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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]

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]

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]

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]

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]

Catalytic turnover of Neurospora crassa 2-nitropropane dioxygenase with nitroethane as substrate occurs through both nonoxidative and oxidative pathways. The pH dependence of the kinetic isotope effects with [1,1-2H2]nitroethane as substrate was measured in the current study by monitoring the formation of the nitronate product in the nonoxidative pathway. The kinetic isotope effect on the second-order rate constant for nitronate formation, kcat/Km, decreased from an upper limiting value of 23 ± I at low pH to a lower limiting value of 11 ± 1 at high pH. These kinetic isotope effects are three times larger than those determined previously through measurements of oxygen consumption that occurs in the oxidative pathway of the enzyme [(2006) Biochemistry 45, 13889]. Analytical expressions for the kcat/Km values determined in each study show that the difference in the kinetic isotope effects arises from the branching of an enzyme-ethylnitronate reaction intermediate through oxidative and nonoxidative turnover. This branching is isotope sensitive due to a kinetic isotope effect on nitronate release rather than on flavin reduction as indicated by the pH-independent Dkred value of 0.99 ± 0.06 with ethylnitronate as substrate. The kinetic isotope effect on ethylnitronate release arises from the deprotonation of histidine 196, which provides electrostatic interactions with the nitronate to keep it bound in the active site for oxidation. The isotope effect on branching results in an inflation of the kinetic isotope observed for the nonoxidative pathway to values that are larger than the intrinsic values associated with CH bond cleavage. [ABSTRACT FROM AUTHOR]

Among the enzymes that catalyze the oxidative denitrification of nitroalkanes to carbonyl compounds, 2-nitropropane dioxygenase is the only one known to effectively utilize both the neutral and anionic (nitronate) forms of the substrate. A recent study has established that the catalytic pathway is common to both types of substrates, except for the initial removal of a proton from the at carbon of the neutral substrates [Francis, K., Russell, B., and Gadda, G. (2005) J. Biol. Chem. 280, 5195–5204]. In the present study, the mechanistic properties of the enzyme have been investigated with solvent viscosity, pH, and kinetic isotope effects. With nitroethane or ethylnitronate, the kcat/Km and kcat values were independent of solvent viscosity, consistent with the substrate and product binding to the enzyme in rapid equilibrium. The abstraction of the proton from the at carbon of neutral substrates was investigated by measuring the pH dependence of the D(kcat/KNE) value with 1,1-[²H2]-nitroethane. The formation of the enzyme-bound flavosemiquinone formed during catalysis was examined by determining the pH dependence of the kcat/Km values with ethylnitronate and nitroethane and the inhibition by m-nitrobenzoate. Finally, α-secondary kinetic isotope effects with 1-[²H]-ethylnitronate were used to propose a non-oxidative tautomerization pathway, in which the enzyme catalyzes the interconversion of nitroalkanes between their anionic and neutral forms. The data presented suggest that enzymatic turnover of 2-nitropropane dioxygenase with neutral substrates is limited by the cleavage of the substrate CH bond at low pH, whereas that with anionic substrates is limited by the non-oxidative tautomerization of ethylnitroante to nitroethane at high pH. [ABSTRACT FROM AUTHOR]

The acetic acid-promoted addition of lithium nitropropanate and the Lewis acid-catalyzed [Sc(OTf)3, Cu(OTf)2, or Ti(OiPr)4] addition of trimethylsilyl nitropropanate to a range of heteroaromatic and simple aliphatic aldimines gave anti-rich (∼3-19:1 β-nitroamines in >95% yields as the kinetic products. It was found that a nonpolar N-imine protecting group was essential for reactivity with the o-methoxybenzyl (0MB) group giving better selectivities and yields than p-methoxybenzyl (PMB) or p-methoxyphenyl (PMP) in the Lewis acid-catalyzed addition reactions. Reduction with SmI2, treatment with COCl2, followed by OMB deprotection gave diastereomerically pure cis-imidazolidinones in 55–79% overall yield from imine. Preliminary results have shown that acetic acid can catalyze the reaction of N-OMB-benzylideneamine with nitropropane, used as solvent, to give the thermodynamically more stable syn-β-nitroamine product. [ABSTRACT FROM AUTHOR]

Demonstrates the novel evidence that the driving force controls the transition between stepwise and concerted mechanisms in dissociative electron transfer or charge exchange. Reaction of 4-nitrocumyl chloride with 2-nitropropanate ion; Initiation of the SRN1 reaction by a simple outersphere electron transfer from the nucleophile to the substrate.

Investigates the electrochemical debromination reactions of erythro-dl-1-aryl-1,2-dibromo-2-nitropropanes at a platinum electrode by cyclic voltammetry in 0.10 Molar LiClO4/DMSO. Irreversibility of cyclic voltammograms; Decrease in reduction current with increase in number of cycles; Current density and substrate concentration; Mechanism of the reactions.

Investigates the kinetics of the debromination reactions of erythro-dl-1-aryl-1,2-dibromo-2-nitropropanes with secondary amines in methyl cyanide. Stereospecificity of reactions; Determination of the element effect of the leaving group for dehalogenation reactions; Assessment of the mechanism and transition-state character of the reactions.

The article describes the reactivity of the monoterpenoid nerol with p-Toluenesulfonic and Chlorosulfonic Acids. The main product when p-toluenesulfonic acid is used as a reagent is α-Terpineol and α-cyclogeranino, 4, is the main product when the superacid chlorosulfonic acid is used as a reagent. The nerol reaction with p-toluenesulfonic acid us conducted at room temperature in a stirred solution of nitromethane or dichloromethane. The reaction of nerol with chlorosulfonic acid is carried out at low temperature in 2-nitropropane.

In this article, dedicated to Professor Fred McLafferty, I wish to recollect early observations with regard to the rearrangement named after him for 1-nitropropane and the methyl ester of γ-nitrobutyric acid. This rearrangement occurs for both cases clearly in a stepwise fashion, although for the ester, it occurs as a hidden rearrangement that catalyzes the tautomerization of the nitro group into its aci-form. [Copyright &y& Elsevier]

Presents information on a study which described an intermolecular dioxygenation reaction using a copper(I) aci-2-nitropropanate complex. Experimental details; Results and discussion.

Reports on reactions of 1-aryl-1,2-dibromo-2-nitropropanes with 2-nitro-2-propyl anion in dimethyl sulphoxide (DMSO). Single-electron transfer (SET) mechanisms; Experimental procedures.