O-NO2 Bond Research Articles

Enhancing accuracy in equivalent in-service-time assessment for homogeneous solid propellants: a novel temperature-independent predictive model utilizing PCA of FTIR data

The present study was devoted to setting a universal T-independent predictive model of equivalent in-service-time (EIST) for homogenous solid propellant (HSP) to surpass the limits of the van't Hoff law particularly when high aging temperatures and/or extended aging durations are employed in artificial aging plans. To achieve this objective, four double base rocket propellants (DBRP) underwent artificial aging for 4 months at temperatures of 323.65 K, 338.65 K, 353.65 K, and 368.65 K, with sampling conducted every 20 days. Fourier Transform Infrared spectrometry (FTIR) showed that the homolytic scission of the ONO2 bonds and the hydrocarbon chains of the nitrate esters are the main processes occurring during the chemical decomposition. With the heating temperature increase, the chemical decomposition becomes more predominant. Furthermore, the scatter plot from Principal Component Analysis (PCA) of FTIR spectra obtained from each aging temperature showed, respectively, that over than 88.9 %, 94.3 %, 97.4 %, and 98.6% of the variances were described by the first principal component. This latter value was found 97.6 % when PCA was applied to all FTIR spectra. Using the PCA/FTIR approach recently developed, EIST was assessed for all the investigated samples. Subsequently, an individual predictive model of EIST was set for each heating temperature, which were used to establish the T-independent predictive model. The final model computed the EIST with a relative deviation of 5.3 % compared to those from the PCA/FTIR experimental way. Moreover, two similar DBRPs aged at different temperatures and durations have been used to validate the predictive model, and the associated mean absolute percentage error (MAPE) was found 4.6 %. The conducted comprehensive statistical analysis highlighted the excellent goodness-of-fit of the model. Furthermore, all the error metrics were found to decrease with the increase of the natural aging of the propellant and the heating temperature.

Structure of lanthanide nitrates in solution and in the solid state: DFT modelling of hydration effects

Five types of [Ln(NO3)3(H2O)4] neutral complexes with different mutual arrangement of nitrato and aqua ligands are established by the analysis of crystallographic data. Quantum chemical calculations performed at the level of density functional theory employing full-electron relativistic approach and effective core potential with different functionals and basis sets demonstrate that each of these structure types converges to a specific energy minimum, thus these types should be considered as isomers. Besides this, two isomers have been found for [Ln(NO3)3(H2O)3] complexes. In all structures of isomers optimized with the gas-phase approximation, Ln–ONO2 bonds are significantly shorter that Ln–OH2 bonds, in contrast to the results of X-ray diffraction and EXAFS studies of single crystals and aqueous solutions, respectively. This discrepancy arises from the fact that in crystals and solutions, complex molecules form numerous hydrogen bonds, which enhance charge transfer in the H2O → Ln3+ → NO3− chains and increase the relative stability of isomers where the nitrate anions are arranged separately from the aqua ligands. The effect of environment on electronic and spatial structures of [Ln(NO3)3(H2O)n] (n = 3, 4) complexes has been modelled at the levels of polarizable continuum model (PCM) and cluster approach. When using PCM, the similarity of quantum chemical and experimental bond lengths enhances, but complete agreement is not reached. Better agreement is achieved within the clusters {[La(NO3)3(H2O)4]∙nH2O} (n = 18, 21, 32, 50), where the effects of hydrogen bonding are modelled explicitly. These clusters are highly flexible with both hydration shells and the central core being easily rearranged under the effect of outer water molecules. With an increase in cluster size, new local energy minima appear related with the structures with monodentate nitrate anion and with nitrate anion positioned in the second coordination sphere of the cation. Joint analysis of simulation results together with literature data on the structure and dynamic behavior of lanthanide nitrates in aqueous solutions allows conclusion that the entire set of equilibria involving [La(NO3)3(H2O)n] complexes should be considered as a dynamic combinatorial library.

Молекулярная структура и ИК-спектры бутилнитратов

The article is devoted to the description of using of two density functional methods B3LYP/6-31+G(2df, p) and wB97X/Def2TZVPP, the geometric parameters and vibration frequencies of the CONO2 group, as well as the enthalpy of formation and dissociation energy of the O-NO2 bond in the molecules of isomeric butyl nitrates (butyl nitrate, 2-butyl nitrate, isobutyl nitrate, tert-butyl nitrate) are determined. The authors show that the observed changes in the geometric parameters of the CONO2 group in the series of compounds studied are insignificant. According to the B3LYP method, they are 4.1 pm for the C–O bond, 0.7 pm for the O–NO2 bond, and about 1 degree for the ONO angle. Another method used in this work (wB97X) predicts similar values of changes in the series. At the same time, the results of calculation make it possible to reliably distinguish, by the value of the geometric parameters, the nitrate groups attached to the primary secondary and tertiary carbon atoms, respectively. It is noted that the highest values of enthalpies of formation and energies (enthalpies) of dissociation are observed for compounds in which nitrate groups are attached to the primary carbon atom. The correlation dependences in the change in the enthalpies of formation of compounds and radicals, which are formed upon homolytic cleavage of the O-NO2 bond, have been revealed. The tendencies of change in the series convey both methods used in the work in the same way. However, a comparison of the results with the available experimental data on the kinetics of thermal decomposition of the studied aliphatic nitrates shows that the most reliable estimates are the wB97X/Def2TZVPP method. The calculated values obtained on the basis of another B3LYP method used in the work are underestimated, by about 3-4 kcal/mol. It was found that of the stretching vibrations of the CONO2 group, only asymmetric vibrations of N-O are characteristic.

ReaxFF Molecular Dynamics Simulation of Hydrostatic and Uniaxial Compression of Nitrate Energetic Materials.

The physical and chemical properties of typical nitrate energetic materials under hydrostatic compression and uniaxial compression were studied using the ReaxFF/lg force field combined with the molecular dynamics simulation method. Under hydrostatic compression, the P–V curve and the bulk modulus (B0) obtained using the VFRS equation of state show that the compressibility of the three crystals is nitroglycerine (NG) > erythritol tetranitrate (ETN) > 2,3-bis-hydroxymethyl-2,3-dinitro-1,4-butanediol tetranitrate (NEST-1). The a- and c-axis of ETN are easy to compress under the action of hydrostatic pressure, but the b-axis is not easy to compress. The b-axis of NEST-1 is the most compressible, while the a- and c-axis can be compressed slightly when the initial pressure increases and then remains unchanged afterward. The a-, b-, and c-axes of NG all have similar compressibilities. By analyzing the change trend of the main bond lengths of the crystals, it can be seen that the most stable of the three crystals is the N–O bond and the largest change is in the O–NO2 bond. The stability of the C–O bond shows that the NO3 produced by nitrates is not from the C–O bond fracture. Under uniaxial compression, the stress tensor component, the average principal stress, and the hydrostatic pressure have similar trends and amplitudes, indicating that the anisotropy behaviors of the three crystals ETN, NEST-1, and NG are weak. There is no significant correlation between maximum shear stress and sensitivity. The maximum shear stresses τxyand τyz of the ETN in the [010] direction are 1.5 GPa higher than τxz. However, the maximum shear stress of NG shows irregularity in different compression directions, indicating that there is no obvious correlation between the maximum shear stress and sensitivity.

Bonding analysis of the effect of strain on trigger bonds in organic-cage energetic materials

Wiberg bond index and natural bond orbital analyses were used to examine the effect of strain on trigger bonds for a series of organic-cage molecules. In substituted cage hydrocarbons, weakening of the interior C–C bonds and strengthening of exterior C–X bonds are explained in terms of the contributions of the carbon 2s and 2p atomic orbitals to the bonds. The interior C–C, rather than C–NO2, bonds are expected to break to initiate explosive decomposition in nitro-substituted tetrahedranes, prismanes, and cubanes. Activation of C–C bonds in cage molecules increases with nitro substitution, but persubstituted cages are not necessarily the most activated. For example, heptanitrocubane is predicted to be more sensitive than octanitrocubane, consistent with experimental studies. In contrast, for a series of hypothetical nitroester substituted prismanes, the strengthening of the exterior C–ONO2 bond weakens the O–NO2 bond more than the interior C–C bonds. In CL-20 and TEX, cage strain as determined by WBI analysis in the fused five- and six-membered rings is less significant than for the cage hydrocarbon. In these known energetic materials, the N–NO2 trigger bonds are activated by the orientation of the nitro groups.

Thermal Decomposition Behavior and Thermal Safety of Nitrocellulose with Different Shape CuO and Al/CuONanothermites.

Bamboo leaf-like CuO(b) and flaky-shaped CuO(f) were prepared by the hydrothermal method, and then combined with Al nanoparticles to form Al/CuO(b) and Al/CuO(f) by the ultrasonic dispersion method. The phase, composition, morphology, and structure of the composites were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy scattering spectrometer (EDS). The compatibility of CuO, Al/CuO and nitrocellulose (NC) was evaluated by differential scanning calorimetry (DSC). The effects of CuO and Al/CuO on the thermal decomposition of NC were also studied. The results show that the thermal decomposition reactions of CuO-NC composite, Al/CuO-NC composite, and NC follow the same kinetic mechanism of Avrami-Erofeev equation. In the cases of CuO and Al/CuO, they could promote the O-NO2 bond cleavage and secondary autocatalytic reaction in condensed phase. The effects of these catalysts have some difference in modifying the thermolysis process of NC due to the microstructures of CuO and the addition of Al nanopowders. Furthermore, the presence of Al/CuO(f) can make the Al/CuO(f)-NC composite easier to ignite, whereas the composites have strong resistance to high temperature. Compatibility and thermal safety analysis showed that the Al/CuO had good compatibility with NC and it could be used safely. This contribution suggests that CuO and Al/CuO played key roles in accelerating the thermal decomposition of NC.

Thermal Decomposition Mechanism of Nitroglycerin by ReaxFF Reactive Molecular Dynamics Simulations

ABSTRACT The decomposition processes of nitroglycerin (NG) at various temperatures (2500, 2750, 3000, 3250 and 3500 K) are simulated by the reactive molecular dynamics simulations with ReaxFF-lg. The initial decomposition pathway of NG, the evolution of the main products and the reaction kinetic parameters for the different stages are analyzed. The results show that the main initial decomposition mechanisms of NG are O-NO2 bond dissociation and the hydrogen capture reaction of NO2. The main products of NG thermal decomposition are NO2, NO, HNO, CO2, N2, and H2O, while CO2, N2, and H2O are the final products. As the temperature increases, the processes of O-NO2 bond dissociation and the hydrogen capture reaction of NO2 accelerate, resulting in accelerated decomposition of NG. The reaction kinetic parameters are calculated for three different reaction stages. The activation energy and the pre-exponential factor obtained in the initial decomposition stage are 69.58 kcal mol−1 and 32.53 s−1. The activation energy and the pre-exponential factor obtained in the intermediate decomposition stage are 111.78 kcal mol−1 and 29.12 s−1. At 3250 K, the rate constants of N2 and CO2 reach maximum while the rate constant of H2O increases continuously with increasing temperature. Accordingly, the mechanism of initial thermal decomposition of NG under the high temperatures is proposed detailedly.

A comparative estimate of the electron-withdrawing effect of polyfluorinated substituents on the polarization of the O-NO2 bond in nitro esters of perfluorocarboxylic acids

A comparative estimate of the electron-withdrawing effect of polyfluorinated substituents on the polarization of the O-NO2 bond in nitro esters of perfluorocarboxylic acids

The Thermal Properties of Nitrocellulose: From Thermal Decomposition to Thermal Explosion

ABSTRACTNitrocellulose is an extremely dangerous explosive substance, which will decompose at a relatively low temperature. This article studied the thermal properties transformed from thermal decomposition to thermal explosion for a less violent nitrocellulose sample (nitrogen content: 10.92%). Four experiments were implemented: XPS analysis and SEM analysis, DSC-TG analysis, and small-scale thermal explosion experiment. From XPS analysis and SEM analysis, high temperatures led to the decrease of N1s and O1s (O-NO2 bond) and the break or even “melt” of the nitrocellulose fibers. The results demonstrated that nitrocellulose would become more unstable if it was exposed to high temperature. From the DSC-TG analysis and small-scale thermal explosion experiment, the upper critical ambient temperatures (UCATs) of the nitrocellulose were calculated. The UCATs of the nitrocellulose sample would decrease from 132.5ºC to 96.4ºC with the dimensions increased from 0.1 m to 1.6 m. The results demonstrated that the risk of spontaneous combustion and thermal explosion increased significantly with the increase of the volume of nitrocellulose.

UV Resonance Raman Investigation of Pentaerythritol Tetranitrate Solution Photochemistry and Photoproduct Hydrolysis.

Ultraviolet resonance Raman spectroscopy (UVRR) is being developed for standoff trace explosives detection. To accomplish this, it is important to develop a deep understanding of the accompanying UV excited photochemistry of explosives, as well as the impact of reactions on the resulting photoproducts. In the work here we used 229 nm excited UVRR spectroscopy to monitor the photochemistry of pentaerythritol tetranitrate (PETN) in acetonitrile. We find that solutions of PETN in CD3CN photodegrade with a quantum yield of 0.08 ± 0.02, as measured by high performance liquid chromatography (HPLC). The initial step in the 229 nm UV photolysis of PETN in CD3CN is cleavage of an O-NO2 bond to form NO2. The accompanying photoproduct is pentaerythritol trinitrate (PETriN), (CH2ONO2)3CCH2OH formed by photolysis of a single O-NO2. The resulting UVRR spectra show a dominant photoproduct band at ∼1308 cm-1, which derives from the symmetric stretch of dissolved NO2. This photoproduct NO2 is hydrolyzed by trace amounts of water, which downshifts this 1308 cm-1 NO2 Raman band due to the formation of molecular HNO3. The dissociation of HNO3 to NO3- in the presence of additional water results in an intense NO3- symmetric stretching UVRR band at 1044 cm-1.

Theoretical study on stabilization mechanisms of nitrate esters using aromatic amines as stabilizers

The propellants of nitrate esters can be stabilized by some aromatic amines practically. To probe the mechanism of this phenomenon, we performed DFT calculations on: (1) The decompositions of nitrate esters (with and without the catalysis of NO2) and (2) the reaction between the stabilizers and the nitro dioxide (NO2 is released during the storage of nitrate esters). The structures on the reaction paths (reactants, intermediates and products) were optimized at the (U)B3LYP/6-31G** level. It was shown that NO2 lowers the activation energy barrier in the decomposition of nitrate ester by 11.82–17.86kJ/mol and efficiently catalyzes the rupture of ONO2 bond. However, the aromatic amines, typical stabilizers for nitrate esters, can easily eliminate NO2 with activation barriers as low as 27–113kJ/mol (with one exception of 128kJ/mol). These values are, for most cases, lower or much lower than the activation energy barriers for reactions between nitrate esters and NO2 (127–137kJ/mol). Consequently, the stabilizers can block the NO2 catalysis for the decompositions of nitrate esters.

Thermal decomposition of n-propyl and n-butyl nitrates: Kinetics and products

Thermal decomposition of n-propyl (C3H7ONO2, PPN) and n-butyl (C4H9ONO2, BTN) nitrates has been studied in a low pressure flow reactor combined with a quadrupole mass spectrometer. The rate constants of the nitrates decomposition were measured as a function of pressure (0.95–12.8Torr of helium) and temperature in the range 473–659K using two different approaches: from kinetics of nitrate loss and those of the formation of the reaction products. The fit of the observed falloff curves with two parameter expression k=k0k∞[M]k0[M]+k∞×0.6(1+(log(k0[M]k∞))2)−1 provided the following low and high pressure limits for the rate constants of the nitrates decomposition: k0(PPN)=0.68×10−4 exp(−15002/T)cm3molecule−1s−1, k∞ (PPN)=7.34×1015 exp(−19676/T)s−1, k0(BTN)=2.80×10−4 exp(−15382/T)cm3molecule−1s−1 and k∞(BTN)=7.49×1015 exp(−19602/T)s−1, which allow to reproduce (via above expression and with 20% uncertainty) all the experimental data obtained for the rate constants of PPN and BTN decomposition in the temperature and pressure range of the study. It was observed that the initial step of the thermal decomposition of the nitrates is ONO2 bond cleavage leading to formation of NO2 and alkoxy radical, which rapidly decomposes or isomerizes to form C2H5 and formaldehyde and C3H7, CH2O and hydroxybutyl radical as final products of PPN and BTN decomposition, respectively. In addition, the kinetic data were used to determine the ONO2 bond dissociation energy of 38.0±1.2 and 37.8±1.0kcalmol−1 in PPN and BTN, respectively.

Thermal Decomposition of Isopropyl Nitrate: Kinetics and Products.

Kinetics and products of the thermal decomposition of isopropyl nitrate (IPN, C3H7NO3) have been studied using a low pressure flow reactor combined with a quadrupole mass spectrometer. The rate constant of IPN decomposition was measured as a function of pressure (1-12.5 Torr of helium) and temperature in the range 473-658 K using two methods: from kinetics of nitrate loss and those of reaction product (CH3 radical) formation. The fit of the observed falloff curves with two parameter expression [Formula: see text] provided the following low and high pressure limits for the rate constant of IPN decomposition: k0 = 6.60 × 10-5exp(-15190/T) cm3 molecule-1 s-1 and k∞ = 1.05 × 1016 exp(-19850/T) s-1, respectively, which allows one to determine (via the above expression) the values of k1 (with 20% uncertainty) in the temperature and pressure range of the study. It was observed that thermal decomposition of IPN proceeds through initial breaking of the O-NO2 bond, leading to formation of NO2 and isopropoxy radical (CH3)2CHO, which rapidly decomposes forming CH3 and acetaldehyde as final products. The yields of NO2, CH3, and acetaldehyde upon decomposition of isopropyl nitrate were measured to be (0.98 ± 0.15), (0.96 ± 0.14), and (0.99 ± 0.15), respectively. In addition, the kinetic data were used to determine the O-NO2 bond dissociation energy in isopropyl nitrate, 38.2 ± 4.0 kcal mol-1.

Effects of α-Fe2O3 nanoparticles on the thermal behavior and non-isothermal decomposition kinetics of nitrocellulose

The effects Fe2O3 nanoparticles on the thermal decomposition of nitrocellulose (NC) have been investigated by the differential scanning calorimetry (DSC) method and the thermogravimetry with Fourier transform infrared analysis (TG-IR). DSC analysis shows that Fe2O3 can be safely used with NC, and the thermal decomposition reactions of Fe2O3-NC composite and NC follow the same thermal decomposition mechanism of Avrami-Erofeev equation f(α)=1.5(1–α)[–ln(1–α)]1/3 in differential form. The as-prepared nanoparticles could reduce the activation energy of the decomposition reaction and the critical temperature of thermal explosion of NC. In addition, TG-IR analysis indicated that Fe2O3 nanoparticles play a crucial role in promoting the ONO2 bond cleavage and secondary autocatalytic reactions in condensed phase. This contribution suggests that introducing Fe2O3 nanostructure may be a promising way to accelerate the thermal decomposition of NC.

A theoretical study on the reaction pathways of peroxynitrite formation and decay at nonheme iron centers

A computational study based on density functional theory was undertaken to identify possible reaction pathways for the formation and decomposition of peroxynitrite at models of the active sites of the nonheme superoxide scavenging enzymes superoxide reductase (SOR) and iron superoxide dismutase (FeSOD). Two peroxynitrite isomers and their possible protonated states were investigated, namely FeOONO−, FeN(O)OO−, FeOONOH, and FeN(O)OOH. Peroxynitrite formation at the active sites was assumed by either the interaction of a peroxynitrite cis/trans anion with the pentacoordinated iron active site or the interaction between a nitric oxide bound adduct and superoxide; both scenarios were found to be facile for all models investigated. The ferrous adducts of the FeOONO−isomer were found to undergo instant heterolytic cleavage of the OONO bond to yield nitrite, whereas for the ferric adducts, the homolytic cleavage of the OONO bond to yield nitrogen dioxide was found to be energetically facile. For the FeN(O)OO− isomer, the active site models of FeSOD and SOR were only able to accommodate the cis isomer of peroxynitrite. Ferric adducts of the cis FeOONO− isomer were found to be energetically more stable than their trans counterparts and were also more stable than the cis adducts of the FeN(O)OO− isomer; conversely, the protonated forms of all adducts of the FeOONOH isomer were found to be lower in energy than their equivalent FeN(O)OOH adducts. Multiple reaction pathways for the decomposition of the formed peroxynitrite adducts (whether the anions or the protonated forms) were proposed and explored. The energy requirements for the decomposition processes ranged from exothermic to highly demanding depending on the peroxynitrite isomer, the type of model (whether an SOR or FeSOD active site), and the oxidation state of iron. © 2014 Wiley Periodicals, Inc.

A DFT study of the unimolecular decomposition of 1,2,4-butanetriol trinitrate

To improve understanding of the unimolecular decomposition mechanism of 1,2,4-butanetriol trinitrate (BTTN) in the gas phase, density functional theory calculations were performed to determine various decomposition pathways at the B3LYP/6-311G** level. Two main mechanisms for the unimolecular decomposition of BTTN were found. In the first, homolysis of one of the O-NO2 bonds occurs to form •NO2 and CH2ONO2CHONO2CH2CH2O•, which subsequently decomposes to form CH3CHO + •CHO + 3NO2 + HCHO. In the second, successive HONO elimination reactions yield three HONO and OHCCH2CHONO2CH2ONO2 fragments, which subsequently decompose to form CH3CHO + 2CO + 3HONO. We also found that the first pathway has a slightly lower activation energy than the second. The results show that the pathway involving O-NO2 cleavage is slightly more energetically favorable than that involving HONO elimination.

Synthesis and pyrolysis studies of bis(nitratomethyl)-1,3-bishomocubane—A high-energy high-density liquid

The synthesis and thermal decomposition of the energetic material, bis(nitratomethyl)-1,3-bishomocubane (DNMBHC) were undertaken. The optimized structure of DNMBHC was obtained by ab initio methods and was utilized to calculate the heat of formation, heat of combustion and detonation properties. The slow thermal decomposition of DNMBHC was investigated by thermogravimetric analysis (TGA) at heating rates of 10°C/min, while fast pyrolysis was investigated utilizing sub-milligram quantities at heating rates of 100°C/s. The gaseous products from fast pyrolysis were detected by rapidscan FTIR spectroscopy to postulate probable decomposition pathways. The primary decomposition pathway was found to involve ONO2 bond scissions to form NO2, subsequently leading to several secondary reactions. A secondary pathway involving detachment of the nitrate ester group from the ring to form MeONO2 was also predicted. The products involving the bishomocubane ring were found to be relegated to the condensed phase.

Atomistic Simulation of Orientation Dependence in Shock-Induced Initiation of Pentaerythritol Tetranitrate

The dependence of the reaction initiation mechanism of pentaerythritol tetranitrate (PETN) on shock orientation and shock strength is investigated with molecular dynamics simulations using a reactive force field and the multiscale shock technique. In the simulations, a single crystal of PETN is shocked along the [110], [001], and [100] orientations with shock velocities in the range 3-10 km/s. Reactions occur with shock velocities of 6 km/s or stronger, and reactions initiate through the dissociation of nitro and nitrate groups from the PETN molecules. The most sensitive orientation is [110], while [100] is the most insensitive. For the [001] orientation, PETN decomposition via nitro group dissociation is the dominant reaction initiation mechanism, while for the [110] and [100] orientations the decomposition is via mixed nitro and nitrate group dissociation. For shock along the [001] orientation, we find that CO-NO(2) bonds initially acquire more kinetic energy, facilitating nitro dissociation. For the other two orientations, C-ONO(2) bonds acquire more kinetic energy, facilitating nitrate group dissociation.

Syntheses, Structural, and Spectroscopic Properties of Copper(II) Complexes of Constrained Macrocyclic Ligands

AbstractThe complexes [Cu(L1)(H2O)2](BF4)2·2H2O (1) [L1 = 5, 16‐dimethyl‐2, 6, 13, 17‐tetraazatricyclo(14, 4, 01.18,07.12)docosane] and 0.5[Cu(L2)(NO3)2][Cu(L2)](NO3)2 (2) [L2 = dibenzyl‐5, 16‐dimethyl‐2, 6, 13, 17‐tetraazatricyclo(14, 4, 01.18,07.12)docosane] were synthesized and characterized by single crystal X‐ray analyses. In these constrained macrocycles, the central copper(II) atoms are in a tetragonally distorted octahedral environment with four nitrogen atoms of the macrocyclic ligands in equatorial positions and oxygen atoms from either water molecules or nitrato groups in axial positions. The macrocyclic ligands in both complexes adopt the most stable trans‐III conformation. The Cu–N distances [1.999(7)–2.095(7) Å] are typical for such complexes, but the axial ligands are weakly coordinating Cu–OH2 bonds [2.693(3) Å] and Cu–ONO2 bonds [2.873(7) Å] due to the combination of the pseudo Jahn–Teller effect and strong in‐plane ligand field. The crystals are stabilized by a three‐dimensional network by hydrogen bonds that are formed among the secondary nitrogen hydrogen atoms, oxygen atoms of water molecules, fluorine atoms of BF4–, and oxygen atoms of NO3–. The electronic absorption and IR spectroscopic properties are also discussed.

Nitric oxide converts fatty acid alkoxyl radicals into fatty acid allyl radicals

Nitric oxide ( NO) is thought to react with fatty acid alkoxyl radical, which is generated from fatty acid hydroperoxide via one-electron reduction. However, detail in the reaction remains obscure. In the present study, we examined the reaction of nitric oxide with fatty acid alkoxyl radical generated in the lipoxygenase/linoleate/13-hydroperoxyoctadecadienoate (13-HpODE) system under anaerobic conditions via HPLC equipped with mass spectrometry and photodiode array detections. In this reaction system, nitric oxide can scavenge linoleate alkoxyl radical, producing 13-ONO- 9Z, 11E-ODE. However, instead of 13-ONO- 9Z, 11E-ODE, 13-NO- 9E, 11E-ODE and 9-NO- 10E, 12E-ODE were alternatively detected in the reaction solution. To explain this contradiction, we proposed a mechanism as follows: (1) 13-ONO- 9E/ 11Z-ODE undergoes homolytic cleavage at >CH ONO bond into the linoleate allyl radical and nitrogen dioxide, (2) the allyl radical undergoes resonance stabilization into the E/ E-form, and (3) nitric oxide scavenges the E/ E-pentadiene radical at C9 or C13 position. Consequently, we concluded that nitric oxide immediately converts fatty acid alkoxyl radical into allyl radical.