Presence Of Dimethylamine Research Articles

Theoretical Investigation on Water-Free, Water- and Self-Assisted H-Abstraction Reactions from Dimethylamine by Hydroxy Radicals.

Accurate branching ratios of the H-abstraction reactions from dimethylamine (DMA) by OH radicals are important in understanding the atmospheric fate of DMA. In this work, the reaction kinetics of the water-free, water-assisted, and self-assisted H-abstraction reactions between DMA and OH radicals are accurately determined using the multipath canonical variational theory with the small-curvature tunneling correction, to explore the catalytic effects of the reactant (DMA) and product (water). To choose a suitable method that well describes the current reaction systems, various combinations with seven DFT methods and six basis sets are first evaluated, and the M08-HX/ma-TZVP method is identified as the most appropriate, with a mean unsigned deviation of 0.9 kcal mol-1 against the gold-standard CCSD(T)/CBS(T-Q) method. Based on the determined potential energy surfaces with the considerations of ground-state structures and specific-reaction parameters of zero-point energies, rate constants and branching ratios are calculated in a wide temperature range. The calculations show that the participation of water and DMA can lead to three-body complexes with a lower energy and influence the energy barriers, but neither of them shows the catalytic effect on the H-abstraction reactions in terms of kinetics. Additionally, the branching ratio analysis demonstrates that the product distribution is significantly altered in the presence of DMA and water.

Reduction of carbon dioxide to dimethylformamide using ruthenium doped Mg/Al hydrotalcites under supercritical conditions

The utilization of carbon dioxide is one of the developing areas due to its significant contribution to global warming. Reducing carbon dioxide (CO2) to formic acid and its derivatives has gained importance because of its thermodynamic limitations and high industrial demand. In this article, we report the synthesis of dimethylformamide (DMF) using ruthenium doped Mg/Al calcined hydrotalcite by CO2 hydrogenation in the presence of dimethylamine (DMA). At optimized conditions, complete conversion of dimethylamine was achieved with more than 92% product yield at 170 °C and 13 MPa pressure with a reaction time of 6 h. Key catalyst properties were determined using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), CO2-temperature programmed desorption (TPD), H2 temperature-programmed reduction (TPR) and Fourier transform infrared (FTIR). The determination of surface morphology was carried out using field emission scanning electron microscope (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). At the same time, the chemical composition was verified by energy-dispersive X-ray (EDS). In addition, kinetic modeling is performed using the two site Langmuir-Hinshelwood-Hougen-Watson model. The regressed kinetic parameters gave an appropriate fit with experimental concentration values and activation energy is calculated as 413 kJ/mol K−1.

Metal-free catalysis for the reaction of nitrogen dioxide dimer with phenol: An unexpected favorable source of nitrate and aerosol precursors in vehicle exhaust

Atmospheric reaction mechanism and dynamics of phenol with nitrogen dioxide dimer were explored by the density functional theory and high-level quantum chemistry combined with statistical kinetic calculations within 220–800 K. The nitric acid and phenyl nitrite, the typical aerosol precursors, are the preponderant products because of the low formation free energy barrier (∼8.7 kcal/mol) and fast rate constants (∼10−15 cm3 molecule−1 s−1 at 298 K). Phenyl nitrate is the minor product and it would be also formed from the transformation of phenyl nitrite in NO2-rich environment. More importantly, kinetic effects and catalytic mechanism of a series of metal-free catalysts (H2O, NH3, CH3NH2, CH3NHCH3, HCOOH, and CH3COOH) on the title reaction were investigated at the same level. The results indicate that CH3NH2 and CH3NHCH3 can not only catalyze the title reaction by lowering the free energy barrier (about 1.4–6.5 kcal/mol) but also facilitate the production of organic ammonium nitrate via acting as a donor-acceptor of hydrogen. Conversely, the other species are non-catalytic upon the title reaction. The stabilization energies and donor-acceptor interactions in alkali-catalyzed product complexes were explored, which can provide new insights to the properties of aerosol precursors. Moreover, the lifetime of phenol determined by nitrogen dioxide dimer in the presence of dimethylamine may compete with that of determined by OH radicals, indicating that nitrogen dioxide dimer is responsible for the elimination of phenol in the polluted atmosphere. This work could help us thoroughly understand the removal of nitrogen oxides and phenol as well as new aerosol precursor aggregation in vehicle exhaust.

Molecular properties affecting the hydration of acid-base clusters.

In the atmosphere, water in all phases is ubiquitous and plays important roles in catalyzing atmospheric chemical reactions, participating in cluster formation and affecting the composition of aerosol particles. Direct measurements of water-containing clusters are limited because water is likely to evaporate before detection, and therefore, theoretical tools are needed to study hydration in the atmosphere. We have studied thermodynamics and population dynamics of the hydration of different atmospherically relevant base monomers as well as sulfuric acid-base pairs. The hydration ability of a base seems to follow in the order of gas-phase base strength whereas hydration ability of acid-base pairs, and thus clusters, is related to the number of hydrogen binding sites. Proton transfer reactions at water-air interfaces are important in many environmental and biological systems, but a deeper understanding of their mechanisms remain elusive. By studying thermodynamics of proton transfer reactions in clusters containing up to 20 water molecules and a base molecule, we found that that the ability of a base to accept a proton in a water cluster is related to the aqueous-phase basicity. We also studied the second deprotonation reaction of a sulfuric acid in hydrated acid-base clusters and found that sulfate formation is most favorable in the presence of dimethylamine. Molecular properties related to the proton transfer ability in water clusters are discussed.

Synthesis of Zn,Al layered double hydroxides in the presence of amines

ZnAl Layered Double Hydroxides with nitrate as interlamellar anion have been synthesized in the presence of different amines [methylamine (MMA), dimethylamine (DMA) and trimethylamine (TMA)] in the coprecipitation medium. Then, the solids were submitted to hydrothermal post-treatment by conventional heating and microwave assisted heating in order to improve the crystallinity and the properties of the solids. The samples were characterized by element chemical analysis, powder X-ray diffraction, FT-IR spectroscopy, thermal analysis, specific surface area analysis, SEM, and particle size distribution. The results showed an enhancement of their crystallinity when the samples had been synthetized in the presence of DMA, such a crystallinity degree improving after a long hydrothermal treatment. Although aggregates were formed, they disaggregated easily after short ultrasound treatments, and thus it was possible to obtain solid with a narrow particle size distribution.

Degradation of N-nitrosodimethylamine and its amine precursors by cumene-induced Rhodococcus sp. strain L4.

N-nitrosodimethylamine (NDMA) is a potential carcinogen that is produced as a disinfection by-product of chloramination or chlorination process in water and wastewater treatment systems. The ability of the dioxygenase-expressing bacteria, Rhodococcus sp. strain L4, to degrade NDMA after induction with cumene was examined in the presence and absence of its potential precursors. Dimethylamine (DMA), aniline (AN) and humic acid (HA) were selected as the precursors. The induced bacteria were able to degrade NDMA from initial concentrations ranging between 1 and 10mgL-1 to an undetectable level (< 0.24µgL-1) while there was no degradation of NDMA by the corresponding non-induced strain. The specific first-order degradation rate of NDMA ranged from 0.337 to 0.426 μgg-protein-1h-1. Successful removal of all precursors was achieved by the induced bacteria. The presence of DMA had no negative effect on NDMA degradation. In contrast, a lag period was observed for the degradation of NDMA when AN or HA was present (except for the presence of 0.1mgL-1 AN). In the presence of all precursors, NDMA degradation was negatively affected by the increased concentration (from 1 to 10mgL-1) of all precursors.

Gas Phase Reactivity of the CN Radical with Methyl Amines at Low Temperatures (23–297 K): A Combined Experimental and Theoretical Investigation

The gas phase reactivity of the CN radical in the presence of dimethylamine (CH3)2NH and trimethylamine (CH3)3N has been investigated experimentally using a uniform supersonic expansion CRESU react...

Particulars of the Sol-Gel Synthesis of Titanium Oxide Micro- and Nanoparticles for Creating a Composite Hybrid Antireflection Coating on Float-Glass

Sol-gel processes occurring during hydrolysis in the presence of the surfactant diethylamine were studied. It is shown that the rate of the hydrolysis of tetrabutoxytitanium with minimal water and in the presence of dimethylamine is determined by the competition between the process of condensation of TiO2 nanoparticles and the process of adsorption of dimethylamine on the surface of TiO2 particles.

Chemical Characterization of Gas- and Particle-Phase Products from the Ozonolysis of α-Pinene in the Presence of Dimethylamine.

Amines are recognized as key compounds in new particle formation (NPF) and secondary organic aerosol (SOA) formation. In addition, ozonolysis of α-pinene contributes substantially to the formation of biogenic SOAs in the atmosphere. In the present study, ozonolysis of α-pinene in the presence of dimethylamine (DMA) was investigated in a flow tube reactor. Effects of amines on SOA formation and chemical composition were examined. Enhancement of NPF and SOA formation was observed in the presence of DMA. Chemical characterization of gas- and particle-phase products by high-resolution mass spectrometric techniques revealed the formation of nitrogen containing compounds. Reactions between ozonolysis reaction products of α-pinene, such as pinonaldehyde or pinonic acid, and DMA were observed. Possible reaction pathways are suggested for the formation of the reaction products. Some of the compounds identified in the laboratory study were also observed in aerosol samples (PM1) collected at the SMEAR II station (Hyytiälä, Finland) suggesting that DMA might affect the ozonolysis of α-pinene in ambient conditions.

Effect of dimethylamine on the gas phase sulfuric acid concentration measured by Chemical Ionization Mass Spectrometry.

Sulfuric acid is widely recognized as a very important substance driving atmospheric aerosol nucleation. Based on quantum chemical calculations it has been suggested that the quantitative detection of gas phase sulfuric acid (H2SO4) by use of Chemical Ionization Mass Spectrometry (CIMS) could be biased in the presence of gas phase amines such as dimethylamine (DMA). An experiment (CLOUD7 campaign) was set up at the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber to investigate the quantitative detection of H2SO4 in the presence of dimethylamine by CIMS at atmospherically relevant concentrations. For the first time in the CLOUD experiment, the monomer sulfuric acid concentration was measured by a CIMS and by two CI‐APi‐TOF (Chemical Ionization‐Atmospheric Pressure interface‐Time Of Flight) mass spectrometers. In addition, neutral sulfuric acid clusters were measured with the CI‐APi‐TOFs. The CLOUD7 measurements show that in the presence of dimethylamine (<5 to 70 pptv) the sulfuric acid monomer measured by the CIMS represents only a fraction of the total H2SO4, contained in the monomer and the clusters that is available for particle growth. Although it was found that the addition of dimethylamine dramatically changes the H2SO4 cluster distribution compared to binary (H2SO4‐H2O) conditions, the CIMS detection efficiency does not seem to depend substantially on whether an individual H2SO4 monomer is clustered with a DMA molecule. The experimental observations are supported by numerical simulations based on A Self‐contained Atmospheric chemistry coDe coupled with a molecular process model (Sulfuric Acid Water NUCleation) operated in the kinetic limit.

Measurements of metal alkylamide density during atomic layer deposition using a mid-infrared light-emitting diode (LED) source.

A nondispersive infrared (NDIR) gas analyzer that utilizes a mid-infrared light emitting diode (LED) source was demonstrated for monitoring the metal alkylamide compound tetrakis(dimethylamido) titanium (TDMAT), Ti[N(CH3)2]4. This NDIR gas analyzer was based on direct absorption measurement of TDMAT vapor in the C-H stretching spectral region, a spectral region accessed using a LED with a nominal emission center wavelength of 3.65 μm. The sensitivity of this technique to TDMAT was determined by comparing the absorbance measured using this technique to the TDMAT density as determined using in situ Fourier transform IR (FT-IR) spectroscopy. Fourier transform IR spectroscopy was employed because this technique could be used to (1) quantify TDMAT density in the presence of a carrier gas (the presence of which precludes the use of a capacitance manometer to establish TDMAT density) and (2) distinguish between TDMAT and other gas-phase species containing IR-active C-H stretching modes (allowing separation of the signal from the LED-based optical system into fractions due to TDMAT and other species, when necessary). During TDMAT-only delivery, i.e., in the absence of co-reactants and deposition products, TDMAT minimum detectable molecular densities as low as ≈4 × 10(12) cm(-3) were demonstrated, with short measurement times and appropriate signal averaging. Reactions involving TDMAT often result in the evolution of the reaction product dimethylamine (DMA), both as a thermal decomposition product in a TDMAT ampoule and as a deposition reaction product in the deposition chamber. Hence, the presence of DMA represents a significant potential interference for this technique, and therefore, the sensitivity of this technique to DMA was also determined by measuring DMA absorbance as a function of pressure. The ratio of the TDMAT sensitivity to the DMA sensitivity was determined to be ≈6.0. To further examine the selectivity of this technique, measurements were also performed during atomic layer deposition (ALD) of titanium dioxide using TDMAT and water. During ALD, potential interferences were expected from the evolution of DMA due to deposition reactions and the deposition on the windows of species containing IR-active C-H stretching modes. It was found that the interfering effects of the evolution of DMA and deposition of species on the windows corresponded to a maximum of only ≈6% of the total observed TDMAT density. However, this level of interference likely is relatively low compared to a typical chemical vapor deposition process in which co-reactants are introduced into the chamber at the same time.

Synthesis of pyran annulated heterocyclic scaffolds: a highly convenient protocol using dimethylamine

A facile and rapid three-component synthesis of pharmaceutically diverse pyran annulated heterocycles has been developed via a one-pot condensation of aromatic aldehydes, malononitrile, and different enolizable C–H-activated acidic compounds in the presence of dimethylamine as a newer and effective organo-catalyst in ethanol under mild reaction conditions. Selectivity of various pyran derivatives depends on the structure of enolates. The present protocol has synthetic advantages of excellent yields in much shorter reaction times with no chromatography.

N1- and C6-substituted adenines: a regioselective and efficient synthesis

New and efficient methods for the synthesis of N1-substituted and C6-substitued adenines were developed from the easily accessible 5-aminoimidazole-4-carboxamidines. Condensation of these compounds with triethyl orthoformate led to the selective synthesis of the N1-substituted adenines. Regioselective preparation of C6-substituted adenines could be accomplished when the same precursors were combined with dimethylformamide diethyl acetal. These C6-substituted adenines could also be obtained from the N1-substituted adenines by Dimroth rearrangement in the presence of dimethyl amine.

COUMARINS VIA KNOEVENAGEL CONDENSATION REACTION (KCR) AND PECHMANN CONDENSATION REACTION

Knoevenagel condensation reaction (KCR) and Pechmann condensation reaction are the simplest and most widely used method to synthesize various substituted coumarins. The compounds such as 3–acetylcoumarin, 3–acetyl–7–(diethylamino)coumarin, and 7–(diethylamino)–3–(1–oxobutyl)coumarin were synthesized by KCR method which involved the condensation of salicylaldehyde or 4–(diethylamino)salicylaldehyde with ethyl acetoacetate, 4–(diethylamino)– salicylaldehyde with ethyl butyrylacetate in the presence of dimethylamine as a catalyst. Meanwhile, 7–hydroxy–4–methylcoumarin, 4–methyl–2H–benzo[h]chromen–2–one, 7–hydroxy–4,8–dimethyl– coumarin, 7–hydroxy–4–propylcoumarin, 4–propyl–2H–benzo[h]chromen–2–one, 7–hydroxy–8–methyl–4–propylcoumarin and 7,8–dihydroxy–4–propylcoumarin were synthesized through Pechmann condensation reaction by condensation of resorcinol, 1–napthol or 2–methylresorcinol with ethyl acetoacetate, and resorcinol, 1–napthol, 2–methylresorcinol or pyrogallol with ethyl butyrylacetate, respectively in the presence of sulphuric acid as a catalyst. All compounds were characterized by spectroscopic techniques using infrared (IR), proton and carbon nuclear magnetic resonance (1H and 13C NMR).

UV-A induced photochemical formation of N-nitrosodimethylamine (NDMA) in the presence of nitrite and dimethylamine

The photochemical nitrosation of dimethylamine (DMA) has been suggested as a possible pathway for the occurrence of N-nitrosodimethylamine (NDMA) in aquatic environments. The aim of this study was to investigate the formation of NDMA from the nitrosation of DMA during nitrite (NO 2 −) photolysis in aqueous solution by varying several of the experimental parameters. NDMA was formed at neutral pH, in the presence of DMA and NO 2 − under UV-A irradiation, and exhibited an increase in concentration with irradiation time. Increasing the concentrations of DMA and NO 2 − led to enhanced NDMA formation. Through experiments employing OH scavenger ( t-BuOH), OH was found to play an important role in the production of nitrosating agents during the photolysis of NO 2 −. The optimum pH for the formation of NDMA was around 10. This pH dependence was explained by the dual role of deprotonated DMA as a nucleophile, which enhances the nitrosation reaction between nitrosating agents and DMA, and a hydroxyl radical ( OH) scavenger, which reduces the production of nitrosating agents. A higher concentration of NDMA was obtained under N 2 condition due to the lower quantum yield for NDMA photolysis in the absence of oxygen. Various anions, including phosphate ions in the buffer solution, retarded the formation of NDMA, possibly due to degradation of the nitrosating agents.

The Influence of Human Neutrophils on N-nitrosodimethylamine (NDMA) Synthesis

N-nitrozodimethyloamine (NDMA) is a carcinogenic compound that can be formed in vivo. NDMA is synthesized from precursors-amines and nitrosating agents. Nitrosating agents are formed through the reaction of oxide, reactive oxygen species and nitric oxide (NO). Human neutrophils (PMN) are an important source of the most reactive oxygen species as well as of the nitric oxide. The increase in oxygen metabolism of PMN can lead to the increase nitrosating agent and nitroso-forms. Inflammatory process is associated with locally decreased pH that may favor nitrosation reaction.In the present study, we estimated the NDMA synthesis by LPS-stimulated PMN in the presence of the iNOS inhibitor – N-nitro-L-arginine methyl ester (L-NAME). In the nitrosation reaction dimethylamine (DMA) was used as substrat. The viability of the cells was measured by cytometric method. NDMA concentrations the culture media was measured by GCMS method. NO production was estimated by Griess's method. Expression of iNOS was determined by western blotting.Results obtained showed that DMA nitrosation is most effective in pH between 3–4.5. Nonstimulated PMN produced lower concentrations of NO than LPS-stimulated cells (1.27 μg/cm3 and 1.57 μg/cm3, respectively). In the culture of nonstimulated PMN supplemented with DMA, there was NDMA (mean – 0.99 ng/cm3). In the culture of LPS-stimulated PMN in the presence of DMA, the concentration of NDMA was higher than in the culture of nonstimulated PMN (median – 1.45 ng/cm3). In the supernatants of cells incubated without DMA and with DMA, LPS and L-NAME, no NDMA was detected. These results indicate that PMN can be one of sources of nitrosating agents and can play a role in endogenous NDMA synthesis. Stimulation of PMN can lead to the increase of NDMA concentration following the increase of NO production. Different pathological conditions associated with PMN activation as well as the decreased pH may favor endogenous NDMA synthesis.

Dynamic NMR studies of base-catalyzed intramolecular single vs. intermolecular double proton transfer of 1,3-bis(4-fluorophenyl)triazene

In this paper, we explore the mechanisms of degenerate base-catalyzed intra- and intermolecular proton transfer using dynamic liquid state NMR. For this purpose, the model compound 1,3-bis(4-fluorophenyl)[1,3- 15N 2]triazene ( 1) was studied with and without the presence of dimethylamine ( 2), trimethylamine ( 3) and water, using tetrahydrofuran- d 8 and methylethylether- d 8 as solvents, down to 130 K. Compound 1 represents an analog of carboxylic acids and of diarylamidines forming cyclic dimers in which a fast double proton transfer takes place. By contrast, the structure of 1 was chosen in such a way that this double proton transfer is suppressed, thus revealing the base catalyzed transfer by dynamic 1H and 19F NMR. Surprisingly, both 2 and 3 can pick up the mobile proton of 1 at one nitrogen atom and carry it to the other nitrogen atom of 1, resulting in an intramolecular transfer process catalyzed each time by a different base molecule. Even more surprising is that the intramolecular transfer catalyzed by 2 is faster than the superimposed intermolecular double proton transfer. In the absence of added bases, a 1 is subject to a slow proton exchange with 2-amino-5,4′-difluoro-diphenyl-diazene ( 4) which is formed in small quantities from 1 in the presence of acid impurities. This process can be minimized by a proper sample preparation technique. The kinetic H/D isotope effects are small, especially in the catalysis by 2, indicating a major heavy atom rearrangement and absence of tunneling. Semi-empirical PM3 and ab initio DFT calculations indicate a reaction pathway via a hydrogen bond switch of the protonated amine representing the transition state. The Arrhenius curves of all processes exhibit strong convex curvatures. This phenomenon is explained in terms of the hydrogen bond association of 1 with the added bases, preceding the proton transfer. At low temperatures, all catalysts are in a hydrogen bonded reactive complex with 1, and the rate constants observed equal to those of the reacting complex. However, at high temperatures, dissociation of the complex occurs, and the temperature dependence of the observed rate constants is affected also by the enthalpy of the hydrogen bond association. Finally, implications of this study for the mechanisms of enzyme proton transfers are discussed.

Bioactive Compounds in Cod (Gadus morhua) Products and Suitability of 1H NMR Metabolite Profiling for Classification of the Products Using Multivariate Data Analyses

This work investigates the suitability of (1)H NMR spectroscopy to identify the fate of some bioactive compounds in seafood submitted to several processing conditions and examines the possibility of using (1)H NMR spectroscopy profiling to classify such products. Perchloric acid extracts of cod white muscle from newly killed and (i) unprocessed, (ii) boiled, and (iii) fried fillets and from (iv) frozen fillets, (v) the frozen fillets after thawing, and (vi) their drip loss and from (vii) rehydrated cod klippfish (n = 5) were analyzed by 500 MHz (1)H NMR spectroscopy. It was possible to identify taurine, betaine, anserine, creatine, and trimethylamine oxide (TMAO) in all extracts examined, and frozen fish was recognizable by the presence of dimethylamine (DMA). None of the heating procedures seemed to induce the loss of bioactive compounds from the fillet, but freezing and thawing did: the compounds were lost in what is known as drip loss. About 80% of the samples were correctly classified using a probabilistic neural network procedure having as inputs the scores of the first 20 principal components of the principal component analysis of a selected region of the NMR spectra.

N‐Germyl derivatives of sulfacetamide and ortho‐(sulfonamido)phenylamines: characterization of N‐[o‐(N′,N′‐dimethylsulfonamido)phenyl]‐N‐dimesitylgermaimine

AbstractTriethylgermylation of sulfacetamide occurs on the sulfonamido nitrogen in competition with the 1,2 addition of the starting triethylgermyl dimethylamine on the carbonyl group. Thermal decomposition in the presence of dimethylamine yields N‐triethylgermylsulfanilamide. Stable 1:1 sulfacetamide–DBU and 1:1 sulfacetamide–Et3N complexes were isolated and fully characterized in the course of dehydrochlorination reactions. o‐Sulfonamidophenylamine yields N,N′‐bis‐triethylgermylated derivatives, whereas o‐(N,N‐dimethylsulfonamido)phenylamine leads to monogermylated compounds. The N‐dimethylaminodimesitylgermyl derivative is thermally stable. Dehydrohalogenation of the N‐dimesitylfluorogermyl compound leads to the thermally stable but water sensitive N‐[o‐(N′,N′‐dimethylsulfonamido)phenyl]‐N‐dimesitylgermaimine. Copyright © 2003 John Wiley &amp; Sons, Ltd.

An Orally Active, Water-Soluble Neurokinin-1 Receptor Antagonist Suitable for Both Intravenous and Oral Clinical Administration

1-(5-[[(2R,3S)-2-([(1R)-1-[3,5-Bis(trifluoromethyl)phenyl]ethyl]oxy)-3-(4-fluorophenyl)morpholin-4-yl]methyl]-2H-1,2,3-triazol-4-yl)-N,N-dimethylmethanamine hydrochloride 3 is a high affinity, orally active, h-NK(1) receptor antagonist with a long central duration of action and a solubility in water of >100 mg/mL. The construction of the 5-dimethylaminomethyl 1,2,3-triazol-4-yl unit, which incorporates the solubilizing group of 3, was accomplished by thermal rearrangement of a propargylic azide in the presence of dimethylamine. Compound 3 is highly effective in pre-clinical tests that are relevant to clinical efficacy in emesis and depression.