NH Groups Research Articles

Mitigating Defect States of All‐Inorganic CsPbI2Br Perovskite via Multifunctional 2‐Amino‐5‐Nitrothiazole Additive for an Efficient Air‐Processed Outdoor/Indoor Photovoltaics

All‐inorganic CsPbI2Br mixed halide perovskites show promise as wide‐bandgap photoabsorbers in photovoltaics. However, the rapid crystal growth observed in solution‐processed CsPbI2Br often leads to morphologies plagued by pinholes and defects, which limit device performance. This study introduces 2‐Amino‐5‐nitrothiazole (ANT), an innovative precursor additive, to enhance film quality. ANT's selective interactions with the perovskite precursor moderate the crystal growth, resulting in a dense, flawless CsPbI2Br film characterized by superior crystallinity and coverage. Furthermore, the NH2 group in ANT coordinates with Pb octahedra, effectively mitigating charge defects through NHI/Br bonds. Simultaneously, SCN sites interact with uncoordinated Pb2+ ions, reducing defect states and nonradiative recombination. This innovation achieves an impressive device efficiency of 17.13% with a fill factor (FF) of 83.41%, surpassing the control's efficiency of 15.21% (FF of 80.45%). Notably, the champion device maintains an efficiency of 29.47% under indoor light‐emitting diode lighting at 1000 lux. Additionally, the optimized perovskite solar cell demonstrates remarkable stability, retaining ≈90% of its efficiency for over 720 h at 85 °C in air, even without encapsulation.

Experimental and computational study on removal of nitric oxide using NH2-MIL-125: Revisiting removal mechanism

The NH2-MIL-125 (NM-125) or modified NM-125 materials are used for photocatalytic removal of nitric oxide (NO). Most researchers attributed few NO2 emission during NO photocatalysis to high selectivity towards the formation of nitrate ions due to the neglect of the principle of electroneutrality and pore structure of NM-125. This may cause misleading photocatalytic mechanism of NO removal. Herein, this work proposes a new mechanism behind NO removal using NM-125 based on experimental investigations and theoretical calculations. First, experimentally, the highest NO removal efficiency of 88.54 % with negligible NO2 emission occurs at the anhydrous condition. In addition, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements verify the presence and accumulation of NO2 as product during photocatalytic conversion of NO. Furthermore, density functional theory (DFT) calculations and grand canonical Monte Carlo (GCMC) computations demonstrate that there exist strong interactions between NO2 and -NH2 group within pores. Few NO2 is detected during experiments is probably due to its subsequent adsorption in the pores of NM-125. The new NO removal mechanism including photocatalytic conversion NO into NO2 and subsequent NO2 adsorption in the pores of NM-125 is thus proposed. This work provides a deeper insight into photocatalytic NO removal over NM-125 and its variants.

Influence of occlusal reduction design on the fracture resistance and biomechanical behavior of endocrowns restoring maxillary premolars

PurposeTo investigate the effect of different occlusal reduction design on stress distribution and fracture resistance of different endocrown systems.Material and methodsSixty-four maxillary human premolars with endodontic treatment, prepared for endocrowns were divided into 2 groups (n = 32) according to the occlusal design: Butt joint preparation (B group) and Anatomical preparation (A group). Each group were subdivided into four groups according to ceramic systems: IPS E max CAD (EM group), monolithic zirconia (ZR group), Nacera Hyprid (NH group) and PEKKTON (PE group). After manufacturing of endocrowns and adhesive bonding the specimens were thermomechanically loaded and subsequently they were tested in a universal testing machine for evaluating the fracture resistance. The specimens failure mode was qualitatively assessed. The stress distribution in each group was assessed using three-dimensional finite element analysis (FEA). 1-way ANOVA and the Post Hoc Tukey HSD test were used to evaluate the data (a = .05).ResultsThe fracture resistance values between the groups showed statistically significant variations. The B PE and A PE groups had a higher ratio of fracture resistance values. Regarding failure mode, ceramic endocrowns recorded mainly irreparable failures. FEA showed that anatomical occlusal preparation have reduced the stress concentration under all endocrown systems.ConclusionEndocrowns could be used to restore endodontically treated maxillary premolars. PEKKTON endocrowns with anatomical preparations revealed most appropriate restoration. The tested new endocrown systems enhanced the biomechanical performance of the tooth.Clinical significanceThe innovative endocrown systems (PEKK, Nacera Hyprid) can be seen as a promising choice for restoration of severely-destructed endodontic treated premolars, with less stress transmit to the residual tooth structure. Although the traditional endocrown technology might increase the longevity of tooth bonding, it shouldn’t be used for clenching cases since the risk of failure is too great overall.

Cu-Catalyzed Tandem C-N and C-C Bond Formation Leading to 4(1H)-Quinolones: A Scaffold with Diverse Biological Properties from Totally New Raw Materials in a Single Step.

A novel Cu-catalyzed tandem C-N and C-C bond-formation reaction has been developed to furnish 2-substituted-4-(1H)-quinolones. 4-(1H)-quinolones play an important role in medicinal chemistry. Many 2-aryl(alkyl)-4(1H)-quinolones are found to exhibit diverse biological properties. While traditional methods have inherent issues [like starting materials with incompatible functional groups (NH2 and keto groups)], many modern methods either require activated starting materials (like Ynones) or employ expensive metals (Pd, Rh, Au, etc.) involving carbonylation using CO or metal complexes. Our protocol presents an environmentally friendly one-step method for the construction of these useful 2-substituted-4-(1H)-quinolones from easily available aryl boronic acid (or pinacolate ester) and nitriles as new raw materials, using a cheap Cu-catalyst and O2 (air) as a green oxidant. We further extended its application to the synthesis of various natural products, including the first formal total synthesis of punarnavine. A plausible mechanism involving an aryl nitrilium ion (formed due to the intermolecular C-N bond-forming coupling between aryl boron species and the nitrile group) followed by tandem intramolecular C-C bond formation has been proposed.

Low‐temperature bonding of glasses: The role of plasma‐engrafted surface amino groups

AbstractLow‐temperature (<∼200°C) bonding of glasses is a key technology for utilizing them for microfluidics, optical applications, and microelectromechanical systems. In the present study, bonding strength of SiO2 glasses was examined for those after several surface treatment methods. As a result, it was found that two‐step (H2O→ NH3) plasma treatment remarkably strengthened the bonding strength (>1 J/m2) at the annealing temperature of 150°C. The improvement was achieved even when only one side of the bonded surfaces was plasma‐treated. X‐ray photoelectron spectroscopy revealed that the two‐step plasma treatment generated Si–NH2 groups on the topmost surface. Upon the annealing (<200°C), the engrafted Si–NH2 was desorbed from the bonded interface, indicating that the Si–NH2 effectively reacted with Si–OH on the other side to form Si–O–Si covalent bonds. This study contributes to understanding of the role of surface functional groups for bonding reaction. Furthermore, the method proposed here would be promising as a production technology because it enables glass bonding at lower temperatures with a simple plasma system.

Postoperative radiotherapy following null-margin hepatectomy in patients with hepatocellular carcinoma adhering to the major vessels: A propensity score-matched survival analysis cohort study

Background & AimsThis study aims to analyze the prognosis of null-margin (≤1.0 mm) hepatectomy (NH) in patients with hepatocellular carcinoma (HCC) adhering to the major vessels and explore the value of postoperative radiotherapy (RT) in these patients. MethodsHCC patients who underwent null-margin or wide-margin (≥1.0 cm) hepatectomy (WH) by our team from January 2008 to March 2016 were recruited and analyzed retrospectively. The patients were divided into the NH, NH + RT, and WH groups. Propensity score matching (PSM) was performed to balance baseline characteristics. ResultsA total of 357 patients were recruited. Of these, 84, 49, and 224 patients were given NH alone, NH plus RT, and WH, respectively. After PSM, the 5-year overall survival (OS) and disease-free survival (DFS) rates of the NH group were significantly worse than those of the WH group (51.5 % vs. 71.4 %, P = 0.003; 32.2 % vs. 50.9 %, P = 0.005). The OS and DFS rates of the NH + RT group were significantly higher than those of the NH group (75.6 % vs. 56.1 %, P = 0.012; 46.6 % vs. 30.2 %, P = 0.015) and similar to those of the WH group (75.6 % vs. 75.1 %, P = 0.354; 46.6 % vs. 56.6 %, P = 0.717). In addition, patients in the NH + RT group experienced significantly lower early (P = 0.023) and intrahepatic (P = 0.015) recurrences than those in the NH group. ConclusionsPatients with HCC adhering to the major vessels who underwent NH alone had a poorer prognosis, and the addition of RT to NH provide a significant survival benefit for these patients, which may yield outcomes comparable to the efficacy of WH.

More Electropositive is More Electronegative: Atom Size Determines C=X Group Electronegativity.

Opposite to what one might expect, we find that the C=X group can become effectively more, not less, electronegative when the Pauling electronegativity of atom X decreases down Groups 16, 15, and 14 of the Periodic Table. Our quantum-chemical analyses, show that, and why, this phenomenon is a direct consequence of the increasing size of atom X down a group. These findings can be applied to tuning and improving the hydrogen-bond donor strength of amides H2 NC(=X)R by increasingly withdrawing density from the NH2 group. A striking example is that H2 NC(=SiR2 )R is a stronger hydrogen-bond donor than H2 NC(=CR2 )R.

Sensing of hyperprolinemia biomarker and its recognition in biological sample through “turn-on” event by Zn-based metal-organic framework

A hydrogen bonded ability metal organic framework (MOF, 1Zn) is used for the ultra-sensitive “turn-on” detection of hyperprolinemia biomarker with ultrafast (within 5 s) colorimetric response making the first MOF based hyperprolinemia biomarker sensor. The detection limit (4.46 ppb) is outperformed compared to all contemporary hyperprolinemia biomarker based sensors. Further, the sensor showed the recognition of biomarker in biological sample (human saliva). The detection of biomarker is also realized through colorimetric response (solution based and paper strip method). The mechanism of sensing is established through the electron transfer and the absorption caused emission (ACE). Moreover, the theoretical study is performed to support the sensing mechanism. The control titration of 1Zn suggest that the free –NH2 group of linker in 1Zn is involved in supramolecular interaction (hydrogen bonding) with the carboxylic group present on biomarker results the facile occurrence of electron transfer and ACE. Consequently, the luminescence “turn-on” effect of 1Zn for hyperprolinemia biomarker is observed.

Pressure-induced luminescence evolution of 3,3′-diamino-4,4′-azofurazan: Role of restricting chemical bond vibration and conformational modification

The luminescence and electronic structure of 3,3′-Diamino-4,4′-azofurazan (DAAzF) were studied under high pressure conditions through experimental and calculation approaches. The transition of π* → π was primarily responsible for DAAzF's broad light emission. Upon applying pressure to DAAzF, high-pressure-stiffened hydrogen-bond interactions enable the restriction of the stretching vibration of NH2 group. The reduced energy loss through nonradiative rotational relaxation and molecular motions lead to a ∼20 times luminescent enhancement of DAAzF from 1 atm to 8.9 GPa. With the further strengthening of interlayer hydrogen bond interactions at higher pressure, the deviation of hydrogen atoms in amino groups from the molecular plane lessens the radiation transition efficiency. In addition, the bending of the C–C–N=N bond further leads to molecular conformation changes at approximately 20.7 GPa, which induces an abrupt redshift and moderate quenching of the luminescence. Furthermore, the band gap of DAAzF is significantly influenced by pressure. As the color undergoes a transition from yellow to red, and becomes darker as the pressure increases, the absorption edge shifted towards red. At 3.4, 9, and 21 GPa, three conformational variations were identified in conjunction with electronic structural alterations.

Mutual influence of non-covalent interactions formed by imidazole: A systematic quantum-chemical study.

Imidazole is a five-membered heterocycle that is part of a number of biologically important molecules such as the amino acid histidine and the hormone histamine. Imidazole has a unique ability to participate in a variety of non-covalent interactions involving the NH group, the pyridine-like nitrogen atom or the π-system. For many biologically active compounds containing the imidazole moiety, its participation in formation of hydrogen bond NH⋯O/N and following proton transfer is the key step of mechanism of their action. In this work a systematic study of the mutual influence of various paired combinations of non-covalent interactions (e.g., hydrogen bonds and π-interactions) involving the imidazole moiety was performed by means of quantum chemistry (PW6B95-GD3/def2-QZVPD) for a series of model systems constructed based on analysis of available x-ray data. It is shown that for considered complexes formation of additional non-covalent interactions can only enhance the proton-donating ability of imidazole. At the same time, its proton-accepting ability can be both enhanced and weakened, depending on what additional interactions are added to a given system. The mutual influence of non-covalent interactions involving imidazole can be classified as weak geometric and strong energetic cooperativity-a small change in the length of non-covalent interaction formed by imidazole can strongly influence its strength. The latter can be used to develop methods for controlling the rate and selectivity of chemical reactions involving the imidazole fragment in larger systems. It is shown that the strong mutual influence of non-covalent interactions involving imidazole is due to the unique ability of the imidazole ring to effectively redistribute electron density in non-covalently bound systems with its participation.

Preparation of Anderson-type CoMo6-2NH2@ECOF for highly active catalysis on aerobic oxidative desulfurization of fuel under O2

Deep desulfurization with high-efficiency is imperia for environmental demands with increasing stringent standard of sulfur content in fuels. To develop high efficiency heterogeneous catalyst for aerobic oxidative desulfurization (AODS) of fuel, an Anderson-type CoMo6-2NH2 (POM) as active site, which was considered to be very effective in catalyzing the activation of O2, was successfully anchored on the sub-stoichiometric ECOF as a carrier by Schiff-base condensation reaction between –NH2 groups in CoMo6-2NH2 and –CHO groups in ECOF. The anchoring of CoMo6-2NH2 on ECOF by covalent bond resulted in the heterogenization of CoMo6-2NH2 enabled CoMo6-2NH2@ECOF to be recyclable during the AODS process. When CoMo6-2NH2@ECOF was applied as catalyst for AODS of fuel with surfactant (OTAC) under O2, it exhibited excellent catalytic activity with almost 100 % removal rates under 95 °C for 6 h. Moreover, the catalyst can be recycled 7 times without significant loss of catalytic activity. Further, the structure-activity relationship was investigated and the reaction mechanism of AODS of fuel was verified by ESR, XPS analysis and selective quenching experiments.

Improving the Efficiency and Stability of MAPbI3 Perovskite Solar Cells by Dipeptide Molecules.

Passivating the electronic defects of metal halide perovskite is regarded as an effective way to improve the power conversion efficiency (PCE) of perovskite solar cells (PVSCs). Here, a series of dipeptide molecules with abundant ─C═O, ─O─ and ─NH functional groups as defects passivators for perovskite films are employed. These dipeptide molecules are utilized to treat the surface of prototype methyl ammonium lead iodide (MAPbI3) films and the corresponding PVSCs exhibit enhanced photovoltaic performance and ambient stability, which can be ascribed to: 1) the ─C═O and ─O─ can interact with the undercoordinated Pb2+ ions and the ─NH groups can form hydrogen bonds with the I- ions, passivating the defects in perovskite film and reducing charge recombination in PVSCs; 2) the long alkyl chain of dipeptide molecules increases the hydrophobicity of the perovskite surface and thus enhance the stability of PVSCs. The passivated MAPbI3-based PVSCs exhibit a champion PCE of 20.3% and retain 60% of the initial PCE after 1000h. It is believed that the defects passivation engineering using polypeptide moleculars can be applied in other perovskite compositions for high device efficiency and stability.

Ethylenediamine control of the solid-state supramolecular chemistry of zinc phthalocyanine

The two axially ligated H-shaped and T-shaped zinc phthalocyanine derivatives, ZnPc(EDA)ZnPc and ZnPc(EDA), were obtained directly by thermal reaction of ZnPc in ethylenediamine (EDA) solution. Both complexes, ZnPc(EDA)ZnPc and ZnPc(EDA), co-crystallize with the EDA and water molecules yielding good-quality single crystals [ZnPc(EDA)ZnPc][ZnPc(EDA)]2∙2EDA·6H2O − 1. The interaction of Zn center of ZnPc with the axial substituent containing lone electron pair on NH2 groups with zinc phthalocyanine in both zinc phthalocyanine derivatives, ZnPc(EDA)ZnPc and ZnPc(EDA), leads to a deviation of Zn from the centre of cavity by 0.442(3) and 0.514(3) Å in the T- and H-shaped molecules as well as causes, as expected, the deformation of the planar molecule ZnPc into a saucer-shape conformation. Thus, in both types of molecules the central Zn atom of ZnPc complexes with EDA molecule exhibits 4 + 1 coordination formed by the four isoindole nitrogen atoms of the Pc macrocycle at the equatorial position and the nitrogen atom of the amino group of the EDA molecule at the axial position. Supramolecular arrangement of the T-shaped and H-shaped ZnPc-derivatives in crystal is characterized by a reduction of π···π interactions and an improvement in inter-system crossing in relation to parent ZnPc, and is controlled by the NH∙∙∙O, NH∙∙∙N and OH∙∙∙O hydrogen bonds formed between the T- and H-shaped molecules and lattice EDA and water molecules, which results in increase its solubility and improved photophysical and photochemical properties. The aggregation behaviour of T- and H-shaped ZnPc derivatives building crystals 1 in solutions was investigated by UV–Vis spectroscopy. In order to support and verify the experimental results, the DFT and time-dependent (TD) DFT calculations were performed.

TATB thermal decomposition: Expanding the molecular profile with cryo‐focused pyrolysis GC‐MS

AbstractUnderstanding the molecular composition of high explosives during thermal decomposition is vital for predicting the sensitivity, safety, and performance of explosive materials. The thermal decomposition of 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) has been linked to the formation of furazans through a series of dehydration reactions of the NO2 and NH2 groups on the phenyl ring, along with breakdown into small molecules (≤120 amu). Molecular identification of compounds formed in this transformation of the furazans to light gases has been lacking. To address this, we have applied a pseudo‐confined sampling system in a cryo‐focused pyrolysis gas chromatography‐mass spectrometry (pyGC‐MS) system to molecularly identify these intermediates. By design, sublimation of TATB, which has complicated MS analyses of thermal degradation, was significantly reduced and additional compounds were identified with potential structural information. In addition to the known furazan compounds, one of these compounds forms from the loss of oxygen from benzo‐trifurazan (F3) and produces an open ring structure that may be the first step in the formation of lower molecular weight furazan breakdown products. The loss of a nitro group from benzo‐monofurazan (F1) was also discovered and implicates the formation of oxidizing NO2 gas in the thermal decomposition mechanism. These findings are vital for understanding the proper heat flow from energetic materials on a molecular level, necessary when measuring enthalpy and developing decomposition models based on kinetic parameters.

Leveraging phosphate group in Pd/PdO decorated nickel phosphate microflowers via pulsed laser for robust hydrogen production in hydrazine-assisted electrolyzer

By driving the electrooxidation of small molecules instead of relying on sluggish oxygen evolution reaction (OER), low-input voltage is obtained for overall water splitting (OWS) and hydrogen generation, requiring active electrocatalysts. Using single-step pulsed laser irradiation, strong metal-support interaction is achieved on Pd/PdO-decorated Ni3(PO4)2·8H2O (NiPh) microflowers, yielding an outstanding bifunctional electrocatalyst for hydrogen evolution (HER) and hydrazine oxidation (HzOR). When Pd/PdO-NiPh-3 serves as both anode and cathode in the OWS electrolyzer (OER||HER), a cell voltage of 2.098 V achieves 10 mA/cm2 in 1.0 M KOH. When evaluated in the hydrazine-coupled electrolyzer (HzOR||HER), Pd/PdO-NiPh-3 exhibits remarkable stability with a low cell voltage of 0.538 V in 0.5 M-N2H4/1.0 M-KOH, which is approximately 1.56 V lower than that of the traditional water electrolyzers. In Pd/PdO-NiPh, the empty 4s and 5s orbitals of Ni2+ and Pd, respectively, serve as two absorption sites. These sites facilitate chemisorption on the electrocatalyst surface by forming a two-electron dipolar bond between the lone-pair electrons of NH2 groups in N2H4 and Ni2+ as well as Pd. A feasible strategy for utilizing Pd/PdO-NiPh catalysts in developing direct N2H4 fuel cells is investigated in this work, enabling the simultaneous production of robust energy-saving H2 fuel and electricity.

Noble metal free double helix binuclear Cu(I) complex as catalyst for carboxylative cyclization of propargylamines with atmospheric carbon dioxide toward oxazolidinones synthesis under mild conditions

The application of economically abundant, renewable and C1-feedstock, carbon dioxide into organically important compounds is considered as the hot topic in modern aspects. In this prospective, a binuclear double helix copper (I) complex (1) was synthesized through insitu reaction between quinolone-2-carbaldehyde and succino-hydrazide with copper (II) nitrate hexahydrate. Single crystal X-ray analysis of complex 1, clearly explained that both tetra co-ordinated Cu(I) ions are in tetrahedral geometric environment, having suprmolecular network arrangement via weak interaction of H-bonding, π…π stacking and CH…π stacking. The complex 1 was found to be effectively active catalyst in carboxylative cyclization reaction of propargylic amines with carbon dioxide towards oxazolidinones synthesis under atmospheric pressure and mild reaction conditions. Due to the initiation of side reaction by –NH2 group of primary propargyliamines, which reduces the yield percentage of respective oxazolidinones as a result the carboxylative cyclization reaction of primary propargylic amines, was rarely developed. In this work both primary and secondary propargylamines smoothly undergoes through this catalytic reaction and produced high percentage of desired oxazolidinones product. Again neat condition for this catalytic reaction makes the methodology more environmentally benign and sustainable. The complex 1 showed luminescent property. Moreover DFT methods were utilized in order to explain the probable mechanistic pathway of carboxylative cyclization reaction.

Theoretical study on initial decomposition paths of energetic materials featuring RDX ring

AbstractThe molecular properties of RDX are affected by the introduction of different functional groups, and the decomposition process of these analogues is studied in this paper. DFT method is used to study the initial decomposition reaction paths of 30 high energy materials based RDX skeleton. In the nitro cleavage reaction, the energy barrier become relatively low by introducing CH(NO2)2 or C(NO2)3 groups on the C site of the six membered ring. In the ring opening reaction, the ring opening process is easier to proceed by introducing NH2 or NHNH2 groups on the C site of the six membered ring.

Long-term Favorable Efficacy of Regular and Repeated Hospitalizations with a Personalized Diet and Exercise Treatment for Steatotic Liver Disease.

Objective The long-term impact of personalized diet and exercise programs for steatotic liver disease (SLD) remains unclear. Materials The subjects of this retrospective cohort study included 104 consecutive Japanese patients with SLD. The long-term treatment efficacy of personalized diet and exercise treatment was evaluated two years after the start of observation. Regular and repeated hospitalizations every 6 months (RRH group, n=23) indicated the 4 times of the number of hospitalizations, and irregular hospitalizations (IH group, n=56) showed the 1 to three times. The group without hospitalization was defined as the no hospitalization group (NH group, n=25). To balance confounding biases, the difference in treatment efficacy between the RRH and IH groups was evaluated using propensity score (PS)-matched analysis. A diet of 25 to 30 kcal/kg multiplied by ideal body weight (BW) daily, and aerobic and resistance exercise (exercise intensity of 4 to 5 metabolic equivalents daily, respectively) was performed for 6 days. Results At 2 years compared to baseline, the decrease rates of liver function tests, HbA1c, and physical findings in the RRH group were significantly higher than those in the NH or IH groups by multiple comparisons. According to the liver function tests and physical findings, the rate of decrease in the RRH group (17 cases) was significantly higher than that in the IH group (17 cases) using a PS-matched analysis. Conclusion The present study indicated the long-term favorable efficacy of personalized diet and exercise programs for SLD. In particular, this RRH program was effective in improving the findings of liver function tests and might help to sustain diet and exercise.

Хімічні властивості та характеристики поверхневої активності гумінової кислоти з бурого вугілля

The article is devoted to the study of some specific physicochemical properties of humic acids, which are attracting increasing attention due to their potential applications. The unique structural composition, which includes both hydrophilic and hydrophobic sites, makes these materials a versatile agent in various technological processes. It has been shown that humic acid solutions have the properties of surfactants and can serve as a natural alternative to surfactants. The paper presents the results of studies of a sample of humic acid obtained from lignite. Infrared spectroscopy has revealed signs of the aromatic structure of humic acid, the presence of phenolic and other functional groups, such as hydroxyl and nitrile. The presence of carboxylic acids, esters, and complex esters was established. The complex and heterogeneous nature of humic acids has been confirmed, which makes them promising for use as surfactants. No clear evidence of the presence of -NH₂ groups was found in the IR spectrum. This suggests that lignite humic acids generally correspond to the structural formula reported in the literature. The potentiometric titration of the lignite humic acid sample made it possible to determine the dissociation constants of functional groups. The obtained values are close to the calculated dissociation constants of carboxyl groups for the model molecule of lignite humic acid. The analysis of the calculated properties of humic acid based on various structural models showed that lignite is a promising raw material for the production of humic acids with certain surface-active properties. Compared to other structures, humic acid from lignite is more hydrophobic and less soluble in water, which indicates the prospects of its use as a surfactant with better interaction with the oil phase. Keywords: humic acids, lignite, surfactant, infrared spectroscopy, composition, functional groupsб structural model. Corresponding author: Bannikov L.P., e-mail: ukhinbannikov@gmail.com

Unveiling the chemical kinetics of aminomethanol (NH2CH2OH): insights into H and O2 photo-oxidation reactions and formamide dominance.

Aminomethanol is released into the atmosphere through various sources, including biomass burning. In this study, we have expounded the chemical kinetics of aminomethanol in the reaction pathways initiated by the hydroxyl radical ( H) with the aid of ab initio//density functional theory (DFT) i.e., coupled-cluster theory (CCSD(T))//hybrid-DFT (M06-2X/6-311++G (3df, 3pd). We have explored various possible directions of the H radical on aminomethanol, as well as the formation of distinct pre-reactive complexes. Our computational findings reveal that the H transfer necessitates activation energies ranging from 4.1 to 6.5kcal/mol from the -CH2 group, 3.5-6.5kcal/mol from the -NH2 group and 7-9.3kcal/mol from the -OH group of three rotational conformers. The H transfer from -CH2, -NH2 and -OH exhibits an estimated total rate constant (k OH) of approximately 1.97 × 10-11cm3 molecule-1s-1 at 300K. The branching fraction analysis indicates a pronounced dominance of C-centered NH2 HOH radicals with a favorability of 77%, surpassing the N-centered HCH2OH (20%) and O-centered NH2CH2 (3%) radicals. Moreover, our investigation delves into the oxidation of the prominently favored carbon-centered NH2 HOH radical through its interaction with atmospheric oxygen molecules. Intriguingly, our findings reveal that formamide (NH2CHO) emerges as the predominant product in the NH2 HOH + 3O2 reaction, eclipsing alternative outcomes such as amino formic acid (NH2COOH) and formimidic acid (HN = C(H)-OH). At atmospheric conditions pertinent to the troposphere, the branching fraction value for the formation of formamide is about 99%, coupled with a rate constant of 5.5 × 10-12cm3 molecule-1 s-1. Finally, we have scrutinized the detrimental impact of formamide on the atmosphere. Interaction of formamide with atmospheric hydroxyl radicals could give rise to the production of potentially perilous compounds such as HNCO. Further, unreacted HCH2OH radicals may initiate the formation of carcinogenic nitrosamines when reacting with trace N-oxides (namely, NO and NO2). This, in turn, escalates the environmental risk factors.