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Using a relative kinetic technique, rate coefficients have been determined at (298 ± 2) K and atmospheric pressure for the gas‐phase reactions of the NO3 radical with three vicinal dihydroxy aromatic compounds. The experiments were carried out in a 1080‐l quartz glass reactor at the Bergische Universität Wuppertal and in the European Photoreactor (EUPHORE), Valencia, Spain. The rate coefficients obtained (in units of cm3 molecule−1 s−1) using 2,3‐dimethyl‐2‐butene as the reference hydrocarbon were kNO3(1,2‐dihydroxybenzene) = (9.8 ± 5.0) × 10−11, kNO3(1,2‐dihydroxy‐3‐methylbenzene) = (17.2 ± 5.6) × 10−11, and kNO3 (1,2‐ dihydroxy‐4‐methylbenzene) = (14.7 ± 6.5) × 10−11. This study represents the first kinetic investigation of the reactions of the NO3 radical with dihydroxybenzenes. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 577–583, 2004

The kinetics and products of the Cl atom initiated oxidation of CH2ClCHClCH2Cl (1,2,3-trichloropropane) have been investigated at (295 ± 2) K in 700−760 Torr of air in a 405 L reaction chamber. The major oxidation product (in terms of carbon balance) was CH2ClC(O)CH2Cl with smaller amounts of HC(O)Cl and CH2ClC(O)Cl. It was observed that chemical activation effects play a significant role in the atmospheric fate of CH2ClCHClO(·) and CH2ClCO(·)ClCH2Cl radicals. Relative rate techniques were used to measure the following:  k(Cl + CH2ClCHClCH2Cl) = (1.86 ± 0.32) × 10^-12, k(Cl + CHCl&dbd;CHCH2Cl) = (1.67 ± 0.18) × 10^-10, k(Cl + CH2&dbd;CClCH2Cl) = (1.46 ± 0.15) × 10^-10, and k(Cl + CH2ClC(O)CH2Cl) = (5.53 ± 0.63) × 10^-13 cm³ molecule^-1 s^-1. The UV−visible spectrum of CH2ClC(O)CH2Cl was measured over the range 270−385 nm and has a maximum at 305 nm where σ = (1.6 ± 0.2) × 10^-19 cm² molecule^-1 (base e). Assuming a photolysis quantum yield of 1.00−0.04, the lifetime of CH2ClC(O)CH2Cl with respect to photolysis on a summer day at 40° latitude is calculated to be 0.5−12 h. Photolysis is likely to be the dominant atmospheric loss mechanism of CH2ClC(O)CH2Cl. The results are discussed in the context of the atmospheric chemistry of 1,2,3-trichloropropane.

The products following Cl atom initiated oxidation of methyl formate in 700−760 Torr of air in the presence and absence of NOx at 296 ± 2 K were investigated using three different FTIR smog chamber techniques. Reaction of Cl atoms with methyl formate proceeds 45 ± 7% via attack at the methyl group (forming HC(O)OCH2· radicals) and 55 ± 7% via attack at the formate group (forming ·C(O)OCH3 radicals). The sole atmospheric fate of HC(O)OCH2· and ·C(O)OCH3 radicals is addition of O2 to give the corresponding peroxy radicals (HC(O)OCH2OO· and ·OOC(O)OCH3). The peroxy radicals react with NO to give alkoxy radicals (HC(O)OCH2O· and ·OC(O)OCH3). The atmospheric fate of ·OC(O)OCH3 radicals is decomposition to give CH3O· and CO2 and was unaffected by the method used to generate the ·OC(O)OCH3 radicals (reaction of ·OOC(O)OCH3 with either NO or with other peroxy radicals). There are two competing atmospheric loss mechanisms for HC(O)OCH2O· radicals; reaction with O2 to give HC(O)OC(O)H (formic acid anhydride) and α-ester rearrangement to give HC(O)OH and HCO· radicals. It was found that α-ester rearrangement is more important when HC(O)OCH2O· radicals were produced via the HC(O)OCH2OO· + NO reaction than when they were produced via the self-reaction of peroxy radicals. We ascribe this observation to the formation of vibrationally excited HC(O)OCH2O· radicals in the HC(O)OCH2OO· + NO reaction. In 1 atm of air ([O2] = 160 Torr) containing NO at 296 K, it can be calculated that 33 ± 5% of the HC(O)OCH2O· radicals undergo α-ester rearrangement, while 67 ± 12% react with O2. The infrared spectrum of the peroxynitrate CH3OC(O)OONO2 was recorded, and absorption cross sections (base e) of (1.8 ± 0.1) × 10^-18 and (4.2 ± 0.2) × 10^-18 cm² molecule^-1 at 1836 and 1236 cm^-1, respectively, were determined. The chain chlorination of methyl formate was studied. Relative rate techniques were used to measure k(Cl +ClC(O)OCH3) = (1.10 ± 0.23) × 10^-13, k(Cl + HC(O)OCH2Cl) = (2.5 ± 0.2) × 10^-13, and k(Cl + ClC(O)OCH2Cl) = (3.0 ± 0.4) × 10^-14 cm³ molecule^-1 s^-1. IR spectra of ClC(O)OCH2Cl, ClC(O)OCHCl2, and ClC(O)OCCl3 are presented. These results are discussed with respect to the atmospheric oxidation mechanism of methyl formate and other esters.

Smog chamber FTIR techniques were used to study the atmospheric oxidation of methyl propionate in 740 Torr of air in the presence of NOx at 296 ± 2K. Relative rate techniques were used to measure k(OH + CH3CH2C(O)OCH3) = (9.29 ± 1.13) × 10^-13, k(Cl + CH3CH2C(O)OCH3) = (1.51 ± 0.22) × 10^-11, k(Cl + CH3CH2C(O)OC(O)H) = (2.89 ± 0.35) × 10^-12, k(Cl + CH3CH2C(O)OH) = (4.72 ± 0.62) × 10^-12, and k(Cl + CH3C(O)C(O)OCH3) = (4.99 ± 0.96) × 10^-13 cm³ molecule^-1 s^-1. The products (and molar yields) formed in the Cl-atom initiated oxidation of methyl propionate were as follows:  propionic formic anhydride (CH3CH2C(O)OC(O)H), 0.099 ± 0.019; propionic acid (CH3CH2C(O)OH), 0.139 ± 0.027; carbon monoxide, 0.132 ± 0.026; methyl pyruvate (CH3C(O)C(O)OCH3), 0.289 ± 0.057; acetaldehyde, 0.077 ± 0.015; methoxy formylperoxynitrate (CH3OC(O)O2NO2), 0.083 ± 0.016; methyl glyoxylate (H(O)CC(O)OCH3), 0.111 ± 0.022; organic nitrates, 0.07 ± 0.02; and formaldehyde. These products account for 79 ± 16% of the loss of methyl propionate. The atmospheric oxidation mechanism of methyl propionate is presented and discussed.

FTIR product studies of the OH-radical-initiated oxidation of di-n-butoxymethane (DNBM) in the presence of NOx were performed in an indoor photoreactor and in the outdoor simulation chamber EUPHORE in Valencia, Spain. The reaction products observed in both reaction chambers were n-butoxymethyl formate (NBMF), propionaldeyhde, and di-n-butyl carbonate (DNBC). In the indoor reactor yields for NBMF and propionaldeyhde of 77 ± 15 and 78 ± 16 mol % were obtained in the system DNBM/MeONO/NOx/air/hν and 88 ± 18 and 69 ± 14 mol % in the system DNBM/H2O2/NOx/air/hν, respectively. In the outdoor chamber, yields of 80 ± 8 and 44 ± 11 mol % were obtained after sunlight irradiation of a DNBM/NOx/HONO/air mixture. For di-n-butyl carbonate (DNBC), an upper limit of ≤10 mol % was estimated for both reaction chambers. In the indoor photoreactor small amounts of n-butyl formate (NBF) and n-butoxymethyl butyrate (NBMB) were also detected with upper limits of 3 mol % for each compound. Bimolecular rate coefficients for the reactions of NBMF and DNBC with OH radicals were determined in the indoor photoreactor using the relative rate technique. Values of kOH+NBMF = (8.00 ± 0.91) × 10^-12 cm³ s^-1 and kOH+DNBC = (7.07 ± 1.64) × 10^-12 cm³ s^-1 were obtained. NBMF was synthesized and authentic samples were used for calibration. A photochemical mechanism was developed to describe the OH-initiated degradation of di-n-butoxymethane (DNBM) in the presence of NOx. The reaction scheme was tested by comparison of computer box model calculations and experimental data. Experimentally obtained and modeled concentration−time profiles for selected reactants are in excellent agreement.

The solubility of HBr in H2SO4/H2O and HNO3/H2SO4/H2O solutions was determined by measuring the HBr vapor pressure over stirred bulk solutions using tunable diode laser spectrometry. The experimental results for the solubility of HBr in sulfuric acid solutions show good agreement with experimental literature data. However, there is a factor 2−6 discrepancy between experimental and model values. The solubility of HBr in sulfuric acid was parameterized as a function of the H2SO4 concentration and temperature in the range 53−75 wt % H2SO4 and 195−250 K, respectively. The solubility of HBr in ternary HNO3/H2SO4/H2O solutions was determined for the first time. An increase in the solubility was observed on exchanging H2SO4 by HNO3 at constant water weight fraction. This observation is in qualitative agreement with model calculations, however, the observed solubility change was much larger than predicted by the model calculations. The solubility of HBr in ternary solutions was parameterized as a function of both the concentration of HNO3/H2SO4 and the temperature. The relations derived can be used for atmospheric modeling of the influence of heterogeneous HBr reactions on atmospheric ozone destruction.

Rate coefficients have been determined for the gas-phase reaction of the hydroxyl (OH) radical with the aromatic dihydroxy compounds 1,2-dihydroxybenzene, 1,2-dihydroxy-3-methylbenzene and 1,2-dihydroxy-4-methylbenzene as well as the two benzoquinone derivatives 1,4-benzoquinone and methyl-1,4-benzoquinone. The measurements were performed in a large-volume photoreactor at (300 ± 5) K in 760 Torr of synthetic air using the relative kinetic technique. The rate coefficients obtained using isoprene, 1,3-butadiene, and E-2-butene as reference hydrocarbons are kOH(1,2-dihydroxybenzene) = (1.04 ± 0.21) × 10⁻¹⁰ cm³ s⁻¹, kOH(1,2-dihydroxy-3-methylbenzene) = (2.05 ± 0.43) × 10⁻¹⁰ cm³ s⁻¹, kOH(1,2-dihydroxy-4-methylbenzene) = (1.56 ± 0.33) × 10⁻¹⁰ cm³ s⁻¹, kOH(1,4-benzoquinone) = (4.6 ± 0.9) × 10⁻¹² cm³ s⁻¹, kOH(methyl-1,4-benzoquinone) = (2.35 ± 0.47) × 10⁻¹¹ cm³ s⁻¹. This study represents the first determination of OH radical reaction-rate coefficients for these compounds. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 696–702, 2000

An absolute rate pulse radiolysis technique was used to measure k(OH + 1,3-dioxolane) = (8.8 ± 0.9) × 10^-12 cm³ molecule^-1 s^-1 at 295 K in 1000 mbar of Ar. Relative rate techniques were used to study the reactions of OH radicals and Cl atoms with 1,3-dioxolane and Cl atoms with ethylene carbonate and methylene glycol diformate at 300 K in 1 bar of synthetic air. Rate coefficients were k(OH + 1,3-dioxolane) = (1.04 ± 0.16) × 10^-11, k(Cl + 1,3-dioxolane) = (1.6 ± 0.3) × 10^-10, k(Cl + ethylene carbonate) = (7.1 ± 1.7) × 10^-12, and k(Cl + methylene glycol diformate) = (5.6 ± 0.7) × 10^-13 cm³ molecule^-1 s^-1. OH radical and chlorine atom initiated oxidation of 1,3-dioxolane in 1 bar of N2/O2 mixtures at 298 K in the presence of NOx gives ethylene carbonate and methylene glycol diformate. Molar yields of ethylene carbonate and methylene glycol diformate were 0.48 ± 0.07 and 0.50 ± 0.14 for OH radical initiation and 0.43 ± 0.07 and 0.53 ± 0.07 for Cl atom initiation. Product yields were independent of O2 partial pressure over the range studied (60−800 mbar). A photochemical mechanism was developed to describe the OH-initiated degradation of 1,3-dioxolane in the presence of NOx. The results are discussed with respect to the available literature data concerning the atmospheric chemistry of ethers.

A FTIR kinetic and product study of the OH-radical initiated oxidation of 1,4-dioxane (DOX) has been performed in a quartz-glass photoreactor in the laboratory under different conditions and also in the outdoor EUPHORE simulation chamber in Valencia, Spain. Using the relative kinetic technique, a rate coefficient of k = (1.24 ± 0.04) × 10^-11 cm³ molecule^-1 s^-1 was determined for the reaction at 298 K in 1000 mbar of synthetic air, which is in good agreement with other published values. The major reaction product both in the presence and absence of NO was ethylene glycol diformate (EDF). This compound has been synthesized, and authentic samples have been used for calibration. Integrated band intensities have been calculated for the three strongest bands of EDF:  (4.99 ± 0.06) × 10^-17 cm molecule^-1 for 1100−1225 cm^-1, (3.90 ± 0.05) × 10^-17 cm molecule^-1 for 1670−1820 cm^-1, (9.34 ± 0.11) × 10^-18 cm molecule^-1 for 2775−3075 cm^-1. In the laboratory reactor, yields for EDF of 87 ± 9 and 95 ± 10 mol % were obtained using the photolysis of MeONO/NO/air and H2O2/NO/air as the OH radical sources, respectively. Using only the photolysis of H2O2/air as the OH source resulted in a molar yield of 55 ± 6 mol % for EDF. In the outdoor EUPHORE simulation chamber a yield of 95 ± 10 mol % was obtained from irradiation of a DOX/NOx/air mixture. The OH-radical- and Cl-atom-initiated oxidation of EDF has also been investigated. Rate coefficients of kOH = (4.72 ± 0.31) × 10^-13 cm³ molecule^-1 s^-1 and kCl = (3.52 ± 0.09) × 10^-12 cm³ molecule^-1 s^-1 have been determined for the reaction of EDF with OH radicals and Cl atoms, respectively, at 298 K and 1000 mbar total pressure. The products determined in the Cl-initiated oxidation in the presence of NOx were formic acid anhydride (FAA), formic acid (FA), and carbon monoxide (CO) with yields of 173 ± 34 mol %, 45 ± 9 mol %, and 41 ± 8 mol %, respectively. Formation of a peroxy formyl nitrate was also observed. In the absence of NOx the yields of FAA, FA and CO were 144 ± 29 mol %, 39 ± 8 mol %, and 22 ± 4 mol %, respectively.

The products following Cl atom initiated oxidation of C2Cl4 at 700−760 Torr of air and 230−299 K in the presence and absence of NOx were investigated using three different FTIR smog chamber techniques. There was no measurable effect of temperature on the product yields. CCl3C(O)Cl and COCl2 were formed with molar yields of 68 ± 6% and 77 ± 12% in the presence of NOx and 87 ± 11% and 32 ± 4% in the absence of NOx. These results give branching ratios for the CCl3C(O)Cl and COCl2 forming channels of 0.64 and 0.36 in the presence of NOx and 0.84 and 0.16 in the absence of NOx. Contrary to a recent report by Hasson and Smith (J. Phys. Chem. A, 1999, 103, 2031), variation of the initial C2Cl4 by a factor of 300 over the range (0.016−5.6) × 10¹⁴ molecule cm^-3 had no discernible effect (<10%) on the product distributions. The different product distribution observed in the presence of NOx may reflect the formation and subsequent decomposition of chemically activated C2Cl5O radicals, formed in the exothermic reaction of C2Cl5O2 with NO. The kinetics of the reaction of Cl atoms with C2Cl4 were measured in 2.0−700 Torr of air at 296 K. The results are in good agreement with the previous study by Nicovich et al. (J. Phys. Chem. 1996, 100, 680). The combined data can be described using Fc = 0.6, ko = (1.8 ± 0.3) × 10^-28 cm⁶ molecule^-2 s^-1 and k∞ = (4.0 ± 0.4) × 10^-11 cm³ molecule^-1 s^-1. Results are discussed with respect to the atmospheric chemistry of C2Cl4.

The products of the Br‐atom initiated oxidation of trans‐2‐butene have been studied in a largevolume reaction chamber between 246 and 298 K using in situ FT‐IR for the analysis. 3‐Bromobutan‐2‐one, acetaldehyde and acetylbromide were the major products of this oxidation process. Additional products included formaldehyde and hydrogen bromide and evidence was found for the formation of 3‐bromobutan‐2‐hydroperoxide. Decreasing the temperature from 298 K down to 246 K resulted in an increase in the yield of 3‐bromobutan‐2‐one and a decrease in the yields of acetaldehyde, acetylbromide, formaldehyde and hydrogen bromide. Addition of NO to the reaction system resulted in nearly a doubling of the yields of 3‐bromobutan‐2‐one, acetaldehyde and formaldehyde. The reaction mechanism is discussed and possible consequences of the results for the involvement of bromine/alkene chemistry in the springtime depletion of ozone in the Arctic are considered.

Lower limits on the nucleon lifetime in channels containing at least one positron or muon are given. The analysis is based on 4 years of data taking with the Fréjus detector. Various approaches to determine the background from atmospheric neutrinos are discussed and two different nuclear models are used in event simulations. The limits obtained range from 1031 years forp?e+K*0 to 1.5·1032 years forp?e+K*0 to 1.5·1032 years forp?µ+?.

Several stages of the copepodBasipodella harpacticola n. gen., n. sp., which lives as a parasite on harpacticoid copepods, are described on the basis of four individuals obtained from the Peruvian deep-sea. The taxonomic position of the new species is discussed.

Rate constants for the reaction of OH radicals with some branched alkyl nitrates have been measured applying a competitive technique. Methyl nitrite photolysis in synthetic air was used as OH radical source at 295±2 K and 1000 mbar total pressure. Using a rate constant of 2.53×10-12 cm3 s-1 for the reaction of OH radicals with n-butane as reference, the following rate constants were obtained (units: 10-12 cm3 s-1): isopropyl nitrate, 0.59±0.22; isobutyl nitrate, 1.63±0.20; 3-methyl-2-butyl nitrate, 1.95±0.15; 2-methyl-1-butyl nitrate, 2.50±0.15; 3-methyl-1-butyl nitrate, 2.55±0.35. These values have been combined with the literature data to recalculate the substituent factors F(X) for the different nitrate groups which can be used to predict OH rate constants for organic nitrates for which experimental data are not available.

This paper describes a fluorescence technique for the detection of sub-ppm-concentrations of formaldehyde in air at atmospheric pressure. The aldehyde is excited by a frequency doubled tunable dye laser covering the 320–345-nm wavelength range. The fluorescence intensity, measured at right angles through a 400-nm cutoff filter, is proportional to the formaldehyde concentration in air. Interferences by NO_2 and SO_2 are negligible. The detection limit of the system is 5 pphm at present, in good agreement with an estimate of the fluorescence yield in 1 atm of air. A considerable increase of the sensitivity is possible, and the use of this technique for measuring formaldehyde in ambient air in the ppb concentration range is projected.

In the densely populated Wuppertal-Düsseldorf area the atmospheric concentrations of CCl2F2 and CCl3F near ground level were measured by ECGC and GC-MS method. Special systems for sampling and calibrating were developed. As mean concentration averages over the time period from December 1976 to May 1977 a value of 650±356 pptv was determined for CCl2F2 (F12) and of 490±279 pptv for CCl3F (F 11).

With the Fréjus detector we studied four astrophysical point-like sources by using and interactions in the detector and interactions in the surrounding rock. No excess of events was found. Therefore upper limits of neutrino fluxes and source luminositics are quoted. These limits confirm results from other experiments. In addition new limits are presented for spectral indices above 3.

Peroxynitrates are thermally unstable intermediates (at ambient temperatures) in the atmospheric degradation of hydrocarbons. In this work, thermal lifetimes of nine peroxynitrates have been measured as a function of temperature and, for two of them, also, as a function of total pressure. In the presence of excess NO, relative concentrations of the peroxynitrates were followed in a 420 I reaction chamber as a function of time by means of longpath IR absorption using a Fourier transform spectrometer. Original data on the unimolecular decomposition rate constants are presented for the peroxynitrates RO2NO2 with R = C6H11, CH3C(O)CH2, C6H5CH2, CH2I, CH3C(O)OC(H)CH3, C6H5OCH2, (CH3)2NC(O), C6H5OC(O), and C2H5C(O). Thermal lifetimes at room temperature and atmospheric pressure are very short (in the order of seconds) for substituted methyl peroxynitrates (i.e., R'CH2O2NO2) but rather long for substituted formyl peroxynitrates (i.e., R"C(O)O2NO2). Kinetic data from this and previous work from our laboratory are used to derive structure-stability relationships which allow an estimate of the thermal lifetimes of peroxynitrates from readily available ¹³C n.m.r. shift data. ©1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 127–144, 1999

An FT-IR kinetic and product study of the Br-atom-initiated oxidation of dimethyl sulfide (DMS) has been performed in a large-volume reaction chamber at 298 K and 1000-mbar total pressure as a function of the bath gas composition (N2 + O2). In the kinetic investigations using the relative kinetic method, considerable scatter was observed between individual determinations of the rate coefficient, suggesting the possibility of interference from secondary chemistry in the reaction system involving dimethyl sulfoxide (DMSO) formation. Despite the experimental difficulties, an overall bimolecular rate coefficient for the reaction of Br atoms with DMS under atmospheric conditions at 298 K of ≤1 × 10⁻¹³ cm³ molecule⁻¹ s⁻¹ can be deduced. The major sulfur products observed included SO2, CH3SBr, and DMSO. The kinetic observations in combination with the product studies under the conditions employed are consistent with rapid addition of Br atoms to DMS forming an adduct that mainly re-forms reactants but can also decompose unimolecularly to form CH3SBr and CH3 radicals. The observed formation of DMSO is attributed to reactions of BrO radicals with DMS rather than reaction of the Br–DMS adduct with O2 as has been previously speculated and is thought to be responsible for the variability of the measured rate coefficient. The reaction CH3O2 + Br → BrO + CH3O is postulated as the source of BrO radicals. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 883–893, 1999

Rate coefficients have been measured at 298 ± 4 K and 1000 mbar total pressure for the reactions of OH with a series of symmetrical acetals (R&bond;O&bond;CH2&bond;O&bond;R, R = C1 to C4) using a relative kinetic technique. The investigations have been performed in a laboratory photoreactor and also in the large outdoor EUPHORE simulation chamber facility in Valencia, Spain. The following rate coefficients (in units of 10⁻¹¹ cm³ molecule⁻¹ s⁻¹) have been obtained: dimethoxy methane (R = CH3), 0.49 ± 0.02; diethoxy methane (R = CH3CH2), 1.84 ± 0.18; di-n-propoxy methane (R = CH3CH2CH2), 2.63 ± 0.49; di-iso-propoxy methane (R = (CH3)2CH), 3.93 ± 0.48; di-n-butoxy methane (R = CH3CH2CH2CH2), 3.47 ± 0.42; di-iso-butoxy methane (R = (CH3)2CHCH2), 3.68 ± 0.57; di-sec-butoxy methane (R = CH3CH2C(CH3)H), 4.68 ± 0.05. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 797–803, 1999

Relative rate techniques were used to measure k(Cl + CF2ClCFClH) = (1.4−1.0^+4.2) × 10⁻¹¹ exp[−(2360 ± 400)/T] cm³ molecule⁻¹ s⁻¹; k(Cl + CF2ClCFClH) = 5.1 × 10⁻¹⁵ cm³ molecule⁻¹ s⁻¹ at 298 K. This result is discussed with respect to the available data. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 785–788, 1999

The products of the Br-atom initiated oxidation of trans-2-butene have been studied in a largevolume reaction chamber between 246 and 298 K using in situ FT-IR for the analysis. 3-Bromobutan-2-one, acetaldehyde and acetylbromide were the major products of this oxidation process. Additional products included formaldehyde and hydrogen bromide and evidence was found for the formation of 3-bromobutan-2-hydroperoxide. Decreasing the temperature from 298 K down to 246 K resulted in an increase in the yield of 3-bromobutan-2-one and a decrease in the yields of acetaldehyde, acetylbromide, formaldehyde and hydrogen bromide. Addition of NO to the reaction system resulted in nearly a doubling of the yields of 3-bromobutan-2-one, acetaldehyde and formaldehyde. The reaction mechanism is discussed and possible consequences of the results for the involvement of bromine/alkene chemistry in the springtime depletion of ozone in the Arctic are considered.

The reactions of OH radicals with SO2, H2S, thiophenol, and a series of aliphatic thiols (1–5 C-atoms) have been investigated in 201 and 381 reaction chambers at 1 atm total pressure and 300 K using a competitive kinetic technique. Initially, OH radicals were produced by photolysis of CH3ONO/NO mixtures in air. Applying this OH source rate constants for OH with SO2, H2S, and thiophenol in synthetic air were determined to be (1.1±0.2)×10-12, (5.5±0.8)×10-12 and (1.1±0.2)×10-11 cm3 s-1, respectively. However, when this method was applied to the aliphatic thiols the rate constants obtained were found to be dependent on the partial pressures of O2 and NO. These effects have been attributed to the built-up of a radical species, not yet identified, which leads to uncontrolled chain reactions in the system. Using the photolysis of H2O2 at wavelengths greater than 260 nm as the OH source in 1 atm N2, rate constants for the 1–5 aliphatic thiols in the range 2.9 to 5.6×10-11 cm3 s-1 were obtained. The rate constants obtained in the present study are compared with recent literature values.

Rate coefficients for the reactions of difunctional nitrates with atmospherically important OH radicals are not currently available in the literature. This study represents the first determination of rate coefficients for a number of C(3) and C(4) carbonyl nitrates and dinitrates with OH radicals in a 38 l glass reaction chamber at 1000 mbar total pressure of synthetic air by 298±2 K using a relative kinetic technique.

Bisoprolol, ±142isopropoxyethoxymethylphenoxy3isopropylamino2propanolhemifumarate, is a new, highly selective 1adrenoceptor blocking agent without intrinsic sympathomimetic activity and low to moderate local anaesthetic activity. As demonstrated in binding experiments, and in classical pharmacological studies using rats, guinea pigs, cats, and dogs, bisoprolol markedly differentiated between 1adrenoceptors of the heart, or the renal juxtaglomerular apparatus, and the 2subtype in arterial blood vessels, bronchi, liver, or skeletal muscle. Up to concentrations nearly 100fold higher than the therapeutic plasma levels in humans, bisoprolol did not affect the functional refractory period of the heart, and was devoid of a direct suppressive effect on myocardial contractility and of calcium antagonistic properties in heart and vascular muscle. The pattern of haemodynamic effects of bisoprolol was typical of blockers and included decreases in blood pressure BP, heart rate HR, and cardiac output, concomitant with an increase in calculated total peripheral resistance. In contrast to other blockers, bisoprolol increased renal blood flow in anaesthetized dogs. Bisoprolol lowered BP in hypertensive dogs and rats, attenuated the development of spontaneous hypertension in rats, decreased plasma renin activity and protected the heart from the sequelae of transient ischemia. It did not block presynaptic adrenoceptors in blood vessels. Serum lipids and the serum lipoprotein profile remained unaltered after bisoprolol. Bisoprolol was devoid of affinity for autonomic receptors other than adrenoceptors or for autacoid receptors. This is probably one of the reasons why bisoprolol did not affect the function of the central nervous, respiratory, and gastrointestinal systems in an obvious way. The high 1selectivity of bisoprolol is linked with extremely favourable pharmacokinetic properties. These include nearly complete enteral absorption and virtual absence of liver firstpass metabolism, both resulting in high bioavailability, long plasma halflife, pharmacokinetics that are linear over a wide dose range and independent of age, food intake and hydroxylator status, low plasma protein binding, and a 1 1 ratio of hepatic metabolization to renal elimination of the unaltered substance. This sum of favourable pharmacological and pharmacokinetic properties characterize bisoprolol as an optimized blocker.

Experiments on the photooxidation of toluene/NOx/air mixtures were performed in the European Photoreactor (EUPHORE), a large-scale outdoor reaction chamber located in Valencia/Spain. The objective of the study was the in situ determination of the yields of ring-retaining products by differential optical absorption spectroscopy (DOAS) and the elucidation of their formation pathways. The experiments were performed with toluene concentrations between 0.68 and 3.85 ppm and initial NOx concentrations ranging from 3 to 300 ppb, i.e., down to the range actually observed in the lower atmosphere. The ring-retaining product yields were found to be 5.8 ± 0.8%, 12.0 ± 1.4%, 2.7 ± 0.7%, and 3.2 ± 0.6% for benzaldehyde, o-cresol, m-cresol, and p-cresol, respectively. Under the experimental conditions, no dependency of the yields on the NOx concentration or the toluene/NOx ratio could be found. The formation kinetics of the cresols are in line with a “prompt” formation mechanism, i.e., abstraction of a hydrogen atom from the toluene−OH adduct (toluene−OH + O2 → cresols + HO2). In addition, substantial evidence was found that reaction with NO3 radicals represents an important sink for cresols in smog chamber studies conducted under conditions of NOx concentrations above the range observed in the troposphere, possibly also under tropospheric conditions.

A pulse radiolysis technique was used to measure the UV absorption spectra of c-C3H5O3(•) and (c-C3H5O3)O2(•) radicals over the range 220−300 nm, with σ(c-C3H5O3(•))250 nm = (5.2 ± 0.7) × 10^-18 and σ((c-C3H5O3)O2(•))250 nm = (3.7 ± 0.4) × 10^-18 cm² molecule^-1. The self-reaction rate constant for the c-C3H5O3(•) radicals, defined as d[c-C3H5O3(•)]/dt = 2k4[c-C3H5O3(•)]², was k4 = (3.1 ± 0.6) × 10^-11 cm³ molecule^-1 s^-1. The rate constants for reactions of (c-C3H5O3)O2(•) radicals with NO and NO2 were k6 = (5.8 ± 1.4) × 10^-12 and k7 = (1.1 ± 0.2) × 10^-11 cm³ molecule^-1 s^-1, respectively. The rate constants for the reaction of F atoms with 1,3,5-trioxane and the reaction of c-C3H5O3(•) radicals with O2 were k3 = (1.1 ± 0.4) × 10^-10 and k2 = (7.4 ± 1.1) × 10^-12 cm³ molecule^-1 s^-1, respectively. Relative rate techniques were used to measure the rate constants for the reactions of OH radicals and Cl atoms with 1,3,5-trioxane and Cl atoms with H(O)COCH2OC(O)H, k20 = (6.0 ± 1.0) × 10^-12, k24 = (1.0 ± 0.2) × 10^-10, and k25 = (5.1 ± 1.0) × 10^-13 cm³ molecule^-1 s^-1, respectively. FTIR−smog chamber systems were used to show that the atmospheric fate of the alkoxy radical (c-C3H5O3)O(•) is decomposition via C−O bond scission leading to the formation of H(O)COCH2OC(O)H (methylene glycol diformate). The IR spectrum of the peroxynitrate (c-C3H5O3)O2NO2 is presented. The results are discussed with respect to the atmospheric chemistry of 1,3,5-trioxane.

The temperature dependence of the NO2 + NO3 + (M) ↔ N2O5 + (M) equilibrium has been studied in the temperature range 279.6−294.2 K at a total pressure of 1000 mbar synthetic air in the 200 m³ EUPHORE simulation chamber facility in Valencia, Spain. Simultaneous determination of the concentration−time behaviors of NO3, NO2, and N2O5 were obtained using the DOAS technique for detection of the NO3 radical and FT-IR spectroscopy for detection of NO2, and N2O5. The experimental data are well described by ln([N2O5]/[NO2][NO3]) = −60.46 ± 0.26 + (10724 ± 75)/T where the errors given are random and expressed as 95% confidence limits. A critical comparison is made between the values of Keq determined in this work and those reported in the literature.

Bei der Bestrahlung von N2O mit der 1470 Å-Xenonlinie und den Kryptonlinien 1236 A und 1165 A wurde die Fluoreszenz von NO (β) - und NO (γ) -Banden nachgewiesen. Die relative Intensität beider Systeme ist sowohl bei 1470 A als auch bei 1236 A und 1165 A stark von der Strömungsgeschwindigkeit des N2O, dem N2O-Druck und dem Zusatz von NO abhängig. Die Bildung von NO (A2∑+) - und NO (B2π) -Molekülen muß bei 1470 Å ausschließlich durch Sekundärreaktionen über metastabile Teilchen, wahrscheinlich über O (1S) und/oder N (2D, 2P), erfolgen. Es ist zu vermuten, daß auch bei den Kryptonlinien, bei denen energetisch die Bildung von NO (A2∑+) - und NO (B2π) bei der N2O-Dissoziation möglich ist, mindestens ein Teil der β - und γ-Fluoreszenz durch Chemilumineszenz-Reaktionen entsteht.

Mit einer Blitzlichtanordnung wurde die Photolyse des NH3in der Gasphase im Vakuum-UV untersucht. Als Filter dienten bis 2000 Å bzw. 1600 Å Quarz und bis 1250 Å CaF2-Fenster. Für Belichtungen unter 1250 Å wurde eine Anordnung ohne Fenster benutzt. Es zeigte sich, daß mit einer fensterlosen Anordnung photochemische Primärprozesse absorptionsspektrographisch qualitativ beobachtet werden können. Voraussetzung ist u. a. eine Blitzlichtquelle mit genügend kurzzeitigem Lichtimpuls, so daß bei großem Abstand zwischen der Entladung und dem Reaktionsraum während der Analysendauer keine Störungen durch die Entladung erfolgen. Bei der vorliegenden Anordnung traten Störungen - wahrscheinlich als Druckwellen - nach mehr als 20 μsec im Reaktionsraum auf, während die Analyse nach 5 bis 10 μsec erfolgte. In Übereinstimmung mit früheren Untersuchungen wurden bei Wellenlängen über 2000 Å das NH2-, unter 1600 Å außer dem NH2- das NH-Radikal als Primärprodukte gefunden. Etwa 10% der NH-Radikale entstanden mit einem Schwingungsquant (υ=1) im Grundzustand. Bei Belichtungen ohne Fenster und relativ niedrigen Drucken wurde außerdem die BALMER-Serie des Η-Atoms in Absorption beobachtet

Steady state fluorescence experiments with mixtures of HD and H2or D2have given effective cross sections for energy exchange processes in collisions of electronically excited HD and ground state H2and D2molecules in well defined quantum states. The experimental results are compared with first order calculations using the Sharma-Brau theory of energy transfer due to the interaction of transition dipole moments.

The lifetimes of OH(2Σ+) and OD(2Σ+) radicals were measured by using pulse-photolysis of water and methanol in the vacuum-uv for the production of the electronically excited radicals. From the fluorescence decay measurements the natural lifetimes, as well as the quenching rate constants for several added gases such as H2O, CH3OH, H2, N2, Ar, and He were determined. In particular, the natural lifetime of OH (2Σ+, v = 0), τ = (1.00 ± 0.06) · 10-6 s, was corrected for rotation-vibration as well as for rotation-electronic interactions resulting in a lifetime of (0.83 ± 0.08) · 10-6 s for the rotationless state. A lifetime of (0.82 ± 0.08) · 10-6s was derived for the rotationless state of OD(2Σ+,v = 0).