (YCp*) are strongly bonded in tilted modes to the metal fragment W(CO), and Cp* rings are mainly η-bonded to atom X.

A density functional theory study on silver and bis-silver complexes with lighter tetrylene: are silver and bis-silver carbenes candidates for SARS-CoV-2 inhibition? Insight from molecular docking simulation.

Ribavirin and remdesivir have been preclinically reported as potential drugs for the treatment of SARS-CoV-2 infection, while light silver tetrylene complexes (NHE-AgCl and (NHE-AgCl) with E = C, Si, and Ge) have gained significant interest due to their promising applicability on the cytological scale. Firstly, the structures and bonding states of silver-tetrylene complexes (NHE-Ag) and bis-silver-tetrylene complexes (NHE-Ag-bis) were investigated using density functional theory (DFT) at the BP86 level with the def2-SVP and def2-TZVPP basis sets. Secondly, the inhibitory capabilities of the carbene complexes (NHC-Ag and NHC-Ag-bis) and the two potential drugs (ribavirin and remdesivir) on human-protein ACE2 and SARS-CoV-2 protease PDB6LU7 were evaluated using molecular docking simulation.

Correction to Investigation into SARS-CoV-2 Resistance of Compounds in Garlic Essential Oil.

[This corrects the article DOI: 10.1021/acsomega.0c00772.

A new diterpenoid from the leaves of .

A new diterpenoid, phyllane C (), along with three known compounds, ovoideal E (), spruceanol (), and fluacinoid B () were isolated from the leaves of growing in Thailand. The structures were determined by analysis of their MS and NMR data as well as by comparison with literature values. DFT-NMR chemical shift calculations and subsequent DP4/DP4+ probability methods were applied to define the relative configuration of .

Dataset of ex-pat teachers in Southeast Asia's intention to leave due to the COVID-19 pandemic.

The COVID-19 pandemic exerted an adverse influence on the global education system, especially since starting school lockdown. The growth of teacher unemployment figures climbed double-digit and spawned these unexpected sequels. For instance, while native teachers seemed indisposed to leave the profession with the aim of seeking another more profited and seasonal jobs, many ex-pat teachers presented themselves with moving or stayed dilemma in the way the government salvaged their situation.

Growth Pattern, Stability, and Properties of Complexes of CHOH and CO ( = 1-5) Molecules: A Theoretical Study.

This work is dedicated to theoretically investigate the formation process of CHOH···CO ( = 1-5) complexes and to shed light on the nature of interactions formed under the variation of CO concentration. It is found that CO molecules tend to locate around the polarized -OH group to interact with the lone pairs of the O atom. The interaction of ethanol with three CO molecules (CHOH···3CO) induces the most stable structure in the sequence considered.