Search

Oxidation flow reactors (OFRs) are an emerging technique for studying the formation and oxidative aging of organic aerosols and other applications. In these flow reactors, hydroxyl radicals (OH), hydroperoxyl radicals ( HO2 ), and nitric oxide (NO) are typically produced in the following ways: photolysis of ozone ( O3 ) at λ=25 4 nm, photolysis of H2O at λ=185 nm, and via reactions of O(1D) with H2O and nitrous oxide (N2O) ; O(1D) is formed via photolysis of O3 at λ=254 nm and/or N2O at λ=185 nm. Here, we adapt a complementary method that uses alkyl nitrite photolysis as a source of OH via its production of HO2 and NO followed by the reaction NO + HO2 → NO2 + OH. We present experimental and model characterization of the OH exposure and NOx levels generated via photolysis of C3 alkyl nitrites (isopropyl nitrite, perdeuterated isopropyl nitrite, 1,3-propyl dinitrite) in the Potential Aerosol Mass (PAM) OFR as a function of photolysis wavelength ( λ=254 to 369 nm) and organic nitrite concentration (0.5 to 20 ppm). We also apply this technique in conjunction with chemical ionization mass spectrometer measurements of multifunctional oxidation products generated following the exposure of α -Pinene to HOx and NOx obtained using both isopropyl nitrite and O3 + H2O + N2O as the radical precursors.

A cyanide-free method for the preparation of 1-(2-pyridyl)isoquinoline-3-carbonitriles (3-cyanoisoquinolines) was developed. The interaction of 5-phenacyl-3-(2-pyridyl)-1,2,4-triazines with 1,2-dehydrobenzene generated in situ from anthranilic acid and an excess of amyl nitrites afforded the target compounds in good yields. The proposed mechanism involves the in situ transformation of the 5-phenacyl group into the 5-cyano group under the action of alkyl nitrite and the following inverse demand aza-Diels–Alder reaction of thus formed 5-cyano-1,2,4-triazines with 1,2-dehydrobenzene affording the target products. The presence of the 5-phenacyl substituent is a key for the reaction, as in case of 5-styryl- or 5-phenylethynyl-3-(2-pyridyl)-1,2,4-triazines the formation of the 1,2,4-triazine ring-transformation products was observed

A catalytic amount of a reduced form of polyaniline (a redox-active π-conjugated polymer) was found to induce C-H direct arylation of (hetero)arenes with arenediazonium salts prepared from anilines with methanesulfonic acid (MeSO3 H) and tert-butyl nitrite (tBuONO). The difficult part of this method is the coexistence of an oxidant and a reductant in this sequential diazotization and arylation system; diazotization requires weak oxidants such as alkyl nitrites, whereas the arylation is induced by a reductant. This was achieved by the careful control of the amount of tBuONO (1.0 equivalent) for the diazotization step, and sequential arylation using 5 mol % of the polyaniline. The reaction took place under mild conditions without any metals or strong bases at room temperature, and the amino group is a formal leaving group. The scope of the substrates demonstrates the versatility in the combination of anilines with a variety of functional groups and several (hetero)arenes. Two-directional arylation for the synthesis of an unsymmetrical 1,4-diarylated (furyl and pyrrolyl groups) benzene was achieved, using mono-Boc-protected 1,4-phenylenediamine as a substrate. This shows potential for the synthesis of more complicated oligoarene compounds.

An efficient, one-pot approach has been described for the synthesis of 3,5-disubstituted isoxazoles from substituted aldoximes (mixture of E and Z) and alkynes, using alkyl nitrites under conventional heating conditions. The key nitrile oxide intermediates that are required for the synthesis of isoxazoles are formed by treatment of substituted aldoxime with either tert-butyl nitrite or isoamyl nitrite. The generated nitrile oxides underwent in situ [3+2] dipolar cycloaddition to the substituted alkynes to give 3,5-disubstituted isoxazoles regioselectively in high to excellent yields. The developed synthetic methodology was applied for the synthesis of a previously reported potent hDGAT1 inhibitor.

Chitosan has received substantial attention as a biomaterial due to its unique properties. It has become increasingly common to derivatize chitosan to produce nitric oxide (NO)-releasing materials that exert various therapeutic effects through the action of NO. It is generally the case that these NO-releasing polymers are prepared by exposure to high-pressure NO or nitrosating agents like nitrous acid (HNO2) or alkyl nitrites (RONO). In our study, mass spectrometry and spectroscopic methods demonstrate that both monomeric and oligomeric glucosamine experience chemical alteration after exposure to HNO2-based nitrosating conditions from the literature. In polymeric chitosan, HNO2-based nitrosating conditions were found to induce degradation through the formation of 2,5-anhydro- d -mannose and oligosaccharides. In contrast, the RONO tert-butyl nitrite and high-pressure NO were not found to significantly degrade or otherwise alter the structure of glucosamine or its oligomers, supporting the suitability of these approaches.

The oxidation of primary and secondary benzylic alcohols was achieved by using tert-butyl nitrite (t-BuONO) as a stoichiometric oxidant. Various substrates were effectively converted into the corresponding ketones or aldehydes in good to excellent yields. The reaction presumably proceeded by a nitrosyl exchange and a subsequent thermal decomposition of benzylic nitrites. This process would realize an oxidation of alcohols with oxygen in theory by combining with a reproduction of alkyl nitrites from NO and alcohols under an O2 atmosphere. In addition, almost pure oxidized products were readily obtained by simple evaporation of the reaction mixtures since t-BuONO produced only volatile side products.

Alkyl nitrites photolyze in air to yield alkoxy radicals and NO which, through secondary reactions, generate OH radicals. This photochemistry is important in the atmosphere and in laboratory studies where nitrites are often used as a source of OH. The overall quantum yield for hydroxyl radical formation from irradiation of isopropyl nitrite (i-C(3)H(7)ONO) between 300 and 425 nm in 1 atm air at 296 ± 2 K is reported for the first time. The OH radical was scavenged by reaction with CF(3)CF═CF(2) and the formation of CF(3)CFO and CF(2)O monitored as a function of time using Fourier transform infrared spectrometry. The quantum yield was found to be 0.54 ± 0.07 (2σ) and is independent of whether or not NO was added (up to 3 × 10(14) molecules cm(-3)) prior to photolysis to increase NO concentrations above those due to the photolysis of the nitrite. Ultraviolet-visible and infrared cross sections of i-C(3)H(7)ONO are also reported. These data on the OH quantum yields as well as the UV-visible and infrared cross sections for isopropyl nitrite are critical for quantitatively interpreting the results of laboratory studies where i-C(3)H(7)ONO is employed as an OH source as well as for assessing the role of alkyl nitrites in the chemistry of the troposphere.

We review studies of the effects of low ambient ozone concentrations on morbidity that found a negative coefficient for ozone concentration. We call this a Paradoxical Ozone Association (POA). All studies were in regions with methyl ether in gasoline. All but one study carefully controlled for the effects of other criterion pollutants, so the phenomenon cannot be attributed to them. One was in southern California in mid-summer when ozone levels are highest.Because ozone is created by sunlight, the most plausible explanation for a POA would be an ambient pollutant that is rapidly destroyed by sunlight, such as methyl nitrite (MN). A previously published model of engine exhaust chemistry suggested methyl ether in the fuel will create MN in the exhaust. MN is known to be highly toxic, and closely related alkyl nitrites are known to induce respiratory sensitivity in humans. Support for the interpretation comes from many studies, including three linking asthma symptoms to methyl tertiary butyl ether (MTBE) and the observation that a POA has not been seen in regions without ether in gasoline. We also note that studies in southern California show a historical trend from more significant to less significant ozone-health associations. The timing of those changes is consistent with the known timing of the introduction of gasoline oxygenated with MTBE in that region. Keywords: Asthma, Biodiesel, California, DME, MTBE, Nocturnal, Nitrogenous compounds, Japan, Ozone, TAME, Cough

Raman and infrared spectra of n-butyl, isobutyl, sec-butyl and tert-butyl nitrite are reported. Density functional theory and Møeller-Plesset calculations with 6-31G* and 6-311G* basis sets were used to determine ground state molecular geometries and vibrational frequencies of these compounds. Calculations and spectral data of these molecules were used to perform partial vibrational mode assignments for the observed transitions. In agreement with previous investigations of alkyl nitrites, cis and trans rotational conformers of n-butyl, isobutyl and sec-butyl nitrite were observed in the gas phase infrared spectra and the condensed phase Raman and infrared spectra. Among the several predicted geometries of these compounds, the cis-trans geometry (cis with respect to the C-O-N=O dihedral angle and trans with respect to the C-C-O-N dihedral) was calculated to be the most stable conformer of n-butyl and isobutyl nitrite, while the cis-gauche conformer was found to be the most stable geometry of sec-butyl nitrite. The cis-type structures of these three molecules are favored due to formation of a pseudo hydrogen bond between the nitrite group and the alpha-carbon hydrogen atoms. Hindrance with the alkyl moiety, however, causes the trans conformer (trans with respect to the C-O-N=O dihedral) of tert-butyl nitrite to lie lower than its cis conformer, a result that was supported by our spectroscopic measurements. The characteristic N=O stretch frequency for the trans conformers of all the compounds examined was observed to decrease with increasing branching at the alpha-carbon, while the same mode for the cis conformers shows no change among the primary and secondary nitrites. Evidence is also provided that suggests that the relative number of cis conformers to trans conformers decreases as the alpha-carbon branching increases.

The photodissociation of alkyl nitrites series (RONO) in gaseous state were studied using density functional theory with Amsterdam Density Functional program (ADF2000) and quantum chemical molecular dynamical method by “Colors-Excite” code. The different dissociative phenomena have been explained by this investigation. Alkyl nitrites were shifted to their excited states by capturing the light energy and the bonds of O–N (RO–NO) were broken. A two-step reaction occurred for methyl nitrite (THN) to yield the diverse products, such as RO radical, NO and HNO, whereas only one-step reaction occurred for tert -butyl nitrite (TBN). The consistent results in theoretical calculation and experiment, including geometrical structures and excitation energies, demonstrated the good performances of “Colors-Excite”.

Although aliphatic nitro compounds, aliphatic nitrates, and aliphatic nitrites have several features in common (nitrogen-oxygen grouping, explosiveness, methemoglobin formation), there are significant differences in their toxic effects. Some of their attributes are summarized. The esters of nitric and nitrous acid, whose nitrogen is linked to carbon through oxygen, are very similar in their pharmacological effects. Both produce methemoglobinemia and vascular dilatation with hypotension and headache. These effects are transient. None of the series has appreciable irritant properties. Pathological changes occur in animals only after high levels of exposure and are generally nonspecific and reversible. The nitric acid esters of the monofunctional and lower polyfunctional alcohols are absorbed through the skin. Information is not available on the skin absorption of alkyl nitrites. Members of both groups are well absorbed from the mucous membranes and lungs. Heinz body formation has been observed with the nitrates but not with the nitrites. Nitro compounds, like nitrates and nitrites, cause methemoglobinemia in animals. Heinz body formation parallels this activity within the series. Although some members are metabolized to nitrate and nitrite, there is no significant effect on blood pressure or respiration. As with the lower nitrates and nitrites, anesthetic symptoms are observed in animals during acute exposures, but these occur late. The prominent effect is irritation of the skin, mucous membranes, and respiratory tract. This is most marked with chlorinated nitroparaffins and nitroolefins. In addition to respiratory tract injury, cellular damage may be observed in the liver and kidneys. Skin absorption is negligible except for the nitroolefins. The nitramines have entirely different activity. RDX is a convulsant for humans and animals. Skin absorption, irritation, vasodilatation, methemoglobin formation, and permanent pathological damage are either insignificant or absent after repeated doses. Transient illness has been associated with the industrial use or manufacture of these materials, but fatalities and chronic intoxication have been uncommon. Some members of each group present extremely high fire and explosion hazards. Keywords: Aliphatic nitro compounds; Aliphatic nitrates; Aliphatic nitrites; Nitroolefins; Alkyl nitrites

A method for the synthesis of peroxynitrite is described. It involves nitrosation of H2O2 at pH> or = 12.5 by isoamyl or butyl nitrite in mixed solvents of isopropyl alcohol (IPA) and water at 25+/-1 degrees C. Maximum yields of peroxynitrite are obtained after 15 min of incubation at IPA concentrations of 30-70% (v/v). The solutions of peroxynitrite are processed for removal of IPA and isoamyl alcohol by solvent extraction. Unreacted H2O2 is removed by catalytic decomposition on granular MnO(2). The post processed solutions of peroxynitrite are useful in several chemical and biochemical investigations where bolus additions are required. The method as reported is amenable for large scale synthesis as it involves sequential mixing of solvents (water and IPA) to alkali followed by the addition of H2O2 and alkyl nitrite.

Allyl nitrite, ONOCH2CHCH2, can exist in conformations which include syn (S) and anti (A) configurations of ONOC, anti or gauche (G) configurations of NOCC, and syn or skew (Sk) configurations of OCCC. Four of them have been observed and characterized by their microwave spectra and quantum chemical calculations to have AGSk′ (0.0 kcal/mol), AGSk (0.2(2) kcal/mol), SASk (0.2(2) kcal/mol), and SAS (0.9(2) kcal/mol) configurations about the three successive dihedral angles. All four are observed in microwave studies of the vapor at 300 and 200 K and the first three are seen in pulsed-jet beams. The SAS form apparently relaxes to the SASk conformer during expansion in the pulsed-jet. Quantum chemical calculations reveal that the two possible conformers with anti–anti configurations of the ONOCC fragment, AAS and AASk, are transition states, unstable configurations, or of marginal stability, consistent with structures observed in this and other previously studied alkyl nitrites. The remaining four possible conformers are predicted to have relative energies within 1 kcal/mol of the observed conformers but were not observed experimentally. Chirality 14:232–240, 2002. © 2002 Wiley-Liss, Inc.

A simple and sensitive method for the determination of liquid methanol and ethanol at trace levels by an alkyl nitrite formation reaction has been established. Alcohol was allowed to react with nitrous acid, which was yielded from sulfuric acid and sodium nitrite in the solution, to form the corresponding alkyl nitrite in the hexane organic phase. Alkyl nitrites in hexane were analyzed by a gas chromatograph with an electron capture detector (GC-ECD). The detection limits, which were determined at a signal-to-noise ratio of 3, were 1.1 and 0.7 micrograms/L for methanol and ethanol, respectively, by 1 microL injection. The relative standard deviations for n = 8 were 4.0 and 3.3% for methanol and ethanol, respectively. The method was applied to determine the alcohol concentration in a rice paddy, pond water, tap water, and well water. Those aqueous samples were also spiked with standard alcohols; the average recoveries of spiked methanol and ethanol were 98 and 91% with relative standard deviations of 6.1 and 4.0%, respectively.

A one-step synthesis of adsorbed alkoxides from alkyl nitrites dosed on Cu(100) is illustrated using methyl nitrite (CH3ONO) to form methoxide (CH3O) and tert-butyl nitrite (t-C4H9ONO) to form tert-butoxide (t-C4H9O). Compared with an alternative, dosing CH3OH on an O-covered Cu surface, only minor differences in the concentration and local chemical environment of CH3O are evident. The potential energy profiles associated with the two synthesis methods are contrasted, and the key role played by the weak RO−NO bond is emphasized.

This paper presents 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. In this method, the ambient air and nitrogen dioxide (1,000 ppmv) were allowed to continuously flow in a glass tube, which had been filled with 10 g of Pyrex glass beads. The flow rates of the ambient air and nitrogen dioxide were 30 and 20 cm3/min, respectively. The gas-phase alkyl nitrites produced by the dark reaction of atmospheric alcohols and nitrogen dioxide on the Pyrex glass beads were then analyzed by gas chromatography with an electron capture detector. The alcohol concentrations of the samples were calculated using a calibrated conversion factor for each alcohol to its nitrite. The detection limits for the methanol and ethanol are 0.7 and 0.5 ppbv, respectively. This flow method was used to determine the atmospheric alcohol concentrations and was found to have the advantages of a short sampling time and simple quantitative procedure compared with the previously reported method (glass bottle method). The feasibility of this method was also established.

The influence of β-cyclodextrin (β-CD) on the base-catalyzed hydrolysis reaction of 1-phenyl-1-propyl, 2-phenyl-1-propyl and 3-phenyl-1-propyl nitrites and on the nitrosation of pyrrolidine, piperidine and N-methylcyclohexylamine by the aforementioned alkyl nitrites (RONO) is studied in aqueous buffers of the amines and in an alkaline medium with [OH−] = 0.20 M. The hydrolysis reaction is catalyzed by the presence of β-CD owing to the formation of reactive 1:1 inclusion complexes between the alkyl nitrite and the ionized β-CD; the addition of potential inhibitors, such as dodecyltrimethylammonium bromide monomers, accelerates the reaction even more. The effect is quite significant in the case of 1-phenyl-1-propyl nitrite and is viewed as a case of allostery. In the presence of neutral β-CD, the nitrosation by 1-phenyl-1-propyl nitrite, either of pyrrolidine or piperidine, is inhibited by β-CD addition; however, the nitrosation reaction of piperidine by 2-phenyl-1-propyl nitrite is catalyzed (passing through a maximum) by β-CD, whereas the nitrosation of pyrrolidine promoted by 3-phenyl-1-propyl nitrite exhibits practically no change upon β-CD addition. In alkaline media (containing ionized β-CD) the nitrosation of pyrrolidine by 1-phenyl-1-propyl nitrite is inhibited by the presence of β-CD; in contrast, the nitrosation of both piperidine and N-methylcyclohexylamine is catalyzed in all cases, but the degree of catalysis depends not only on the alkyl nitrite structure, but also on the type and concentration of the amine. Kinetic results are quantitatively interpreted on the basis of the proposed reaction mechanism in each case, and the kinetic rate constants of the different steps are determined. Comparison of the results obtained in aqueous alkaline media and in aqueous buffers of the amines themselves allows us to establish important characteristics of the transition state of the reaction.

A new method for measuring the concentration of atmospheric alcohols was developed and applied to ambient air samples. In the method, air samples were collected in 200 ml Pyrex glass bottles whose surface had been cleaned and treated with a chromic acid mixture. Alcohols in the sample were allowed to react in the dark with intentionally added nitrogen dioxide (200 ppm by volume (ppmv) concentration level) on the glass surface to yield corresponding alkyl nitrites. The concentration of the nitrite thus yielded is determined separately by gas chromatography (GC) with an electron capture detector (ECD). Alcohol concentration in the sample is calculated using a calibrated conversion factor of each alcohol to its nitrite. Detection limits for methanol, ethanol, and isopropanol are 0.9, 0.7, and 1.8 ppbv (parts per billion by volume), respectively, using 500 μl injection of the reaction mixture by this method. In order to examine the feasibility of this method for an ambient air sample, several measurements were done. Air samples were taken on a road with heavy traffic near the campus of Osaka Prefecture University. Concentration levels of methanol, ethanol, and isopropanol were 4–10, 3–25, and 1.5–20 ppbv, respectively. Diurnal variation of these alcohols’ concentration was also measured. Generally, alcohol concentrations were higher in the evening than those in the daytime, increasing up to the levels of 10–20, 10–25, and 10–20 ppbv for methanol, ethanol, and isopropanol, respectively.

The photolysis of thin layers of tert- and iso-butyl nitrite, physisorbed on a transparent insulating MgF2 surface, has been investigated. (1+1′)-Resonance-enhanced multiphoton ionization (REMPI) spectroscopy was used to characterize the desorbed NO. For high-J rotational levels, a preference for the Π(A″) Λ-doublet and a small degree of alignment is observed. The axis of alignment is found to be parallel to the plane of polarization of the photolysis laser and perpendicular to the surface normal, indicating a cartwheeling mode of desorption. The photofragment yield (PHOFRY) spectrum of iso-butyl nitrite is also reported.

The oxidative reactions using alkyl nitrites (RONO) as oxidant have been developed by Ube Industries, Ltd. The substrates such as CO and/or unsaturated-and/or carbonyl-compounds are oxidized by RONO over the palladium catalyst with no contact of molecular oxygen. Dialkyl carbonates, dialkyl oxalates and other useful chemicals are synthesized efficiently under moderate conditions by this alkyl nitrite technology.

The influence of β-cyclodextrin (β-CD) on the hydrolysis reaction of a variety of structural types of alkyl nitrites (RONO) is studied in acid and in basic aqueous solutions. Acid-catalysed hydrolysis of alkyl nitrites is inhibited by the presence of β-cyclodextrin. The results are accounted for by assuming the formation of host–guest complexes between β-cyclodextrin and alkyl nitrite, which are unreactive or much less reactive than the uncomplexed RONO. We propose that the result is a consequence of the orientation of the alkyl nitrite in the cavity of CD. The degree of inhibition increases with the greater inclusion of the alkyl nitrite in the CD cavity. The kinetic data are quantitatively analyzed to afford the stability constants of the host–guest complexes. On the contrary, the presence of β-cyclodextrin strongly increases the rate of hydrolysis of alkyl nitrites in a basic medium, that is at a pH value higher than the pKa of β-cyclodextrin. This feature suggests the formation of a reactive complex between the alkyl nitrite and β-cyclodextrin, whose ionized CD hydroxy group promotes a nucleophilic attack in the rate-limiting step. This behaviour is consistent with a higher reactivity towards alkyl nitrites of an ionized CD hydroxy group as compared with the OH–; the contrary occurs in the case of esters, whose cleavage by cyclodextrins in basic aqueous media has been studied extensively over the last several years.

Reaction of alkyl radicals (generated from alkyl iodides or benzyl bromides with hexabutylditin) in the presence of alkyl nitrites affords oximes as products in good yields.

The oxidative reactions using the alkyl nitrites (RONO) as an oxidant have been developed by Ube Industries, Ltd. In the alkyl nitrite reactions, substrates such as CO andyor unsaturated- andyor carbonyl-compounds are oxidized over the palladium catalysts in no direct contact with molecular oxygen. The dimethyl carbonate (DMC), dialkyl oxalates and other useful chemicals are synthesized efficiently under moderate conditions by the alkyl nitrite reactions.

This paper examines the self-reported effects of alkyl nitrite use. The aim of this research into the social contextual use of nitrites was to provide qualitative data to assist with policy-making ...

The kinetics of the nitrosation of piperidine by propyl,iso-propyl, butyl,iso-butyl,sec-butyl, andtert-butyl nitrites in 0.1M NaOH and of the hydrolysis of the nitrite esters were studied spectrophotometrically by monitoring the absorbance of the nitrites at 381 nm. The observed correlation between logk2 and σ* (ρ*=4.5) shows the reaction to proceedvia electrophilic attack by the nitrites; the existence of an isokinetic relationship suggests a single mechanism for the whole series. Comparison of the relative reactivities of the alkyl nitrites (primary>secondary>tertiary) with characteristic parameters of theirR groups (vertical ionization potentials and heats of formation ofR+) suggests that these reactions are orbital controlled. All hydrolysis reactions were slower than the corresponding aminolysis reactions. This is attributed to a retardation of the former reaction by unfavourable interactions between the lone pairs of the nucleophile and the nitroso nitrogen atom.

In a procedure of extreme simplicity and rapidity a mixture of an aromatic primary amine, copper (I) cyanide and an alkyl nitrite in dimethyl sulphoxide yielded fair to moderate yields of the corresponding nitriles. Side processes observed were reduction (NH 2 → H), nitration (NH 2 → NO 2 ) and hydroxylation (NH 2 → OH). In the case of polyhaloanilines halogen dance products could be detected.

The present work has addressed the question of the dissociation time of four alkyl nitrites upon photoexcitation in the S1 state (methyl nitrite, n‐ , and t‐butyl nitrites and i‐amyl nitrite). The time resolved Laser Induced Fluorescence technique has been used in the femtosecond regime under bulk conditions. The photodissociation has been initiated at 351 nm by 150 fs pump pulses, and has been probed using a two‐photon process at 467 nm by 200 fs pulses. The LIF signal has qualitatively the same shape for the four nitrites: it passes through a transient peak before reaching a plateau. The two‐photon process that induces the detected fluorescence is nonresonant for detection of the dissociation product NO through the A←X transition. Conversely, the two‐photon process is resonant or quasiresonant for detection of the excited nitrite molecule in the S1 level before it dissociates. This leads to an enhanced detection efficiency of the non‐dissociated excited molecule versus that of the NO fragment. A simple ...

The alkyl nitrites, tert-butyl nitrite and iso-butyl nitrite have been photolysed at 351 nm on a dielectric surface. This involves excitation to the A 1A″ state with two quanta in the localized NO stretching mode of iso-butyl nitrite and three quanta in the case of tert-butyl nitrite. The vibrational, rotational and translational energy distributions of the NO product are compared with the results of previous gas phase work. The vibrational distributions mimic those in the gas phase, but the rotational distributions do not do so.

The effects of alkyl nitrates, alkyl nitrites and organic peroxides on cetane number were investigated to provide the mechanism of the improvement of cetane number improvers. It was found that all the alkyl nitrates, alkyl nitrites and organic peroxides improved cetane number of diesel fuel. In the thermolysis of cetane number improvers, free radicals were formed. Aldehydes, ketones, nitric oxides and nitric diox-ides produced were not concerned with the increment of cetane number. We consider that free radicals have influences on cetane number improvement. The n-alkyl nitrite containing more carbon atoms makes higher improvement on cetane number. The alkyl radicals containing more carbon atoms make higher increment on cetane number.

Although aliphatic nitro compounds, aliphatic nitrates, and aliphatic nitrites have several features in common (nitrogen–oxygen grouping, explosiveness, methemoglobin formation), there are significant differences in their toxic effects. Some of their attributes are summarized. The esters of nitric and nitrous acids, whose nitrogen is linked to carbon through oxygen, are very similar in their pharmacological effects. Both produce methemoglobinemia and vascular dilatation with hypotension and headache. These effects are transient. None of the series has appreciable irritant properties. Pathological changes occur in animals only after high levels of exposure and are generally nonspecific and reversible. The nitric acid esters of the monofunctional and lower polyfunctional alcohols are absorbed through the skin. Information is not available on the skin absorption of alkyl nitrites. Members of both groups are well absorbed from the mucous membranes and lungs. Heinz body formation has been observed with the nitrates but not with the nitrites. Nitro compounds, like nitrates and nitrites, cause methemoglobinemia in animals. Heinz body formation parallels this activity within the series. Although some members are metabolized to nitrate and nitrite, there is no significant effect on blood pressure or respiration. As with the lower nitrates and nitrites, anesthetic symptoms are observed in animals during acute exposures, but these occur late. The prominent effect is irritation of the skin, mucous membranes, and respiratory tract. This is most marked with chlorinated nitroparaffins and nitroolefins. In addition to respiratory tract injury, cellular damage may be observed in the liver and kidneys. Skin absorption is negligible except for the nitroolefins. The nitramines have entirely different activity. RDX is a convulsant for humans and animals. Skin absorption, irritation, vasodilatation, methemoglobin formation, and permanent pathological damage are either insignificant or absent after repeated doses. Transient illness has been associated with the industrial use or manufacture of these materials, but fatalities and chronic intoxication have been uncommon. Some members of each group present extremely high fire and explosion hazards. Keywords: Aliphatic nitrates; aliphatic nitrites; aliphatic nitro compounds; alkyl nitrites; nitroolefins

Reflection-absorption infrared spectroscopy (RAIRS) is used to explore the photochemistry of primary and tertiary alkyl nitrites deposited on a gold surface. The primary alkyl nitrites examined for this study were n-butyl, isobutyl, and isopentyl nitrite. These compounds showed qualitatively similar spectra to those observed in previous condensed-phase measurements. The photolysis of the primary nitrites involved the initial formation of an alkoxy radical and NO, followed by production of nitroxyl (HNO) and an aldehydic species. In addition, the formation of nitrous oxide, identified from its distinctive transition near 2230 cm(-1), was observed to form from the self-reaction of nitroxyl. The reaction rates for cis and trans conformer decay, as tracked through their intense N═O stretching modes, were found to be significantly different, potentially due to a structural bias that favors HNO formation for the initial trans conformer photoproducts over recombination. Tert-butyl nitrite demonstrates only the trans conformer in the RAIRS spectra prior to photolysis; however, recombination of the initial NO and RO(•) photoproducts was observed to produce the cis conformer in the photolyzed samples. The primary photoproducts from tert-butyl nitrite can also react to form acetone and nitrosomethane, but the absence of HNO prohibits the formation of N(2)O that was observed for the primary alkyl nitrites. Additionally, the RAIRS spectrum of isobutyl nitrite co-deposited with water was measured to examine the photolysis of this species on a water-ice surface. No change in the identity of the photoproducts was observed in this experiment, and minimal frequency shifting (1-3 cm(-1)) of the vibrational modes occurred. In addition to being a known atmospheric source of NO and various aldehydes, our results point to cold surface processing of alkyl nitrites as a potential environmental source of nitrous oxide.

Rate constants for the reactions of OH radicals and Cl atoms with CH3ONO, C2H5ONO, n-C3H7ONO, n-C4H9ONO, and n-C5H11ONO have been determined at 298 ± 2 K and a total pressure of approximately 1 atm. The OH rate data were obtained using both the absolute rate technique of pulse radiolysis combined with kinetic spectroscopy and a relative rate method involving simultaneous measurement of the loss of the nitrite and the reference compound. The Cl rate constants were measured using the relative rate method. Values of the rate constants in units of 10−13 cm3 molecule−1 s−1 are: Text Table Text. Relative Cl Relative OH Absolute OH CH3ONO 94.4 ± 7.4 3.0 ± 1.0 2.6 ± 0.5 C2H5ONO 295 ± 13 7.0 ± 1.5 7.0 −1.1 n-C3H7ONO 646 ± 58 11.0 ± 1.5 12.0 ± 0.5 n-C4H9ONO 1370 ± 58 22.7 ± 0.8 27.2 ± 6.0 n-C5H11ONO 2464 ± 444 37.4 ± 5.0 42.5 ± 8.0 When compared to rate data for the corresponding alkanes the results show that the -ONO group decreases the rate constant for H atom abstraction by the OH radical from groups bonded to the -ONO group and also decreases that for groups in the β position. Similar results were found for the reaction of Cl atoms with these compounds. The results are discussed in terms of reactivity trends.

Reaction of alkyl radicals (generated from alkyl iodides or benzyl bromides with hexabutylditin) in the presence of alkyl nitrites affords oximes as products in good yields.

The typical oxidative reactions ((1) dialkyl oxalate synthesis from carbon monoxide, (2) dialkyl carbonate synthesis from carbon monoxide, (3) acetals and ketals synthesis from olefins, and (4) oxidative carbonylation of olefins) catalyzed by palladium in the presence of alkyl nitrites, are described. The mechanistic studies are conducted based on reaction kinetics. In addition, derivation of acetals obtained by olefin oxidation to various useful fine chemicals is also described.

The oxidative reactions using the alkyl nitrites (RONO) as an oxidant have been developed by Ube Industries, Ltd. In the alkyl nitrite reactions, substrates such as CO andyor unsaturated- andyor carbonyl-compounds are oxidized over the palladium catalysts in no direct contact with molecular oxygen. The dimethyl carbonate (DMC), dialkyl oxalates and other useful chemicals are synthesized efficiently under moderate conditions by the alkyl nitrite reactions.

A one-colour photolysis-ionisation study of the photodissociation of methyl and t -butyl nitrite near 380 nm in a supersonic jet has been performed. The NO photoproduct has been characterised by state-resolved probing by (2 + 1) REMPI via the C→X δ bands of NO. The photodissociation of methyl nitrite yields predominantly vibrationally cold NO, while t -butyl nitrite photodissociation shows a propensity for formation of NO in the first excited vibrational level. The NO fragments are rotationally highly excited in both cases, and the rotational population distributions can be fitted by Gaussian curves in agreement with recent dynamical calculations. The different vibrational energy disposal is attributed to the different excitation of a rapidly predissociating complex. Previous results that were at variance with knowledge of the dynamics of the predissociation of alkyl nitrites may have been affected by experimental problems.

Electronic absorption spectra of cis- and trans-2-butyl, cyclopentyl, and cyclohexyl nitrite radical are reported. These new species were generated photochemically in an Ar matrix at 12 K. All alkyl nitrite radicals exhibit a long wavelength absorption that extends into the red spectral region. It is assigned to excitation of a charge transfer state involving transfer of the electron on the C radical center to the nitrite group. The 300–400 nm region shows a vibronic progression similar to the well known S1(n(N)π*)→S0 system of closed shell alkyl nitrites.

Photodissociation of methyl nitrite and n-butyl nitrite at 266 and 355 nm has been investigated in the gas phase at room temperature. OH photoproducts were observed, and their internal state distributions were measured by the one-photon laser-induced fluorescence (LIF) technique. It was found that the nascent OH from the 266 nm photolysis of methyl nitrite was vibrationally cold, and its rotational state distribution conformed to a Boltzmann behavior with a rotational temperature of T(rot) = 2200 +/- 150 K. In contrast, the nascent OH from the 266 nm photolysis of n-butyl nitrite was found to be vibrationally excited, and the measured relative population of upsilon '' = 0: 1 was 0.78: 0.22. The rotational state distribution of the OH upsilon '' = 1 state conformed to Boltzmann behavior, with a rotational temperature of T(rot) = 1462 +/- 120 K. However, a simple Boltzmann distribution was not found for the OH upsilon '' = 0 state. In the photolysis of n-butyl nitrite at 355 nm, the OH fragment was found to be vibrationally cold and its rotational state distribution showed non-Boltzmann behavior. A photodissociation mechanism involving an intramolecular hydrogen atom transfer process is proposed for the OH product pathway for methyl nitrite, which has been compared with the potential energy surfaces obtained from density functional theory (DFT) calculations. A photodissociation mechanism of n-butyl nitrite is also proposed for the OH product pathway, which differs from that of methyl nitrite due to the effects of the different alkoxy substituents.

Rate constants for the reactions of OH radicals and Cl atoms with CH3ONO, C2H5ONO, n-C3H7ONO, n-C4H9ONO, and n-C5H11ONO have been determined at 298 ± 2 K and a total pressure of approximately 1 atm. The OH rate data were obtained using both the absolute rate technique of pulse radiolysis combined with kinetic spectroscopy and a relative rate method involving simultaneous measurement of the loss of the nitrite and the reference compound. The Cl rate constants were measured using the relative rate method. Values of the rate constants in units of 10−13 cm3 molecule−1 s−1 are: Text Table Text. Relative Cl Relative OH Absolute OH CH3ONO 94.4 ± 7.4 3.0 ± 1.0 2.6 ± 0.5 C2H5ONO 295 ± 13 7.0 ± 1.5 7.0 −1.1 n-C3H7ONO 646 ± 58 11.0 ± 1.5 12.0 ± 0.5 n-C4H9ONO 1370 ± 58 22.7 ± 0.8 27.2 ± 6.0 n-C5H11ONO 2464 ± 444 37.4 ± 5.0 42.5 ± 8.0 When compared to rate data for the corresponding alkanes the results show that the -ONO group decreases the rate constant for H atom abstraction by the OH radical from groups bonded to the -ONO group and also decreases that for groups in the β position. Similar results were found for the reaction of Cl atoms with these compounds. The results are discussed in terms of reactivity trends.

A 38-year-old man was admitted to hospital with several days of malaise and dyspnoea. He was on no prescribed medications, and had previously been well apart from an episode of gangrenous cholecystitis due to mixed gallstones three years previously. Full blood examination showed haemoglobin 110 g/l, white cell count 12AE9 · 10/l with neutrophil count 9AE2 · 10/l, and platelet count 266 · 10/l. The blood film (left) demonstrated marked polychromasia with features of oxidative haemolysis and hyposplenism. Supravital staining with methyl-violet demonstrated numerous Heinz bodies (top right). Other indicators of haemolysis included a reticulocytosis of 241 · 10/l, lactate dehydrogenase 374 IU/l, bilirubin 54 lmol/l with undetectable haptoglobin and a negative direct antiglobulin test. On further enquiry, the patient denied fava bean ingestion but disclosed heavy recreational use of inhalational amyl nitrite. Avoidance of further nitrite exposure resulted in resolution of haemolysis, and the patient was provided with counselling on drug use. Laboratory testing in the convalescent phase did not detect evidence of glucose-6-phosphate dehydrogenase deficiency or an underlying haemoglobinopathy. Nitrite inhalants, such as amyl nitrite, are highly volatile yellow liquids that cause rapid vasodilation and hence were once used as anti-anginals. Nitrites efficiently oxidize haemoglobin to methaemoglobin and may also increase the proteolytic susceptibility of haemoglobin leading to globin chain denaturation and Heinz body formation. The recreational use of alkyl nitrites, colloquially known as ‘poppers’ (bottom right), should be considered in apparently idiopathic episodes of oxidative haemolysis. Significant complications may occur even in patients with intact red cell reduction pathways.

The reaction between alkyl nitrites, particularly n-butyl nitrite, and tertiary aromatic amines under a variety of experimental conditions promptly yielded products of N-dealkylation-N-nitrosation, ring nitration, ipso-substitution and, occasionally, combinations of these processes. Aminoethers were detected as final products and intermediates on the way to N-nitrosations. Reaction pathways are suggested for some of the observed behaviours on the basis of experimental evidences whereas other alternatives are discarded.

The most commonly used reagent for bringing about electrophilic nitrosation is nitrous acid, generated in aqueous acid solution from a nitrite salt, usually sodium nitrite, and used in situ. Pure nitrous acid has never been isolated, because decomposition occurs, giving various oxides of nitrogen as final products. Where decomposition is a problem, such as for slow nitrosation reactions, better quantitative work can be achieved by carrying out the reactions anaerobically. Another important fact is that apart from the generation of nitrosyl halides in low concentration in aqueous acid solutions of nitrous acid containing halide ions, the nitrosyl halides can be used in solution in a variety of non-aqueous solvents to bring about nitrosation. Also, alkyl nitrites or nitrite esters have been known for a long time and are, under many conditions, effective nitrosating agents. They are mostly colorless–yellow volatile liquids derived in the main from aliphatic alcohols. There has been an upsurge, in recent years, in the range of rather unusual nitrosating agents, which have been developed. Some do not appear to have major synthetic advantages over the reagents already discussed, but others might be appropriate reagents under certain circumstances. These include sodium nitrite under phase-transfer condition, oxyhyponitrite, various complexes of HalNO and N 2 O 4 , sodium nitrite on silica and silica chloride bases and N 2 O 4 immobilized on polyvinylpyrrolidone.

Alcohols react readily with acidified aqueous nitrous acid solutions to generate alkyl nitrites. The reaction sets up an equilibrium, which can be driven to the right by the use of a large excess of the alcohol or by removal of the alkyl nitrite by distillation, since alkyl nitrites have lower boiling points than do the corresponding alcohols. These reactions are O-nitrosation reactions and were first demonstrated by Allen who showed that a chiral alcohol gave the corresponding alkyl nitrite without racemization. Similarly, the reverse reaction, the hydrolysis of alkyl nitrites, occurs by N–O bond fission, again shown by the retention of configuration and by absence of an excess of 18 O in the alcohol product when the hydrolysis is carried out in 18 O-enriched water. There is much kinetic evidence that suggests that carboxylic acids undergo nitrosation reactions generating nitrosyl carboxylates, which can act as nitrosating reagents just as is the case for the in situ generation of nitrosyl halides and other derivatives. There have been no significant developments in this area either in mechanistic or synthetic studies since 1988, so the earlier account, gives the presently known position.

The biological activities of endogenously produced nitric oxide (NO; nitrogen monoxide) can be affected not only by NO itself but also by relatively stable NO-derived substances or by-products of NO. It is well known that NO-derived nitrosation at the center of nitrogen, sulfur, and carbon (N-, S-, and C-nitrosation) have a great biological significance, while that at oxygen center (O-nitrosation) remains to be detected. During the course of a physiologic study on ethanol-induced gastric injury employing an ex vivo gastric chamber system of rats, we found that ethanol could be nitrosated by endogenously produced NO. Luminal nitrite and nitrate (NOx) levels in gastric lumen were decreased sharply about 70% during ethanol saline solution infusion to the chamber and then immediately returned to the basal levels by infusion of ethanol-free saline solution. On the other hand, NO levels in gastric mucosa were slightly increased during the infusion of ethanol saline solution, suggesting that ethanol never inhibits NO biosynthesis. These results demonstrate that ethanol perfused in gastric lumen can scavenge gastric tissue-derived NO and ethanol may react with NO-derived species (probably, N(2)O(3)) to form an ethylnitrite in oxygen-containing luminal solution. Alkyl nitrites including ethylnitrite have been not only widely used as a nitrovasodilator but also shown to act as a nitrosating agent. Thus, in vivo O-nitrosation also has important biological meaning in the same manner as N-, S-, and C-nitrosation.

(OEP)Os(CO) reacts with n-butyl nitrite to give, after workup, the (OEP)Os(NO)(O-n-Bu) trans addition product (OEP = octaethylporphyrinato dianion). Similarly, the reaction of (OEP)Os(CO) or [(OEP)Os](2) with isoamyl nitrite gives the corresponding nitrosyl alkoxide, (OEP)Os(NO)(O-i-C(5)H(11)). The related reactions of (OEP)Os(CO) or [(OEP)Os](2) with isoamyl thionitrite gives the (OEP)Os(NO)(S-i-C(5)H(11)) nitrosyl thiolate. The reaction of the [(OEP)Os](2)(PF(6))(2) reagent with isoamyl thionitrite gives the nitrosylation product, [(OEP)Os(NO)]PF(6), which undergoes anion hydrolysis to give the isolable difluorophosphate (OEP)Os(NO)(O(2)PF(2)) derivative. Interestingly, the reaction of O(2)NC(6)H(4)N=NSPh with [(OEP)Os](2) gives the (OEP)Os(SPh)(2) product with loss of the arylazo fragments. The solid-state structures of (OEP)Os(NO)(O-n-Bu), (OEP)Os(NO)(O(2)PF(2)), and (OEP)Os(SPh)(2) have been determined by X-ray crystallography.

Glutathione transferase (GST)-catalysed S-nitrosoglutathione (GSNO) formation from alkyl nitrites was determined with the homodimers 1-1, 2-2, 3-3, and 4-4 isolated from rat liver. The 4-4 isoform showed a high specificity for the alkyl nitrites. Total GST activities were studied in homogenates from different organs. The liver showed highest GST activity both with amyl nitrite and with 1-chloro-2,4-dinitrobenzene (CDNB) as substrate, the activity ratio of amyl nitrite over CDNB being 3.8. In lung and heart, these ratios were 6.2 and 5.7, respectively, indicating a selectivity of these organs for alkyl nitrite metabolism and GSNO formation.

The present work has addressed the question of the dissociation time of four alkyl nitrites upon photoexcitation in the S1 state (methyl nitrite, n‐ , and t‐butyl nitrites and i‐amyl nitrite). The time resolved Laser Induced Fluorescence technique has been used in the femtosecond regime under bulk conditions. The photodissociation has been initiated at 351 nm by 150 fs pump pulses, and has been probed using a two‐photon process at 467 nm by 200 fs pulses. The LIF signal has qualitatively the same shape for the four nitrites: it passes through a transient peak before reaching a plateau. The two‐photon process that induces the detected fluorescence is nonresonant for detection of the dissociation product NO through the A←X transition. Conversely, the two‐photon process is resonant or quasiresonant for detection of the excited nitrite molecule in the S1 level before it dissociates. This leads to an enhanced detection efficiency of the non‐dissociated excited molecule versus that of the NO fragment. A simple ...

The most common alkyl nitrites encountered in forensic toxicology are iso-butyl, n-butyl and iso-pentyl(amyl) nitrites. All have become popular as an aphrodisiac, especially among the homosexual population. Alkyl nitrites are a volatile and unstable group of compounds, which hydrolyse in aqueous matrices to the alcohol and nitrite ion. Here we describe a fast, clean and sensitive procedure for the detection of hydrolysed n-butyl nitrite in whole human blood using a new, solvent-free sampling technique, the headspace solid-phase micro-extraction (HSPME), combined with GC/FID analysis. Sample preparation was investigated using two different stationary phases (100 microns polydimethylsiloxane and 85 microns polyacrylate), coating a fused silica fibre. The effect of different sampling times at fixed temperatures was also studied. Our results demonstrate that the HSPME/GC/FID procedure allows tracing of n-butyl nitrite abuse and detects hydrolysed n-butyl nitrite, i.e., released n-butanol, in whole blood at the 1 ng/mL level.

The reaction between alkyl nitrites, particularly n-butyl nitrite, and tertiary aromatic amines under a variety of experimental conditions promptly yielded products of N-dealkylation-N-nitrosation, ring nitration, ipso-substitution and, occasionally, combinations of these processes. Aminoethers were detected as final products and intermediates on the way to N-nitrosations. Reaction pathways are suggested for some of the observed behaviours on the basis of experimental evidences whereas other alternatives are discarded.

The kinetics of spontaneous and human glutathione transferase catalysed formation of S-nitrosoglutathione(GSNO) from glutathione(GSH) and n-butyl- or amyl nitrite have been studied. At physiological pH and temperature, k2 values of 22.3 and 21.0 M−1 · min−1 were obtained for n-butyl- and amyl nitrites, respectively. Rate enhancements, (kcat/Km × k2) × 10−4, due to purified human GSH transferases A1−1, A2−2 and Mla−la were, respectively, 7.00, 2.94 and 10.6 for n-butyl nitrite and 121, 3.92 and 34.5 for amyl nitrite. GSH transferase P1−1 showed no detectable catalysis of the formation of GSNO. The data suggest that the presence of GSTs A1−1, A2−2 or M1−1 contribute substantially to intracellular metabolism of alkyl nitrites to GSNO. The results may be significant with regard to the immunotoxicity of alkyl nitrites.