- Kinetic Study of Reactions of C2H5O and C2H5O2 with NO at 298 K and 0.55 - 2 torr
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The kinetics of C2H5O and C2H5O2 radicals with NO have been studied at 298 K using the discharge flow technique coupled to laser induced fluorescence (LIF) and mass spectrometry analysis.The temporal profiles of C2H5O were monitored by LIF.The rate constant for C2H5O + NO -> Products (2), measured in the presence of helium, has been found to be pressure dependent: k2 = (1.25 +/- 0.04) x 10-11, (1.66 +/- 0.06) x 10-11, (1.81 +/- 0.06) x 10-11 at P (He) = 0.55, 1 and 2 torr, respectively (units are cm3 molecule-1 s-1).The Lindemann-Hinshelwood analysis of these rate constant data and previous high pressure measurements indicates competition between association and disproportionation channels: C2H5O + NO + M -> C2H5ONO + M (2a), C2H5O + NO -> CH3CHO + HNO (2b).The following calculated average values were obtained for the low and high pressure limits of k2a and for k2b : k02a = (2.6 +/- 1.0) x 10-28 cm6 molecule-2 s-1, kinfinite2a = (3.1 +/- 0.8) x 10-11 cm3 molecule-1 s-1 and k2b ca. 8 x 10-12 cm3 molecule-1 s-1.The present value of k02a, obtained with He as the third body, is significantly lower than the value (2.0 +/- 1.0) x 10-27 cm6 molecule-2 s-1 recommended in air.The rate constant for the reaction C2H5O2 + NO -> C2H5O + NO2 (3) has been measured at 1 torr of He from the simulation of experimental C2H5O profiles.The value obtained for k3 = (8.2 +/- 1.6) x 10-12 cm3 molecule-1 s-1 is in good agreement with previous studies using complementary methods.
- Daele, V.,Ray, A.,Vassalli, I.,Poulet, G.,Bras, G. Le
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- Synthesis and structure of dinitrosyl iron complexes with secondary thiolate bridging ligands [Fe2(μ-SCHR2)2(NO)4], R = Me, Ph
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New dinitrosyl iron complexes of binuclear structure [Fe2(μ-SCHMe2)2(NO)4] and [Fe2(μ-SCHPh2)2(NO)4] were first synthesized employing new method from Fe(CO)5, corresponding thiol, and EtONO. Complexes structures were determined by XRD technique. DFT calculations were performed to probe the cis-conformer structures in gas and solution phases. NO donor ability of the complex with isopropyl thiolate ligand was studied.
- Davidovich,Gurzhiy,Sanina,Shchukarev,Garabadzhiu,Belyaev
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- Mechanism of Gas-Phase Nucleophilic Displacement Reaction of NO2(1-) with Ethyl Nitrate
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A mechanism for the gas-phase nucleophilic displacement reaction, NO2(1-) + C2H5ONO2 --> NO3(1-) + C2H5ONO, has been postulated on the basis of the calculated stabilities of the (NO2(1-)*C2H5ONO2) complex.The potential-energy diagram for the reaction pathway is characterized by three minima.The relative yield of NO3(1-) in mixtures with various bath gases has been examined with high-pressure mass spectrometry.The results indicate that the efficiency of NO3(1-) production depends upon the nature of the third body.
- Wlodek, S.,Wincel, H.
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- Reaction of alcohol with NO2 on a Cleaned Glass Surface
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Formation of alkyl nitrite from alcohol and NO2 was very fast on a Pyrex glass surface cleaned with chromic acid mixture.The reaction was practically zero order with respect to NO2.The rate constant was (1.7 +/- 0.08)*10E-18 cm3*molecule-1*s-1 for methyl nitrile formation and the apparent activation energy was -53.5 kJ*mol-1.
- Maeda, Yasuaki,Fujio, Yoshifumi,Munemori, Makoto
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- Rate Constants for the Reactions of CH3O and C2H5O with NO2 over a Range of Temperature and Total Pressure
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The kinetics of the reactions of CH3O and C2H5O radicals with NO2 have been studied using pulsed laser photolysis to create the radicals from the corresponding alkyl nitrite and by time-resolved, laser-induced fluorescence to observe the decay of the radical concentration.At 295 K, rate constants for CH3O+NO2 have been measured in the presence of Ar (6-100Torr), He(30-100 Torr) and CF4 (30-125 Torr).The association reaction to CH3ONO2 appears to predominate, and rate constants in the limit of low and high pressure are deduced: (k0/10E-29 cm6 molecule-2 s-1) =2.8+/-0.6(M=Ar); 1.6 +/- (M=He); 3.4+/-1.0(M=CF4), and (kinfinite/10E-11 cm3 molecule-1 s-1)=2.0+/-0.4, where the quoted errors correspond to two standard deviations.A limited number of measurements is also reported for this reaction at 390K.The rate of the reaction of C2H5O with NO2 at 295 K is found to be same in the presence of 15 and 100 Torr of Ar, and the measurements yield a rate constant: (kinfinite/10E-11 cm3 molecule-1 s-1) =2.8+/-0.3.
- Frost, Michael J.,Smith, Ian W. M.
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- Flow analysis method for determining the concentration of methanol and ethanol in the gas phase using the nitrite formation reaction
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The emission sources of alcohols are significant from plants. The use of alcohol-fueled vehicles has increased. Due to the emission from these alcohol-fueled vehicles, the atmospheric alcohol concentrations are expected to be higher than that in the past from plant emission sources. A flow determination method for low molecular weight alcohols (methanol, ethanol) in the gas phase using the nitrite formation reaction, which was developed from an earlier method using a glass bottle was presented. The ambient air and NO2 (1000 ppm vol) were allowed to continuously flow in glass tube, which had been filled with 10 g of Pyrex glass beads. The flow rates of the ambient air and NO2 were 30 and 20 cc/min, respectively. The gas-phase alkyl nitrites produced by the dark reaction of atmospheric alcohols and NO2 on the Pyrex glass beads were analyzed by GC with an electron capture detector. The alcohol concentrations of the samples were computed using a calibrated conversion factor for each alcohol to its nitrite. The detection limits for the methanol and ethanol were 0.7 and 0.5 ppb vol, respectively. The method indicated significant improvement compared with the other methods for measuring ambient alcohol due to its high sensitivity, no required concentration process, and rather high yields of the alkyl nitrite from alcohol. It can be an automated analysis system for atmospheric alcohol.
- Takenaka,Nguyen,Bandow,Maeda
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- Rate Constants for the Reactions of CH3O and C2H5O with NO over a Range of Temperature and Total Presuure
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The kinetics of the reactions of CH3O and C2H5O radicals with NO have been studied using pulsed laser photolysis to create the radicals from the corresponding alkyl nitrite and time-resolved, laser-induced fluorescence to observe the decay of the radical concentration.For the CH3O + NO reaction, rate constants have been determined at four temperatures between 296 and 573 K and over a range of total pressures up to 125 Torr using Ar and CF4 as diluent gases.The results clearly indicate competition between association to CH3ONO and reaction to H2CO + HNO.The experimental results are fitted well by an extended Lindemann-Hinshelwood mechanism, with values of the limiting high- and low-pressure rate constants of 3.6 (T/298)E-0.6*10E-11cm3 molecule-1s-1 and 1.35(T/298)E-3.8*10E-29 cm6 molecules-2s-1 (the latter being the value that the association rate constant would have in the absence of the rearrangment channel to CH3O + HNO).The rate constant for this last channel in the limit of low pressure is found to be almost independent of temperature and is fitted fairly well by 5.0(T/298)E-0.6*10E-12 cm3 molecule-1 s-1.The rate of the reaction between C2H5O and NO at 298K is found to be the same in the presence of 15 and 100 Torr of Ar, and the measurements yieled a rate constant of (4.4+/-0.4)*10E-11 cm3 molecule-1 s-1.
- Frost, Michael J.,Smith, Ian W. M.
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- Temperature dependence of the near UV absorption spectra and photolysis products of ethyl nitrate
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The UV absorption cross sections for ethyl nitrate were measured as a function of temperature between 265 and 340 nm by using cavity ring-down spectroscopy.Absorption cross sections increased with temperature between 238 and 298 K.The variation with temperature was greater at longer wavelengths.Photodissociation product channels of ethyl nitrate at 308 nm were determined using an excimer laser and a cavity ring-down spectrometer.C2H5O + NO2 were the sole photofragmentation products with a quantum yield of 1.0+/-0.1, independent of temperature.Atmospheric implications are discussed.
- Zhu, Lei,Ding, Chuan-Fan
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- Gas-phase Reaction of Hydroxyl Radicals with Alkyl Nitrite Vapors in H2O2+NO2+CO Mixtures
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The yields of CO2 from the chain reaction in H2O2+NO2+CO+alkyl nitrite mixtures, in wich OH is the chain carrier and alkyl nitrites induce a chain termination step, have been used to deduce rate constants (ks) for OH attack on alkyl nitrites (RONO) in the vapour phase at ambient temperatures.Values of ks/E9 dm3 mol-1 s-1 as a function of R were determined as follows: 0.71 +/-0.12 (CH3), 1.15+/-0.23 (C2H5), 1.56+/-0.32 (n-C3H7), 3.41+/-1.48 (n-C4H9), 3.89+/-0.58 (sec-C4H9), 3.47+/-0.52 (i-C4H9), 0.91+/-0.15 (t-C4H9), all based on ks=(1.63+/-0.16)E9 dm3 mol-1 s-1 for OH +n-butane.The small increase in ks from R=CH3 to t-4H9 is considered to support a recent postulate that both H-abstraction and NO-abstraction pathways are operative, at least for R=CH3.Under typical, sunlit urban atmosphere conditions it is deduced that OH attack on alkyl nitrites is a minor removal process compared to their photodissociative destruction.
- Audley, Gary J.,Baulch, Donald L.,Campbell, Ian M.,Waters, Des J.,Watling, Gillian
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- α-Nitrohydrazones: Versatile intermediates for phosphonate derivatives formation from primary nitro compounds
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Primary nitro compounds can be easily converted into hydrazonophosphonate derivatives through coupling with aryldiazonium salts followed by an Arbuzov-type reaction with phosphite.
- El Ka?m,Grimaud,Jana,Tirla
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- Formation of Organic Mitro-compounds in Flowing H2O2+NO2+N2+Organic Vapour Systems. Part 1.-Surface Initiation Efficiency and Reactions of Ethane
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When H2O2 vapour is added to an excess of NO2 in a flow system with ethane as the carrier gas in the presence of a boric-acid-coated surface at temperatures in the range 298-363 K, the organic products are niroethane, ethyl nitrate and smaller amounts of ethyl nitrite.On the basis of the initiating steps the total yield of nitro-compounds, extrapolated to =0, provides a direct measure of the H2O2 to OH conversion efficiency in step(1).This is shown to correspond to that indicated by the previously applied indirect method involving measurement of the variation of CO2 yields with the ratio / in H2O2+NO2+CO systems containing diethyl ether (S) as the internal kinetic calibrant.This efficiency does not change significantly throughout the above temperature range.The mechanism of formation of the nitrocompounds involves the following competitive steps: .Arguments are presented that step (8) may proceed by way of partial dissociation of chemically activated C2H5ONO molecules rather than by bimolecular O-abstraction route.A rate constant of k4=(1.3+/-0.2)xE10 dm3mol-1s-1 is obtained for the reaction at ambient temperature for M=C2H6 at a pressure of 40 kPa.
- Audley, Gary J.,Baulch, Donald L.,Campbell, Ian M.
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- Reaction of naphthalene and its derivatives with hydroxyl radicals in the gas phase
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Naphthalene is the most abundant polycyclic aromatic hydrocarbon (PAH) found in urban air. It is reactive in the atmosphere under ambient conditions, its chief reaction partner being the hydroxyl radical, OH·. In this work, the reactions of OH· with naphthalene, 1- and 2-naphthol, and 1- and 2-nitronaphthalene were studied in a 9.4 m3 smog chamber. Relative rates of reaction accorded well with previous studies and allowed estimates to be made of the atmospheric lifetimes of these compounds. Numerous oxidation products were identified, and mechanisms proposed for their formation were based on the further transformation of benzocyclohexadienyl radicals formed by addition of OH· to naphthalene. The naphthols and nitronaphthalenes were deduced not to be on the major reaction pathway to the more oxidized products. Because of the high reactivity of PAH in air, we suggest that priority be given to identifying and quantitating their reaction products, some of which may be relatively persistent air toxics. Naphthalene is the most abundant polycyclic aromatic hydrocarbon (PAH) found in urban air. It is reactive in the atmosphere under ambient conditions, its chief reaction partner being the hydroxyl radical, OH·. In this work, the reactions of OH· with naphthalene, 1- and 2-naphthol, and 1- and 2-nitronaphthalene were studied in a 9.4 m3 smog chamber. Relative rates of reaction accorded well with previous studies and allowed estimates to be made of the atmospheric lifetimes of these compounds. Numerous oxidation products were identified, and mechanisms proposed for their formation were based on the further transformation of benzocyclohexadienyl radicals formed by addition of OH· to naphthalene. The naphthols and nitronaphthalenes were deduced not to be on the major reaction pathway to the more oxidized products. Because of the high reactivity of PAH in air, we suggest that priority be given to identifying and quantitating their reaction products, some of which may be relatively persistent air toxics.
- Bunce, Nigel J.,Liu, Lina,Zhu, Jiang,Lane, Douglas A.
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- Kinetics of the Reaction between Ethylperoxy Radicals and Nitric Oxide
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The kinetic of the C2H5O2 + NO -> C2O5O + NO2 reaction is examined by two real-time techniques.NO consumption and NO2 formation are measured using transient diode laser absorption, whereas ethylperoxy loss and ethylnitrite formation are monitored by time-resolved UV spectrometry.Simultaneous fits of the NO and NO2 concentration versus time profiles yield rate constants consistent with the results of the C2H5O2 and C2H5ONO measurements.The combined data yield a rate constant of k5 = (3.1-1.0+1.5)E-12 e (330+/-11)/T cm3 s-1 over the 220-355 K temperature range.The small negative temperature dependence is consistent with the accepted mechanism of the reaction proceeding through a C2H5O2NO adduct.
- Maricq, M. Matti,Szente, Joseph J.
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- Improved synthesis and crystallographic analysis of (E)-ethyl 2-(hydroxyimino)-3-(4-methoxyphenyl)-3-oxopropanoate and erythro-N-acetyl-β-(4-methoxyphenyl)serine ethyl ester
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(E)-Ethyl 2-(hydroxyimino)-3-(4-methoxyphenyl)-3-oxopropanoate has been synthesized by the oximation of ethyl 3-(4-methoxyphenyl)- 3-oxopropanoate with ethyl nitrite in the presence of multi-pore activated-K2CO3. A one-pot procedure has also been developed for the conversion of this oxime to the corresponding erythro-2-acetamido-3-hydroxy-3-(4-methoxyphenyl)propionic ethyl ester. Their configurations were unambiguously confirmed by X-ray crystallographic determination. The oxime crystallized as a monoclinic system with space group P21/c and the following cell parameters: a = 11.524(3) ?, b = 7.2367(16) ?, c = 14.866(4) ?, β = 111.027(4) and Z = 4, whereas the erythro-N-acetyl-β-(4-methoxyphenyl)serine ethyl ester crystallized as a triclinic system with space group P-1 and the following cell parameters: a = 7.6451(6) ?, b = 13.3326(10) ?, c = 16.2679(13) ?, α = 67.314(7), β = 79.917(7), γ = 88.516(7) and Z = 2. The crystal packing in both of these structures was stabilized by intermolecular O-H-O and C-H-O hydrogen bonds.
- Fan,Han,Jin,Liu
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- Disproportionation to Combination Ratios of Alkoxy Radicals with Nitric Oxide
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The disproportionation to combination ratios were measured at 175 deg C for the reactions RO + 15NO -> RO15NO (2a) and RO + 15NO -> RCHO + H15NO (2b), with the following alkoxy radicals: C2H5O, n-C3H7O, n-C4H9O, and i-C4H9O.The alkoxy radical was generated by the termal decomposition of the corresponding alkyl nitrite in the presence of 15NO.The rate of the corresponding isotopically enriched alkyl nitrite was measured by mass spectrometry while the aldehyde rate was determined by gas chromatography.The results obtained for k2b/k2 were 0.22 +/= 0.02, 0.26 +/= 0.03, 0.29 +/= 005, and 033 +/= 0.03, respectively, for C2H5O, n-C3H7O, n-C4H9O, and i-C4H9O.With these values of k2b/k2 we were able to determine the primary quantum yield of the photolysis of the corresponding alkyl nitrites at 366 nm to be, respectively, 0.32 +/= 0.04, 0.44 +/= 0.06, 0.19 +/= 0.04, and 0.19 +/= 0.02.
- Morabito, Paul,Heicklen, Julian
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- A New Method for the Synthesis of Nitroethane, Ethyl Nitrite, and Ethyl Nitrate
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When H2O2 vapour and NO2 are mixed in an ethane carrier in a flow system in the presence of a boric acid-coated surface, ethyl nitrate, nitroethane, and some ethyl nitrite are synthesized; a mechanism is advanced in which OH* and C2H5* radicals are the intermediates.
- Audley, Gary J.,Baulch, Donald L.,Campbell, Ian M.
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- Biocatalytic Synthesis of Enantiopure β-Methoxy-β-arylalanine Derivatives
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Chiral β-hydroxy-β-arylalanine and β-methoxy-β-arylalanine derivatives, which occur widely in marine nature products, were stereoselectively synthesized with 99 % ee values. The two erythro isomers were prepared by L- or D-aminoacylase-catalyzed resolution of the corresponding N-acetyl derivatives, whereas the two threo isomers were obtained only by D-aminoacylase-catalyzed resolution of the derivatives. erythro-β-Hydroxy-β-arylalanine derivatives were prepared by diastereoselective hydrogenation of ethyl 2-(hydroxyimino)-3-oxo-3-arylpropanoates, which were in turn acquired by the oximation of ethyl 3-oxo-3-arylpropanoates with ethyl nitrite in the presence of nano-K2CO3 with yields of 72 % to 80 %. β-Methoxy-β-arylalanine derivatives were synthesized through Williamson reactions between the corresponding β-hydroxy-β-arylalanines and iodomethane with silver oxide as base.
- Fan, Shiming,Liu, Shouxin,Zhang, Hubo,Liu, Ying,Yang, Yihuang,Jin, Longyi
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p. 5591 - 5597
(2014/10/15)
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- S-alkylation of thiacalixarenes: A long-neglected possibility in the calixarene family
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Despite the high nucleophilicity of sulfur atoms, thiacalixarenes have been alkylated only on oxygen atoms thus far. Using strong alkylating agents (triflates, trialkyloxonium salts), the substitution of the sulfur bridges has been successfully accomplished. The corresponding sulfonium salts of thiacalix[4]arene are formed regio- and stereoselectively as a completely new type of substitution pattern in thiacalixarene chemistry. These compounds possess interesting conformational behavior and could be used as unusual alkylating agents with uncommon selectivity.
- Kundrat, Ondrej,Eigner, Vaclav,Dvorakova, Hana,Lhotak, Pavel
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supporting information; scheme or table
p. 4032 - 4035
(2011/09/20)
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- Process for Producing C1-C4 Alkyl Nitrite
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A process of producing C1-C4 alkyl nitrite, comprising the following steps: a) firstly feeding nitrogen oxide and oxygen into Reactor I, contacting with an aluminosilicate catalyst, and reacting to produce an effluent I containing NO2 and unreacted NO; b) feeding the effluent I and C1-C4 alkanol into Reactor II, and reacting to produce an effluent II containing C1-C4 alkyl nitrite; and c) separating the effluent II containing C1-C4 alkyl nitrite to obtain C1-C4 alkyl nitrite; wherein reactor I is a fixed bed reactor, and Reactor II is a rotating high-gravity reactor; said nitrogen oxide in step a) is NO, or a mixed gas containing NO and one or more of N2O3 and NO2, wherein the molar number of NO is greater than that of NO2, if any; and the molar ratio of NO in nitrogen oxide to oxygen is 4-25:1.
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Page/Page column 4
(2011/10/31)
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- Process for Producing Cl-C4 Alkyl Nitrite
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The present invention relates to a process for producing C1-C4 alkyl nitrite, comprising loading a resin catalyst layer and/or a porous filler layer into a reactor, passing nitrogen oxide, oxygen and C1-C4 alkanol as raw materials through the resin catalyst layer and/or porous filler layer in a counter current, parallel current or cross current manner, reacting under the conditions including a reaction temperature of from 0 to 150° C., a reaction pressure of from ?0.09 to 1.5 MPa, a molar ratio of C1-C4 alkanol/nitrogen oxide of 1-100:1, a molar ratio of nitrogen oxide/oxygen of 4-50:1, to obtain an effluent containing C1-C4 alkyl nitrite, wherein said nitrogen oxide is NO, or a mixed gas containing NO and one or more selected from N2O3 and NO2.
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Page/Page column 4
(2011/10/31)
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- Formation of nitric oxide, ethyl nitrite and an oxathiolone derivative of caffeic acid in a mixture of saliva and white wine
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Reactions of salivary nitrite with components of wine were studied using an acidic mixture of saliva and wine. The formation of nitric oxide (NO) in the stomach after drinking wine was observed. The formation of NO was also observed in the mixture (pH 3.6) of saliva and wine, which was prepared by washing the oral cavity with wine. A part of the NO formation in the stomach and the oral cavity was due to the reduction of salivary nitrite by caffeic and ferulic acids present in wine. Ethyl nitrite produced by the reaction of salivary nitrite and ethyl alcohol in wine also contributed to the formation of NO. In addition to the above reactions, caffeic acid in wine could be transformed to the oxathiolone derivative, which might have pharmacological functions. The results obtained in this study may help in understanding the effects of drinking wine on human health.
- Takahama, Umeo,Tanaka, Mariko,Hirota, Sachiko
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body text
p. 293 - 303
(2011/10/09)
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- Vapor generation of inorganic anionic species after aqueous phase alkylation with trialkyloxonium tetrafluoroborates
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Aqueous phase reaction of trialkyloxonium tetrafluoroborates, R 3O+BF4- (R=Me, Et) has been tested in the alkylation of simple inorganic anionic substrates such as halogen ions, cyanide, thiocyanate, sulphide an
- D'Ulivo, Alessandro,Pagliano, Enea,Onor, Massimo,Pitzalis, Emanuela,Zamboni, Roberto
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experimental part
p. 6399 - 6406
(2010/04/06)
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- NEW METHOD FOR THE MANUFACTURE OF THERAPEUTIC COMPOUNDS AND COMPOSITIONS, COMPOUNDS AND COMPOSITIONS PRODUCED THEREWHITH, AND THEIR USE
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Organic nitrites can be produced from a compound which is a mono/polyhydric alcohol or an aldehyde- or ketone-derivate thereof after de-aeration of the same, using NO gas, and stored in an environment saturated with gaseous NO. Organic nitrites produced according to the invention exhibit less impurities and improved storage stability compared to conventionally produced nitrites. The organic nitrites of the invention can easily be formulated into pharmaceutical compositions and have utility for the treatment of various conditions.
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Page/Page column 26-27
(2008/06/13)
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- ETHYL NITRITE AS A GASTROINTESTINAL SMOOTH MUSCLE RELAXANT AND DIAGNOSTIC AND THERAPEUTIC USES THEREOF
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The present invention provides compositions comprising a gas and a gastrointestinal smooth muscle relaxing agent comprising ethyl nitrite in a therapeutically effective amount. The present invention also provides methods of relaxing gastrointestinal smooth muscle, alleviating contraction or spasm of gastrointestinal smooth muscle to facilitate a diagnostic medical procedure and treating or preventing a gastrointestinal disorder using the compositions of the invention.
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Page/Page column 12-14
(2008/06/13)
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- Gas phase kinetics of the reaction system of 2NO2 ? N 2O4 and simple alcohols between 293-358 K
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The reversible reactions between nitrogen dioxide and alcohols (CH 3OH, CH3CH2OH, CH3CH 2CH2OH, CH3CHOHCH3) have been studied in the gas phase, using the spectrophotometric method. RONO (R = CH 3, CH3CH2, CH3CH2CH 2, CH3CHCH3) were identified by UV spectra. The equilibrium constants as well as the bimolecular rate constants were determined by computer modeling, using the programme MINICHEM. We calculated the following values for the forward rate constants k3av: (3.0±0.9)×10-18, (8.0±2.4)×10 -18, (5.4±1.6)×10-18, (2.0±0.6) ×10-18 cm3 molec-1 s-1 and the equilibrium constants Kav: 100±30, 40±12, 109±33, 39±12 at 298 K for the reactions with methanol, ethanol, 1-propanol and 2-propanol, respectively. The temperature dependence of the rate constants and the equilibrium constants were studied and it allowed to obtain the activation energy for the forward and for the reverse reaction, as well as thermochemical parameters. The equilibrium constants and the rate constants suggest that symmetrical N2O4 is the reactive species.
- Wojcik-Pastuszka,Gola,Ratajczak
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p. 1301 - 1313
(2007/10/03)
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- Rate constants for the reactions of C2H5O, i-C3H7O, and n-C3H7O with NO and O2 as a function of temperature
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The rate constants of the reactions of ethoxy, i-propoxy and n-propoxy radicals with O2 and NO was investigated as function temperature. The radicals were generated by laser photolysis from the appropriate alkyl nitrite and characterized by laser-induced fluorescence. For the reactions with O2, the ethoxy radical reacted somewhat slower than recently recommended. The values obtained for i- and n-propoxy had been combined with the measurements from a recent study at lower temperatures, allowing a more reliable determination of the Arrhenius parameters.
- Fittschen,Frenzel,Imrik,Devolder
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p. 860 - 866
(2007/10/03)
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- Nitrosation by Alkyl Nitrites. Part 5. Kinetics and Mechanism of Reactions in Acetonitrile
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Simple alcohols and thioglycolic acid react with alkyl nitrites and nitrous acid in acidic acetonitrile solution to give the O- and S-nitrosated products, in reactions which are kinetically zero order in the alcohol or thiol concentration.The results are consistent with rate-liminiting NO+ formation.On addition of the parent alcohol (derived from the alkyl nitrite) reactions are slower and there is a change towards a first order dependence upon the substrate concentration, indicating that under these conditions the reaction of NO+ with the substrate is partly rate limiting.The reactivity order is found to be HNO2 > t-butyl-nitrite > i-propyl nitrite > isopentyl nitrite.Similarly aromatic amines yield nitrosamine or diazonium ion products, but now the kinetics are consistent with rate-limiting attack of NO+ with the unprotonated amine.At higher acidities it is proposed that reaction occurs with the protonated form of the amine.The mechanistic implications of the kinetic results are discussed.
- Crookes, Michael J.,Williams, D. Lyn H.
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p. 1319 - 1322
(2007/10/02)
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- A kinetic study of the influence of alcohols on the nitrosation of morpholine in acid media. Equilibrium constants for the formation of alkyl nitrites
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The effect of the aliphatic alcohols methanol, ethanol, propanol, isopropanol, 2-butanol, isobutanol, and tert-butanol on the rate of nitrosation of morpholine at pH 3 and 25 deg C has been studied.The inhibition observed is attributed to the formation of alkyl nitrites, which are poor nitrosating agents in acid media.The equilibrium constants for the formation of alkyl nitrites from nitrous acid and alcohols have been calculated both spectrophotometrically and from kinetic data for the inhibitory effect, and there is agreement between the two sets of results.The molar absorptivities at 265 nm of the alkyl nitrites have also been determined.When the concentration of alkyl nitrite is very low, a slight catalytic effect considered to be an effect of the medium has been observed.
- Casado, Julio,Lorenzo, Francisco Manuel,Mosquera, Manuel,Prieto, Maria Flor Rodriguez
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p. 136 - 138
(2007/10/02)
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- Formation of Organic Nitro-compounds in Flowing H2O2+NO2+N2+Organic Vapour Systems. Part 2.-H2O2+NO2+N2+Alkane System
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The principal products from the surface-initiated reactions in flowing mixtures of H2O2, NO2,N2 and RH, where RH=ethane, propane, n-butane and n-pentane, have been identified as the nitroalkane, alkyl nitrite and alkyl nitrate.The product yields have been measured; in the case of propane the variation of the yields with total gas pressure has also been studied.Values have been obtained for the relative rates of primary and secondary H-atom abstraction from each alkane by OH and for the rate-constant ratios k3/k4 and k5/k6 at 298 K:.The trends in the product yields with the variation of pressure and change of R indicate that RO radicals are produced via reactions (4)-(6) rather than by a single-step reaction of R with NO2.
- Baulch, Donald L.,Campbell, Ian M.,Chappel, Jonathan M.
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p. 609 - 616
(2007/10/02)
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- Hydrolysis, Nitrosyl Exchange, and Synthesis of Alkyl Nitrites
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Alkyl nitrites undergo relatively slow hydrolysis in phosphate-buffered aqueous media under neutral conditions with small but significant dependence of reactivity on structure.However, rapid nitrosyl exchange with alcohols is observed, and equilibrium constants for this transformation exhibit remarkable correlation with equilibrium constants for nitrosyl exchange of alcohols with nitrosyl chloride and with nitrous acid. tert-Butyl nitrite has the greatest driving force for nitrosyl transfer among the 12 alkyl nitrites examined, and this capability is used for the synthesis of alkyl nitrites derived from steroidal alcohols and of alkyl thionitrites.
- Doyle, Michael P.,Terpstra, Jan W.,Pickering, Ruth A.,LePoire, Diane M.
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p. 3379 - 3382
(2007/10/02)
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- The formation of ozone and peroxyacetyl nitrate (PAN) in the urban atmospheres of Alberta
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Atmospheric temperature inversions frequently trap pollutants in the urban atmospheres of Alberta leading to photochemical air pollution.Peroxyacetyl nitrate (PAN) was monitored, for the first time in Alberta, from November 1980 to August 1981 at the University of Calgary using electron capture gas chromatography.Measurements were made at one-half-hour intervals from July, 1981 to February, 1982 at a downtown location.Maximum PAN concentrations were recorded at the University and downtown sites on August 14 at 1400 h, 1981 and values were 2.4 and 6.6 ppb, respectively.In each case the maximum PAN peak coincided with the afternoon peak in ozone concentrations, 79 ppb at the University and 59 ppb at the downtown site.Surprisingly, a high value of 2.3 ppb PAN was recorded at the University during January of 1981 giving rise to questions regarding the influence of low temperatures and solar radiation on the photochemical formation of PAN.Calculations employinga simple photochemical model for PAN and ozone formation have been carried out and comparisons made between the observed and the computed values.
- Peake, E.,Sandhu, H. S.
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p. 927 - 935
(2007/10/02)
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- Kinetics and Mechanism of the Nitrosation of Alcohols, Carbohydrates, and a Thiol
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Rate constants have been determined by stopped-flow spectrometry for the nitrosation in water of the following alcohols and carbohydrates: methanol, ethanol, propan-l-ol, propan-2-ol, ethane-1,2-diol, propane-1,2,3-triol, mannitol, sucrose, and glucose, in some cases at 25o and others at 0o.In all cases the reactions were reversible, forming equilibrium concentrations of the corresponding alkyl nitrites.With a large excess of the alcohol present over the total nitrous acid concentration, the observed first order rate constants increased linearly with the alcohol concentration, and from the slope and the intercept the rate constants of the forward and reverse reactions were obtained.Both reactions were acid catalysed and also catalysed by chloride and bromide ion.The forward reaction is interpreted as one involving O-nitrosation by H2NO2+ (or NO+), NOCl or NOBr.For methanol, rate constants for attack by nitrosyl chloride and by nitrosyl bromide were 2.1 x 105 mol-1s-1, respectively.There was little difference between the rate constants for chloride ion and bromide ion attack for the reverse reaction, suggesting that the reactions for attack on the protonated alkyl nitrite are very rapid, possibly approaching the diffusion-controlled limit.There was a decrease in the overall equilibrium constant for the non-halide ion-catalysed pathway, along the series MeOH, EtOH, PriOH, and ButOH; the value for the latter was so small as to make the quantitative determination of the rate constants impossible by this method.This decrease was due almost entirely to a decreasing value for the forward rate constant along the series, which implies that a steric effect is operational.All the carbohydrates studied had very similar equilibrium constants of ca. 1.5.In contrast the nitrosation of N-acetylpenicillamine gave the thionitrite quantitatively at low acidities.Again the reaction was acid- and halide (and thiocyanate) ion-catalysed and the reactivity sequence NOCl > NOBr > NOSCN was established.For both the alcohols and the thiol, the forward rate constants are well below the diffusion controlled values and are several powers of ten less than the corresponding values for the reactions of aniline.The results are discussed in terms of the nucleophilicities of the oxygen and sulphur sites for the forward reaction and in terms of the protonation equilibria of the nitrites and thionitrite for the reverse reaction.
- Aldred, S. Elaine,Williams. D. Lyn H.,Garley, Michael
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p. 777 - 782
(2007/10/02)
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- ACIDITY CONSTANTS OF 1,2,3-CYCLOHEXANE TRIONE DIOXIME (1,3) AND OF 1,2,3-CYCLOHEXANE TRIONE TRIOXIME
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1,2,3-Cyclohexane trione dioxime (1,3) (I) and 1,2,3-cyclohexane trione trioxime (II) were synthesized.Their acidity constants were determined both by potentiometric and spectrophotometric methods, at 20 deg C and ionic strength of μ=0.1 M.UV and visible absorption spectra are presented.The correlation between acidity and moleculer structure is discussed.
- Zsako, J.,Benkoe, A.,Horak, J.,Varhelyi, Cs.
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- One step diazotization coupling process
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A process for producing metal-free azo pigments in purely organic liquid or aqueous/organic liquid containing at most 10% of water calculated on the total weight of the suspension is described. In this one-step process, a suitable aromatic amine is diazotized without isolation of the obtained diazo compound and coupled with a coupling component. Both reactions are carried out in purely or essentially organic medium. The latter consists essentially of such amount of an organic liquid that a substantial portion either of the diazo component or of the coupling component or of both these reactants remain undissolved. Both reactants must be free from sulphonic acid groups. If the resulting azo pigment contains carboxylic acid groups, these can be subsequently converted to the corresponding amido or ester groups.
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