Ethyl Hydroperoxide Research Articles

Unimolecular Decomposition of Ethyl Hydroperoxide: Ab Initio/Rice−Ramsperger−Kassel−Marcus Theoretical Prediction of Rate Constants

Alkyl hydroperoxides are found to be important intermediates in the combustion and oxidation processes of hydrocarbons. However, studies of ethyl hydroperoxide (CH(3)CH(2)OOH) are limited. In this work, kinetics and mechanisms for unimolecular decomposition of CH(3)CH(2)OOH have been investigated. The potential energy surface of decomposition reactions have first been predicted at the CCSD(T)/6-311+G(3df,2p)//B3LYP/6-311G(d,p) level. The results show that the formation of CH(3)CH(2)O + OH via O-O direct bond dissociation is dominant, the branching ratio of which is over 99% in the whole temperature range from 300 to 1000 K, and its rate constant can be expressed as k1 = 9.26 × 10(52)T(-11.91)exp(-26879/T) s(-1) at 1 atm. The rate constants of the reaction CH(3)CH(2)OOH → CH(3)CH(2)O + OH at different temperatures and pressures have been calculated, which can help us to comprehend the reactions of CH(3)CH(2)OOH at experimental conditions.

Measurement of atmospheric hydrogen peroxide and organic peroxides in Beijing before and during the 2008 Olympic Games: Chemical and physical factors influencing their concentrations

For the 2008 Beijing Olympic Games full‐scale control (FSC) of atmospheric pollution was implemented to improve the air quality from 20 July to 20 September 2008, resulting in a significant decrease in the emission of pollutants in urban Beijing, especially vehicular emissions. The combination of reduced emissions and weather condition changes provided us with a unique opportunity to investigate urban atmospheric chemistry. Hydrogen peroxide (H2O2) and organic peroxides play significant roles in atmospheric processes, such as the cycling of HOx radicals and the formation of secondary sulfate aerosols and secondary organic aerosols. We measured atmospheric H2O2 and organic peroxides in urban Beijing, at the Peking University campus, from 12 July to 30 September, before and during the FSC. The major peroxides observed were H2O2, methyl hydroperoxide (MHP), and peroxyacetic acid (PAA), having maximal mixing ratios of 2.34, 0.95, and 0.17 ppbv (parts per billion by volume), respectively. Other organic peroxides were detected occasionally, such as bis‐hydroxymethyl hydroperoxide, hydroxymethyl hydroperoxide, ethyl hydroperoxide, and 1‐hydroxyethyl hydroperoxide. On sunny days the concentrations of H2O2, MHP, and PAA exhibited pronounced diurnal variations, with a peak in the afternoon (1500–1900) and, occasionally, a second peak in the evening (2000–0200). The night peaks can be attributed to local night production from the ozonolysis of alkenes, coupled with the reaction between NO3 radicals and organic compounds. Sunny‐day weather dominated during 16–26 July, and we found that the concentrations of H2O2, MHP, and PAA increased strikingly on 22–26 July, compared with the concentrations during 16–19 July. This effect was mainly attributed to the NOx (NO and NO2) decline because of the FSC, due to (i) the suppressing effect of NO and NO2 on the production of peroxides and (ii) the indirect effect of reduced NOx on the concentration of peroxides via O3 production in the volatile organic compound‐sensitive area. Although the time period from 29 July to 15 August fell within the FSC, the concentrations of H2O2, MHP, and PAA decreased significantly. This can be explained by a combination of chemical and physical factors during this period, when rainy‐ and cloudy‐day weather dominated. Weaker irradiation and lower temperatures resulted in a lower photochemical production of peroxides; the higher humidity resulted in their greater loss through their aqueous‐phase oxidation of S(IV) and through heterogeneous removal, and lower temperatures and higher nighttime humidity resulted in a quicker surface deposition of peroxides. Furthermore, our observations seem to imply that the heterogeneous removal of H2O2 is faster than that of MHP, as indicated by the strong negative correlation between the H2O2‐to‐MHP ratio and the aerosol surface area.

ESI–MS study of copper chloride/phase-transfer catalytic systems for oxidation of cumene with 1-methyl-1-phenylethyl hydroperoxide

Oxidation of cumene with 1-methyl-1-phenyl- ethyl hydroperoxide in the presence of copper chloride/ phase transfer catalytic systems was investigated by ESI- MS. For catalytically active copper(II) chloride/crown ethers, copper(II) chloride/crown ethers/alkaline metal salts, and copper(II) chloride/tetrabutylammonium chloride systems, the presence of a few kinds of copper complexes in the organic phase was detected by use of ESI-MS. When copper(II) chloride/podand systems were used, the con- version of hydroperoxide and the yield of oxidation product were close to zero, although the concentration of copper complexes in the organic phase was high. Addition of bis(2-hydroxyethyl) ether to the catalytically active copper(II) chloride/18-crown-6 system resulted in an inhibition effect.

Studies on the mechanism of decomposition of 1-methyl-1-(1-naphthyl)ethyl hydroperoxides to 2-(1-naphthyloxy)propenes

AbstractThermal decomposition of 1-methyl-1-(4-methyl-1-naphthyl)ethyl hydroperoxide under gas chromatography-mass spectroscopy (GC-MS) conditions gives 2-((4-methyl-1-naphthyl)oxy)propene as the main product (50.5%), without any detectable traces of the isomeric 2-((5-methyl-1-naphthyl)oxy)propene. This finding excludes the rearrangement pathway of 1-methyl-1-(1-naphthyl)ethyl hydroperoxides to the corresponding 2-(1-naphthyloxy)propenes, which involves formation of a naphthofuran derivative as an intermediate and transfer of the isopropenyloxy group to the 8 position. This result, as well as our previous density functional theory (DFT) calculations, points to the rearrangement pathway involving an oxirane-type intermediate as the most plausible pathway to 2-(1-naphthyloxy)propenes. This rearrangement is responsible for the unusual inhibition effects of 1-methyl-1-(1-naphthyl)ethyl hydroperoxide on the liquid-phase oxidation of isopropylarenes with oxygen.Graphical Abstract[IMAGE]

Atmospheric hydrogen peroxide and organic hydroperoxides during PRIDE-PRD'06, China: their concentration, formation mechanism and contribution to secondary aerosols

Abstract. Atmospheric hydrogen peroxide (H2O2) and organic hydroperoxides were measured from 18 to 30 July in 2006 during the PRIDE-PRD'06 campaign at Backgarden, a rural site located 48 km north of Guangzhou, a mega-city in southern China. A ground-based instrument was used as a scrubbing coil collector to sample ambient air, followed by on-site analysis by high-performance liquid chromatography (HPLC) coupled with post-column derivatization and fluorescence detection. The H2O2 mixing ratio over the 13 days ranged from below the detection limit to a maximum of 4.6 ppbv, with a mean (and standard deviation) of (1.26±1.24) ppbv during the daytime (08:00–20:00 LT). Methyl hydroperoxide (MHP), with a maximum of 0.8 ppbv and a mean (and standard deviation) of (0.28±0.10) ppbv during the daytime, was the dominant organic hydroperoxide. Other organic peroxides, including bis-hydroxymethyl hydroperoxide (BHMP), peroxyacetic acid (PAA), hydroxymethyl hydroperoxide (HMHP), 1-hydroxy-ethyl hydroperoxide (1-HEHP) and ethyl hydroperoxide (EHP), were detected occasionally. The concentration of H2O2 exhibited a pronounced diurnal variation on sunny days, with a peak mixing ratio in the afternoon (12:00–18:00 LT), but lacked an explicit diurnal cycle on cloudy days. Sometimes a second peak mixing ratio of H2O2 was observed during the evening, suggesting that H2O2 was produced by the ozonolysis of alkenes. The diurnal variation profile of MHP was, in general, consistent with that of H2O2. The estimation indicated that in the morning the H2O2 detected was formed mostly through local photochemical activity, with the rest probably attributable to vertical transport. It is notable that relatively high levels of H2O2 and MHP were found in polluted air. The unexpectedly high level of HO2 radicals detected in this region can account for the production of hydroperoxides, while the moderate level of NOx suppressed the formation of hydroperoxides. High concentrations of hydroperoxides were detected in samples of rainwater collected in a heavy shower on 25 July when a typhoon passed through, indicating that a considerable mixing ratio of hydroperoxides, particularly MHP, resided above the boundary layer, which might be transported on a regional scale and further influence the redistribution of HOx and ROx radicals. It was found that hydroperoxides, in particular H2O2, play an important role in the formation of secondary sulfate in the aerosol phase, where the heterogeneous reaction might contribute substantially. A negative correlation between hydroperoxides and water-soluble organic compounds (WSOC), a considerable fraction of the secondary organic aerosol (SOA), was observed, possibly providing field evidence for the importance of hydroperoxides in the formation of SOA found in previous laboratory studies. We suggest that hydroperoxides act as an important link between sulfate and organic aerosols, which needs further study and should be considered in current atmospheric models.

An experimental study for rate constants of the gas phase reactions of CH 3CH 2OOH with OH radicals, O 3, NO 2 and NO

The rate constants for ethyl hydroperoxide (EHP, CH 3CH 2OOH) reactions with OH radicals, O 3, NO 2 and NO in the gas phase have been investigated, by use of in situ long-path Fourier transform infrared spectroscopy. At 293 ± 2 K temperature and 760 Torr pressure, the measured values are k EHP+OH = (5.92 ± 0.36) × 10 −12, k EHP + O 3 ≤ ( 8.4 ± 0.1 ) × 10 − 21 , k EHP + NO 2 ≤ ( 9.7 ± 0.3 ) × 10 − 21 and k EHP+NO ≤ (1.2 ± 0.1) × 10 −21 cm 3 molecule −1 s −1. The atmospheric lifetimes of EHP with respect to these reactions have been estimated from these values, and the atmospheric implications have been briefly discussed.

Vibrational−Torsional Excitation and Direct Overtone Photodissociation of Ethyl Hydroperoxide at 5νOH

We have observed OH radical products from the unimolecular dissociation of ethyl hydroperoxide (CH3-CH2OOH) excited to 5nuOH and have collected an action spectrum from 15,600 to 16,800 cm(-1) and an OH product state distribution at the maximum (16,119 cm(-1)). We use a vibrational-torsional model to simulate spectra in the 5nuOH region for the trans and gauche conformers. A combination of the two simulated spectra resembles the experimental action spectrum, provided that the trans conformer is assumed to dominate at room temperature. Energy disposal in the OH fragment yields an upper limit for the O-O bond dissociation energy at D0 < 44 kcal mol(-1).

Photooxidation of methylhydroperoxide and ethylhydroperoxide in the aqueous phase under simulated cloud droplet conditions

The photooxidation of methylhydroperoxide (MHP) and ethylhydroperoxide (EHP) was studied in the aqueous phase under simulated cloud droplet conditions. The kinetics and the reaction products of direct photolysis and OH-oxidation were studied for both compounds. The photolysis frequencies obtained were J MHP=4.5 (±1.0)×10 −5 s −1 and J EHP=3.8 (±1.0)×10 −5 s −1 for MHP and EHP respectively at 6 °C. The rate constants of OH-oxidation of MHP at 6 °C were 6.3 (±2.6)×10 8 M −1 s −1 and 5.8 (±1.9)×10 8 M −1 s −1 relative to ethanol and 2-propanol respectively, and the rate constant of OH-oxidation of EHP was 2.1 (±0.6)×10 9 M −1 s −1 relative to 2-propanol at 6 °C. The reaction products obtained were not only the corresponding aldehydes, but also the corresponding acids, and hydroxyhydroperoxides as primary reaction products. The yields for these products were sensitive to the pH value. The carbon balance was higher than 85% for all experiments, showing that most reaction products were detected. A chemical mechanism was proposed for each reaction, and the atmospheric implications were discussed.

A Systematic Computational Study of the Reactions of HO2 with RO2: The HO2 + C2H5O2 Reaction

The reaction of HO2 with C2H5O2 has been studied using the density functional theory (B3LYP) and the coupled-cluster theory [CCSD(T)]. The reaction proceeds on the triplet potential energy surface via hydrogen abstraction to form ethyl hydroperoxide and oxygen. On the singlet potential energy surface, the addition-elimination mechanism is revealed. Variational transition state theory is used to calculate the temperature-dependent rate constants in the range 200-1000 K. At low temperatures (e.g., below 300 K), the reaction takes place predominantly on the triplet surface. The calculated low-temperature rate constants are in good agreement with the experimental data. As the temperature increases, the singlet reaction mechanism plays more and more important role, with the formation of OH radical predominantly. The isotope effect of the reaction (DO2 + C2D5O2 vs HO2 + C2H5O2) is negligible. In addition, the triplet abstraction energetic routes for the reactions of HO2 with 11 alkylperoxy radicals (CnHmO2) are studied. It is shown that the room-temperature rate constants have good linear correlation with the activation energies for the hydrogen abstraction.

Copper(II) chloride/tetrabutylammonium bromide as a catalytic system for the oxidation of 2-isopropylnaphthalene with oxygen

The catalytic oxidation of 2-isopropylnaphthalene with oxygen was studied. The system composed of copper(II), cobalt(II) or manganese(II) chloride with tetrabutylammonium bromide was used as catalysts. Depending on the metal ion as well as process conditions, different compositions of products were obtained. The mixture of 2-(2-naphthyl)-2-propanol, 2-acetylnaphthalene, bis(1-methyl-1-(2-naphthyl)ethyl) peroxide as well as a small amount of 1-methyl-1-(2-naphthyl)ethyl hydroperoxide was obtained in the presence of copper(II) chloride and tetrabutylammonium bromide.

The liquid‐phase oxidation of isomeric methoxy‐(1‐methylethyl)benzenes with oxygen to the hydroperoxides

AbstractThe kinetics of liquid‐phase oxidation of 1‐methoxy‐2‐(1‐methylethyl)benzene (1a), 1‐methoxy‐3‐(1‐methylethyl)benzene (1b), and 1‐methoxy‐4‐(1‐methylethyl)benzene (1c) with oxygen as oxidant to yield the corresponding 1‐methyl‐1‐(2‐methoxyphenyl)ethyl (2a), 1‐methyl‐1‐(3‐methoxyphenyl)ethyl (2b), and 1‐methyl‐1‐(4‐methoxyphenyl)ethyl (2c) hydroperoxides was studied. The oxidizabilities of 1a, 1b, and 1c were established over the temperature range 50–120°C. The overall activation energies of oxidation were determined for 1b and 1c over the temperature range 50–120°C. Thermal stability of 2a and 2b and the initiating properties of hydroperoxides 2a, 2b, and 2c were studied. Long‐term noncatalytic oxidations of 1b and 1c to respective hydroperoxides were carried out. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 37: 10–16, 2005

O−H Stretch Overtone Excitation in Methyl and Ethyl Hydroperoxides

We use laser photoacoustic spectroscopy to obtain vibrational overtone spectra in the regions of four and five quanta of O−H stretch (4νOH and 5νOH) for gas-phase methyl (MeOOH), ethyl (EtOOH), and tert-butyl hydroperoxide (t-BuOOH). Integrated cross sections for the main peak due to O−H stretch excitation to 4νOH are similar for all three hydroperoxides (∼2 × 10-21 cm2 molecule-1 cm-1); cross sections for excitation to and 5νOH are an order of magnitude smaller. Interpretation of spectral features using a previously reported vibration−torsion model for ROOH molecules, where excitation of torsional motion about the O−O bond accompanies vibrational excitation, yields plausible fits to the spectra. Simulations with the vibration−torsion model and ab initio calculations suggest barriers for torsional motion about the O−O bond to be higher in t-BuOOH than in MeOOH and EtOOH, with a trend of increasing trans torsional barrier height with increasing size of the R group.

Structures, Rotational Barriers, and Thermochemical Properties of β-Chlorinated Ethyl Hydroperoxides

Structures, internal rotational barriers, and thermochemical properties of 2-chloroethyl hydroperoxide, 2,2-dichloroethyl hydroperoxide, and 2,2,2-trichloroethyl hydroperoxide are computed by ab initio and density functional calculations. Molecular structures and vibrational frequencies are determined at the B3LYP/6-31G(d,p) density functional level, with single-point calculations for the energy at the B3LYP/6-311+G(3df,2p), QCISD(T)/6-31G(d,p), and CBSQ//B3LYP/6-31G(d,p) levels. The S°298 and Cp(T) values (0 ≤ T/K ≤ 5000) from vibrational, translational, and external rotational contributions are calculated using statistical mechanics based on the vibrational frequencies and structures obtained from the density functional study. Potential barriers for the internal rotations are calculated at the B3LYP/6-31G(d,p) level, and all minima and maxima on the torsional potentials are fully optimized. The hindered rotational contributions to S°298 and Cp(T) are calculated by using direct integration over energy levels of the internal rotational potentials. The enthalpies of formation are calculated using isodesmic reactions, and the recommended ΔHf°298 values for CH2ClCH2OOH, CHCl2CH2OOH, and CCl3CH2OOH are −45.47 ± 1.20, −48.92 ± 1.50, and −50.21 ± 1.36 kcal/mol, respectively. Interaction terms for a peroxy group with chlorine(s) on a β carbon are developed for the group additivity approach. Bond energies calculated from the enthalpies of β-chlorinated ethyl hydroperoxides and their corresponding radicals show good agreement with those from our previous studies.

Liquid‐phase oxidation of 1‐isopropyl‐ and 1‐ethyl‐4‐methoxybenzenes with oxygen to hydroperoxides

AbstractA study was carried out on the kinetics of free‐radical chain oxidation of 1‐isopropyl‐4‐methoxybenzene (1a) and 1‐ethyl‐4‐methoxybenzene (1b) with oxygen in the liquid phase to yield 1‐methyl‐1‐(4‐methoxyphenyl)ethyl hydroperoxide (2a) and 1‐(4‐methoxyphenyl)ethyl hydroperoxide (2b). The oxidizability of 1a and 1b was studied over the temperature range 50–100°C. Long‐term oxidations of 1a and 1b to the corresponding hydroperoxides were carried out and the properties and thermal stability of 2a were established. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 89–94, 2003

Simultaneous Determination of Hydrogen Peroxide and Organic Hydroperoxides in Water

The kinetics of the reactions of H 2 O 2 and of methyl, ethyl, tert -butyl, and cumene hydroperoxides with I m were investigated in the presence and absence of molybdate as catalyst. These results were utilized to develop an analytical method for the simultaneous determination of H 2 O 2 and organic hydroperoxides in aqueous solutions. The total amount of H 2 O 2 and organic hydroperoxides can be determined by the spectrophotometric measurement of $ {\\rm I}_3^ - $ formed quantitatively during 30 min of heating at 60°C. Catalase selectively decomposes H 2 O 2 in solutions containing organic hydroperoxides. The total amount of the latter can therefore be determined iodometrically after H 2 O 2 decomposition. In the oxidation of leuco crystal violet to crystal violet by H 2 O 2 and organic hydroperoxides, horseradish peroxidase exerts similar activities in the reactions involving methyl and ethyl hydroperoxides and H 2 O 2 , but its activity is much lower with tert -butyl and cumene hydroperoxide. It was observed that acetate buffer is unsuitable for pH adjustment in this type of hydroperoxide determination in consequence of the slow oxidation of the dye in the blank solution.

A New Method for the Synthesis of Primary Hydroperoxides. A Useful Application of Bis(tributyltin) Oxide in the Hydrolysis of Peroxyesters

Hydrolysis of peroxyesters in the presence of bis(tributyltin) oxide provides a new method for the synthesis of hydroperoxides including methyl and ethyl hydroperoxide.

Negative-ion photoelectron spectroscopy, gas-phase acidity, and thermochemistry of the peroxyl radicals CH(3)OO and CH(3)CH(2)OO.

Methyl, methyl-d(3), and ethyl hydroperoxide anions (CH(3)OO(-), CD(3)OO(-), and CH(3)CH(2)OO(-)) have been prepared by deprotonation of their respective hydroperoxides in a stream of helium buffer gas. Photodetachment with 364 nm (3.408 eV) radiation was used to measure the adiabatic electron affinities: EA[CH(3)OO, X(2)A' '] = 1.161 +/- 0.005 eV, EA[CD(3)OO, X(2)A' '] = 1.154 +/- 0.004 eV, and EA[CH(3)CH(2)OO, X(2)A' '] = 1.186 +/- 0.004 eV. The photoelectron spectra yield values for the term energies: Delta E(X(2)A' '-A (2)A')[CH(3)OO] = 0.914 +/- 0.005 eV, Delta E(X(2)A' '-A (2)A')[CD(3)OO] = 0.913 +/- 0.004 eV, and Delta E(X(2)A' '-A (2)A')[CH(3)CH(2)OO] = 0.938 +/- 0.004 eV. A localized RO-O stretching mode was observed near 1100 cm(-1) for the ground state of all three radicals, and low-frequency R-O-O bending modes are also reported. Proton-transfer kinetics of the hydroperoxides have been measured in a tandem flowing afterglow-selected ion flow tube (FA-SIFT) to determine the gas-phase acidity of the parent hydroperoxides: Delta(acid)G(298)(CH(3)OOH) = 367.6 +/- 0.7 kcal mol(-1), Delta(acid)G(298)(CD(3)OOH) = 367.9 +/- 0.9 kcal mol(-1), and Delta(acid)G(298)(CH(3)CH(2)OOH) = 363.9 +/- 2.0 kcal mol(-1). From these acidities we have derived the enthalpies of deprotonation: Delta(acid)H(298)(CH(3)OOH) = 374.6 +/- 1.0 kcal mol(-1), Delta(acid)H(298)(CD(3)OOH) = 374.9 +/- 1.1 kcal mol(-1), and Delta(acid)H(298)(CH(3)CH(2)OOH) = 371.0 +/- 2.2 kcal mol(-1). Use of the negative-ion acidity/EA cycle provides the ROO-H bond enthalpies: DH(298)(CH(3)OO-H) = 87.8 +/- 1.0 kcal mol(-1), DH(298)(CD(3)OO-H) = 87.9 +/- 1.1 kcal mol(-1), and DH(298)(CH(3)CH(2)OO-H) = 84.8 +/- 2.2 kcal mol(-1). We review the thermochemistry of the peroxyl radicals, CH(3)OO and CH(3)CH(2)OO. Using experimental bond enthalpies, DH(298)(ROO-H), and CBS/APNO ab initio electronic structure calculations for the energies of the corresponding hydroperoxides, we derive the heats of formation of the peroxyl radicals. The "electron affinity/acidity/CBS" cycle yields Delta(f)H(298)[CH(3)OO] = 4.8 +/- 1.2 kcal mol(-1) and Delta(f)H(298)[CH(3)CH(2)OO] = -6.8 +/- 2.3 kcal mol(-1).

Organic peroxide production in the Cl2-ethane-air photoreaction system

HPLC along with FT-IR technique was used to study the formation of organic peroxides in the Cl2-ethane-air photoreaction system. Ethyl hydroperoxide (CH3CH21OOH, EHP) and peroxyacetic acid ( CH3C(O)OOH, PAA) were conformed to be the peroxide product in the reaction system. In addition, methyl hydroperoxide (CH3OOH, hydroxymethyl hydroperoxide (HOCH2OOH, HMHP) and two unidentified organic peroxides were detected for the first time. EHP and were the dominant peroxide products. The identification of HMHP showed that Criegee biradical CH2OO may be formed as an intermediate in the oxidation of ethane. Simulation results showed that photooxidation of ethane may make substantial contribution to source of organic peroxides in the atmosphere.

Two-electron reduction and one-electron oxidation of organic hydroperoxides by human myeloperoxidase

The reaction of native myeloperoxidase (MPO) and its redox intermediate compound I with hydrogen peroxide, ethyl hydroperoxide, peroxyacetic acid, t-butyl hydroperoxide, 3-chloroperoxybenzoic acid and cumene hydroperoxide was studied by multi-mixing stopped-flow techniques. Hydroperoxides are decomposed by MPO by two mechanisms. Firstly, the hydroperoxide undergoes a two-electron reduction to its corresponding alcohol and heme iron is oxidized to compound I. At pH 7 and 15°C, the rate constant of the reaction between 3-chloroperoxybenzoic acid and ferric MPO was similar to that with hydrogen peroxide (1.8×107 M−1 s−1 and 1.4×107 M−1 s−1, respectively). With the exception of t-butyl hydroperoxide, the rates of compound I formation varied between 5.2×105 M−1 s−1 and 2.7×106 M−1 s−1. Secondly, compound I can abstract hydrogen from these peroxides, producing peroxyl radicals and compound II. Compound I reduction is shown to be more than two orders of magnitude slower than compound I formation. Again, with 3-chloroperoxybenzoic acid this reaction is most effective (6.6×104 M−1 s−1 at pH 7 and 15°C). Both reactions are controlled by the same ionizable group (average pKa of about 4.0) which has to be in its conjugated base form for reaction.

Product study of the C 2H 5O 2+HO 2 reaction in 760 Torr of air at 284–312 K

The title reaction was studied in 1 atmosphere pressure of synthetic air at 284, 298, and 312 K. FTIR spectroscopy was used to identify two products; ethyl hydroperoxide and acetaldehyde. Acetaldehyde was a minor product formed in a yield consistent with that expected from unwanted secondary reactions. In 1 atmosphere pressure of air at 284–312 K the title reaction produces ethyl hydroperoxide in a yield of (104±5)% and acetaldehyde in a yield of (2±4)%. We recommend that in atmospheric models the reaction of C 2H 5O 2 with HO 2 radicals be represented by a single-reaction pathway giving C 2H 5OOH.