N-propyl Nitrate Research Articles

A Successful Case of an Acquired Methemoglobinemia Treated with Methylene Blue

Methylene blue has been advocated for multiple indications, but data reporting its use on intoxication is rare. Acquired methemoglobinemia can be caused by a wide variety of chemicals and toxins and on severe cases, with high methemoglobin levels (>20%), methylene blue is the first line treatment. We describe a case report of a 45-year-old man with acute methemoglobinemia due to involuntary exposure to n-propyl nitrate. The patient came into the emergency department conscious, with profound peripheral and central cyanosis and oxygen saturation of 88% on air, with no response to oxygen supplementation. Arterial blood gas showed methemoglobin of 22.9%. Methylene blue was administered intravenously and symptoms improved dramatically, with control arterial blood gas with 2.6% of methemoglobin. Despite the rarity of occurrence of methemoglobinemia in occupational set, and since methylene blue is highly effective, a high degree of suspicious and good training aiming for prompt diagnosis is crucial in treating this emergency situation.

A study of the conformational isomerism of n-propyl nitrate by microwave spectroscopy

The rotational spectrum of n-propyl nitrate was measured in the frequency range between 6 and 18 GHz using a Balle-Flygare Fourier transform microwave jet/cavity spectrometer. Parent, 13C and 15N isotopologue transitions for the lower-energy anti-gauche (AG) conformer were found using this instrument. The search for spectra from other conformers was performed using a broadband chirped-pulse jet spectrometer. Transitions from the anti-anti (AA) conformer were observed in this manner. Parent, 13C and 15N isotopologue transitions for the AA conformer were rescanned using the cavity instrument to improve resolution and the signal-to-noise ratio. Rotational, centrifugal distortion, and nuclear electric quadrupole coupling constants for all conformers/isotopologues were fit using Pickett’s SPFIT program. The structure of n-propyl nitrate is discussed considering these results.

Thermal decomposition behaviour and kinetics of a mixed solution: n-propyl nitrate and nitric acid solution

To provide a theoretical basis for improving the thermal safety of spent acid, its decomposition behaviour was studied. A mixed solution of n-propyl nitrate (NPN) and nitric acid was analysed using isoperibolic experiments and differential scanning calorimetry. An accurate kinetic model based on the analysis was proposed to describe the decomposition of the spent acid by applying an isoconversional method and nonlinear regression to the DSC data. We found that the thermal decomposition in the mixed solution involved two competing reactions: the decomposition of NPN in the nitric acid solution and the decomposition of nitric acid. The decomposition of the mixed solution followed a 0.9082th Prout–Tompkins equation with autocatalysis, with a differential kinetic mechanism function of f(α) = (1 − α)0.9082·α0.1291. Lastly, the thermal safety evaluation and thermodynamic parameters were studied. The self-accelerating decomposition temperature and the critical temperature of thermal runway were 338.70 K and 346.76 K, respectively, in an approximately closed system, and 347.25 K and 355.73 K, respectively, in an open system. These results show that the spent acid was more hazardous than the NPN and nitric acid solution. In addition, the thermal stability of the mixed solution in an open system was higher than that of the mixed solution in an approximately closed system.

Quantum chemical calculations of the vibrational spectrum of aliphatic nitro compounds. Cluster analysis of torsion oscillations

The data of theoretical analysis of vibrational spectra in the long-wave range of different isomers of methyl nitrite, methyl, ethyl, n-propyl nitrate, as well as the electron density distribution obtained within the B3LYP Density Functional Theory method with the 6 - 31G(d) basis set are presented. The cluster analysis of charge distribution on carbon, oxygen, nitrogen atoms and torsion oscillation frequencies in the range of 10-400 cm-1 is carried out.

N-propyl nitrate vibrational spectrum analysis using DFT B3LYP quantum-chemical method

Calculation of a molecular structure, conformation and related vibrational spectra of the n- propyl nitrate C3H7NO3 was carried out by means of density functional theory (DFT) by employing the Gaussian 03 package. The molecular geometries were fully optimized by using the Becker's three-parameter hybrid exchange functional combined with the Lee–Yang–Parr correlation functional (B3LYP) and using the 6-31G(d) basis set. By scanning the dihedral angles around C-O and C-C bonds, five energetically most favorable conformers of n-propyl nitrate - TG, TT, GT, GG and G´G forms were found. Vibrational spectra of the most energetically favorable conformers were calculated. The comparative analysis of calculated and experimental spectra is carried out, the spectral features of the conformational state of n-propyl nitrate and the spectral effects of formation of intramolecular hydrogen bonds are established.

Quantum Yields for Photochemical Production of NO2 from Organic Nitrates at Tropospherically Relevant Wavelengths

Absorption cross-sections and quantum yields for NO2 production (ΦNO2) are reported for gaseous methyl, ethyl, n-propyl, and isopropyl nitrate at 294 K. Absorption cross-sections in the wavelength range of 240-320 nm agree well with prior determinations. NO2 quantum yields at photoexcitation wavelengths of 290, 295, and 315 nm are unity within experimental uncertainties for all of the alkyl nitrates studied and are independent of bath gas (N2) pressure for total sample pressures in the range of 250-700 Torr. When averaged over all wavelengths and sample pressures, values of ΦNO2 are 1.03 ± 0.05 (methyl nitrate), 0.98 ± 0.09 (ethyl nitrate), 1.01 ± 0.04 (n-propyl nitrate), and 1.00 ± 0.05 (isopropyl nitrate), with uncertainties corresponding to 1 standard deviation. Absorption cross-sections for ethyl nitrate, isopropyl nitrate, and two unsaturated dinitrate compounds, but-3-ene-1,2-diyl dinitrate and (Z)-but-2-ene-1,4-diyl dinitrate in acetonitrile solution, are compared to gas-phase values, and over the wavelength range of 260-315 nm, the gas-phase values are well-reproduced by dividing the liquid-phase cross-sections by 2.0, 1.6, 1.7, and 2.2, respectively. Reasonable estimates of the gas-phase absorption cross-sections for low-volatility organic nitrates can therefore be obtained by halving the values for acetonitrile solutions. The quantum yield for NO2 formation from photoexcitation of but-3-ene-1,2-diyl dinitrate at 290 nm is significantly lower than those for the alkyl (mono) nitrates: a best estimate of ΦNO2 ≤ 0.25 is obtained from the experimental measurements.

Experimental study on detonation parameters and cellular structures of fuel cloud

In this paper, detonation parameters of fuel cloud, such as propylene oxide (PO), isopropyl nitrate (IPN), hexane, 90# oil and decane were measured in a self-designed and constructed vertical shock tube. Results show that the detonation pressure and velocity of PO increase to a peak value and then decrease smoothly with increasing equivalence ratio. Several nitrate sensitizers were added into PO to make fuel mixtures, and test results indicated that the additives can efficiently enhance detonation velocity and pressure of fuel cloud and one type of additive n-propyl nitrate (NPN) played the best in the improvement. The critical initiation energy that directly initiated detonation of all the test liquid fuel clouds showed a U-shape curve relationship with equivalence ratios. The optimum concentration lies on the rich-fuel side (ϕ > 1). The critical initiation energy is closely related to molecular structure and volatility of fuels. IPN and PO have similar critical values while that of alkanes are larger. Detonation cell sizes of PO were respectively investigated at 25°C, 35°C and 50°C with smoked foil technique. The cell width shows a U-shape curve relationship with equivalence ratios at all temperatures. The minimal cell width also lies on the rich-fuel side (ϕ > 1). The cell width of PO vapor is slightly larger than that of PO cloud. Therefore, the detonation reaction of PO at normal temperature is controlled by gas phase reaction.

Alkyl nitrate photochemical production rates in North Pacific seawater

Low molecular weight alkyl nitrates are produced in surface seawater from the photochemically initiated reaction of NO with organic peroxy radicals. In this study, methyl, ethyl, isopropyl, and n-propyl nitrate photochemical production rates were determined from shipboard incubation experiments. Surface water samples from a variety of different North Pacific water masses were irradiated in sunlight, with and without added nitrite. Production was observed in some, but not all unmodified waters. Production rates increased with increasing addition of nitrite. The relative rates of production of C 1, C 2, and C 3 alkyl nitrates were roughly constant in all production experiments, and similar to the concentration ratios in ambient waters. This constancy most likely reflects consistency in the ratios of the various organic peroxy radicals involved in the reaction ROO + NO. Alkyl nitrate production rates at 1 μM nitrite concentrations generally did not vary markedly by water type, indicating that distribution of nitrite, not organic matter may control photochemical alkyl nitrate formation in the oceans. At higher nitrite levels, differences in production rates may reflect variations in the concentration or reactivity of dissolved organics.

Experimental and theoretical studying the thermolysis of nitrate

This paper presents calorimeter measurement for the thermal decomposition of n-propyl nitrate (NPN), isopropyl nitrate (IPN) and 2-ethylhexyl nitrate (EHN). Similar experimental results of triethylene glycol dinitrate (tri-EGDN) and tetraethylene glycol dinitrate (tetra-EGDN) are included for comparison. The potential energy surfaces (PESs) along O-NO2 bond stretch are investigated using the DFT (B3P86, B3PW91 and B3LYP), ab initio Hartree-Fock and PM3 methods. The good coincidence of experimental with theoretical results indicates that initial stage in the thermal decomposition of five nitrates is only unimolecular homolytical dissociation of the O-NO2 bonds and the activation energies of thermolysis by DSC correspond to the energies of O-NO2 bond scission of nitrates.

A theoretical study of five nitrates: Electronic structure and bond dissociation energies

Three density-functional methods (B3P86, B3PW91, and B3LYP) are employed to investigate the O–NO 2 bond lengths, frontier orbital energies, and O–NO 2 bond dissociation energies (BDEs) of n-propyl nitrate (NPN), isopropyl nitrate (IPN), 2-ethylhexyl nitrate (EHN), triethylene glycol dinitrate (Tri-EGDN), and tetraethylene glycol dinitrate (Tetra-EGDN). It is found that the O–NO 2 bond lengthens (destabilizes) in the order of IPN, NPN, EHN, Tetra-EGDN, and Tri-EGDN. From the data of frontier orbital energies ( E HOMO, E LUMO), and energy gaps (Δ E), we estimate the relative thermal stability ordering of five nitrates and their corresponding radicals. The predicted BDEs of O–NO 2 bond in NPN, IPN, EHN, Tri-EGDN, and Tetra-EGDN, are 176.6, 174.5, 168.1, 156.1, and 159.3 kJ mol −1, respectively. Based on the finding that the present results of BDEs are well coincident with the experimental results of apparent activation energies from the literature, we can draw a conclusion that the experimental thermolysis of five nitrates is only unimolecular homolytical cleavage of the O–NO 2 bonds.

Molecular Structure, Electronic Structure and Heats of Formation of Explosive Sensitizers

Quantum chemical calculations at the HF/6-31G* and B3LYP/6-31G* levels have been carried out on five explosive sensitizers: ethyl nitrate (EN), n-propyl nitrate (NPN), isopropyl nitrate (IPN), 2-ethylhexyl nitrate (EHN), and tetraethylene glycol dinitrate (TEGDN). Theoretical studies have yielded a wealth of quantum chemical information on the molecular geometries, electronic structures, and energies of the title compounds. On the basis of the Mulliken populations and bond lengths, the O 2–N 3 fission is acceptable. Charge distribution analysis indicates that the five nitrates produce NO 2 gas during the dissociation of the O 2–N 3 weak bond. The relative thermal stability ordering of the five nitrates was estimated on the basis of the frontier orbital energy ( E HOMO, E LUMO) and the energy gap (Δ E). The heats of formation (HOFs) of the five sensitizers, EN, IPN, NPN, EHN, and TEGDN, were calculated from the isodesmic reactions and were -155.972, -190.896, -175.279, -272.376, and -790.733 kJ·mol −1, respectively.

A theoretical study of explosive sensitizers

Quantum chemical calculations at the HF/6-31G* and B3LYP/6-31G* levels have been performed on five explosive sensitizers, ethyl nitrate (EN), n-propyl nitrate (NPN), isopropyl nitrate (IPN), 2-ethylhexyl nitrate (EHN) and tetraethylene glycol dinitrate (TEGDN). Theoretical study has made a detailed molecular-level investigation of the title compounds. Based on the Mulliken populations and bond lengths, the fission of the O2–N3 can be acceptable reasonably. Charge distribution analysis indicates that the five nitrates produce NO2 gas during the dissociation of the O2–N3 weak bond. We also order the relative thermal stability of five nitrates on the basis of frontier orbital energy (E HOMO, E LUMO) and energy gap (ΔE = E HOMO − E LUMO).

Analysis of C 2–C 4 peroxyacyl nitrates and C 1–C 5 alkyl nitrates with a non-polar capillary column

Analysis of peroxyacetyl nitrate (PAN), peroxypropionyl nitrate, peroxy- n-butyryl nitrate, and peroxyisobutyryl nitrate (PiBN) with a non-polar capillary column indicated PAN not to coelute with PiBN. Isopropyl nitrate coeluted with PAN, n-butyl nitrate with PiBN and ethyl nitrate with chloroform, at oven temperature 30°C. In addition methyl nitrate, n-propyl nitrate, 2-butyl nitrate, 2-methyl-2-butyl nitrate, 3-pentyl nitrate and 2-pentyl nitrate were studied. Their response factors in the electron-capture detector were also determined. Tetrachloroethylene, carbon tetrachloride and chloroform whose vapors occur in the atmosphere were also examined.

Simple cryoconcentration technique for the determination of peroxyacyl and alkyl nitrates in the atmosphere

A gaseous mixture of methyl nitrate, n-propyl nitrate, peroxyacetyl nitrate and peroxypropionyl nitrate was successfully cryoconcentrated using a gas sampling valve with its loop filled with glass beads placed inside the GC oven which was cooled at –50°C. The technique offered linearity over a ten fold concentration variation and sample volume range of 1–280 ml. The detection limit for 150 ml sample varied from 0.02–10 pptv depending on the compound.

Application of H-ZSM-5 Zeolite for Regioselective Mononitration of Toluene

The nitration of toluene with n-propyl nitrate has been carried out in the presence of H-ZSM-5 as the catalyst. Several H-ZSM-5 catalysts with different Si/Al ratios were investigated to determine the influence of varying Si/Al ratios on the catalytic activity. It was found that high Si/Al ratios enhanced the regioselectivity for the p-nitrotoluene over the ortho isomer under comparable conditions. The best o:m:p product distribution (5:0:95) was achieved using H-ZSM-5 with a Si/Al ratio of 1000. The isolable yield is 54%. In contrast to conventional nitration methods, the product distribution reported in this study is remarkable

ChemInform Abstract: A Relative Rate Study of the Reaction of Cl Atoms with a Series of Alkyl Nitrates and Nitro Alkanes in Air at 295 .+‐.2 K

The relative rate technique has been used to measure rate constants for the reaction of chlorine atoms with nitro methane, nitro ethane, nitro propane, nitro butane, nitro pentane, ethyl nitrate, isopropyl nitrate, n-propyl nitrate, 2-pentyl nitrate, and 2-heptyl nitrate. Decay rates of these organic species were measured relative to one or more of the following reference compounds; n-butane, ethane, chloroethane, and methane. Using rate constants of 2.25 × 10−10 5.7 × 10−11, 8.04 × 10−12, and 1.0 × 10−13 cm3 molecule−1 s−1 for the reaction of Cl atoms with n-butane, ethane, chloroethane, and methane, respectively, the following rate constants were derived, in units of cm3 molecule−1 s−1: nitro methane, <7 × 10−15; nitro ethane, (2.05 ± 0.14) × 10−13; nitro propane, (1.13 ± 0.05) × 10−11; nitro butane, (5.13 ± 0.68) × 10−11; nitro pentane, (1.40 ± 0.14) × 10−10; ethyl nitrate, (3.70 ± 0.24) × 10−12; n-propyl nitrate, (2.15 ± 0.13) × 10−11; i-propyl nitrate, (3.94 ± 0.48) × 10−12; 2-pentyl nitrate, (1.00 ± 0.06) × 10−10; and 2-heptyl nitrate, (2.84 ± 0.50) × 10−10. Quoted errors represent 2σ and do not include possible systematic errors due to errors in the reference rate constants. Experiments were performed at 295 ± 2 K and atmospheric pressure (≃740 torr) of synthetic air. The results are discussed with respect to the previous literature data and to the modeling of these compounds in the atmosphere.

The behavior of some organic nitrates at Boulder and Niwot Ridge, Colorado

Observations show that the ratio of peroxypropionyl nitrate (PPN) to peroxyacetyl nitrate (PAN) increases to a maximum in the afternoon period at Boulder and at Niwot Ridge. In Boulder air and in easterly flow reaching Niwot Ridge, maximum average PPN/PAN ratios were near 15%, while in westerly flow or more remote continental air, the ratio was much smaller and averaged 4%. Relative to the PAN‐mixing ratios, methyl nitrate (MN) was less than 0.2% in the afternoon and less than 0.9% at night in Boulder air masses. The sum of ambient n‐propyl nitrate (NPN) and 2‐butyl nitrate (2BN) mixing ratios was also small, the diurnal average at Niwot Ridge being about 2% of the PAN‐mixing ratio. The diurnal average contribution of MN + PPN + (NPN+2BN) to the total odd nitrogen budget at Niwot Ridge was at most 4%, leaving a 21–27% shortfall between the sum of individual measurements of odd nitrogen species and the total odd nitrogen (NOy) measurement.

A ground‐based intercomparison of NO, NOx, and NOy measurement techniques

At a site near Boulder, Colorado, simultaneous atmospheric measurements were made of NO, NOx, and NOy in a field intercomparison of instruments involving two currently employed techniques of NOx and NOy measurement. Both NOy instruments depended upon the reduction of the NOy species to NO with detection by chemiluminescence, but different catalysts were employed for the reduction: (1) a gold catalyst (with addition of 0.3% CO) at 300°C, or (2) a molybdenum catalyst at 400°C. The two systems of NOx detection involved (1) photolysis of NO2, and (2) reduction of NO2 by solid ferrous sulfate. Several times during the intercomparison the response to calibrated samples of reference compounds NO, NO2, PAN, HNO3, n‐propyl nitrate (NPN), and NH3 was measured. From the results the following conclusions were made: (1) The two NO instruments agreed on NO mixing ratios that were measured during the daytime hours over a range from the limits of detection to 35 parts per billion by volume (ppbv), (2) the two NOy instruments gave similar estimates of NOy in ambient air over a wide range of mixing ratios (0.4–10 ppbv), and (3) the ferrous sulfate converter used for NOx detection showed a significant interference from NPN and PAN.

Evaluation of the tungsten oxide denuder tube technique as a method for the measurement of low concentrations of nitric acid in the troposphere

The applicability of the tungsten oxide denuder tube technique for the measurement of nitric acid in the rural troposphere was investigated. The technique is based on selective chemisorption of HNO3 from the gas stream, thermal desorption, conversion to NO, and analysis by NO−O3 chemiluminescence. Ammonia, which is also collected and desorbed as NH3 and NO, was separated from the HNO3-derived NO by linear temperature-programed thermal desorption. Possible interferences by NO2, HCN, PAN, and n-propyl nitrate (NPN) were tested and found to be significant under conditions found in the lower troposphere. Simultaneous ambient measurements of HNO3 were made with the tungsten oxide denuder tube and nylon filter methods at a rural site in the Colorado mountains (Niwot Ridge, CO). Nitric acid levels measured by the tungsten oxide denuder tube averaged a factor of 3 higher than levels measured by the nylon filter technique. Tests involving the placement of nylon materials in front of the tungsten oxide denuder tube show that there are species, as yet unidentified, present in the atmosphere that interfere with the measurement of HNO3 by the tungsten oxide technique.

ArF Laser-induced decomposition of simple energetic niolecules

Chemiluminescent products formed from ArF laser-induced decomposition of nitromethane, n-propyl nitrate and nitrobenzene have been studied. Implications to explosive chemistry are briefly, discussed.