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Conducting polymers are versatile semiconductors whose applications cover a wide range of devices. Their versatility is due, in addition to other factors, to properties that can be easily modulated according to the intended application. It is therefore important to study and map the electronic structure of these materials to allow for a better correlation between structure and properties. Electrochemical scanning tunnelling spectroscopy (EC-STS) can be a powerful tool to characterize the electronic structure of the semiconductor electrolyte interface. In this work we have used image-based EC-STS (IB-EC-STS) to describe quantitatively the band structure of an electrochemically deposited polypyrrole (PPy) film. IB-EC-STS located the band edge of the polymer’s valence band (VB) at 0.95 V vs. RHE (-5.33 eV in the absolute potential scale) and the intragap polaron states formed when the polymer is oxidised (doped) at 0.46 V vs. RHE (-4.84 eV in the absolute potential scale). The IB-EC-STS data were cross checked with electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis of the interfacial capacitance. The DOS spectrum obtained from EIS data is consistent with the STS-deduced location of the VB and the polarons.

The nonequilibrium self-consistent generalized Langevin equation theory of irreversible processes in liquids is extended to describe the positional and orientational thermal fluctuations of the instantaneous local concentration profile n(r,Ω,t) of a suddenly quenched colloidal liquid of particles interacting through nonspherically symmetric pairwise interactions, whose mean value n(r,Ω,t) is constrained to remain uniform and isotropic, n (r,Ω, t) = n (t). Such self-consistent theory is cast in terms of the time-evolution equation of the covariance [Formula: see text] of the fluctuations [Formula: see text] of the spherical harmonics projections nlm(k;t) of the Fourier transform of n(r,Ω,t). The resulting theory describes the nonequilibrium evolution after a sudden temperature quench of both, the static structure factor projections Slm(k,t) and the two-time correlation function [Formula: see text], where τ is the correlation delay time and t is the evolution or waiting time after the quench. As a concrete and illustrative application we use the resulting self-consistent equations to describe the irreversible processes of equilibration or aging of the orientational degrees of freedom of a system of strongly interacting classical dipoles with quenched positional disorder.

The oscillatory electro-oxidation of methanol was studied on polycrystalline Ptpc and Ptpc/Rh2.0/Pt1.0 metallic multilayers. The surfaces investigated consisted of 1.0 Pt outlayer surface deposited onto 2.0 Rh intralayers beneath a Pt outlayer and over the polycrystalline Ptpc substrate. In addition to experimental studies, numerical simulations were performed using a dimensionless kinetic model for the electro-oxidation of methanol in order to provide a better understanding of the role played by the nanostructured metallic multilayer electrode in the electrocatalytic activity. A comparable electrochemical behavior found for cyclic voltammetry in blank acidic media was observed in both electrodes. Remarkably, an increase of 90% in the peak current density around 0.88 V vs. RHE in the electro-oxidation of methanol appeared when Ptpc/Rh2.0/Pt1.0 was utilized. The numerical simulations suggested that this increase in the electrocatalytic activity for the metallic multilayer electrode is due to the prevention...

Dichlorvos [2,2-dichlorovinyl dimethyl phosphate, (CH(3)O)(2)P(O)OCH═CCl(2)] is a relatively volatile in-use insecticide. Rate constants for its reaction with OH radicals have been measured over the temperature range 296-348 K and atmospheric pressure of air using a relative rate method. The rate expression obtained was 3.53 × 10(-13) e((1367±239)/T) cm(3) molecule(-1) s(-1), with a 298 K rate constant of (3.5 ± 0.7) × 10(-11) cm(3) molecule(-1) s(-1), where the error in the 298 K rate constant is the estimated overall uncertainty. In addition, rate constants for the reactions of NO(3) radicals and O(3) with dichlorvos, of (2.5 ± 0.5) × 10(-13) cm(3) molecule(-1) s(-1) and (1.7 ± 1.0) × 10(-19) cm(3) molecule(-1) s(-1), respectively, were measured at 296 ± 2 K. Products of the OH and NO(3) radical-initiated reactions were investigated using in situ atmospheric pressure ionization mass spectrometry (API-MS) and (OH radical reaction only) in situ Fourier transform infrared (FT-IR) spectroscopy. For the OH radical reaction, the major initial products were CO, phosgene [C(O)Cl(2)] and dimethyl phosphate [(CH(3)O)(2)P(O)OH], with equal (to within ±10%) formation yields of CO and C(O)Cl(2). The API-MS analyses were consistent with formation of (CH(3)O)(2)P(O)OH from both the OH and NO(3) radical-initiated reactions. In the atmosphere, the dominant chemical loss processes for dichlorvos will be daytime reaction with OH radicals and nighttime reaction with NO(3) radicals, with an estimated lifetime of a few hours.

Using relative rate methods, rate constants for the gas-phase reactions of divinyl sulfoxide [CH 2CHS(O)CHCH 2; DVSO] with NO 3 radicals and O 3 have been measured at 296 +/- 2 K, and rate constants for the reaction with OH radicals have been measured over the temperature range of 277-349 K. Rate constants obtained for the NO 3 radical and O 3 reactions at 296 +/- 2 K were (6.1 +/- 1.4) x 10 (-16) and (4.3 +/- 1.0) x 10 (-19) cm (3) molecule (-1) s (-1), respectively. For the OH radical reaction, the temperature-dependent rate expression obtained was k = 4.17 x 10 (-12)e ((858 +/- 141)/ T ) cm (3) molecule (-1) s (-1) with a 298 K rate constant of (7.43 +/- 0.71) x 10 (-11) cm (3) molecule (-1) s (-1), where, in all cases, the errors are two standard deviations and do not include the uncertainties in the rate constants for the reference compounds. Divinyl sulfone was observed as a minor product of both the OH radical and NO 3 radical reactions at 296 +/- 2 K. Using in situ Fourier transform infrared spectroscopy, CO, CO 2, SO 2, HCHO, and divinyl sulfone were observed as products of the OH radical reaction, with molar formation yields of 35 +/- 11, 2.2 +/- 0.8, 33 +/- 4, 54 +/- 6, and 5.4 +/- 0.8%, respectively, in air. For the experimental conditions employed, aerosol formation from the OH radical-initiated reaction of DVSO in the presence of NO was minor, being approximately 1.5%. The data obtained here for DVSO are compared with literature data for the corresponding reactions of dimethyl sulfoxide.

Rate constants for the reactions of OH radicals and NO 3 radicals with dimethyl phosphonate [DMHP, (CH 3 O) 2 P-(O)H], dimethyl methylphosphonate [DMMP, (CH 3 O) 2 P(O)CH 3 ], and dimethyl ethylphosphonate [DMEP, (CH 3 O) 2 P(O)C 2 H 5 ] have been measured at 296 ′ 2 K and atmospheric pressure using relative rate methods. The rate constants obtained for the OH radical reactions (in units of 10 - 1 2 cm 3 molecule - 1 s - 1 ) were as follows: DMHP, 4.83 ′ 0.25; DMMP, 10.4 ′ 0.6; and DMEP, 17.0 ′ 1.0, with a deuterium isotope effect of k(OH + DMMP)/k(OH + DMMP-d 9 ) = 4.8 ′ 1.2. The rate constants obtained for the NO 3 radical reactions (in units of 10 - 1 6 cm 3 molecule - 1 s - 1 ) were as follows: DMHP

Rate constants for the reactions of OH radicals and NO(3) radicals with diethyl methylphosphonate [DEMP, (C(2)H(5)O)(2)P(O)CH(3)], diethyl ethylphosphonate [DEEP, (C(2)H(5)O)(2)P(O)C(2)H(5)], and triethyl phosphate [TEP, (C(2)H(5)O)(3)PO] have been measured at 296 +/- 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained for the OH radical reactions (in units of 10(-11) cm(3) molecule(-1) s(-1)) were as follows: DEMP, 5.78 +/- 0.24; DEEP, 6.45 +/- 0.27; and TEP, 5.44 +/- 0.20. The rate constants obtained for the NO(3) radical reactions (in units of 10(-16) cm(3) molecule(-1) s(-1)) were the following: DEMP, 3.7 +/- 1.1; DEEP, 3.4 +/- 1.4; and TEP, 2.4 +/- 1.4. For the reactions of O(3) with DEMP, DEEP, and TEP, an upper limit to the rate constant of6 x 10(-20) cm(3) molecule(-1) s(-1) was determined for each compound. Products of the reactions of OH radicals with DEMP, DEEP, and TEP were investigated using in situ atmospheric pressure ionization mass spectrometry (API-MS) and, for the TEP reaction, gas chromatography with flame ionization detection (GC-FID) and in situ Fourier transform infrared (FT-IR) spectroscopy. The API-MS analyses show that the reactions are analogous, with formation of one major product from each reaction: C(2)H(5)OP(O)(OH)CH(3) from DEMP, C(2)H(5)OP(O)(OH)C(2)H(5) from DEEP, and (C(2)H(5)O)(2)P(O)OH from TEP. The FT-IR and GC-FID analyses showed that the major products (and their molar yields) from the TEP reaction are (C(2)H(5)O)(2)P(O)OH (65-82%, initial), CO(2) (80 +/- 10%), and HCHO (55 +/- 5%), together with lesser yields of CH(3)CHO (11 +/- 2%), CO (11 +/- 3%), CH(3)C(O)OONO(2) (8%), organic nitrates (7%), and acetates (4%). The probable reaction mechanisms are discussed.

Products of the gas-phase reactions of O3 with cyclohexene and cyclohexene-d10 were investigated in the presence of OH radical scavengers by gas chromatography with flame ionization detection, combined gas chromatography−mass spectrometry, in situ Fourier transform infrared spectroscopy, and in situ atmospheric pressure ionization mass spectrometry (API-MS). Cyclohexane and cyclohexane-d12 were used as OH radical scavengers in the experiments using API-MS analyses to allow products formed from the O3 reactions with cyclohexene and cyclohexene-d10 to be differentiated from those from the reactions of OH radicals with cyclohexane and cyclohexane-d12. The gas-phase products observed from the reaction of O3 with cyclohexene in the presence of an OH radical scavenger were pentanal (23.6 ± 1.8%); OH radicals (54 ± 8%); formic acid (3.5% initial yield); glutaraldehyde [HC(O)CH2CH2CH2CHO]; adipaldehyde [HC(O)CH2CH2CH2CH2CHO], a C6H10O3 product attributed to the secondary ozonide; a C5H7O2(OOH) product, a molecula...

The aim of this study is to immobilize an enzyme, namely, organophosphorus hydrolase (OPH), and to detect the presence of paraoxon, which is an organophosphorus compound, using the layer-by-layer (LbL) deposition technique. To lift the OPH from the solid substrate, a pair of polyelectrolytes (positively charged chitosan (CS) and negatively charged poly(thiophene-3-acetic acid) (PTAA)) were combined. These species were made charged by altering the pH of the solutions. LbL involved alternate adsorption of the oppositely charged polyions from dilute aqueous solutions onto a hydrophilic quartz slide. This polyion cushion was held together by the electrostatic attraction between CS and PTAA. The growing process was monitored by fluorescence spectroscopy. OPH was then adsorbed onto the five-bilayer CS/PTAA system. This five-bilayer macromolecular structure compared to the solid substrate rendered stability to the enzyme by giving functional integrity in addition to the ability to react with paraoxon solutions. The ultimate goal is to use such a system to detect the presence of organophosphorus compounds with speed and sensitivity using the absorption and fluorescence detection methodologies.

4,5-Dihydro-2-methylfuran (DHMF) can be formed from cyclization of 5-hydroxy-2-pentanone, an important gas-phase photooxidation product of n-pentane and a representative 1,4-hydroxycarbonyl. At very low (≪1%) relative humidity a lifetime of ∼1.1 h was obtained for the transformation of 5-hydroxy-2-pentanone to DHMF. Rate constants and products of the gas-phase reactions of DHMF with OH radicals, NO3 radicals, and ozone have been determined at 298 ± 2 K and atmospheric pressure of air using in situ Fourier transform infrared (FT-IR) spectroscopy, in situ atmospheric pressure ionization tandem mass spectrometry (API-MS/MS), and combined gas chromatography−mass spectrometry (GC−MS). Rate constants (in cm3 molecule-1 s-1) for the reactions of DHMF with OH radicals, NO3 radicals, and O3 were measured to be (2.18 ± 0.11) × 10-10, (1.68 ± 0.12) × 10-10, and (3.49 ± 0.24) × 10-15, respectively, resulting in estimated tropospheric lifetimes of 1.3 h, 24 s, and 7 min for the OH radical, NO3 radical, and O3 reaction...

The kinetics of the gas-phase reactions of phosphorus oxychloride [P(O)Cl3], methylphosphonic dichloride [CH3P(O)Cl2], dimethyl phosphonate [(CH3O)2P(O)H], and trimethyl phosphite [(CH3O)3P] with t...

Glycol ethers are widely used as solvents and are hence liable to be released into the atmosphere where they may contribute to the formation of photochemical air pollution in urban and regional areas. The dominant reaction of glycol ethers in the atmosphere has been previously shown to be with OH radicals. Using a relative rate method, rate constants have been measured at 296+/-2 K for the gas-phase reactions of the OH radical with 1-butoxy-2-propanol [CH3CH2CH2CH2OCH2CH(OH)CH3], diethylene glycol ethyl ether [CH3CH2OCH2CH2OCH2CH2OH], and diethylene glycol n-butyl ether [CH3CH2CH2CH2OCH2CH2OCH2-CH2OH] of (in units of 10(-11) cm3 molecule(-1) s(-1)) 3.76+/-0.54, 5.72+/-0.85, and 7.44+/-0.94, respectively, where the error limits include the estimated overall uncertainties in the rate constants for the reference compounds. Products of the OH radical-initiated reactions of these glycol ethers have been investigated using gas chromatography with flame ionization detection (GC-FID), combined gas chromatography-mass spectrometry (GC-MS), in situ Fourier transform infrared (FT-IR) spectroscopy, and in situ atmospheric pressure ionization tandem mass spectrometry (API-MS). The products identified and quantified account for 102+/-11% of the reaction products from 1-butoxy-2-propanol, 87+/-9% of those from diethylene glycol ethyl ether, and 83+/-12% of those from diethylene glycol n-butyl ether. An empirical estimation method for calculating reaction rates of alkoxy radicals under atmospheric conditions appears to fairly well predict the products formed and their yields. Detailed reaction schemes after the initial OH radical reactions are formulated for each of these glycol ethers, with the majority of the reactions involving H-atom abstraction from the CH2 groups adjacent to the ether linkage.

The current widespread use of poly(dimethylsiloxane)s (PDMS) in a broad range of applications leads to their release into soil environments where they degrade to monomeric products, primarily dimet...

The paper is concerned with the small signal ac impedance of porous film electrodes in contact with solution. An overview is presented of the standard transmission line model with two transport channels and a crosswise element. The simplest configurations are discussed: a single resistance in one of the channels, and either an interfacial capacitor or a RC transfer circuit at the pore's wall. The resulting relaxation functions are classified in terms of two characteristic frequencies: one for coupled transport and interfacial polarization and another one for the interfacial reaction. Subsequently, these models are extended in order to describe porous electrodes where the interfacial polarization displays complex properties, i.e., frequency dispersion. The capacitive element is described by a constant-phase element (CPE), and it is shown that the fractionary exponent provides an additional and measurable degree of freedom in the parameter space of the relaxation function, whose determination can be explo...

2-Pentanone and 2-heptanone are available for commercial use, which will lead to their possible release into the atmosphere where they are expected to primarily react with the hydroxyl (OH) radical...

1,3-Butadiene is emitted into the atmosphere from a number of sources including combustion sources and is listed in the United States as a hazardous air pollutant. In the atmosphere, 1,3-butadiene reacts with OH radicals, NO3 radicals, and O3 with the dominant tropospheric removal processes being daytime reaction with the OH radical and nighttime reaction with the NO3 radical. We have used gas chromatography, in situ Fourier transform infrared (FT-IR) absorption spectroscopy, and in situ atmospheric pressure ionization tandem mass spectrometry (API-MS) to identify and quantify the products formed from the reactions of 1,3-butadiene with OH radicals (in the presence of NO) and NO3 radicals. Acrolein, formaldehyde, and furan were identified and quantified from the OH radical-initiated reaction, with formation yields of 0.58 ± 0.04, 0.62 ± 0.05, and 0.03−0.04, respectively. Organic nitrates were observed by FT-IR spectroscopy with an estimated yield of 0.07 ± 0.03, and the API-MS analyses indicated that thes...

Dibasic esters are potentially important commercial solvents and their use will lead to possible release into the atmosphere, where they will react with the hydroxyl (OH) radical and contribute to the formation of photochemical air pollution in urban and regional areas. The authors have investigated the products formed from the gas-phase reaction of the OH radical with the dibasic ester dimethyl glutarate [CH[sub 3]-OC(O)CH[sub 2]CH[sub 2]CH[sub 2]C(O)OCH[sub 3]] in the presence of NO in large volume chambers with analysis by in situ Fourier transform infrared (FTIR) absorption spectroscopy, in situ atmospheric pressure ionization tandem mass spectrometry (API-MS), gas chromatography with flame ionization detection, and combined gas chromatography-mass spectrometry. No information was obtained concerning the reaction products using the gas chromatographic analyses. The in situ API-MS and API-MS/MS analyses indicated the formation of products with molecular weights 146, 174, and 221, and, based on plausible reaction schemes, these could be mono-methyl glutarate [CH[sub 3]OC(O)CH[sub 2]CH[sub 2]-CH[sub 2]C(O)OH], dimethyl 1,3-acetonedicarboxylate [CH[sub 3]OC(O)-CH[sub 2]C(O)CH[sub 2]C(O)OCH[sub 3]], and/or its isomers, and an organic nitrate(s), respectively. The in situ FT-IR spectroscopic analyses were consistent with these expectations, with the identification and quantification of organic nitrate(s), mono-methyl glutarate, and dimethyl 1,3-acetonedicarboxylate with formation yields of 15more » [+-] 6, 34 [+-] 16, and 28 [+-] 8 [percent], respectively. These products therefore account for 77 [+-] 19 [percent] of the total reaction products and reaction pathways, recognizing that the quantifications of mono-methyl glutarate and dimethyl 1,3-acetonedicarboxylate are subject to significant uncertainties.« less

A new methodology was developed to obtain cubic, stabilized zirconium oxide films prepared at room temperature. The zirconium oxide films were prepared electrochemically by anodic oxidation of metallic zirconium at constant current density. The oxide films were analyzed by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The oxide films grown in H3PO4 solutions are monoclinic, and the ones prepared in phosphoric acid solution containing Na2[Ca(EDTA)] complex are cubic. An explanation for the zirconium oxide stabilization obtained by the electrochemical method is proposed that assumes a destruction and rebuilding of the oxide film during the dielectric breakdown.

Glycol ethers are used as solvents and are hence liable to be released to the atmosphere, where they react and contribute to the formation of photochemical air pollution. In this work, products of the gas-phase reactions of the OH radical with 1-methoxy-2-propanol and 2-butoxyethanol in the presence of NO have been investigated at 298 {+-} 2K and 740 Torr total pressure of air by gas chromatography, in situ Fourier transform infrared spectroscopy, and in situ atmospheric pressure ionization tandem mass spectrometry. The products observed from 1-methoxy-2-propanol were methyl formate, methoxyacetone, and acetaldehyde with molar formation yields of 0.59 {+-} 0.05, 0.39 {+-} 0.04, and 0.56 {+-} 0.07, respectively. The products observed and quantified from 2-butoxyethanol were n-butyl formate, 2-hydroxyethyl formate, propanal, 3-hydroxybutyl formate, and an organic nitrate with molar formation yields of 0.57 {+-} 0.05, 0.22 {+-} 0.05, 0.21 {+-} 0.02, 0.07 {+-} 0.03, and 0.10 {+-} 0.03, respectively. An additional product of molecular weight 132, attributed to one or more hydroxycarbonyl products, was also observed from the 2-butoxyethanol reaction by atmospheric pressure ionization mass spectrometry. For both glycol ethers, the majority of the reaction products and reaction pathways are accounted for, and detailed reaction mechanisms are presented which accountmore » for the observed products.« less

Alkenes are a significant component of ambient air in urban areas, and in the atmosphere they react with OH radicals, NO{sub 3} radicals, and O{sub 3}, with the OH radical reaction often dominating as the tropospheric removal process. Products of the gas-phase reactions of the OH radical with 2-methylpropene, cis-2-butene, 2-methyl-2-butene, and 2,3-dimethyl-2-butene in the presence of NO have been investigated at room temperature and 740 Torr total pressure of air by gas chromatography with flame ionization detection, in situ Fourier transform infrared absorption spectroscopy, and in situ atmospheric pressure ionization tandem mass spectrometry (API-MS). For all four alkenes, hydroxynitrate formation from the {beta}-hydroxyalkyl peroxy radical plus NO reaction accounted for {approximately} 10% of the overall products observed, with decomposition of the intermediate {beta}-hydroxyalkoxy radical dominating over the alternative reaction with O{sub 2} (isomerization via a six-member transition state is not possible for any of the intermediate {beta}-hydroxyalkoxy radicals formed in these reactions) and leading to the formation of the carbonyls expected from >C{double_bond}C< bond cleavage in {approximately} 90% yield each.

Products of the gas-phase reactions of the OH radical with ethyl acetate, isopropyl acetate, tert-butyl acetate in the presence of NO were investigated using in situ Fourier transform infrared spectroscopy and gas chromatography. The products identified and their molar formation yields (corrected for secondary reactions with the OH radical) were acetic acid (0.96 ± 0.08) from ethyl acetate; acetic acid (0.09 ± 0.03), acetic anhydride (0.76 ± 0.07), and acetone (0.24 ± 0.02) from isopropyl acetate; and acetic anhydride (0.49 ± 0.05) and acetone (0.20 ± 0.02) from tert-butyl acetate. Consideration of the potential reaction pathways of the intermediate alkoxy radicals leads to the conclusion that alkoxy radicals of structure RC(O)OCH(Ȯ)Ŕ can undergo a rapid rearrangement and decomposition (α-ester rearrangement) to RC(O)OH plus ŔĊO, presumably via a five-membered ring transition state. However, our product studies provided no evidence for the analogous β-ester rearrangement proceeding via a six-membered tran...

Alkenes are important constituents of ambient air in polluted urban areas and are highly reactive in the atmosphere, reacting with OH radicals, NO3 radicals, and O3. The products of the gas-phase reactions of O3 with propene, cis-2-butene, trans-2-butene, 2-methylpropene, 2-methyl-2-butene, and 2,3-dimethyl-2-butene were investigated, using gas chromatography with flame ionization detection and in situ Fourier transform infrared absorption spectroscopy, in the presence of sufficient cyclohexane to scavenge >90% (and generally >95%) of the OH radicals formed in these reac tions. The “primary” carbonyl products identified and quantified from these O3 reactions were HCHO and CH3CHO from propene; HCHO and CH3C(O)CH3 from 2-methylpropene; CH3CHO from cis- and trans-2-butene; CH3CHO and CH3C(O)CH3 from 2-methyl-2-butene; and CH3C(O)CH3 from 2,3-dimethyl-2-butene. The formation yields of these primary carbonyls were in the range 0.98−1.19 apart from the 2-methylpropene reaction where the decomposition of the [(C...

The Cl atom-initiated photooxidations of the hydrofluoropolyethers (HFPEs) HCF 2 OCF 2 OCF 2 CF 2 OCF 2 H, HCF 2 OCF 2 CF 2 -OCF 2 H, and HCF 2 OCF 2 OCF 2 H in air produced C(O)F 2 as the only carbon-containing product, with observed average C(O)F 2 molar formation yields of 4.73, 3.77, and 2.82, respectively. The C(O)F 2 molar formation yields during the early stages of the reactions were observed to be closer to the number of C atoms in each parent HFPE. On the basis of current knowledge concerning the degradation pathways of hydrofluorocarbons and hydrochlorofluorocarbons, it is expected that C(O)F 2 will also be produced with near unit yield per C atom from the above HFPEs in the troposphere, where loss processes would be initiated primarily by reaction with OH radicals. The rate constants for reaction with the Cl atom at 298 ± 2 K were determined for the HFPEs by a relative rate method that employed CF 3 CF 2 H as the reference compound [k(Cl + CF 3 CF 2 H) = (2.4 ± 0.51 x 10 -16 cm 3 molecule -1 s -1 ], with measured values of (in units of 10 -17 cm 3 molecule -1 s -1 ) HCF 2 OCF 2 OCF 2 CF 2 -OCF 2 H, 3.6 ± 0.8; HCF 2 OCF 2 CF 2 OCF 2 H, 4.5 ± 1.0; and HCF 2 -OCF 2 OCF 2 H, 5.0 ± 1.1.

Linalool [(CH3)2CCHCH2CH2C(CH3)(OH)CHCH2] is a terpene derivative emitted from vegetation, including orange blossoms and certain trees and vegetation in the Mediter ranean area. Linalool reacts rapidly in the gas phase in the troposphere with OH radicals, NO3 radicals, and O3, with a calculated lifetime due to these reactions of ∼1 h or less. The products of these gas-phase reactions have been studied in ∼6500−7900-L Teflon chambers using gas chro matography, in situ Fourier transform infrared absorption spectroscopy, and direct air sampling atmospheric pres sure ionization tandem mass spectrometry. The products identified and their formation yields are as follows: from the OH radical reaction, acetone, 0.505 ± 0.047; 6-methyl-5-hepten-2-one, 0.068 ± 0.006; 4-hydroxy-4-methyl-5-hexen-1-al (or its cyclized isomer), 0.46 ± 0.11; from the NO3 radical reaction, acetone, 0.225 ± 0.052; 4-hydroxy-4-methyl-5-hexen-1-al (or its cyclized isomer), 0.191 ± 0.051; and a non-quantified nitrooxycarbonyl; from the O3 r...

The products of the gas-phase reactions of O 3 with 1-pentene, 1-hexene, 1-heptene, 1-octene, 2,3-dimethyl-1-butene, cyclopentene, and 1-methylcyclohexene have been investigated at room temperature and 740 Torrtotal pressure of air in the presence of cyclohexane or n-octane to scavenge OH radicals. Products were identified and quantified by gas chromatography and in situ Fourier transform infrared absorption spectroscopy. In the presence of cyclohexane, cyclohexanone and cyclohexanol were observed as products, showing the formation of OH radicals from these O 3 reactions. The OH radical formation yields derived were as follows : 1-pentene, 0.37 ; 1-hexene, 0.32 ; 1-heptene, 0.27 ; 1-octene, 0.18 ; 2,3-dimethyl-1-butene, 0.50 ; cyclopentene, 0.61 ; and 1-methylcyclohexene, 0.90, all with estimated overall uncertainties of a factor of ∼1.5. The carbonyl products identified and quantified were as follows : from 1-pentene : butanal, 0.541 ± 0.065, and HCHO, 0.595 ± 0.055 ; from 1-hexene : pentanal, 0.518 ± 0.095, and HCHO, 0.575 ± 0.057 ; from 1-heptene : hexanal, 0.582 ± 0.078, and HCHO, 0.533 ± 0.049 ; from 1-octene : heptanal, 0.527 ± 0.070, and HCHO, 0.519 ± 0.054 ; from 2,3-dimethyl-1-butene : 3-methyl-2-butanone, 0.391 ± 0.050, and HCHO, 0.776 ± 0.071 ; from cyclopentene : butanal, 0.195 ± 0.027 ; and from 1-methylcyclohexene : 5-acetylpentanal, 0.100 ± 0.024. For the 1-alkenes, the sum of the two carbonyl products expected from the decomposition of the initially formed primary ozonide is 1.1 ± 0.1, consistent with the presently believed reaction mechanism. The 3-methyl-2-butanone and HCHO yields from 2,3-dimethyl-1-butene showthatthe primary ozonide decomposes preferentially to HCHO plus the dialkyl-substituted [(CH 3 ) 2 CHC(CH 3 )OO] * biradical rather than to 3-methyl-2-butanone plus the [CH 2 00] * biradical.

The products of the gas-phase reactions of the OH radical with 1-pentene, 1-hexene, 1-heptene, 1-octene, 2,3-dimethyl-1-butene, and 1-methylcyclohexene have been investigated in the presence of NO at room temperature and 740 Torr total pressure of air. Products were identified and quantified by gas chromatography and in situ Fourier transform infrared absorption spectroscopy. The carbonyl products identified and their yields were as follows : from 1 -pentene, butanal (0.73 ± 0.09) and HCHO (0.88 ± 0.11) ; from 1-hexene, pentanal (0.46 ± 0.07) and HCHO (0.57 ± 0.08) ; from 1-heptene, hexanal (0.30 ± 0.04) and HCHO (0.49 ± 0.06) ; from 1-octene, heptanal (0.21 ± 0.03) and HCHO (0.39 ± 0.06) ; from 2,3-dimethyl-1-butene, acetone (0.27 ± 0.04), 3-methyl-2-butanone, (0.45 ± 0.06), and HCHO (0.50 ± 0.04) ; and from 1-methylcyclohexene, 5-acetylpentanal (0.31 ± 0.08). These product yield data suggest that the intermediate β-hydroxyalkoxy radicals undergo isomerization and/or reaction with O 2 in competition with decomposition, and the decrease in the carbonyl and HCHO yields with increasing carbon number in the 1-alkenes 1-pentenethrough 1 -octene suggests that isomerization of the intermediate β-hydroxyalkoxy radical is occurring.

The Cl atom-initiated photooxidation of CF 3 CF 2 COCl 2 (HCFC-225ca) produced CF 3 CF 2 C(O)Cl in 100% yield, while CF 2 ClCF 2 CHFCl (HCFC-225cb) yielded CF 2 ClCF 2 -C(O)F (99%) and C(O)FCl (1%). The two-carbon aldehydes CFCl 2 CHO and CF 2 ClCHO were positively observed as photooxidation products of CFCl 2 CH 3 (HCFC-141b) and CF 2 ClCO 3 (HCFC-142b), respectively. Their calculated 100% formation yields show conclusively that under lower tropospheric conditions the alkoxy radicals CFCl 2 -CH 2 O and CF 2 ClCH 2 O do not undergo C-C bond scission, but rather react with 0, to form the aldehydes and HO 2

The products of the gas-phase reactions of styrene and 2-vinylpyridine with O 3 , OH radicals, and NO 3 radicals have been studied at room temperature and atmospheric pressure of air. The reaction kinetics were also measured for those reactions not previously examined. The major products of the ozone reaction with styrene were formaldehyde and benzaldehyde, each with yields of ∼40%. The OH radical reaction with styrene also formed benzaldehyde and formaldehyde with yields of 63±6% and 72±7%, respectively. The reaction of styrene with the NO 3 radical formed equal, minor yields (ca. 11%) of HCHO and C 6 H 6 CHO, with the remaining unidentified products consisting of transient and stable species which contain ONO 2 , OONO 2 , and C=O groups

Formic acid is an ubiquitous component of urban smog. Sources of formic acid in urban air include direct emissions from vehicles and in situ reaction of ozone with olefins. Ambient levels of formic acid in southern California air were first measured some 15 years ago by Hanst et al. using long-path Fourier transform infrared spectroscopy (FTIR). All subsequent studies of formic acid in the Los Angeles area have involved the use of two methods, either FTIR or collection on alkaline traps followed by gas chromatography, ion chromatography, or liquid chromatography analysis with UV detection, ATLC-UV. The Carbon Species Methods Comparison Study (CSMCS), a multilaboratory air quality study carried out in August 1986 at a southern California smog receptor site, provided an opportunity for direct field comparison of the FTIR and alkaline trap methods. The results of the comparison are presented in this brief report.