Methylamine Research Articles

Theoretical study of hydrogen abstraction by HO2 radicals from primary straight chain amines CnH2n+1-NH2 (n = 1-4).

Hydrogen abstraction reactions by HO2 radicals from four primary amines including methylamine (MA), ethylamine (EA), n-propylamine (PA), and n-butylamine (BA), are investigated and the effect of the functional group on rate constants at different reaction sites is examined. A hybrid functional BH&HLYP coupled with cc-pVTZ as the basis set is utilized to determine geometry optimizations, frequencies, and connections between transition states and corresponding local minima. By comparing the reaction energies obtained by several density functional theory methods to those obtained using the gold-standard CCSD(T)/CBS(T-Q) method, the M08-HX/maug-cc-pVTZ combination is identified as the best suitable method with a mean unsigned deviation of 0.81 kcal mol-1. This method is then applied to construct the potential energy surface for all the reaction systems. High-pressure limit rate constants at 500-2500 K are calculated through variation transition state theory and conventional transition state theory, including a one-dimensional hindered rotor treatment and asymmetrical Eckart tunneling correction. The branching ratio analysis suggests that the hydrogen abstraction at the C site adjacent to the NH2 functional group (α reaction site) dominates the reactions. Linear Bell-Evans-Polanyi and Bell-Evans correlations are observed for the hydrogen abstractions at the C reaction sites. Furthermore, a scheme to estimate the rate constants for the CnH2n+1-NH2 + HO2 reaction system is presented.

Photocatalytic System using Iron-Based Catalysts: Effect of External Ions on CO2-to-CO Conversion

Herein, we report four self-assembly Iron(II/III) complex consisting triethanolamine (TEOA) as ligand and an FeIII(TPA)Cl3 (TPA= 3-(2-pyridine methyl) amine) as contrast catalyst, for photochemical reduction of CO2 to CO under visible light. The photocatalytic systems were assembled by [Ru(bpy)3]Cl2 as photosensitizer, and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo-[d]-imidazole (BIH) as electron donor. Experiments are conducted to study the relationship between CO production and the external ions. Different external counterions are provided to assist the discussion of the influence of these external ions on catalysis. Density functional theory calculations confirmed that the external ions have an effect on the CO yield. Moreover, a mechanism involving proton-coupled electron transfer is proposed.

Base-promoted tandem synthesis of 2-azaaryl indoline.

A novel tandem method to synthesize 2-azaaryl indoline promoted by LiN(SiMe3)2 from 2-azaaryl methyl amine and 2-fluoro benzyl bromides was developed. Mechanistic investigation indicated that this tandem cyclization was initiated by selective benzyl C-SN2 substitution followed by an intramolecular SNAr reaction. Diverse 2-azaaryl indoles could also be obtained via simple functional transformations.

Visible‐Light‐Driven One‐Pot Synthesis of Benzimidazoles, Benzothiazoles, and Quinazolinones Catalyzed by Scalable and Reusable Ba‐Doped CoMoO4 Nanoparticles Under Air Atmosphere

AbstractHerein we report a simple and efficient oxidative coupling of various aryl methyl amines with diverse coupling partners, such as o‐phenylenediamine (benzene‐1,2‐diamine), 2‐aminobenzenethiol and 2‐aminobenzamide, to synthesize the corresponding heterocycles using scalable and reusable heterogeneous catalysts under visible light irradiation. A systematic investigation led to the synthesis of benzimidazoles, benzothiazoles and quinazolinones under air atmosphere in very good to excellent yields. The strategy is atom economical and found to be tolerance towards different functional groups, and wide range of substrate scope. Furthermore, the methodology was demonstrated for its suitability on scale up and reusability. The density functional theory (DFT) calculations and the analysis of band structures of pristine and Ba doped CoMoO4 systems showed that the doping of Ba in place of Co improved the catalytic performance of the system.

Treatment of methylamine containing wastewater using combined processes based on ultrasound

Methylamine (MA) degradation has been studied using different processes based on cavitation and oxidants such as hydrogen peroxide (H2O2), Fenton's reagent (H2O2/Fe2+), ozone (O3), and potassium persulfate (KPS, K2S2O8). Effects of different operating parameters such as treatment temperature, US power, pH of the solution, and oxidant loading on the extent of degradation have been studied. Acoustic power of 100 W with a frequency of 22 kHz and duty cycle of 70 % (7 s ON, 3 s OFF) were elucidated as the best treatment conditions for only ultrasound induced degradation (US). Amongst all the combined approaches, US+KPS scheme was the most efficient and economical treatment scheme for the highest removal of MA (97.3 %) within 2 h of treatment. The optimized US+KPS scheme at conditions of pH of 10, KPS loading of 0.5 g/L, and temperature of 30 °C was exploited for MA degradation at a pilot level using a longitudinal horn based sonoreactor at a capacity of 4 L, which resulted in 94 % of MA removal. Cavitational yield for longitudinal horn (1.23 × 10−3 mg/J) was almost 4 times higher than that seen in a simple US horn (0.33 × 10−3 mg/J) under similar conditions. Additionally, it was shown that a combined strategy based on cavitation and oxidants is preferred compared to an individual approach involving ultrasound or oxidants. Overall, the longitudinal horn reactor in combination with KPS was shown to be the most energy-efficient and economical treatment method, giving 94 % of degradation at an operating cost of 0.03 $/L.

Unraveling the mechanism of the supramolecular self-assembly during the in vivo metabolism of geniposide from Chinese medicine

Unraveling the detailed mechanism of Chinese medicine in curing diseases is of vital importance for the development of such long-standing traditional medicine. Here, we investigated the exposed form in vivo and bioactivity of Chinese medicine from an aspect of supramolecular chemistry. We demonstrated that the genipin (GP), an aglycone of geniposide (GE) transformed by β-glucosidase, can react with methylamine (MA), a harmful metabolite in the gut, to produce gardenia blue in vivo, which leads to a significant decrease of MA. The gardenia blue is supramolecular assemblies (SA), which can alleviate the interference with intestinal bacteria. Moreover, the formation mechanism of SA was revealed, in which genimethylamine reacted from GP and MA, was covalently polymerized into dimers and then non-covalently self-assembled into the SA. This study provides evidence that the supramolecular pigments can be formed in vivo during the metabolism of Chinese medicine through simultaneously covalent and non-covalent assembly, which may play key roles in their pharmacological activity.

Niobium Bis‐ and Mono(Pentafulvene) Complexes: E−H Bond Cleavage and Insertion Reactions (E=C, N, O)

AbstractBis(η5:η1‐(di‐para‐tolyl)pentafulvene)niobium chloride (1) reacts with methyl lithium via salt metathesis to the methylated bis(pentafulvene)niobium complex 2, and with lithium 2,6‐diisopropylanilide addition and subsequent N−H bond activation to the imido mono(pentafulvene)niobium complex 3. Avoiding the competing protonation of the chloride, bis(pentafulvene)niobium complex 2 reacts with primary aromatic and aliphatic amines to form terminal niobocene imido complexes, and with water to form the analog terminal oxo complex. Secondary methyl amines undergo a simultaneous N−H and C−H activation to form niobaaziridines under mild conditions. In contrast to other reported examples, 3 can be employed to investigate the uncontested reactivity of mono(pentafulvene)niobium complexes. Reaction with 4‐tert‐butylphenol selectively yields a niobocene phenolate complex. Unprecedented for mono(pentafulvene)niobium complexes, treating 3 with multiple‐bond‐containing substrates (nitriles, isocyanates) smoothly results the insertion into the Nb‐Cexo σ‐bond, forming the corresponding alkylidene amido and imidato complexes.

Divergent Sequential Reactions of β‐(2‐Aminophenyl)‐α,β‐ynones with Malonyl Chloride

AbstractA viable one‐pot synthesis of challenging 4H‐[3,4‐c]quinolone‐4,5(6H)‐diones by the reaction of β‐(2‐aminophenyl)‐α,β‐ynones with ethyl malonyl chloride is described. Their further elaboration in the presence of an excess of 40 % methyl amine aqueous solution in EtOH gives the benzo[c][2,7]naphthyridine‐4,5(3H,6H)‐diones of pharmacological interest in high yields. The product selectivity control of the divergent sequential condensation/C‐annulation/intramolecular transesterification vs condensation/O‐annulation/ring opening reactions of β‐(2‐aminophenyl)‐α,β‐ynones with malonyl chloride under metal free conditions has been addressed.

Cheminformatics analysis of chemicals that increase estrogen and progesterone synthesis for a breast cancer hazard assessment

Factors that increase estrogen or progesterone (P4) action are well-established as increasing breast cancer risk, and many first-line treatments to prevent breast cancer recurrence work by blocking estrogen synthesis or action. In previous work, using data from an in vitro steroidogenesis assay developed for the U.S. Environmental Protection Agency (EPA) ToxCast program, we identified 182 chemicals that increased estradiol (E2up) and 185 that increased progesterone (P4up) in human H295R adrenocortical carcinoma cells, an OECD validated assay for steroidogenesis. Chemicals known to induce mammary effects in vivo were very likely to increase E2 or P4 synthesis, further supporting the importance of these pathways for breast cancer. To identify additional chemical exposures that may increase breast cancer risk through E2 or P4 steroidogenesis, we developed a cheminformatics approach to identify structural features associated with these activities and to predict other E2 or P4 steroidogens from their chemical structures. First, we used molecular descriptors and physicochemical properties to cluster the 2,012 chemicals screened in the steroidogenesis assay using a self-organizing map (SOM). Structural features such as triazine, phenol, or more broadly benzene ramified with halide, amine or alcohol, are enriched for E2 or P4up chemicals. Among E2up chemicals, phenol and benzenone are found as significant substructures, along with nitrogen-containing biphenyls. For P4up chemicals, phenol and complex aromatic systems ramified with oxygen-based groups such as flavone or phenolphthalein are significant substructures. Chemicals that are active for both E2up and P4up are enriched with substructures such as dihydroxy phosphanedithione or are small chemicals that contain one benzene ramified with chlorine, alcohol, methyl or primary amine. These results are confirmed with a chemotype ToxPrint analysis. Then, we used machine learning and artificial intelligence algorithms to develop and validate predictive classification QSAR models for E2up and P4up chemicals. These models gave reasonable external prediction performances (balanced accuracy ~ 0.8 and Matthews Coefficient Correlation ~ 0.5) on an external validation. The QSAR models were enriched by adding a confidence score that considers the chemical applicability domain and a ToxPrint assessment of the chemical. This profiling and these models may be useful to direct future testing and risk assessments for chemicals related to breast cancer and other hormonally-mediated outcomes.

Photooxidation browning mechanism of small α-dicarbonyl compounds on natural mineral particle in the presence of methylamine/ammonia

The browning mechanism of glyoxal (GL)/methylglyoxal (MGL) with methylamine (MA) and ammonia (AM) on kaolinite (KAO, proxy of natural mineral particle) surface was investigated using density functional theory. Our results reveal that GL and MGL form mixture with KAO through hydrogen bonding. Notably, the browning reaction of GL and MGL is necessarily initiated by photooxidation. Browning products (imine and diimine) are subsequently formed via reaction of GL/MGL radical with MA/AM on KAO surface. Our results highlight the significant role of photooxidation in browning reaction of small α-dicarbonyl compounds on mineral surface, providing a new insight into Brown Carbon formation during dust storm.

Defect assisted Reactive Oxygen Species generation for photocatalytic degradation of methylene blue by nano-structured zinc oxide synthesized in CTAB medium

Herein, we report facile, room temperature synthesis of undoped zinc oxide semiconductor nanoparticles and their efficient photocatalytic property towards methylene blue dye degradation. Synthesis of zinc oxide nanoparticles was carried out by facile, eco-friendly and cost-effective, CTAB-assisted method using various aliphatic amines (methyl amine, dimethyl amine and n-butyl amine) as bases. The phase purity, structure, crystallinity, morphology and optical properties of the materials obtained with different aliphatic amines were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis and photoluminescence spectroscopy investigations. It was proved that the different aliphatic amines used manipulates both photodegradation properties and morphology of the undoped ZnO materials. The nanomaterial synthesized with n-butyl amine showed the highest catalytic degradation due to high absorption (∼40%) in visible region. The presence of oxygen and zinc vacancies were confirmed from the two emission bands under UV excitation in photoluminescence (PL) studies. Visible light-driven photocatalytic activity of the prepared ZnO nanorods was evaluated by measuring the photodegradation of widely used industrial organic pollutants methylene blue, showed good efficiency of the catalytic samples. In this present study, we propose a mechanism involving e-h pair generation through bandgap and ROS generation assisted aptly by the presence of defects, facilitating the photo-catalytic activity towards dye degradation.

Hydrolysis and aminolysis of aldehydes catalyzed by water and amines: Formation of diols/aminol and the implication to atmospheric particle formation

The hydrolysis and aminolysis reactions of aldehydes were proved to be associated with the secondary organic aerosols (SOA) in the atmosphere. However, these reactions are forbidden owing to the high energy barriers. To make these reactions feasible and assess the catalytic ability of water molecules and amines, the hydrolysis and aminolysis of glyoxal (GL) and glycolaldehyde (GA) were investigated using quantum chemical calculations. The results show that water molecules and amines can catalyze effectively the hydrolysis and aminolysis of aldehydes and the catalytic ability of water molecules is stronger than that of methylamine (MA) and dimethylamine (DMA). Glycine (Gly) can play a stronger role than water molecules in the GL/GA hydrolysis and aminolysis reactions owing to the carboxyl group. At low relative humidity and high pollution condition, the effective rate constants of Gly-catalyzed reactions can be comparable to that of water-catalyzed reactions. The results of MD simulations indicate that the products of GL/GA hydrolysis and aminolysis can participate in the new particle formation (NPF) involving sulfuric acid (SA).

Gut Microbiome and Kidney Disease: Reconciling Optimism and Skepticism.

Gut Microbiome and Kidney Disease: Reconciling Optimism and Skepticism.

Synthesis and antimicrobial activity of novel 5-methyl-1-(4-(6-methylimidazo[1,2-b]isoxazol-3-yl)phenyl)-3-aryl-1,3,5-triazinane-2-thiones

Synthesis of novel 5-methyl-1-(4-(6-methylimidazo[1,2- b ]isoxazol-3-yl)phenyl)-3-aryl-1,3,5-triazinane-2-thiones (6) has been achieved by the reaction of 3-amino-5-methylisoxazole 1 with p -nitro phenacyl bromide, followed by reduction of 3 with stannous chloride. Compounds 4 on treatment with different aryl isothiocyanates in refluxing benzene, followed by trimolecular condensation with 30% HCHO and methyl amine in ethanol afforded the title compounds (6). The newly synthesized compounds ( 6) have been evaluated for their in vitro antimicrobial activity. Compounds 6 exhibited potent antimicrobial activity compared to that of standard drugs.

Aluminium‐Catalyzed Selective Reduction of Heteroallenes Through Hydroboration: Amide/Thioamide/Selenoamide Bond Construction and C=X (X=O, S, Se) Bond Activation**

AbstractAn unprecedented conjugated bis‐guanidinate (CBG) stabilized aluminium dihydride, [LAlH2; (L={(ArNH)(ArN)−C=N−C=(NAr)(NHAr)}; Ar=2,6‐Et2‐C6H3)] (I) catalyzed chemoselective hydroboration of heteroallenes such as carbodiimide (CDI)s, isocyanates, isothiocyanates, and isoselenocyanates is reported. A wide range of heteroallenes, including electron‐donating and withdrawing groups, experience hydroboration to obtain selectively N‐boryl amide, N‐borylaminal, and N‐boryl methyl amine products. More importantly, a single sustainable molecular aluminium‐based catalyst effectively catalyzes CDIs, isocyanates, isothiocyanates, and isoselenocyanates into formamidines, formamides, thioformamides, and selenoformamides, respectively. Further, heteroallene substrates undergo hydrodeoxygenation (HDO), hydrodesulfurization (HDS), and hydrodeselenization (HDSe) reactions leading to N‐boryl methyl amines. In addition, a series of control and kinetic experiments indicate that the aluminium hydride species are essential for all partial and complete reduction steps and breaking the C=X (X=O, S, and Se) bonds in heteroallenes.

Seasonal variations of low molecular alkyl amines in PM2.5 in a North China Plain industrial city: Importance of secondary formation and combustion emissions

Atmospheric amines have unique acid-neutralizing capacity and play an important role in atmospheric chemical reactions. An integrated observation of PM2.5 samples (from Dec 2015 to Nov 15, 2016) was conducted in a typical industrial city (Xuzhou), China. Concentrations of total measured amines (∑amines, including methylamine (MA), ethylamine (EA), dimethylamine (DMA), propanamine (PA) and trimethylamine (TMA) + diethylamine (DEA)) were 172.0 ± 98.2 ng m−3, accounting 1.5 ± 0.6 ‰ of PM2.5 mass. ∑amines were higher in winter (249.0 ± 112.3 ng m−3) and spring (192.4 ± 75.9 ng m−3) than in summer (114.7 ± 33.3 ng m−3) and autumn (103.7 ± 34.3 ng m−3). Concentrations of MA and EA (the dominant amines) were highest in winter, while DMA, PA and TMA + DEA showed opposite seasonality. EA/MA ratios ranged from 0.04 to 8.7 with a median value of 0.3, and the averaged EA/MA ratio was 2.0 in winter, indicating large contribution of EA. Environmental factors including temperature (T), relative humidity (RH) and atmospheric oxidizing capacity (O3 and Ox represented) were found to influence concentrations of amines in PM2.5. The Positive Matrix Factorization (PMF) model identified secondary products (41.6 %), combustion emissions (39.8 %), soil and waste incineration emissions (13.2 %) and biological emissions and aging products (5.4 %) as the 4 sources of amines in PM2.5. MA was mainly secondary products (82.5 %) and had high contribution of local secondary formation, while EA was mainly derived from combustion emissions (83.7 %) and influenced by regional transportation. In winter, combustion emissions (including coal combustion, biomass burning and traffic emissions, contributed 57.7 %) surpassed secondary products (31.6 %) as the predominant sources of amines, especially under the influence of regional transportation (75.7 %).

Chemoselective Hydroboration of Isocyanates Catalyzed by Commercially Available NaH

AbstractA simple, efficient, and economical method for the chemoselective hydroboration of isocyanates is reported. Commercially available NaH, at very low loadings, efficiently catalyzes the selective conversion of isocyanates to N‐boryl formamides, bis(boryl)hemiaminals, and N‐boryl methyl amines. NaH catalyzes isocyanates to controllably open the N=C bond to build an amide bond, and can also remove the C=O bond to obtain N‐boryl methyl amines. Both aliphatic and aromatic isocyanates can be quantitatively converted to the corresponding hydroboration products. Furthermore, there is excellent functional group selectivity over imines, nitriles, and olefins. Additionally, through in situ monitoring, a possible reaction mechanism is proposed. And the chemical intermediates generated by NaH and HBpin are responsible for all the reduction steps.

Resolving the amine-promoted hydrolysis mechanism of N2O5 under tropospheric conditions

Hydrolysis of N2O5 under tropospheric conditions plays a critical role in assessing the fate of O3, OH, and NOx in the atmosphere. However, its removal mechanism has not been fully understood, and little is known about the role of entropy. Herein, we propose a removal path of N2O5 on the water clusters/droplet with the existence of amine, which entails a low free-energy barrier of 4.46 and 3.76 kcal/mol on a water trimer and droplet, respectively, at room temperature. The free-energy barrier exhibits strong temperature dependence; a barrierless hydrolysis process of N2O5 at low temperature (≤150 K) is observed. By coupling constrained ab initio molecular dynamics (constrained AIMD) simulations with thermodynamic integration methods, we quantitively evaluated the entropic contributions to the free energy and compared NH3-, methylamine (MA)-, and dimethylamine (DMA)-promoted hydrolysis of N2O5 on water clusters and droplet. Our results demonstrate that methylation of NH3 stabilizes the product state and promotes hydrolysis of N2O5 by reducing the free-energy barriers. Furthermore, a quantitative analysis of the internal coordinate distribution of the reaction center and the relative position of surrounding species reveals that the significant entropic contribution primarily results from the ensemble effect of configurations observed in the AIMD simulations. Such an ensemble effect becomes more significant with more water molecules included. Lowering the temperature effectively minimizes the entropic contribution, making the hydrolysis more exothermic and barrierless. This study sheds light on the importance of the promoting effect of amines and the entropic effect on gas-phase hydrolysis reactions, which may have far-reaching implications in atmospheric chemistry.

Modulation of the carrier balance of lead-halide perovskite nanocrystals by polyelectrolyte hole transport layers for near-infrared light-emitting diodes

An alternative material, methylamine (MA)-doped poly[3-(4-carboxymethyl)thiophene-2,5-diyl] (P3CT) as hole transport layer (HTL) was investigated for efficient solution-processed near-infrared perovskite light-emitting diodes (NIR PeLEDs). The best NIR PeLEDs performance was achieved with an optimized composition ratio of the MA-doped P3CT (1:1) due to the balance of the electron and hole carrier in the active layer. The charge-balanced NIR PeLEDs exhibit the highest radiance of 858.37 W sr−1 m−2, a low turn-on voltage of 1.82 V, and an external quantum efficiency of 7.44%. Our findings show that using P3CT as an alternative HTL has the potential to significantly improve PeLED performance, allowing it to play a role in the development of practical applications in high-power NIR LEDs.

Clusteromics IV: The Role of Nitric Acid in Atmospheric Cluster Formation.

Nitric acid (NA) has previously been shown to affect atmospheric new particle formation; however, its role still remains highly uncertain. Through the employment of state-of-the-art quantum chemical methods, we study the (acid)1–2(base)1–2 and (acid)3(base)2 clusters containing at least one nitric acid (NA) and sulfuric acid (SA) or methanesulfonic acid (MSA) with bases ammonia (A), methylamine (MA), dimethylamine (DMA), trimethylamine (TMA), and ethylenediamine (EDA). The initial cluster configurations are generated using the ABCluster program. PM7 and ωB97X-D/6-31++G(d,p) calculations are used to reduce the number of relevant configurations. The thermochemical parameters are calculated at the ωB97X-D/6-31++G(d,p) level of theory with the quasi-harmonic approximation, and the final single-point energies are calculated with high-level DLPNO–CCSD(T0)/aug-cc-pVTZ calculations. The enhancing effect from the presence of nitric acid on cluster formation is studied using the calculated thermochemical data and cluster dynamics simulations. We find that when NA is in excess compared with the other acids, it has a substantial enhancing effect on the cluster formation potential.