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In drinking water chloramination, monochloramine autodecomposition occurs in the presence of excess free ammonia through dichloramine, the decay of which was implicated in N -nitrosodimethylamine (NDMA) formation by (i) dichloramine hydrolysis to nitroxyl which reacts with itself to nitrous oxide (N 2 O), (ii) nitroxyl reaction with dissolved oxygen (DO) to peroxynitrite or mono/dichloramine to nitrogen gas (N 2 ), and (iii) peroxynitrite reaction with total dimethylamine (TOTDMA) to NDMA or decomposition to nitrite/nitrate. Here, the yields of nitrogen and oxygen-containing end-products were quantified at pH 9 from NHCl 2 decomposition at 200, 400, or 800 μeq Cl 2 ·L -1 with and without 10 μM-N TOTDMA under ambient DO (∼500 μM-O) and, to limit peroxynitrite formation, low DO (≤40 μM-O). Without TOTDMA, the sum of free ammonia, monochloramine, dichloramine, N 2 , N 2 O, nitrite, and nitrate indicated nitrogen recoveries ±95% confidence intervals were not significantly different under ambient (90 ± 6%) and low (93 ± 7%) DO. With TOTDMA, nitrogen recoveries were less under ambient (82 ± 5%) than low (97 ± 7%) DO. Oxygen recoveries under ambient DO were 88-97%, and the so-called unidentified product of dichloramine decomposition formed at about three-fold greater concentration under ambient compared to low DO, like NDMA, consistent with a DO limitation. Unidentified product formation stemmed from peroxynitrite decomposition products reacting with mono/dichloramine. For a 2:2:1 nitrogen/oxygen/chlorine atom ratio and its estimated molar absorptivity, unidentified product inclusion with uncertainty may close oxygen recoveries and increase nitrogen recoveries to 98% (ambient DO) and 100% (low DO).

Half-sandwich Cp*RhIII complexes (Cp* = η5-1,2,3,4,5-pentamethylcyclopentadienyl) supported by 2,2′-bipyridine or 4,4′-di-tert-butyl-2,2′-bipyridine catalyze dehydrogenation of dimethylamine-borane (Me2NH·BH3) to produce H2 and dimethylamino-borane dimer (Me2N--BH2)2 with turnovers of 2200. The IrIII analogues, on the other hand, display dramatically poorer catalytic activity. Mechanistic inferences drawn from stoichiometric reactions and DFT calculations suggest noninnocent involvement of the Cp* moiety as a proton shuttle. [ABSTRACT FROM AUTHOR]

We present an analytical strategy, dimethylation-deuteration and oxygen-exchange IPTL (diDO-IPTL), for high-precision, broad-coverage quantitative proteomics. The diDO-IPTL approach combines two advances in isobaric peptide terminal labeling (IPTL) methodology: first, a one-pot chemical labeling strategy for attaching isotopic tags to both the N- and C-termini of tryptic peptides, and second, a search engine (based on the Morpheus algorithm) optimized for identification and quantification of twinned peaks from peptide fragment ions in MS2 spectra. The diDO-IPTL labeling chemistry uses only high-purity, relatively inexpensive isotopic reagents (18O water and deuterated formaldehyde) and requires no postlabeling cleanup or isotopic impurity corrections. This strategy produces proteome-scale relative quantification results with high accuracy and precision, suitable for the detection of small protein abundance variations between complex biological samples. In a two-proteome mixture experiment, diDO-IPTL quantification discriminates 1.5-fold changes in abundance of over 1000 proteins with 88% accuracy. The diDO-IPTL methodology is a high-precision, economical approach to quantitative proteomics that is applicable to a wide variety of sample types. [ABSTRACT FROM AUTHOR]

Some reactions (e.g., oxidation of nitrite, denitrification of ammonium) are accelerated in freeze-concentrated solution (FCS) compared to those in aqueous solution. Ice is highly intolerant to impurities, and the ice excludes those that would accelerate reactions. Here we show the acceleration of the N-nitrosation reaction of dimethylamine (DMA) with nitrite to produce N-nitrosodimethylamine (NDMA) in FCS. NDMA is a carcinogenic compound, and this reaction is potentially accelerated in frozen fish/meat. The eaction rate of the N-nitrosation reaction becomes fastest at specific pH. This means that it is a third-order reaction. Theoretical pH values of the peak in the third-order reaction are higher than the experimental one. Freeze-concentration of acidic solution causes pH decrement; however, the freeze-concentration alone could not explain the difference of pH values. The theoretical value was obtained under the assumption that no solute took part in ice. However, solutes are incorporated in ice with a small distribution coefficient of solutes into ice. This small incorporation enhanced the decrement of pH values. Using the distribution coefficient of chloride and sodium ion and assuming those of nitrite and DMA to explain the enhancement, we succeeded in estimating the distribution coefficients of nitrite: 2 × 10-3 and DMA: 3 × 10-2. [ABSTRACT FROM AUTHOR]

Five high-nuclear lanthanide (Ln) substituted heteropolytungstates [H2N(CH3)2]16Na9LnH10{[W16Ln10(H2O)38O50][B-α-SeW9O33]8}.56H2O [Ln = LaIII (1), CeIII (2)], [H2N(CH3)2]22Na4H12{[W18Ln10(H2O)34O56][B-α-SeW9O33]8}.80H2O [Ln = LaIII (3), CeIII (4)], and Na4[H2N(CH3)2]18H21[Nd(H2O)7][W16Nd10O50(H2O)34(B-α-AsW9O33)8].60H2O (5) were prepared by reaction of Na2WO4.2H2O and Ln(NO3)3.6H2O in the presence of dimethylamine hydrochloride (DMAHC) and Na2SeO3 or NaAsO2 in an aqueous medium. The octameric polyoxoanions {[W16Ln10(H2O)38O50][B-α-SeW9O33]8}38- in 1 and 2 are assembled from eight [B-α-SeW9O33]8- building blocks linked by 16 extra bridging WVI centers and ten LnIII cations, whereas the octameric polyoxoanions {[W18Ln10(H2O)34O56][B-α-SeW9O33]8}38- in 3 and 4 are constructed from eight [B-α-SeW9O33]8- building blocks joined by 18 additional bridging WVI centers and ten LnIII cations [Ln = LaIII (3), CeIII (4)]. The octameric polyoxoanion [W16Nd10O50(H2O)34(B-α-AsW9O33)8]40- in 5 is constituted by eight [B-α-AsW9O33]9- building blocks connected by 16 extra bridging WVI centers and ten NdIII cations. It should be noted that neighboring {[W16Nd10(H2O)38O50][B-α-AsW9O33]8}46- polyoxoanions in 5 are further polymerized by two W-O-Nd-O-W linkers into a 1-D chain-like alignment. The thermolysis processes of 1, 4, and 5 were investigated by variable-temperature IR spectra, coloration changes, and variable-temperature PXRD patterns. The solid-state NIR luminescence properties of 5 were systematically studied at room temperature. [ABSTRACT FROM AUTHOR]

The shape-dependent properties of gold nanostars (NSs) have motivated massive research efforts in the field of colloidal chemistry to gain a better control over the morphology of these promising nanostructures. Nevertheless, this challenge requires a better understanding of the atomic-scale processes leading to the formation of stellated nanoparticles. We hereby report an unprecedented in situ study focused on the seed-mediated synthesis of symmetric gold NSs performed by radiolysis in methanol. We take advantage of the spatial and temporal resolutions of liquid-cell transmission electron microscopy to unravel the key effects of the growth speed, seed-crystal morphology, and dimethylamine functionalization on the formation mechanisms, shape, and stability of NSs enclosed by high-index facets. Surprisingly, the stellation processes transforming icosahedral nanoparticles into NSs with 20 sharp arms entails a continuous restructuring of NS facets driven by surface diffusion, which provide a fresh look at faceting mechanisms. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics simulations of a flow reactor provided 3D spatial distributions of its temperature and flow profiles and abundances of sulfuric acid, nitrogeneous base, and the acid-base clusters formed from them. Clusters were simulated via their kinetic formation and decomposition involving sulfuric acid and base molecules. Temperature and flow profiles and the base and sulfuric acid distributions are characterized and the latter is compared to mass spectrometer measurements. Concentrations of simulated clusters of sulfuric acid with either NH3 or dimethylamine were compared to experimentally measured particle concentrations. Cluster thermodynamics were adjusted to better the agreement between simulated and experimental results. Free energies of acid-base clusters derived here are also compared to recent quantum chemistry calculations. Sensitivities to the thermodynamics were explored with a 2D laminar flow simulation and the abundance of large clusters was most sensitive to the thermodynamics of the smallest cluster, consisting of 1 base and 1 acid. Comparisons of this model to the computational fluid dynamics models provide verification of the implemented cluster chemistry. A box model was used to calculate nucleation rates for the conditions of other experimental work, and to provide predictions of nucleation for typical atmospheric conditions. [ABSTRACT FROM AUTHOR]

Amines are recognized as key compounds in new particle formation (NPF) and secondary organic aerosol (SOA) formation. In addition, ozonolysis of a-pinene contributes substantially to the formation of biogenic SOAs in the atmosphere. In the present study, ozonolysis of a-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 a-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 a-pinene in ambient conditions. [ABSTRACT FROM AUTHOR]

Ultrafast nuclear driven charge transfer prior to dissociation is an important process in modular systems as was demonstrated experimentally in the bifunctional molecule 2-phenylethyl-N,N-dimethylamine (PENNA) in work by Lehr et al. (J. Phys. Chem. A 2005 109 8074). The ultrafast dynamics of PENNA photoexcited to the three lowest electronic states of the cation (D0, D1, and D2) was studied using quantum chemistry and surface hoping. We show that a conical intersection, localized in the Franck-Condon region, between the D0 and the D1 states, leads to an ultrafast charge transfer, computed here to be on a time scale of 65 fs, between the phenyl and the amine charged subunits. On the D0 ground state, the dissociation proceeds on the 60 ps time scale through a 19 kcal/mol late barrier. The computed kinetic energy release is in good agreement with a new experimental measurement of PENNA ionization by an 800 nm 30 fs intense laser pulse. [ABSTRACT FROM AUTHOR]

Short-chain alkyl amines can undergo gas-to-particle partitioning via reactive uptake by ammonium salts, whose phases have been thought to largely influence the extent of amine uptake. Previous studies mainly focused on particles of single ammonium salt at either dry or wet conditions without any addition of organic compounds. Here we report the uptake of dimethylamine (DMA) by ammonium sulfate (AS) and AS-sucrose mixed particles at different relative humidities (RHs) using an electrodynamic balance coupled with in situ Raman spectroscopy. DMA is selected as a representative of short-chain alkyl amines, and sucrose is used as a surrogate of viscous and hydrophilic organics. Effective DMA uptake was observed for most cases, except for the water-limiting scenario at <5% RH and the formation of an ultraviscous sucrose coating at 10% RH and below. DMA uptake coefficients (γ) were estimated using the particle mass measurements during DMA uptake. Addition of sucrose can increase γ by absorbing water or inhibiting AS crystallization and decrease γ by elevating the particle viscosity and forming a coating layer. DMA uptake can be facilitated for crystalline AS or retarded for aqueous AS with hydrophilic viscous organics (e.g., secondary organic material formed via the oxidation of biogenic volatile organic compounds) present in aerosol particles. [ABSTRACT FROM AUTHOR]

The effects on the hydrolysis of NO2 in the presence of methylamine and dimethylamine molecules were investigated by theoretical calculations of a series of the molecular clusters 2NO2-mH2O-CH3NH2 (m = 1-3) and 2NO2-mH2O-(CH3)2NH (m = 1, 2). With methylamine included in the clusters, the energy barrier is reduced by 3.2 kcal/mol from that with ammonia, and the corresponding products may form without an energy barrier. The results show that amines have larger effects than ammonia in promoting the hydrolysis of NO2 on thermodynamics. The additional water molecules can stabilize the transition states and the product complexes, and we infer that adding more water molecules in the reactions mainly act as solvent and promoting to form the methylamine nitrate (CH3NH3+NO3-). In addition, the interactions of CH3NH2 and (CH3)2NH on the hydration of HNO3 are also more effective than NH3, and the NH4NO3, CH3NH3NO3, and (CH3)2NH2NO3 complexes tend to form the larger aerosols with the increasing of water molecules. The equilibrium geometries, harmonic vibrational frequencies, and intensities of both HONO-CH3NH2 and HONO-NH3 complexes were investigated. Calculations predict that the binding energies of both HONO-CH3NH2 complexes are larger than HONO-NH3 complexes, and the OH stretching vibrational frequencies and intensities are most affected. The natural bond orbital analysis was performed to describe the donor-acceptor interactions on a series of complexes in the reactions 2NO2 + H2O + CH3NH2 and 2NO2 + H2O + (CH3)2NH, as well as the complexes of HONO-NH3 and HONO-CH3NH2. The results show that the interactions with amines are relatively larger, and the higher stabilization energies between CH3NH2 and HONO are found. [ABSTRACT FROM AUTHOR]

Recently, an array of eight genes involved in the biotransformation of benzalkonium chlorides (BACs)?an active ingredient of many disinfectants?to benzyldimethyl amine (BDMA) was identified in the genome of Pseudomonas sp. BIOMIG1, which is a bacterium present in various environments and mineralizes BACs. In this study, we showed that heterologous expression of an oxygenase gene (oxyBAC) present in this gene array in E. coli resulted in formation of BDMA from BACs at a rate of 14 ?M h-1. oxyBAC is phylogenetically classified as a Rieske-type oxygenase (RO) and belongs to a group which catalyzes the cleavage of C-N+ bond between either methyl or alkyl ester and a quaternary nitrogen (N) of natural quaternary ammonium compounds such as stachydrine, carnitine, and trimethylglycine. Insertion of two glycines into the Rieske domain and substitution of tyrosine with leucine in the mononuclear iron center differentiate oxyBAC from other ROs that cleave C-N+, and presumably facilitate the cleavage of saturated alkyl chain from quaternary N via N-dealkylation reaction. In addition, unlike other ROs, oxyBAC did not require a specific reductase to function. Our results demonstrate that oxyBAC represents a new member of RO associated with BAC degradation, and have applications for controlling the fate of BACs in the environment. [ABSTRACT FROM AUTHOR]

A detailed investigation of the spectral and photophysical properties of minocycline (MC) in water at different pHs, solvents of different polarity, and micellar surfactant solutions was carried out in this study. An unusual behavior was highlighted with respect to other tetracyclines due to the presence of an additional dimethylamino group in the MC molecular structure. In particular, four equilibrium constants associated with mono-deprotonation reactions were characterized by steady-state spectroscopy. Femtosecond time-resolved pump-probe and fluorescence up-conversion measurements allowed the dynamics of the lowest excited singlet state of the five different acid-base species of MC to be characterized in terms of lifetimes and transient spectra. Two emissive species associated with keto-enol tautomerism resulting from excited-state intramolecular proton transfer (ESIPT) were revealed with time constants of a few and tens of picoseconds. TD-DFT quantum mechanical calculations were also performed to define the state order and nature of the differently protonated species, together with their absorption spectra. The role of pH proved to be fundamental in modulating the drug charge and therefore the interaction with cationic micelles where the neutral form of MC, that is the biologically active one, resulted efficiently included. [ABSTRACT FROM AUTHOR]

N-nitrosodimethylamine (NDMA), as a representative of endogenously formed N-nitroso compounds (NOCs), has become the focus of considerable research interest due to its unusually high carcinogenicity. In this study, effects of ethanol and acetic acid on the formation of NDMA from dimethylamine (DMA) and nitrite in simulated gastric fluid (SGF) were investigated. Experimental results showed that ethanol in the concentrations of 1-8% (v/v) and acetic acid in the concentrations of 0.01-8% (v/v) exhibit inhibitory and promotion effects on the formation of NDMA, respectively. Moreover, they are both in a dose-dependent manner with the largest inhibition/promotion rate reaching ∼70%. Further experimental investigations indicate that ethanol and acetic acid are both able to scavenge nitrite in SGF. It implies that there are interactions of ethanol and acetic acid with nitrite or nitrite-related nitrosating agents rather than DMA. Theoretical calculations confirm the above experimental results and demonstrate that ethanol and acetic acid can both react with nitrite-related nitrosating agents to produce ethyl nitrite (EtONO) and acetyl nitrite (AcONO), respectively. Furthermore, the reactivities of ethyl nitrite, acetyl nitrite, and dinitrogen trioxide reacting with DMA were found in the order of AcONO > N2O3 ⪢EtONO. This is probably the main reason why there are completely different effects of ethanol and acetic acid on NDMA formation. On the basis of the above results, two requirements for a potential inhibitor of NOCs formation in SGF were provided. The results obtained in this study will be helpful in better understanding the inhibition/promotion mechanisms of compounds on NDMA formation in SGF and searching for protective substances to prevent carcinogenic NOCs formation. [ABSTRACT FROM AUTHOR]

We investigate the molecular interaction between methyl-substituted N, N, N',N'-ethylenediamines, propane-1,3-diamine, butane-1,4-diamine, and sulfuric acid using computational methods. Molecular structure of the diamines and their dimer clusters with sulfuric acid is studied using three density functional theory methods (PW91, M06-2X, and ωB97X-D) with the 6-31++G(d,p) basis set. A high level explicitly correlated CCSD(T)-F12a/VDZ-F12 method is used to obtain accurate binding energies. The reaction Gibbs free energies are evaluated and compared with values for reactions involving ammonia and atmospherically relevant monoamines (methylamine, dimethylamine, and trimethylamine). We find that the complex formation between sulfuric acid and the studied diamines provides similar or more favorable reaction free energies than dimethylamine. Diamines that contain one or more secondary amino groups are found to stabilize sulfuric acid complexes more efficiently. Elongating the carbon backbone from ethylenediamine to propane-1,3-diamine or butane-1,4-diamine further stabilizes the complex formation with sulfuric acid by up to 4.3 kcal/mol. Dimethyl-substituted butane-1,4-diamine yields a staggering formation free energy of -19.1 kcal/mol for the clustering with sulfuric acid, indicating that such diamines could potentially be a key species in the initial step in the formation of new particles. For studying larger clusters consisting of a diamine molecule with up to four sulfuric acid molecules, we benchmark and utilize a domain local pair natural orbital coupled cluster (DLPNO-CCSD(T)) method. We find that a single diamine is capable of efficiently stabilizing sulfuric acid clusters with up to four acid molecules, whereas monoamines such as dimethylamine are capable of stabilizing at most 2-3 [ABSTRACT FROM AUTHOR]

The complex and multifaceted pathology of Alzheimer's disease (AD) continues to present a formidable challenge to the establishment of long-term treatment strategies. Multifunctional compounds able to modulate the reactivities of various pathological features, such as amyloid-β (Aβ) aggregation, metal ion dyshomeostasis, and oxidative stress, have emerged as a useful tactic. Recently, an incorporation approach to the rational design of multipurpose small molecules has been validated through the production of a multifunctional ligand (ML) as a potential chemical tool for AD. In order to further the development of more diverse and improved multifunctional reagents, essential pharmacophores must be identified. Herein, we report a series of aminoquinoline derivatives (AQ1-4, AQP1-4, and AQDA1-3) based on ML's framework, prepared to gain a structure-reactivity understanding of ML's multifunctionality in addition to tuning its metal binding affinity. Our structure-reactivity investigations have implicated the dimethylamino group as a key component for supplying the antiamyloidogenic characteristics of ML in both the absence and presence of metal ions. Two-dimensional NMR studies indicate that structural variations of ML could tune its interaction sites along the Aβ sequence. In addition, mass spectrometric analyses suggest that the ability of our aminoquinoline derivatives to regulate metal-induced Aβ aggregation may be influenced by their metal binding properties. Moreover, structural modifications to ML were also observed to noticeably change its metal binding affinities and metal-to-ligand stoichiometries that were shown to be linked to their antiamyloidogenic and antioxidant activities. Overall, our studies provide new insights into rational design strategies for multifunctional ligands directed at regulating metal ions, Aβ, and oxidative stress in AD and could advance the development of improved next-generation multifunctional reagents. [ABSTRACT FROM AUTHOR]

Pinonaldehyde, which is among the most abundant oxidation products of a-pinene, and dimethylamine were selected to study the formation of N-containing low volatile compounds from aldehyde-amine reactions in the atmosphere. Gas phase reactions took place in a Tedlar bag, which was connected to a mass spectrometer ionization source via a short deactivated fused silica column. In addition to on-line analysis, abundance of gaseous precursors and reaction products were monitored off-line. Condensable products were extracted from the bag's walls with a suitable solvent and analyzed by gas chromatography coupled to chemical ionization high-resolution quadrupole time-of-flight mass spectrometry and by ultra-high-performance liquid chromatography coupled to electrospray ionization Orbitrap mass spectrometry. The reactions carried out resulted in several mid-low vapor pressure nitrogen-containing compounds that are potentially important for the formation of secondary organic aerosols in the atmosphere. Further, the presence of brown carbon, confirmed by liquid chromatography-UV-vis-mass spectrometry, was observed. Some of the compounds identified in the laboratory study were also observed in aerosol samples collected at SMEAR II station (Hyytiälä, Finland) in August 2015 suggesting the importance of aldehyde-amine reactions for the aerosol formation and growth. [ABSTRACT FROM AUTHOR]

The one-pot assembly reaction of Na2WO4•2H2O, RE(NO3)3•6H2O, and NaAsO2 in the participation of dimethylamine hydrochloride as an organic solubilizing agent in the acidic aqueous solution led to a class of trigonal pyramidal {AsO2(OH)} bridging rare-earth substituted arsenotungstate (AT) aggregates [H2N(CH3)2]8Na8{[W3RE2(H2O)8AsO8(OH)][B-α-AsW9O33]2}2•65H2O [RE = EuIII (1), GdIII (2), TbIII (3), DyIII (4), HoIII (5), YIII (6)], which were structurally characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, and thermogravimetric (TG) analyses. The common structural feature of 1-6 is that their polyoxoanions consist of a novel tetrameric unit [(W3RE2(H2O)8AsO8(OH))(B-α-AsW9O33)2]216-constituted by four trivacant Keggin [α-AsW9O33]9- fragments linked through an unseen elliptical [W6RE4(H2O)16As2O16(OH)2]20+ moiety. Their polyoxoanionic infrastructures can also be described as a fusion of two equivalent dimeric subunits [(W3RE2(H2O)8O7)(B-α-AsW9O33)2]8-bridged via two μ2-{AsO2(OH)} linkers. To the best of our knowledge, such a linking mode with trigonal pyramidal {AsO2(OH)} groups as linkers connecting adjacent RE containing polyoxometalate moieties together is very rare. The thermal stability of 1-6 was also investigated on the crystalline samples, and the thermal decomposition processes of 1, 4, and 6were comparatively deeply studied. The fluorescent properties and decay times of 1, 3, and 4were measured, and they exhibit the characteristic emissions of RE centers. The lifetimes of 1and 3 mainly originate from the contribution of RE ions whereas the overall lifetime of 4 is contributed by the synergistic interactions of AT fragments and Dy3+ ions. [ABSTRACT FROM AUTHOR]

Dimethylamine and 2,4,6-triformylphloroglucinol react to form a product with a highly contorted nonplanar geometry due to favorable electron delocalization. This new heteroradialene compound has been studied by X-ray diffraction, variable-temperature multinuclear NMR spectroscopy, IR spectroscopy, UV-vis spectroscopy, and ab initio calculations. Electron delocalization throughout the periphery of the central ring leads to a structure that retains very little of the aromatic characteristics of the starting material. [ABSTRACT FROM AUTHOR]

We investigate the molecular interaction between sulfuric acid and a C6H8O7 ketodiperoxy acid compound (a proxy for highly oxidized products of, e.g., monoterpene autoxidation) in the presence of water, ammonia, or dimethylamine. The molecular geometries are obtained using density functional theory (M06-2X, PW91, and ωB97X-D) with the 6-31++G(d,p) basis set, and the binding energy is corrected utilizing a high-level DLPNO-CCSD(T)/def2-QZVPP calculation. The formation free energies were calculated (ΔG at 298 K and 1 atm), and the stability of the molecular clusters was evaluated. The presence of bases is found to enhance the interaction between ketodiperoxy acid compounds and sulfuric acid. The addition of C6H8O7 compounds to (H2SO4)(NH3) or (H2SO4)((CH3)2NH) clusters is, however, not able to compete with the corresponding uptake of another sulfuric acid molecule, even at a high loading of organic compounds. We furthermore investigate the origin of the weak binding of peroxyacid compounds using atoms in molecules and natural bonding orbital analysis. The weak binding is caused by an internal hydrogen bond and the lack of a strong hydrogen bond acceptor in the peroxyacid group. These findings indicate that autoxidation products containing solely or mainly hydroperoxide and carbonyl functional groups do not participate in the initial step of new particle formation and thereby only contribute to the growth of atmospheric particles. [ABSTRACT FROM AUTHOR]

We demonstrate a fast, flexible, parallel, and highly controllable method by which to synthesize a variety of nanoscale and mesoscale structures. This method addresses one of the most significant challenges in nanoscience: the in situ parallel placement and synthesis of nano-objects over the mesoscale. The method is based on electroless nanowire deposition on micropatterned substrates (ENDOM). In ENDOM nanostructures are produced at the boundary between two unlike materials if two conditions are met: (a) deposition is kinetically preferred on one of the materials while (b) transport of reactants is favored on the other. In this study, copper structures were deposited on patterned -OH/-CH3-terminated alkanethiolate self-assembled monolayers (SAMs) by exploiting the different reaction rates of electroless deposition on these using the reducing agent dimethylamine borane (DMAB). We demonstrate production of nanowires (width < 100 nm), mesowires (100 nm < width < ~3000 nm), nanorings, nanopores, and nanochannels. We show that a variety of experimental conditions can be employed, making this method compatible with many substrates. We have also studied the nucleation and growth kinetics of the ENDOM process. The width of the deposit grows exponentially with deposition time and can be modeled using classical nucleation theory. Although the deposit width increases, the height and grain size of the copper deposit is constant (to within experimental uncertainty) with deposition time. These observations indicate that the minimum deposit width is controlled by the nanoparticle dimensions and so can be controlled using the reaction conditions. [ABSTRACT FROM AUTHOR]

We use ab initio calculations to investigate the energetics and kinetics associated with carbinolamine formation resulting from the addition of dimethylamine to formaldehyde catalyzed by a single water molecule. Further, we compare the energetics for this reaction with that for the analogous reactions involving methylamine and ammonia separately. We find that the reaction barrier for the addition of these nitrogen-containing molecules onto formaldehyde decreases along the series ammonia, methylamine, and dimethylamine. Hence, starting with ammonia, the reaction barrier can be "tuned" by the substitution of an alkyl group in place of a hydrogen atom. The reaction involving dimethylamine has the lowest barrier with the transition state being 5.4 kcal/mol below the (CH3)2NH + H2CO + H2O separated reactants. This activation energy is significantly lower than that for the bare reaction occurring without water, H2CO + (CH3)2NH, which has a barrier of 20.1 kcal/mol. The negative barrier associated with the single-water molecule catalyzed reaction of dimethylamine with H2CO to form the carbinolamine (CH3)2NCH2OH suggests that this reaction should be energetically feasible under atmospheric conditions. This is confirmed by rate calculations which suggest that the reaction will be facile even in the gas phase. As amines and oxidized organics containing carbonyl functional groups are common components of secondary organic aerosols, the present finding has important implications for understanding how larger, less volatile organic compounds can be generated in the atmosphere by combining readily available smaller components as required for promoting aerosol growth. [ABSTRACT FROM AUTHOR]

A new microporous luminescent coordination polymer [(CH3)2NH2]·[Cu2(CN)3] (1) with channels occupied by dimethylamine cations was synthesized due to the inducing effect of 2-(2'-pyridyl)imidazole. Complex 1 exhibits bright-green emission in the solid state, and its emission intensity would be significantly enhanced, especially by DMAc and cupric ion after immersing the as-synthesized crystals of 1 into common organic solvents or methanol solutions of various metal ions. In addition, 1 exhibits photocatalytic activity for the degradation of RhB and MB under natural light and is stable during the photocatalysis process. Thus, 1 can act as a multifunctional material for selectively sensing of Cu2+ and effectively photocatalytic degradation of dyes. [ABSTRACT FROM AUTHOR]

Significanteffect of coupling between the electron donor and acceptorgroups in intramolecular charge transfer (ICT) dynamics has been demonstratedby comparing the photophysical properties of two isomeric N,N-dimethylaminochalcone derivatives (namely,DMAC-A and DMAC-B). In the case of the DMAC-B molecule, the distancebetween the donor (N,N-dimethylanilineor DMA) and the acceptor (carbonyl) groups is larger by one ethyleneunit as compared to that in the case of DMAC-A. The excited singlet(S1) states of both the isomers have strong ICT characterbut their photophysical properties are remarkably different. In polarsolvents, fluorescence quantum yields (and the lifetimes of the S1state) of DMAC-A are more than 2 orders of magnitude lower(and shorter) than those of DMAC-B. Remarkable differences in thephotophysical properties of these two isomers arise due to occurrenceof the ultrafast twisting of the DMA group (or the TICT process) duringthe course of deactivation of the S1state of the DMAC-Amolecule, but not in the case of DMAC-B. In the later case, becauseof the presence of a large energy barrier along the twisting coordinate(s),TICT is not a feasible process, and hence, the S1stateof DMAC-B has the planar ICT structure. In the DMAC-A molecule, thestrength of coupling between the donor and acceptor groups is relativelystronger because of a shorter distance between these groups. Femtosecondtransient absorption spectroscopic measurements and DFT/TDDFT calculationshave been adopted to establish the above aspects of the relaxationdynamics of the S1states of these two isomeric chalcones. [ABSTRACT FROM AUTHOR]

Chiral N,N-4-(dimethylamino)pyridine(DMAP) derivatives, which can be readily prepared by the Ugi multicomponentreaction in a one-pot manner, have been efficiently applied to theenantioselective Steglich rearrangement of oxindole derivatives togive the desired products bearing a quaternary carbon center in highyield (>98% yield) and with high enantioselectivity (up to 99:1er). [ABSTRACT FROM AUTHOR]

Alkalizing aminessuch as cyclohexylamine and dimethylamine havegreat potential for protecting steam–water cycles against corrosion,but their thermal stability is limited and anionic decomposition productsare a concern because of increased corrosion risk. In this study,morpholine, ethanolamine, cyclohexylamine, dimethylamine, and 3-methoxypropylaminewere exposed to temperatures of 500, 530, and 560 °C at pressuresof 9.5, 13.5, and 17.5 MPa to investigate the effects of temperatureand pressure on amine thermolysis kinetics. The surface/volume ratioof the reactor tube was 0.4 mm–1, close to the valuefor superheater tubes in steam–water cycles. All amines thermolyzedby first-order kinetics, with the exception of dimethylamine. TheArrhenius constants Ea, ln(A), and Vawere obtained from the experimentaldata for all investigated amines. The effect of pressure on the thermolysiskinetics was less pronounced than in previous studies and was differentfor each amine. Dimethylamine did not degrade below 20% and 10% at500 and 530 °C, respectively, despite the application of longerretention times, suggesting the synthesis might occur. Limited practicaldata showed some promise for the applicability of the model to steam–watercycles. More plant data are needed to fully validate the model. Inall cases, thermolysis of the amines led to the formation of between150 and 600 ppb organic acid anions. In most cases, the concentrationsincreased linearly with increasing degradation percentage. Acetateand formate were found to be major degradation products, with somepropionate and traces of glycolate. Cationic degradation productswere ammonia and some amines, meaning that the complete thermolysisof an amine does not necessarily lead to acidic conditions. [ABSTRACT FROM AUTHOR]

The reactivity of monoanionic amidinateligands containing a dimethylamine side arm with variable lengthsof the linker chain and aromatic substituents of the ipso carbon atomwas investigated for the early actinides thorium and uranium. Thebis(amidinate) actinide complexes obtained were structurally characterized,displaying a coordination of both dimethylamine nitrogen atoms tothe respective metal center, allowing for a fine tuning of the reactivityof the complex by manipulation of the coordination environment aroundthe metal center. The reactivity of the actinide amidinate complexeswas studied in the catalytic ring-opening polymerization of ε-caprolactone. [ABSTRACT FROM AUTHOR]

The weakly interacting complexesof dimethylamine with dimethylether (DMA–DME) and with dimethylsulfide (DMA–DMS) havebeen detected in the gas phase using Fourier transform infrared spectroscopyat room temperature. The observed redshift of the fundamental NH-stretchingfrequency was found to be extremely small with only 5 and 19 cm–1for DMA–DME and DMA–DMS, respectively.The experimentally determined integrated absorbance has been combinedwith a calculated oscillator strength to determine an equilibriumconstant of 2 × 10–3and 4 × 10–3for the DMA–DME and DMA–DMS complexes, respectively.The topological analyses reveal that several hydrogen bond interactionsare present in the complexes. The calculated binding energies, geometricparameters, observed redshifts, and topological analyses suggest thatoxygen and sulfur are hydrogen bond acceptors of similar strength. [ABSTRACT FROM AUTHOR]

The branching ratios for the reaction of the OH radical with the primary and secondary alkylamines: methylamine (MA), dimethylamine (DMA), and ethylamine (EA), have been determined using the technique of pulsed laser photolysis-laserinduced fluorescence. Titration of the carbon-centered radical, formed following the initial OH abstraction, with oxygen to give HO2 and an imine, followed by conversion of H 0 2 to OH by reaction with NO, resulted in biexponential OH decay traces on a millisecond time scale. Analysis of the biexponential curves gave the HO2 yield, which equaled the branching ratio for abstraction at aC-H position, rac-H. The technique was validated by reproducing known branching ratios for OH abstraction for methanol and ethanol. For the amines studied in this work (all at 298 K): raC-H,MA = 0.76 ± 0.08, raC-H,DMA = 0.59 ± 0.07, and raC-H,EA = 0-49 ± 0.06 where the errors are a combination in quadrature of statistical errors at the 2σ level and an estimated 10% systematic error. The branching ratios H for OH reacting with (CH3)2NH and CH3CH2NH2 are in agreement with those obtained for the OD reaction with (CH3)2ND (d-DMA) and CH3CH2ND2 (d-EA): raC-H,d-DMA = 0.71 ± 0.12 and raC-H,d-EA = 0.54 ± 0.07. A master equation analysis (using the MESMER package) based on potential energy surfaces from G4 theory was used to demonstrate that the experimental determinations are unaffected by formation of stabilized peroxy radicals and to estimate atmospheric pressure yields. The branching ratio for imine formation through the reaction of 0 2 with a carbon-centered radicals at 1 atm of N2 are estimated as rCH2NH2 = 0.79 ± 0.15, rCH2NHCH3 = 0.72 ± 0.19, and rCH3CHNH2 = 0.50 ± 0.18. The implications of this work on the potential formation of nitrosamines and nitramines are briefly discussed. [ABSTRACT FROM AUTHOR]

Thestructures and thermochemistry of molecular clusters containingsulfuric acid, water, ammonia, and/or dimethylamine ((CH3)2NH or DMA) are explored using a combination of MonteCarlo configuration sampling, semiempirical calculations, and densityfunctional theory (DFT) calculations. Clusters are of the generalform [(BH+)n(HSO4–)n(H2O)y], where B = NH3or DMA, 2 ≤ n≤ 8, and 0 ≤ y≤10. Cluster formulas are written based on the computed structures,which uniformly show proton transfer from each sulfuric acid moleculeto a base molecule while the water molecules remain un-ionized. Clusterformation is energetically favorable, owing to strong electrostaticattraction among the ions. Water has a minor effect on the energeticsof cluster formation, lowering the free energy of formation by ∼10%depending on the cluster size and number of water molecules. Clustergrowth (addition of one base molecule and one sulfuric acid moleculeto a pre-existing cluster) and base substitution (substituting DMAfor ammonia) are also energetically favorable processes for both anhydrousand hydrated clusters. However, the effect of water is different fordifferent bases. Hydrated ammonium bisulfate clusters have a morefavorable free energy for growth (i.e., incrementing nwith fixed y) than anhydrous clusters, while thereverse is observed for dimethylammonium bisulfate clusters, wherethe free energy for growth is more favorable for anhydrous clusters.The substitution of DMA for ammonia in bisulfate clusters is favorablebut exhibits a complex water dependence. Base substitution in smallerbisulfate clusters is enhanced by the presence of water, while basesubstitution in larger bisulfate clusters is less favorable for hydratedclusters than that for anhydrous clusters. While DMA substitutioncan stabilize small clusters containing one or a few sulfuric acidmolecules, the free energy advantage of forming amine clusters relativeto ammonia clusters becomes less pronounced at larger sizes, especiallywhen the effect of water is considered. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effects of combined low-pressure ultraviolet (LPUV) irradiation and free chlorination on the formation of trichloronitromethane (TCNM) byproduct from amine precursors, including a commonly used polyamine coagulant aid (poly(epichlorohydrin dimethylamine)) and simple alkylamines dimethylamine (DMA) and methylamine (MA). Results showed that TCNM formation can increase up to 15 fold by combined UV/chlorine under disinfection to advanced oxidation conditions. The enhancement effect is influenced by UV irradiance, chlorine dose, and water pH. Extended reaction time leads to the decay of TCNM by direct photolysis. The combined UV/chlorine conditions significantly promoted degradation of polyamine to generate intermediates, including DMA and MA, which are better TCNM precursors than polyamine, and also facilitated transformation of these amine precursors to TCNM. Under combined UV/chlorine, polyamine degradation was likely promoted by radical oxidation, photodecay of chlorinated polyamine, and chlorine oxidation/substitution. Promoted TCNM formation from primary amine MA was primarily due to radicals' involvement. Promoted TCNM formation from secondary amine DMA likely involved a combination of radical oxidation, photoenhanced chlorination reactions, and other unknown mechanisms. Insights obtained in this study are useful for reducing TCNM formation during water treatment when both UV and chlorine will be encountered. [ABSTRACT FROM AUTHOR]

The overall rate constants of hydroxylradicals (OH) with ethylamine(EA: CH3CH2NH2) and dimethylamine(DMA: CH3NHCH3) were investigated behind reflectedshock waves using UV laser absorption of OH radicals near 306.7 nm. tert-Butyl hydroperoxide (TBHP) was used as the fast sourceof OH at elevated temperatures. Test gas mixtures of individual aminesand TBHP, diluted in argon, were shock-heated to temperatures from901 to 1368 K at pressures near 1.2 atm. The overall rate constantswere determined by fitting the measured OH time-histories with thecomputed profiles using a detailed mechanism developed by Lucassenet al. (Combust. Flame2012, 159, 2254–2279). Over the temperature range studied,the measured rate constants can be expressed as kEA+OH= 1.10 × 107·T1.93exp(1450/T) cm3mol–1s–1, and kDMA+OH= 2.26 × 104·T2.69exp(1797/T) cm3mol–1s–1. Detailed error analyses wereperformed to estimate the overall uncertainties of the measured reactionrate constants, and the estimated (2σ) uncertainties were foundto be ±31% at 901 K and ±22% at 1368 K for kEA+OH, and ±29% at 925 K and ±21% at 1307 Kfor kDMA+OH. Variational transition statetheory was used to compute the H-abstraction rates by OH for ethylamineand dimethylamine, with the potential energy surface, geometries,frequencies, and electronic energies calculated by Galano and Alvarez-Idaboy(J. Chem. Theory Comput.2008, 4, 322–327) at CCSD(T)/6-311++G(2d,2p) level of theory.The calculated reaction rate constants are in good agreement withthe experimental data. [ABSTRACT FROM AUTHOR]

Ammonia is a very useful chemical ionization (CI) reagent gas for the qualitative analyses of compounds by positive ion gas chromatography–mass spectrometry (GCMS). The gas is readily available, inexpensive, and leaves no carbon contamination in the MS source. Compounds of interest to our laboratory typically yield abundant protonated or ammoniated species, which are indicative of a compound’s molecular weight. Nevertheless, some labile compounds fragment extensively by substitution and elimination reactions and yield no molecular weight information. In these cases, a CI reagent gas mixture of methylamine in methane prepared dynamically was found to be very useful in obtaining molecular weight data. Likewise, deuterated ammonia and deuterated methylamine are useful CI reagent gases for determining the exchangeable protons in organic compounds. Deuterated methylamine CI reagent gas is conveniently prepared by dynamically mixing small amounts of methylamine with excess deuterated ammonia. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Regioselectivity is an important aspect in the design of organic protocols involving Directed ortho-Lithiation (DoL) of arenes, in particular with those arenes containing heteroatom substituents as directing groups. The DoL of 2-[(dimethylamino)methyl]naphthalene (dman) that proceeds with low regioselectivity was revisited by varying both the nature of the lithiating reagent (either n-BuLi or t-BuLi) and/or the solvent (pentane or diethyl ether); the 3-deuterated substrate, 3-Ddman, was also investigated as a substrate to compare to that of dman. The 3-lithio regioisomer exists as tetranuclear [2-(Me2NCH2)C10H6Li-3]4, 1, both in the solid state (X-ray) and in solution (NMR). The 1-lithio regioisomer, 2a, is insoluble; in the presence of additional coordinating solvents (Et2O) or ligands (dman), it exists as dinuclear [2-(Me2NCH2)C10H6Li-1]2·L (coordinated L = Et2O: 2b, dman: 2c) in apolar solvents. Heating solutions of 2c in toluene-d8 (to 90 °C) induced a surprisingly clean and quantitative 1-lithio to 3-lithio conversion of the 1-lithio-naphthalene isomer. This type of reaction is rare in organolithium chemistry and has obvious significant implications for the design of regioselective DoL protocols; this thus represents the synthetically useful protocol for the DoL of dman in a one-pot/two-step process in toluene solution. The results of the use of 3-Ddman in these reactions gives strong credence to a mechanism involving formation of the heteroleptic species [(2-(Me2NCH2)C10H6-1)(2-(Me2NCH2)C10H6-3)Li2]·[dman], A, as the key intermediate. Intramolecular trans-lithiation takes place with A; dman becomes selectively lithiated at its 3-position, while the formerly 1-lithio-naphthalene fragment, acting as a highly unusual ortho-lithiating reagent, is converted into the N-coordinated amine, dman. In this intramolecular DoL process, free dman can be considered to act as a catalyst. [ABSTRACT FROM AUTHOR]

Radical reactions of titanium(III) [Ti(tBu2O2NN')Cl(S)] (S = THF, 1; S = py, 2; tBu2O2NN' = Me2N(CH2)2N(CH2-2-O-3,5-tBu2C6H2)2) are described. Reactions with neutral electron acceptors led to metal oxidation to Ti(IV), [Ti(tBu2O2NN')Cl(TEMPO)] (4) being formed with the TEMPO radical and [Ti(tBu2O2NN')Cl2] (9) with PhN=NPh. [Ti(tBu2O2NN')Cl2] was also formed when [Ti(tBu2O2NN')Cl(S)] was oxidized by [Cp2Fe][BPh4], but the [Cp2Fe][PF6] analogue yielded [Ti(tBu2O2NN')ClF] (8). The reactions of [Ti(tBu2O2NN')Cl(S)] with O2 gave [Ti(tBu2O2NN')Cl]2(µ-O) (3). The DFT calculated Gibbs energy for the above reaction showed it to be exergonic (ΔG298 = -123.6 kcal·mol-1). [Ti(tBu2O2NN')(CH2Ph)(S)] (S = THF, 5; py, 6) are not stable in solution for long periods and in diethyl ether gave 1:1 cocrystals of [Ti(tBu2O2NN')(CH2Ph)2] (7) and [Ti(tBu2O2NN')Cl]2(µ-O) (3), most probably resulting from a disproportionation process of titanium(III) followed by oxygen abstraction by the resulting Ti(II) species. The oxidation of [Ti(tBu2O2NN')(?²-{CH2-2-(NMe2)-C6H4})] (10), which is a Ti(III) benzyl stabilized by the intramolecular coordination of the NMe2 moiety, led to a complex mixture. Recrystallization of this mixture under air led to a 1:1 cocrystal of two coordination isomers of the titanium oxo dimer (3). In one of these isomers, one metal is pentacoordinate and the dimethylamine moiety of the diamine bis(phenolate) ligand is not bonded to the metal, displaying a coordination mode of the ligand never observed before. The other titanium center is distorted octahedral with two cis-phenolate moieties. In the second unit, the coordination of the two ancillary ligands to the titanium centers reveals mutually cis-phenolate groups in one-half of the molecule and trans-coordinated in the other titanium center, keeping a distorted octahedral environment around each titanium. [ABSTRACT FROM AUTHOR]

Coordinatively unsaturated Pt(II) complex [Pt(ItBu′)(ItBu)]+ stabilized by N-heterocyclic carbene (NHC) ligands dehydrogenates N,N-dimethylamineborane through a mechanism that involves hydride abstraction, assisted by an amine, to yield a platinum-hydride complex [PtH(ItBu′)(ItBu)] with concomitant formation of the boronium cation [(NHMe2)2BH2]+. This latter species is very likely in equilibrium with the THF stabilized borenium cation [(NHMe2)(THF)BH2]+, bearing an acidic NH group that is able to protonate the platinum hydride [PtH(ItBu′)(ItBu)] releasing H2, the amino borane H2B-NMe2 and regenerating the catalytic [Pt]+ species. [ABSTRACT FROM AUTHOR]

Thephotophysical properties of 7-(dimethylamino)coumarin-3-carbaldehyde 3and its phenylsemicarbazone 4were investigatedin solvents of various polarity and in differing solvent mixtures.The different fluorescent quantum yield (ΦF) behaviorof 3and 4in highly polar solvents is discussedin terms of Twisted Intramolecular Charge-Tranfer (TICT) state formationand the specific solute–solvent interactions. Because of theweak intermolecular hydrogen bonding ability of both the radiativeICT and nonradiative TICT excited state of 3and thelinear steep decrease in ΦFfrom a medium to highpolarity region, coumarin 3could be a useful polarityprobe for microenvironments containing hydrogen bonding groups. Comparedto 3, coumarin 4exhibits the highest ΦFvalues in highly polar solvents with strong hydrogen bondacceptor ability. The high quantum yield of fluorescence in DMSO,DMF, and alcohols qualifies coumarin 4as a laser dyein the given medium, with kFhigher than knr. Contrary to previous reports that many H-aggregatesare nonfluorescent in nature, coumarin 3forms highlyfluorescent H-aggregates in MeOH and EtOH. On the basis of the restrictionsof the Kasha-exciton theory model, we assume that the formation offluorescent H-dimer aggregates of 3is driven by π+–π–interactions. To the bestof our knowledge, this is the first report on aggregation of coumarindye in alcoholic solutions. In addition, restrictions in the fittingprocedure relating to determination of the solvation number, n, using the Covington–Newman model of preferentialsolvation and also the solvent nonideality parameter, h′, are discussed in this article. [ABSTRACT FROM AUTHOR]

TheAsp-Phe-Gly (DFG) motif plays an important role in the regulationof kinase activity. Structure-based drug design was performed to designcompounds able to interact with the DFG motif; epidermal growth factorreceptor (EGFR) was selected as an example. Structural insights obtainedfrom the EGFR/2acomplex suggested that an extensionfrom the meta-position on the phenyl group (ring-5) would improveinteractions with the DFG motif. Indeed, introduction of an N,N-dimethylamino tail resulted in 4b, which showed almost 50-fold improvement in inhibitioncompared to 2a. Structural studies confirmed this N,N-dimethylamino tail moved toward theDFG motif to form a salt bridge with the side chain of Asp831. Thatthe interactions with the DFG motif greatly contribute to the potencyof 4bis strongly evidenced by synthesizing and testingcompounds 2a, 3g, and 4f: whenthe charge interactions are absent, the inhibitory activity decreasedsignificantly. [ABSTRACT FROM AUTHOR]

The formation ofatmospheric aerosol particles through clusteringof condensable vapors is an important contributor to the overall concentrationof these atmospheric particles. However, the details of the nucleationprocess are not yet well understood and are difficult to probe byexperimental means. Computational chemistry is a powerful tool forgaining insights about the nucleation mechanism. Here, we report accurateelectronic structure calculations of the potential energies of smallclusters made from sulfuric acid, ammonia, and dimethylamine. We alsoassess and validate the accuracy of less expensive methods that mightbe used for the calculation of the binding energies of larger clustersfor atmospheric modeling. The PW6B95-D3 density-functional-plus-molecular-mechanicscalculation with the MG3S basis set stands out as yielding excellentaccuracy while still being affordable for very large clusters. [ABSTRACT FROM AUTHOR]

A safe, practical, and scalable continuous flow protocol for the in situ generation of dimethylamine from DMF followed by nucleophilic aromatic substitution of a broad range of aromatic and heteroaromatic halides is reported. [ABSTRACT FROM AUTHOR]

A constrained model compound of trans-4-(N,N-dimethylamino)-4′-nitrostilbene(DNS), namely, compound DNS-B3 that is limited to torsions about thephenyl-nitro C–N bond and the central CC bond, wasprepared to investigate the structural nature of the radiative andnonradiative states of electronically excited DNS. The great similaritiesin solvent-dependent electronic spectra, fluorescence decay times,and quantum yields for fluorescence (Φf) and trans→ cis photoisomerization (Φtc) between DNSand DNS-B3 indicate that the fluorescence is from a planar charge-transferstate and torsion of the nitro group is sufficient to account forthe nonradiative decay of DNS. This conclusion is supported by TDDFTcalculations on DNS-B3 in dichloromethane. The structure at the conicalintersection for internal conversion is associated with not only atwisting but also a pyramidalization of the nitro group. The mechanismof the NO2torsion is discussed in terms of the effectsof solvent polarity, the substituents, and the volume demand. Thedifferences and analogies of the NO2- vs amino-twistedintramolecular charge-transfer (TICT) state of trans-aminostilbenes are also discussed. [ABSTRACT FROM AUTHOR]

An efficient Cu(I)-catalyzed synthesis of 3-aroylindoles has been achieved from o-alkynylated N,N-dimethylamines via a sp3C–H bond activation α to the nitrogen atom followed by an intramolecular nucleophilic attack with the alkyne using an aqueous solution of tert-butyl hydroperoxide (TBHP) as the oxidant. In this tandem catalytic synthesis of 3-aroylindoles both C–C and C–O bonds are installed at the expense of two sp3C–H bond cleavages. [ABSTRACT FROM AUTHOR]

The Rh(III) species Rh(PCy3)2H2Cl is an effective catalyst (2 mol%, 298 K) for the dehydrogenation of H3B-NMe2H (0.072 M in 1,2-F2C6H4 solvent) to ultimately afford the dimeric aminoborane [H2BNMe2]2. Mechanistic studies on the early stages in the consumption of H3B-NMe2H, using initial rate and H/D exchange experiments, indicate possible dehydrogenation mechanisms that invoke turnover limiting N--H activation, which either precedes or follows B-- H activation, to form H2B=NMe2, which then dimerizes to give [H2BNMe2]2. An additional detail is that the active catalyst Rh(PCy3)2H2Cl is in rapid equilibrium with an inactive dimeric species, [Rh(PCy3)H2Cl]2. The reaction of Rh(PCy3)2H2Cl with [Rh(PCy3)H2(H2)2][BArF4] forms the halide-bridged adduct [Rh(PCy3)2H2(μ-Cl)H2(PCy3)2Rh][BArF4] (ArF = 3,5-(CF3)2C6H3), which has been crystallographically characterized. This dinuclear cation dissociates on addition of H3B NMe2H to reform Rh(PCy3)2H2Cl and generate [Rh(PCy3)2H2(n²-H3B-NMe2H)][BArF4]. The fate of the catalyst at low catalyst loadings (0.5 mol %) is also addressed, with the formation of an inactive borohydride species, Rh(PCy3)2H2(n²-H2BH2), observed. On addition of H3B-NMe2H to Ir(PCy3)2H2Cl, the Ir congener Ir(PCy3)2H2(n2-H2BH2) is formed, with concomitant generation of the salt [H2B(NMe2H)2]Cl. [ABSTRACT FROM AUTHOR]

Methods for online characterization and quantification of gas- and particle-phase species greatly facilitate the study of aerosol particle formation and reaction mechanisms. An online method for aerosol analysis has been developed by altering a conventional electrospray ionization mass spectrometer to direct the aerosol flow through the nebulizing gas inlet. Interaction between the aerosol and electrospray droplets produces ions that are subsequently analyzed by MS or MS/MS with a quadrupole ion trap mass analyzer. Performance is assessed using both particle-phase (cesium iodide, glycine) and gas-phase (dimethylamine, dimethylnapthylamine) analytes as well as a secondary organic aerosol (SOA) produced by ozonolysis of a-pinene. Analyte signal intensity is strongly dependent on solubility in the electrospray solvent, suggesting that the predominant ionization mechanism involves extraction of the analyte into the electrospray droplets. For gas-phase analytes, gas-phase charge transfer also appears to play a minor role in ion formation. As currently configured, the source is capable of characterizing oligomers in a SOA at a mass loading of <30 μg/m³ and quantifying alkyl amine concentrations between approximately 8 ppb and 1 ppm. [ABSTRACT FROM AUTHOR]

The "element effect" in nucleophilic aromatic substitution reactions (SNAr) is characterized by the leaving group order, F > NO2 > Cl ≈ Br > I, in activated aryl halides. Multiple causes for this result have been proposed. Experimental evidence shows that the element effect order in the reaction of piperidine with 2,4-dinitrophenyl halides in methanol is governed by the differences in enthalpies of activation. Computational studies of the reaction of piperidine and dimethylamine with the same aryl halides using the polarizable continuum model (PCM) for solvation indicate that polar, polarizability, solvation, and negative hyperconjugative effects are all of some importance in producing the element effect in methanol. In addition, a reversal of polarity of the C--X bond from reactant to transition state in the case of ArCl and ArBr compared to ArF also contributes to their differences in reactivity. The polarity reversal and hyperconjugative influences have received little or no attention in the past Nor has differential solvation of the different transition states been strongly emphasized. An anionic nucleophile, thiolate, gives very early transition states and negative activation enthalpies with activated aryl halides. The element effect is not established for these reactions. We suggest that the leaving group order in the gas phase will be dependent on the exact combination of nucleophile, leaving group, and substrate framework. The geometry of the SNAr transition state permits useful, qualitative conceptual distinctions to be made between this reaction and other modes of nucleophilic attack. [ABSTRACT FROM AUTHOR]

Heterogeneous uptake of methylamine (MA), dimethylamine (DMA), and trimethylamine (TMA) onto citric acid and humic acid was investigated using a Knudsen cell reactor coupled to a quadrupole mass spectrometer at 298 K. Acid-base reactions between amines and carboxylic acids were confirmed. The observed uptake coefficients of MA, DMA, and TMA on citric acid at 298 K were measured to be 7.31 ± 1.13 × 10-3, 6.65 ± 0.49 × 10-3, and 5.82 ± 0.68 × 10-3, respectively, and showed independence of sample mass. The observed uptake coefficients of MA, DMA, and TMA on humic acid at 298 K increased linearly with sample mass, and the true uptake coefficients of MA, DMA, and TMA were measured to be 1.26 ± 0.07 × 10-5, 7.33 ± 0.40 × 10-6, and 4.75 ± 0.15 × 10-6, respectively. Citric acid, having stronger acidity, showed a higher reactivity than humic acid for a given amine; while the steric effect of amines was found to govern the reactivity between amines and citric acid or humic acid. [ABSTRACT FROM AUTHOR]

The study presents a novel chemo-mechanical joint-sensing method to distinguish a certain molecule from its homologous chemicals, using both a resonant cantilever for gravimetric sensing and a static cantilever for surface-stress sensing. Homologous amines of trimethylamine (TMA, Me3N), dimethylamine (DMA, Me2NH), and monomethylamine (MMA, MeNH2) are herein used as model objects for investigation. The molecular identification is based on experimental characterizations on both molecule adsorbing capability (by the resonant cantilever) and intermolecular lateral interaction (by the static cantilever). The intensities of the two sets of sensing signals are expected to be in opposite sequence with each other, due to the complementary relationship among the interhomologue molecule structures, i.e., a molecule containing a greater number of methyl substituents must possess a fewer number of nonsubstituted hydrogens. On the basis of the proposed idea, ppm-level vapors of the three amines are sequentially detected by a resonant microcantilever to characterize the molecular adsorption speed and another static cantilever to characterize the intermolecular lateral attraction induced surface stress. From the experiment, a pair of opposite sequence in sensing-signal amplitude has indeed been obtained that verifies the proposed joint-sensing method. In addition, the two sensing signals both show a linear relationship with chemical concentration (at low-concentration range). Further comparison between the two sensing results can help to build a model to identify the molecule among a series of its homologous chemicals by eliminating the influence from concentration. Since a complementary relationship among homologous molecule structures widely exists, the dual-sensing method is promising in on-the-spot rapid molecular identification among homologous chemicals. [ABSTRACT FROM AUTHOR]

Asymmetric dimethylation of arginine side chains is a common post-translational modification of eukaryotic proteins, which serves mostly to regulate protein-protein interactions. The modification is catalyzed by type I protein arginine methyltransferases, PRMT1 being the predominant member of the family. Determinants of substrate specificity of these enzymes are poorly understood. The Nuclear poly(A) binding protein 1 (PABPN1) is methylated by PRMT1 at 13 arginine residues located in RXR sequences in the protein's C-terminal domain. We have identified a preferred Site for PRMT1-catalyzed methylation in PABPN1 and in a corresponding synthetic peptide. Variants of these substrates were analyzed by steady-state kinetic analysis and mass spectrometry. The data indicate that initial methylation is directed toward the preferred arginine residue by an N-terminally adjacent proline. Enhanced methylation upon peptide cyclization suggests that induction of a reverse turn structure is the basis for the ability of the respective proline residue to enable preferred methylation of the neighboring arginine residue, and this notion is supported by far-UV circular dichroism spectroscopy. We suggest that the formation of a reverse turn facilitates the access of arginine side chains to the active sites of PRMT1, which are located in the central cavity of a doughnut-shaped PRMT1 homodimer. [ABSTRACT FROM AUTHOR]

Following the same philosophy of our previous force fieldfor primaryamines (J. Phys. Chem. B2011, 115, 14617), we present an extension for secondary and tertiaryamines using the anisotropic united atom (AUA4) approach. The forcefield is developed to predict the phase equilibrium and transportproperties of secondary and tertiary amines. The transferability wasstudied for an important set of molecules including as secondary aminesdimethylamine, diethylamine, di-n-propylamine, di-iso-propylamine,and di-iso-butylamine. We have also tested diethylenetriamine, a multifunctionalmolecule which includes two primary and one secondary amino groups.For tertiary amines, we have included simulations for trimethylamine,triethylamine, tri-n-propylamine, and methyldiethylamine.Monte Carlo simulations in the Gibbs ensemble were carried out tostudy thermodynamic properties such as equilibrium densities, vaporizationenthalpies, and vapor pressures. Critical coordinates (critical densityand critical temperature) and normal boiling points were also calculated.The shear viscosity coefficients were studied for dimethyl, diethyl,di-n-propyl, trimethyl, triethyl, and tri-n-propylamine at different temperatures using moleculardynamics in the isothermal isobaric ensemble. Our results show a verygood agreement with experimental values for all the studied moleculesfor both thermodynamic and transport properties, demonstrating thetransferability of our force field. [ABSTRACT FROM AUTHOR]

A Calix[6]arene scaffold was functionalized to provide a tridentate binding site at the small rim and three bidentate chelate sites at the large rim of the cone to generate a heteropolytopic ligand. Its complexation to one equivalent of ZnII at the small rim yields a funnel complex displaying both host-guest properties and preorganization of the three chelate groups at the large rim. These two aspects allowed the full control of the binding events to regioselectively form dinuclear ZnII and heteropolynuclear ZnII/CuI complexes. The heteropolynuclear systems all rely on the host-guest relationship thanks to the induced-fit behavior of the calix cavity. With the short guest MeCN, the large rim is preorganized into a trigonal tris-triazole core and accommodates a single CuI ion. A long guest breaks this spatial arrangement, and three CuI ions can then be bound at the tris-bidentate triazole-dimethylamine site at the large rim. In a noncoordinating solvent however, the tetranuclear complex is submitted to scrambling and the addition of exogenous π-acceptor ligands is required to control the binding of CuI in a well-defined environment. Hindrance selectivity was then induced by the accessibility at the small rim site. Indeed, while CO can stabilize CuI at both coordination sites, PPh3 cannot fit into the cavity and forces CuI to relocate at the large rim. The resulting well-defined symmetrical tetranuclear complex thus arises from the quite remarkable selective supramolecular assembly of nine partners (1 ZnII, 3 CuI, 1 calixarene, 1 guest alkylamine, 3 PPh3). [ABSTRACT FROM AUTHOR]