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Nitroalkanes such as nitromethane, nitroethane, 1-nitropropane (1NP), and 2-nitropropane (2NP), derived from anthropogenic activities, are hazardous environmental pollutants due to their toxicity and carcinogenic activity. In nature, 3-nitropropionate (3NPA) and its derivatives are produced as a defense mechanism by many groups of organisms, including bacteria, fungi, insects, and plants. 3NPA is highly toxic as its conjugate base, propionate-3-nitronate (P3N), is a potent inhibitor of mitochondrial succinate dehydrogenase, essential to the tricarboxylic acid cycle, and can inhibit isocitrate lyase, a critical enzyme of the glyoxylate cycle. In response to these toxic compounds, several organisms on the phylogenetic scale express genes that code for enzymes involved in the catabolism of nitroalkanes: nitroalkane oxidases (NAOs) and nitronate monooxygenases (NMOs) (previously classified as nitropropane dioxygenases, NPDs). Two types of NMOs have been identified: class I and class II, which differ in structure, catalytic efficiency, and preferred substrates. This review focuses on the biochemical properties, structure, classification, and physiological functions of NMOs, and offers perspectives for their in vivo and in vitro applications. Key points: • Nitronate monooxygenases (NMOs) are key enzymes in nitroalkane catabolism. • NMO enzymes are involved in defense mechanisms in different organisms. • NMO applications include organic synthesis, biocatalysts, and bioremediation. [ABSTRACT FROM AUTHOR]

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Photoexcitation of 2-bromo-2-nitropropane (BNP) at 248 and 193 nm generates OH, Br, and NO2 among other products. The OH fragment is detected by laser-induced fluorescence spectroscopy, and its translational and internal state distributions (vibration, rotation, spin-orbit, and Λ-doubling components) are probed. At both 248 and 193 nm, the OH fragment is produced translationally hot with the energy of 10.8 and 17.2 kcal/mol, respectively. It is produced vibrationally cold (v″ = 0) at 248 nm, and excited (v″ = 1) at 193 nm with a vibrational temperature of 1870 ± 150 K. It is also generated with rotational excitation, rotational populations of OH(v″ = 0) being characterized by a temperature of 550 ± 50 and 925 ± 100 K at 248 and 193 nm excitation of BNP, respectively. The spin-orbit components of OH(X2Π) are not in equilibrium on excitation at 193 nm, but the Λ-doublets are almost in equilibrium, implying no preference for its π lobe with respect to the plane of rotation. The NO2 product is produced electronically excited, as detected by measuring UV-visible fluorescence, at 193 nm and mostly in the ground electronic state at 248 nm. The Br product is detected employing resonance-enhanced multiphoton ionization with time-of-flight mass spectrometer for better understanding of the dynamics of dissociation. The forward convolution analysis of the experimental data has provided translational energy distributions and anisotropy parameters for both Br(2P3/2) and Br*(2P1/2). The average translational energies for the Br and Br* channels are 5.0 ± 1.0 and 6.0 ± 1.5 kcal/mol. No recoil anisotropies were observed for these products. Most plausible mechanisms of OH and Br formation are discussed based on both the experimental and the theoretical results. Results suggest that the electronically excited BNP molecules at 248 and 234 nm relax to the ground state, and subsequently dissociate to produce OH and Br through different channels. The mechanism of OH formation from BNP on excitation at 193 nm is also discussed. [ABSTRACT FROM AUTHOR]

The thermodynamic consistency of the isobaric heat capacity per unit volume at constant composition Cp,x and the density ρ near the liquid-liquid critical point is studied in detail. To this end, Cp,x(T), ρ(T), and the slope of the critical line (dT/dp)c for five binary mixtures composed by 1-nitropropane and an alkane were analyzed. Both Cp,x(T) and ρ(T) data were measured along various quasicritical isopleths with a view to evaluate the effect of the uncertainty in the critical composition value on the corresponding critical amplitudes. By adopting the traditionally employed strategies for data treatment, consistency within 0.01 K MPa-1 (or 8%) is attained, thereby largely improving the majority of previous results. From temperature range shrinking fits and fits in which higher-order terms in the theoretical expressions for Cp,x(T) and ρ(T) are included, we conclude that discrepancies come mainly from inherent difficulties in determining the critical anomaly of ρ accurately: specifically, to get full consistency, higher-order terms in ρ(T) are needed; however, the various contributions at play cannot be separated unambiguously. As a consequence, the use of Cp,x(T) and (dT/dp)c for predicting the behavior of ρ(T) at near criticality appears to be the best choice at the actual experimental resolution levels. Furthermore, the reasonably good thermodynamic consistency being encountered confirms that previous arguments appealing to the inadequacy of the theoretical expression relating Cp,x and ρ for describing data in the experimentally accessible region must be fairly rejected. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Thermophile W-2 could degrade nitroalkane under aerobic and anaerobic conditions. • Three NOEs displayed high optimum active temperature and wide substrate specificity. • Gt2929 possessed excellent specific activity, thermostability and pH stability. • Gt1378 played an important role in anaerobic degradation. Abstract In this study, a thermophilic facultative anaerobic strain Geobacillus thermoglucosidasius W-2 was found to degrade nitroalkane under both aerobic and anaerobic conditions. Bioinformatical analysis revealed three putative nitroalkane-oxidizing enzymes (Gt-NOEs) genes from the W-2 genome. The three identified proteins Gt2929, Gt1378, and Gt1208 displayed optimal activities at high temperatures (70, 70, and 80 °C, respectively). Among these, Gt2929 exhibited excellent degradation capability, pH stability, and metal ion tolerance for nitronates under aerobic condition. Interestingly, under anaerobic condition, only Gt1378 still maintained high activity for 2-nitropropane and nitroethane, indicating that the W-2 strain utilized various pathways to degrade nitronates under aerobic and anaerobic conditions, respectively. Taken together, the first revelation of thermophilic nitroalkane-degrading mechanism under both aerobic and anaerobic conditions provides guidance and platform for biotechnological and industrial applications. [ABSTRACT FROM AUTHOR]

Nitromethylation of nitrones occurred efficiently in CH3NO2 in the presence of tetramethylammonium fluoride or triazabicyclodecene as promoters. The obtained adducts might be conveniently transformed into vicinal diamines. The process was extended to nitroethane and nitropropane affording mixtures of syn and anti stereoisomers with low diastereoselectivity. Comprehensive study of the addition of nitroalkanes to nitrones was conducted. The reaction proved efficient with TMAF or TBD as bases, in the presence of a large excess of R–NO2. Phase‐transfer catalysis gave also acceptable yields. Nitroethane or nitropropane afforded mixtures of isomerisable diastereomers. The reaction was applied to the synthesis of biologically relevant compounds. [ABSTRACT FROM AUTHOR]

The activity coefficients γ 13 ∞ at infinite dilution for 64 solutes were determined in the 1-(3-hydroxypropyl)-3-methylimidazolium dicyanamide, [ N -C 3 OHMIM][DCA] and 58 solutes in (3-hydroxypropyl)-1-methylmorpholinium dicyanamide, [ N -C 3 OHMMor][DCA] using the gas-liquid chromatography technique. Measurements were undertaken at six temperatures, in 10 K intervals, in the range of (298.15–368.15) K. The solutes studied included both non-polar and polar compounds, as alkanes, alkenes, and alkynes, as well as aromatic hydrocarbons, alcohols, water, ethers, ketones, acetonitrile, pyridine, 1-nitropropane, thiophene, and esters. Density, ρ , measurements for a range of temperatures (298.15–368.15) K for the synthesized, new ionic liquids (ILs) were also undertaken at pressure, p  = 101 kPa. The gas-liquid partition coefficients, K L at infinite dilution, and the fundamental thermodynamic functions, partial molar excess Gibbs energy, enthalpy and entropy at infinite dilution were calculated from the experimental data measurements. The values of selectivity and capacity for three separation cases, viz . hexane/hex-1-ene, cyclohexane/cyclohexene, and ethylbenzene/styrene were calculated from γ 13 ∞ values and compared to literature for imidazolium-based, morfolinium-based, or dicyanamide-based, ILs. The results from the study indicate that [ N -C 3 OHMIM][DCA] has large selectivity values for all three of the separation cases studied and that [ N -C 3 OHMMor][DCA] has the largest selectivity ever noted for cyclohexane/cyclohexene, and ethylbenzene/styrene separation processes. [ABSTRACT FROM AUTHOR]

A novel method has been developed for the direct, sensitive, and rapid detection of bronopol in rice using a simple solid-phase extraction (SPE) procedure followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), with electrospray ionization (ESI). Bronopol was stable under acidic conditions, and an acidic environment was thus needed before sample loading to ensure the stability of bronopol. Rice extracts containing bronopol were pretreated using a hydrophilic-lipophilic balanced (Bond Elut Plexa) cartridge to reduce the matrix effect. An XDB-C18 column (150 mm × 2.1 mm, 3.5 μm) was used for chromatographic separations, with a mobile phase comprising methanol and aqueous ammonium formate (5 mM). The linearity of the method was satisfactory with regression coefficient ( R ) = 0.9992. The limit of quantification was 3.3 μg kg. Three spiked levels (25, 125 and 625 μg kg) were used to determine the recovery of bronopol, which was found to be 73.3-96.7%, with relative standard deviations (RSD) in the range 1.2-7.9%. The RSD for intra-day precision ( n = 7) was 7.6% and the RSD for inter-day precision ( n = 15) was 8.3%. The newly developed analytical method was successfully used to quantify bronopol in rice samples. [ABSTRACT FROM AUTHOR]

Thermochemical properties of aliphatic nitroalkanes available in the literature are scarce and inconsistent. New standard molar enthalpies of vaporization and sublimation of 2-nitropropane, 2-methyl-2-nitropropane, and 2,3-dimethyl-2,3-dinitrobutane were derived from the vapor pressure temperature dependence measured by the transpiration method. Thermodynamic data on linear and branched aliphatic mono- and di-nitroalkanes available in the literature were combined with own experimental results and evaluated with help of empirical and theoretical methods aiming at recommendation of the sets of vaporization and formation enthalpies for aliphatic nitroalkanes as the reliable benchmark properties for further thermochemical calculations. Gas phase standard molar enthalpies of formation of aliphatic nitro-compounds derived by high-level quantum-chemical method G4 were found in a good agreement with the evaluated and recommended experimental data. Group-additivity procedure for calculation of vaporization and formation enthalpies have been developed and tested. [ABSTRACT FROM AUTHOR]

Previously, we isolated several genes that potentially affected the expression of type III secretion system (T3SS) in Ralstonia solanacearum OE1-1. Here, we focused on the rsp0316, which encodes a putative 2-nitropropane dioxygenase (hereafter designated NpdA). The deletion of npdA substantially reduced the T3SS expression and virulence in OE1-1, and the complementation with functional NpdA could completely restore its reduced T3SS expression and virulence to that of wild type. The NpdA was highly conserved among diverse R. solanacearum species and the NpdA-dependent expression of T3SS was not specific to OE1-1 strain, but not the virulence. The NpdA was important for the T3SS expression in planta, while it was not required for the bacterial growth in planta. Moreover, the NpdA was not required for the elicitation of hypersensitive response (HR) of R. solanacearum strains in tobacco leaves. The T3SS in R. solanacearum is directly controlled by the AraC-type transcriptional regulator HrpB and regulated by a complex regulation network. The NpdA affected the T3SS expression mediated with HrpB but through some novel pathway. All these results from genetic studies demonstrate that NpdA is a novel factor for the T3SS expression in diverse R. solanacearum species in medium, but specifically for the T3SS expression in strain OE1-1 in planta. And the NpdA-dependent expression of T3SS in planta plays an important role in pathogenicity of R. solanacearum OE1-1 in host plants. [ABSTRACT FROM AUTHOR]

New measurements on infinite dilution activity coefficients ( γ ∞ ) of 48 molecular solutes (including: alkanes, alkenes, alkynes, aromatics, ethers, alcohols, ketones, pyridine, thiophene, acetonitrile and 1-nitropropane) in 1-(3-cyanopropyl)-3-methylimidazolium dicyanamide ionic liquid (IL) are reported in temperature range from T = (308.15 to 368.15) K and addressed to previously published data. Relationships between the chemical structure of the solute and the observed value of γ ∞ , closely related to relative strength and nature of molecular interactions, are elucidated by the data and discussed. An effect of substitution of methyl group by cyano functional group in the cation's side chain is analyzed based on a comparison of the measurements with the data published previously for a “plain” counterpart of the studied IL, namely, 1-butyl-3-methylimidazolium dicyanamide. Besides, infinite dilution selectivity is adopted to evaluate the IL under study as an entrainer for common separation problems. Three modeling approaches are demonstrated to be capable of capturing the substitution effects observed experimentally. First, representation of the investigated systems by linear solvation-energy relationship (LSER) is shown and an effect of cyano group is confirmed in terms of the coefficients of the obtained correlation. Hildebrand solubility parameters of pure IL are calculated by regressing the γ ∞ data with regular solution theory in order to check an influence on enthalpy of vaporization. Finally, conductor-like screening model for real solvents (COSMO-RS) calculations is demonstrated along with a discussion of an impact of molecular geometry of cation and solute on the accuracy of predicted γ ∞ data. [ABSTRACT FROM AUTHOR]

The crystal structure of 1,1-bis(methoxy-NNO-azoxy)-3,3,3-trinitropropane is studied. [ABSTRACT FROM AUTHOR]

The thermal decomposition of gaseous nitromethane and the subsequent bimolecular reaction between CH3 and NO2 have been experimentally studied using time-resolved cavity-enhanced absorption spectroscopy behind reflected shock waves in the temperature range 1336-1827 K and at a pressure of 100 kPa. Temporal evolution of NO2 was observed following the pyrolysis of nitromethane (diluted to 80-140 ppm in argon) by monitoring the absorption around 400 nm. The primary objectives of the current work were to evaluate the rate constant for the CH3 + NO2 reaction (k2) and to examine the contribution of the roaming isomerization pathway in nitromethane decomposition. The resultant rate constant can be expressed as k2 = (9.3 ± 1.8) x 10-10(T/K)-0.5 cm² molecule-1 s-1, which is in reasonable agreement with available literature data. The decomposition of nitromethane was found to predominantly proceed with the C-N bond fission process with the branching fraction of 0.97 ± 0.06. Therefore, the upper limit of the branching fraction for the roaming pathway was evaluated to be 0.09. [ABSTRACT FROM AUTHOR]

Conformational study of 5-bromo-2-(2-methylpropyl)-5-nitro-1,3,2-dioxaborinane at the DFT PBE/3ξ level of theory revealed the only sofa-sofa interconversion pathway through a transition state corresponding to 2,5- twist conformer. The barrier to internal rotation of the axial nitro group is several times higher than that for the equatorial nitro group. According to the H, C, and B NMR, IR, and X-ray diffraction data, the main autooxidation products of 5-bromo-2-(2-methylpropyl)-5-nitro-1,3,2-dioxaborinane are 2-bromo-2-nitropropane-1,3-diol and boric acid. [ABSTRACT FROM AUTHOR]

The thermal decomposition of nitropropane (CHCHCHNO) has been investigated at the CBS-QB3 level of theory. The pyrolysis of CHCHCHNO mainly includes the simple bond ruptures mechanism, hydrogen abstraction processes, isomerization and secondary reactions. As a result, for the simple bond ruptures mechanism, the formation of $${\text{CH}}_{3} {\text{CH}}_{2} {\text{CH}}_{2}^{\cdot} +\,^{\cdot}{\text{NO}}_{2}$$ products is dominant with the energy barrier of 49.77 kcal mol. The process of H atom on the β-CH abstracted by one O atom of NO moiety in CHCHCHNO(CHCHCHNO → CHCH=CH + HONO) needs to overcome lower energy barrier than that of the rate-determining step (one of H atom on the α-CH and γ-CH abstracted of reaction) of the other hydrogen abstraction reactions. Therefore, we predict that the corresponding alkenes and HONO are the main products in the hydrogen abstraction reaction of nitroparaffin. Besides, the channel of the CHCHCHO + HNO formations (CHCHC(α)HNO → CHCHC(α)HONO → CHCHCHO + HNO), occurring through the H atom of C(α) abstracted by the N atom of NO moiety after the isomerization reaction from CHCHCHNO to CHCHCHONO, is favorable in the isomerization secondary reactions. Rate constants and branching ratios are estimated by means of the conventional transition state theory with zero curvature tunneling over the temperature range of 400-1500 K. The calculation shows that the overall rate constant in the temperature of 400-1500 K is mainly dependent on the competitive channels of formations of CHCH=CH + HONO and $${\text{CH}}_{3} {\text{CH}}_{2} {\text{CH}}_{2}^{\cdot} +\,^{\cdot}{\text{NO}}_{2}$$ The three-parameter expression for the total rate constant is fitted to be k = 1.74 × 10 T exp(17038.7/ T) (s) between 400 and 1500 K. [ABSTRACT FROM AUTHOR]

The structure and internal rotation of the 2-methyl-2-nitropropane molecule is studied by electron diffraction and quantum chemical calculations with the use of microwave and vibrational spectroscopy data. The electron diffraction data are analyzed within the general intramolecular anharmonic force field model and the quantum chemical pseudoconformer model, considering the adiabatic separation of the degree of freedom of large amplitude motion, i.e., the internal rotation of the NO group. The equilibrium eclipsed configuration of the C symmetry molecule has the following experimental bond lengths and valence angles: r (N=O) = 1.226//1.226(8) Å, r (C-N)// r (C-C) = 1.520//1.515/1,521(4) Å, ∠C-C-N = = 109.1/106,1(8)°, ∠O=N=O = 124.2(6)°, ∠C-C-H = 110(3)°. The equilibrium geometry parameters are well consistent with MP2/cc-pVTZ quantum chemical calculations and microwave spectroscopy data. The thermally average parameters previously obtained within the small vibration model show a satisfactory agreement with the new results. The electron diffraction data used in this work do not allow a reliable determination of the barrier to internal rotation. However, at a barrier of 203(2) cal/mol, which is derived from the microwave study, it follows from the electron diffraction data that the equilibrium configuration must correspond to an eclipsed arrangement of C-C and N=O bonds, which is also consistent with the results of quantum chemical calculations of various levels. [ABSTRACT FROM AUTHOR]

The effect of interaction between organic solvents or water on the interfacial and bulk properties of 1-allyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide ([AMIM][NTf 2 ]) and on activity coefficients ( γ 13 ∞ ) at infinite dilution for 64 solutes. The observations monitored by gas-liquid chromatography at six temperatures in range of (318.15–368.15) K are explained for polar and non-polar solutes as alkanes, alkenes and alkynes as well as aromatic hydrocarbons, alcohols, water, ethers, ketones, acetonitrile, pyridine, 1-nitropropane, thiophene, and esters. Density, ρ and viscosity η as a function of temperature, T for chosen ionic liquid, [AMIM][NTf 2 ] at pressure p = 101 kPa were measured. The gas-liquid partition coefficients, K L at infinite dilution and the fundamental thermodynamic functions, the partial molar excess Gibbs energy, enthalpy and entropy at infinite dilution were calculated. The values of selectivity and capacity for three separation problems as hexane/hex-1-ene, cyclohexane/cyclohexene and ethylbenzene/styrene were calculated from γ 13 ∞ and compared to literature values for imidazolium-based or bis{(trifluoromethyl)sulfonyl}imide-based ionic liquids (ILs) for the same separation problems. The data presented here show that [AMIM][NTf 2 ] reveals average selectivity in the comparison to measured earlier ILs in the chosen separation problems. These findings seem useful for future applications of ILs especially for alkanes/alkenes separation process. [ABSTRACT FROM AUTHOR]

As a continuation of our effort to understand degradation mechanisms of a eutectic mixture of bis(2,2-dinitropropyl) acetal (BDNPA) and bis(2,2-dinitropropyl) formal (BDNPF) (referred to as NP) under various environmental conditions, we investigated the thermal stability of NP under water and 74% relative humidity (RH) environments at temperatures below 70 °C. Based on a comprehensive characterization of samples aged over a period of two years, we conclude that in the presence of water the reaction pathways of NP degradation are different from those observed in air or under nitrogen atmosphere. We found that the physical state of water molecules plays an important role as it determines the ability of oxygen to participate in the NP degradation process. Based on the results obtained in Parts A and B of these studies, we conclude that the rate of NP degradation increases in the following order: nitrogen < water < air < water vapor + air. [ABSTRACT FROM AUTHOR]

In this work, a highly reproducible standard gas generating vial is proposed. The vial is comprised of a silicon diffusion pump oil spiked with an appropriate calibration compound, such as modified McReynolds probes (benzene, 2-pentanone, pyridine, 1-nitropropane, 1-pentanol, and n-octane), and then mixed with polystyrene/divinylbenzene (PS/DVB) particles. The concentrations of these compounds in gaseous headspace were found to substantially decrease in comparison to previously developed hydrocarbon pump oil based vials; hence, the amount of standard loaded onto SPME fibers was at most, half that of the previous vial design. Depletion for all compounds after 208 successive extractions was shown to be less than 3.5%. Smaller quantities of standards being used resulted in a vial that depleted slower while remaining statistically repeatable over a wider number of runs. Indeed, it was found that depletion could be largely predicted by using a mass balance theoretical model. This behavior allowed a further increase in the number of loadings that could be performed repeatedly. At a 95% level of confidence, the ANOVA test demonstrated that the prepared vials were statistically identical, with no significant intra- or inter-batch differences. In addition, it was found that vials stored under different conditions (e.g. under light exposure, room temperature, and within a refrigerator) were stable over 10 weeks. Silicon based vials proved to be ideal for performing instrument quality control and loading of internal standards onto fibers, both of which are of great importance when performing on-site analysis using portable GC–MS instrumentation and high throughput determinations in laboratory. [ABSTRACT FROM AUTHOR]

An explosion that occurred during a nitromethane rectification process is investigated. Experiments were performed in an effort to elucidate the cause of the explosion. All test samples analyzed, including reaction product, crude product, 99% pure product and raffinate, were collected from the accident site. Gas chromatography was used to analyze the components of the samples, thermal analysis determined the exothermic character of the samples and the sample evaporating experiment recorded the reaction phenomena occurring at low liquid level. Based on the experimental results, the excess heat released by the decomposition of overheated raffinate is pinpointed as the root cause of the explosion. [ABSTRACT FROM AUTHOR]

The utility of the repeated-dose liver micronucleus (RDLMN) assay in the detection of a genotoxic hepatocarcinogen was evaluated. In this paper, a rat hepatocarcinogen, 2-nitropropane (2-NP), was administered orally to young adult rats for 14 and 28 days without a partial hepatectomy or a mitogen, and the micronucleus induction in liver was examined using a simple method to isolate hepatocytes. In addition, a bone marrow micronucleus assay was conducted concomitantly. The frequency of micronucleated hepatocytes induced by 2-NP increased significantly in both the 14- and 28-day repeated-dose studies, while the bone marrow micronucleus assays were negative in each study. These results indicate that the RDLMN assay is useful for detecting a genotoxic hepatocarcinogen that is negative in bone marrow micronucleus assays and is a suitable in vivo genotoxicity test method for integration into a repeated-dose general toxicity study. [ABSTRACT FROM AUTHOR]

A simple and mild Pd-catalysed carbonylative α-arylation of nitromethane has been realised providing access to α-nitro aryl ketones from an array of aryl and heteroaryl iodides. The methodology requires only a mild base and uses the convenient solid CO releasing molecule, COgen in a two-chamber system. Changing to the isotopically labelled 13COgen, [13C]-acyl labelling can be effected through the generation of a near stoichiometric amount of 13CO. Lastly, the significance of the generated products as synthetic intermediates is demonstrated. [ABSTRACT FROM AUTHOR]

An easily available N,N'-dioxide/Cu(I) complex has been developed for the catalytic asymmetric nitroaldol (Henry) reaction of aldehydes with nitroethane. Under mild reaction conditions, a series of substituted aromatic, heteroaromatic and α,β-unsaturated aldehydes are transformed to the corresponding anti-β-nitroalcohols in good to excellent yields (up to 99%) with moderate to good dr (up to 16.7:1 anti/syn) and high ee values (up to 97%). Besides nitroethane, nitromethane and 1-nitropropane were also employed as nucleophiles, and good enantioselectivities were obtained. [ABSTRACT FROM AUTHOR]

Polydentate ligands 1 and 2, which incorporate a terminal pyridyl moiety and an oxygen-rich oxalate dihydrizide/malonic dihydrizide spacer moiety, as well as their binuclear metal complexes [Cu212] and [Cu222], which adopt a 1:1 metal/ligand ratio, were synthesized and characterized. Both complexes were screened for their catalytic activity in the nitroaldol reaction, in which [Cu212] worked efficiently as catalyst for both substituted benzaldehyde and pyridinecarboxaldehyde, whereas [Cu222] is highly substrate specific and showed activity towards nitro-substituted aldehydes and pyridinecarboxaldehyde. Furthermore, as helicates are intrinsically chiral, the stereochemical architecture in the binuclear double-stranded Cu2 helicates as catalyst favored the diastereoselective syn product with nitroethane and nitropropane and their respective diastereoselectivities were determined by using ¹H NMR spectroscopy. [ABSTRACT FROM AUTHOR]

A convenient and practical catalytic method for the preparation of caffeic acid esters is reported. This esterification was carried out with high efficiency in the presence of ytterbium triflate in nitromethane without any other auxiliary reagents. The wide scope of application and especially the higher reactivity and more convenient procedure than previous methods make it a valuable application for the synthesis of caffeic acid esters and other cinnamic acid esters. [ABSTRACT FROM AUTHOR]

A series of 3-nitro-2-trifluoromethyl-2 H-chromenes was synthesized by the reactions of salicylaldehyde derivatives with 3,3,3-trifluoro-1-nitroprop-1-ene. Further transformations of the synthesized chromenes gave hitherto unknown 3-amino-2-trifluoromethylchromanes promising as precursors for the synthesis of fused heterocyclic systems. Cytotoxicity assay first revealed the pronounced activity of several 2-nitro-2-trifluoromethyl-2 H-chromenes against human tumor cell lines. [ABSTRACT FROM AUTHOR]

Three main primary fragmentation channels of molecular ion (m/z > 89) of 1-nitropropane induced by γ-hydrogen shift: (1) McLafferty rearrangement, (2) formation of nitric oxide and (3) detachment of hydroxyl induced by γ-hydrogen transfer were studied employing ab initio UMP2 level of theory. Gibbs energies for all stationary points were computed using CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ technique. Results obtained in the course of present theoretical study give additional support to stepwise mechanism of McLafferty rearrangement which has recently sparked much argument in the mass spectrometry community. We have performed for the first time, the reaction pathways for hydroxyl loss from ion m/z??89 accompanied by formation of four and five-membered heterocyclic cations with m/z 72. Rice-Ramsperger-Kassel-Marcus (RRKM) theory was employed for calculation of the unimolecular rate constants of fragmentation channels. [ABSTRACT FROM AUTHOR]

Theseexperiments investigate the decomposition mechanisms of geminaldinitro energetic materials by photolytically generating two key intermediates:2-nitropropene and 2-nitro-2-propyl radicals. To characterize theunimolecular dissociation of each intermediate, we form them undercollision-free conditions using the photodissociation of 2-bromo-2-nitropropane;the intermediates are formed at high internal energies and undergoa multitude of subsequent unimolecular dissociation events investigatedherein. Complementing our prior work on this system, the new dataobtained with a crossed-laser molecular beam scattering apparatuswith VUV photoionization detection at Taiwan’s National SynchrotronRadiation Research Center (NSRRC) and new velocity map imaging databetter characterize two of the four primary 193 nm photodissociationchannels. The C–Br photofission channel forming the 2-nitro-2-propylradicals has a trimodal recoil kinetic energy distribution, P(ET), suggesting that the 2-nitro-2-propylradicals are formed both in the ground electronic state and in twolow-lying excited electronic states. The new data also revise theHBr photoelimination P(ET) forming the 2-nitropropene intermediate. We then resolved the multiplecompeting unimolecular dissociation channels of each photoproduct,confirming many of the channels detected in the prior study, but notall. The new data detected HONO product at m/e= 47 using 11.3 eV photoionization from both intermediates;analysis of the momentum-matched products allows us to establish thatboth 2-nitro-2-propyl → HONO + CH3CCH2and 2-nitropropene → HONO + C3H4occur.Photoionization at 9.5 eV allowed us to detect the mass 71 coproductformed in OH loss from 2-nitro-2-propyl; a channel missed in our priorstudy. The dynamics of the highly exothermic 2-nitro-2-propyl →NO + acetone dissociation is also better characterized; it evidencesa sideways scattered angular distribution. The detection of some stable2-nitropropene photoproducts allows us to fit signal previously assignedto H loss from 2-nitro-2-propyl radicals. Overall, the data providea comprehensive study of the unimolecular dissociation channels ofthese important nitro-containing intermediates. [ABSTRACT FROM AUTHOR]

Highlights: [•] We have studied 2-methyl-2-nitropropane hydrogenation. [•] We consider homogeneous steps, reactions on the support and on the metal. [•] Hydrogen activation takes place on the metal, and may spillover and jumpover. [•] Organic reactants and intermediates may be activated on the metal and on the carbon support. [•] A synergic effect is observed, depending on the chemical surface of the support. [ABSTRACT FROM AUTHOR]

Highlights: [•] Modelling of degree of adiabaticity for diffusional electrode processes is considered. [•] A potential energy curve formalism has been employed in the kinetic model. [•] 2-Nitropropane reduction on mercury is studied via temperature-variable voltammetry. [•] Cyclic voltammograms are recorded in DMSO solutions at temperatures 22.0–44.5°C. [•] The adiabatic character depends on the size of the supporting electrolyte cation. [ABSTRACT FROM AUTHOR]

Abstract: 3-Nitropropionic acid (3-NP), a mitochondrial toxin, has been reported to induce an acute cochlear damage. Korean red ginseng (KRG) is known to have protective effects from some types of hearing loss. This study aimed to observe the protective effect of KRG in an ototoxic animal model using 3-NP intratympanic injection. BALB/c mice were classified into 5 groups (n =15) and dose-dependent toxic effects after intratympanic injection with 3-NP (300–5000mM) on the left ear were investigated to determine the appropriate toxicity level of 3-NP. For observation of the protective effects of KRG, 23 mice were grouped into 3-NP (500mM, n =12) and KRG+3-NP groups (300mg/kg KRG for 7 days before 500mM 3-NP administration, n =11). Auditory brain response (ABR) and cochlear morphological evaluations were performed before and after drug administration. The ABR thresholds in the 800–5000mM groups exceeded the maximum recording limit at 16 and 32kHz 1 day after 3-NP administration. The ABR threshold in the 500mM 3-NP+KRG group was significantly lower than that in the 500mM 3-NP group from post 1 week to 1 month. The mean type II fibrocyte counts significantly differed between the control and 3-NP groups and between the 3-NP and 3-NP+KRG groups. Spiral ganglion cell degeneration in the 3-NP group was more severe than that in the 3-NP+KRG group. This animal model exhibited a dose-dependent hearing loss with histological changes. KRG administration ameliorated the deterioration of hearing by 3-NP. [Copyright &y& Elsevier]

Abstract: It is a common misconception that the amount of explosive is the chief contributor to the quantity of vapor that is available to trained canines. In fact, this quantity (known as odor availability) depends not only on the amount of explosive material, but also the container volume, explosive vapor pressure and temperature. In order to better understand odor availability, headspace experiments were conducted and the results were compared to theory. The vapor-phase concentrations of three liquid explosives (nitromethane, nitroethane and nitropropane) were predicted using the Ideal Gas Law for containers of various volumes that are in use for canine testing. These predictions were verified through experiments that varied the amount of sample, the container size, and the temperature. These results demonstrated that the amount of sample that is needed to saturate different sized containers is small, predictable and agrees well with theory. In general, and as expected, once the headspace of a container is saturated, any subsequent increase in sample volume will not result in the release of more vapors. The ability of canines to recognize and alert to differing amounts of nitromethane has also been studied. In particular, it was found that the response of trained canines is independent of the amount of nitromethane present, provided it is a sufficient quantity to saturate the container in which it is held. [Copyright &y& Elsevier]

Abstract: The asymmetric Marcus–Hush (MH) model for electrode kinetics is applied to the kinetic study of the electroreduction of 2-methyl-2-nitropropane in acetonitrile, cyclooctatetraene in dimethylsulfoxide and europium(III) in aqueous solution, using mercury microhemispheres as working electrodes. This kinetic model includes the possibility of the oxidative and reductive processes having different reorganization energies due to differences between the force constants of the electroactive species. For each redox couple, the response obtained in cyclic and square wave voltammetries can be fitted satisfactorily with the four-parameter asymmetric MH model. From the fitting of the voltammograms the values of the kinetic parameters are extracted and analyzed in terms of physical properties of the electroactive species. A comparison of the asymmetric model against the simpler, phenomenological Butler–Volmer (BV) approach is discussed, as well as a possible physical interpretation for the BV transfer coefficient. [Copyright &y& Elsevier]

The tandem reaction of trisubstituted epoxides to cyclopentanes promoted by TIPSOTf in nitromethane has been found. It consists of stereospecific rearrangement of epoxides into aldehydes accompanied with selective alkyl migration and subsequent Prinstype cyclization of the aldehydes generated to cyclopentanes. [ABSTRACT FROM AUTHOR]

A chemoenzymatic approach towards benzoylated uronic acid building blocks has been investigated starting with benzoylated hexapyranosides using regioselective C-6 enzymatic hydrolysis as the key step. Two of the building blocks were reacted with the antiepileptic drug lamotrigine. Glucuronidation of lamotrigine using methyl (2,3,4-tri-O-benzoyl-α-D-glycopyranosyl bromide)uronate proceeded to give the N2-conjugate. However, lamotrigine-N2-glucuronide was most efficiently synthesised from methyl (2,3,4-tri-O-acetyl-α-D-glucopyranosyl bromide)uronate. Employing nitromethane as solvent with CdCO3 as a base lamotrigine-N2 glucuronide was prepared in a high yield (41%). Also methyl (2,3-di-O-benzoyl-4-deoxy-4-fluoro-α-D-glucosyl bromide)uronate underwent N-glucuronidation, but the product was unstable, eliminating hydrogen fluoride to give the corresponding enoate conjugate. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the concordance of results for a pair of structural isomers, 2-nitropropane (2-NP) and 1-nitropropane (1-NP), using the rat medium-term liver carcinogenesis bioassay (Ito test) and previously published long-term carcinogenicity tests. Male F344 rats were given a single intraperitoneal injection of DEN (200 mg/kg b.w.) to initiate hepatocarcinogenesis. After 2 weeks, they received per os 0, 0.8, 4 or 20 mg/kg/day of 2-NP or 1-NP six times a week and were subjected to two-thirds partial hepatectomy at week 3. Non-initiated groups receiving 0 or 20 mg/kg/day were also included. The animals were sacrificed for quantitative analysis of GST-P-positive foci at week 8. With the highest dose of 2-NP, significantly increased numbers and areas of GST-P-positive foci were demonstrated as compared with the respective control but were not noted with 1-NP. In the non-DEN-initiated groups, many small GST-P-positive foci of less than 0.2 mm in diameter were also induced in the rats treated with 2-NP at 20 mg/kg/day but were lacking with 1-NP. These results strongly support that 2-NP is a complete hepatocarcinogen with a potent initiation activity, whereas 1-NP is not. [ABSTRACT FROM AUTHOR]

Abstract: V79-hCYP2E1-hSULT1A1, a V79-derived cell line co-expressing both human CYP2E1 and SULT1A1, has been constructed and efficiently used in detection of the mutagenic activities of a number of promutagens. 2-Nitropropane (2-NP) and N-nitrosodimethylamine (NDMA), both being hepatocarcinogenic to animals but inactive in standard genotoxicity assays in vitro, are activated to mutagenic metabolites by human SULT1A1 and CYP2E1, respectively. Nevertheless, little is known about the chromosomal effects of these two carcinogens. In the present study, we investigated the effects of 2-NP and NDMA on frequencies of micronucleated (F mi) and multinucleated cells (F mu) in V79-hCYP2E1-hSULT1A1 cells. The results showed induction of both F mi and F mu by 2-NP and NDMA individually, and this effect was completely suppressed by relatively specific inhibitor of SULT1A1 and CYP2E1, i.e., pentachlorophenol and 1-aminobenzotriazole, respectively. The F mu/F mi ratio in 2-NP groups was significantly higher than NDMA groups, probably indicating an aneugenic activity of 2-NP based on proposed F mu/F mi ratio as a simple index to discriminate aneugens from clastogens. The present study has established biotransformation enzyme-dependent formation of multinuclei and micronuclei induced by 2-NP and NDMA. [Copyright &y& Elsevier]

5,5-Dimethylpyrroline N-oxide (15N) and 5,5-di(trideuteromethyl)pyrroline N-oxide were synthesized from the respective isotopically labeled 2-nitropropane analogs obtained from the reaction of sodium nitrate with 2-halopropanes. This facile, straightforward process allows synthesizing isotopically labeled DMPO analogs in a 4-step reaction without special equipment. [ABSTRACT FROM AUTHOR]

Abstract: The Marcus-Hush and Butler–Volmer kinetic electrode models are compared experimentally by studying the reduction of 2-methyl-2-nitropropane in acetonitrile at mercury microelectrodes using Reverse Scan Square Wave Voltammetry. This technique is found to be very sensitive to the electrode kinetics and to permit critical comparison of the two models. The Butler–Volmer model satisfactorily fits the experimental data whereas Marcus-Hush does not quantitatively describe this redox system. [Copyright &y& Elsevier]

To elucidate the accelerating effect of 1-nitropropane on the thermal cracking of normal alkanes, ab initio and density functional theory calculations were performed to investigate the elementary reactions involved in the initiated thermal cracking of a 1-nitropropane/n-heptane mixture. The kinetic parameters were evaluated on the basis of standard transition state theory (TST) or variational transition state theory (VTST) with Wigner tunneling correction. The activation energy for the C–N bond rupture of 1-nitropropane to produce primary n-propyl and nitro radicals is calculated to be 234–269 kJ/mol, while the bond dissociation energy of the C–C bond within the n-heptane molecule is predicted to be at least 335 kJ/mol. These calculated results demonstrate that the presence of 1-nitropropane makes the free radical formation become relatively easier compared with single n-heptane cracking. Furthermore, compared with the C–H bond cleavage and 1,3-H intramolecular transfer, the unstable n-propyl radical mainly follows the C–C bond cleavage pathway to produce ethylene and secondary ĊH3radical. After formation of these free radicals, the H-abstraction of n-heptane with radicals occurs readily with considerably lower activation energy than the radical formation step to initiate the chain reaction. The analysis result indicates that the thermal cracking of n-heptane is accelerated mainly due to the change of the initial step from the C–C bond cleavage of n-heptane to the C–N bond rupture of 1-nitropropane. [ABSTRACT FROM AUTHOR]

This is the second in a series of papers to summarize results of the impact of nonmetallic fuel additives on soot. The research was conducted by a university, industry, and government team with the primary objective of obtaining fundamental understanding of the mechanisms through which additive compounds blended into a fuel affect soot emissions. The work involved coordinated testing across a suite of laboratory devices: a shock tube, a well-stirred reactor, a premixed flat flame, an opposed-jet diffusion flame, and a high-pressure turbulent reactor. This article summarizes results on the addition of nitroalkanes to a base fuel consisting of n-heptane and toluene as a simple surrogate for jet fuels. In these experiments, the nitroalkanes serve as chemical probes of key reactions leading to soot. The effects of nitroalkane addition on soot were found to be device and condition dependent with no simple trends across the suite of devices. [ABSTRACT FROM AUTHOR]

Cyclization of pseudoionone (PI) to β-ionone is an important reaction used in the synthesis of vitamin A and in perfumery. Though the reaction is used for commercial production, its mechanism and kinetics are not known, and the same holds for the optimal performance of the process. This paper deals with experimental investigations of reaction mechanism and kinetics. The inherent characteristics of the reaction such as heat of reaction, thermal stability, and reactants/products distribution in biphasic (sulfuric acid-toluene) system was investigated experimentally. To overcome the mass transfer limitations, the intrinsic kinetics was studied in a batch reactor using a solvent (1-nitropropane) miscible with the reactant and the homogeneous catalyst. It was revealed that the reaction consists of two steps with the first being rapid, while the second is relatively slower. Therefore, the kinetics of only the second step was investigated which was observed to be first order with an activation energy of 65 kJ/mol. [ABSTRACT FROM AUTHOR]

Abstract: The absolute photoionization cross-sections of 24 nitrogenous compounds were measured in the photon energy range from their respective ionization thresholds to 11.5eV, including n-propylamine, iso-propylamine, n-butylamine, 2-butylamine, iso-butylamine, tert-butylamine, diethylamine, dibutylamine, triethylamine, aniline, benzylamine, n-methylaniline, cyclohexanamine, nitromethane, nitroethane, nitropropane, nitrobenzene, pyrrole, pyridine, pyrrolidine, morpholine, N,N-dimethylethanolamine, benzonitrile and benzeneacetonitrile. The experiments were performed by photoionization mass spectrometry with tunable synchrotron vacuum ultraviolet (VUV) light as an ionization source. Binary-liquid-mixtures of investigated and standard species were used in this measurement. As a good solvent, benzene was chosen as a calibration standard, since its photoionization cross-section had been well know. Moreover, photodissociative fragments were also presented. [Copyright &y& Elsevier]

2, 2-Dinitro-l-butanol was obtained using 1-nitropropane as a raw material through the reaction of the oxidative-nitration and methylolation. 2,2-Dinitrobutyl acrylate was prepared from 2,2- dinitro-l-butanol and acrylic acid through direct esterification. The energetic binder poly (2, 2- dinitrobutyl acrylate) was synthesized by the free radical polymerization of 2,2-dinitrobutyl acrylate in toluene and using azobisiosbutyronitrile as initiator. The polymerization rate equation was determined experimentally. The structure and thermal properties of poly (2, 2-dinitrobutyl acrylate) were also characterized by the methods of FTIR, ¹HNMR, TG, DSC. The results show that the polymerization rate equation for 2, 2-dinitrobutyl acrylate is Rp = k[M]1, 27 [I]0, 63 , which displays that the chain termination reaction is the coexistence mode of mono- and bi-molecular termination, and the initiating process is dependent on monomer concentration. The thermal decomposition temperature of poly (2,2- dinitrobutyl acrylate) is 260°C with mass loss of 21%. [ABSTRACT FROM AUTHOR]

Synthesis of a new series of (5-bromo-5-nitro-2-oxido-1,3,2-dioxaphosphinan-2-yl)amino acid esters (3a-l) was accomplished via a two step process, which involves the prior preparation of the monochloride intermediate (2) and its subsequent reaction with the amino acid esters in dry tetrahydrofuran in the presence of triethylamine at reflux temperature. The title compounds (3a-l) structures were established by analytical, IR, ¹H-, 13C- and 31P-NMR, and mass spectral data. They exhibited significant antibacterial and antifungal activity. [ABSTRACT FROM AUTHOR]