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Although significant amounts of polymers associated with adverse health effects in oils are produced during frying, the chemical bonds forming these polymers are not well understood. This study revealed that ester bonds are responsible for the polymerization of soybean oil during frying and heating at 175 °C. The ester value of soybean oil increased during frying up to day 3 of the experiment and slightly decreased on day 4 of the experiment indicating that esterification and hydrolysis concomitantly occurred. The 13C NMR spectra showed further evidence of the formation of ester bonds. This study also examined unidentified chemical bonds in the polymer products, other than ester bonds, with NMR spectroscopy. No NMR signals indicating ether bonds were observed. The NMR study after the reaction of oxidized soybean oil with acetyl chloride clarified assignments of proton signals, confirming some previous assignments, and assigning a new proton signal as an alcohol.

The UV absorption spectra of CF(3)CHO, C(2)F(5)CHO, C(3)F(7)CHO, C(4)F(9)CHO, CF(3)CH(2)CHO, and C(6)F(13)CH(2)CHO were recorded over the range 225-400 nm at 249-297 K. C(x)F(2)(x)(+1)CHO and C(x)F(2)(x)(+1)CH(2)CHO have broad absorption features centered at 300-310 and 290-300 nm, respectively. The strength of the absorption increases with the size of the C(x)F(2)(x)(+1) group. There was no discernible (

Smog chamber/FTIR techniques were used to measure (Cl + n-CxF2x+1CHO, x = 1, 3, 4) = (2.1 ± 0.5) × 10-12 and k(OH + n-CxF2x+1CHO, x = 1, 3, 4) = (6.5 ± 1.2) × 10-13 cm3 molecule-1 s-1 in 700 Torr o...

The UVand IR spectra of CxF2x+1CHO (x = 1–4) were investigated using computational and experimental techniques. CxF2x+1CHO (x =1 – 4) have broad UV absorption features centered at 300–310 nm. The maximum absorption cross-section increases significantly and shifts slightly to the red with increased length of the CxF2x+1 group: CF3CHO, 3.10 � 10 � 20 (300 nm); C2F5CHO, 6.25 � 10 � 20 (308 nm); C3F7CHO, 8.96 � 10 � 20 (309 nm); and C4F9CHO, 10.9 � 10 � 20 (309 nm). IR spectra for CxF2x+1CHO were recorded, calculated, and assigned. Results are discussed with respect to the literature data and to the atmospheric fate of CxF2x+1CHO. # 2004 Elsevier B.V. All rights reserved.

The photolysis of Cl2 molecules in the presence of toluene and oxygen, at levels of ∼1014 radicals/cm-3, initiates a sequence of chemical reactions that rapidly produce an aerosol. Size distributions of the aerosol particles are examined, using a scanning mobility particle sizer, as a function of time, photolysis energy, the initial concentrations of toluene and chlorine, and of added NO and HO2. The number of particles and the volume of aerosol both exhibit a steep nonlinear increase as the initial chlorine atom level is raised. Surprisingly, the number of particles displays a strong inverse dependence on the initial toluene concentration, whereas the aerosol volume remains nearly unaffected by toluene level. Kinetic measurements of particle formation made using a flow reactor reveal an incubation period after initiation of the Cl + C6H5CH3 reaction, followed by steep increases in particle number and volume. The particle number rapidly reaches a plateau, whereas the aerosol volume continues to increase w...

Pulse radiolysis and FT-IR smog chamber experiments were used to investigate the atmospheric fate of C6H5O(•) radicals. Pulse radiolysis experiments gave σ(C6H5O(•))235 nm = (3.82 ± 0.48) × 10-17 cm2 molecule-1, k(C6H5O(•) + NO) = (1.88 ± 0.16) × 10-12, and k(C6H5O(•) + NO2) = (2.08 ± 0.15) × 10-12 cm3 molecule-1 s-1 at 296 K in 1000 mbar of SF6 diluent. No discernible reaction of C6H5O(•) radicals with O2 was observed in smog chamber experiments, and we derive an upper limit of k(C6H5O(•) + O2) < 5 × 10-21 cm3 molecule-1 s-1 at 296 K. These results imply that the atmospheric fate of phenoxy radicals in urban air masses is reaction with NOx. Density functional calculations and gas chromatography−mass spectrometry are used to identify 4-phenoxyphenol as the major product of the self-reaction of C6H5O(•) radicals. As part of this study, relative rate techniques were used to measure rate constants for reaction of Cl atoms with phenol [k(Cl + C6H5OH) = (1.93 ± 0.36) × 10-10], several chlorophenols [k(Cl + 2-c...

Real-time kinetic measurements are reported for the Cl + CH3CO CH2CO + HCl reaction. The experiments utilize infrared spectroscopy to determine the time dependence of the ketene formed via this reaction and of the CO produced from the subsequent rapid reaction between chlorine atoms and ketene. The reaction is investigated over a pressure range of 10–200 torr and a temperature range of 215–353 K. Within experimental error the rate constant under these conditions is k5a = (1.8 ± 0.5) × 10−10 cm3 s−1. We have also examined the Cl + CH2CO reaction and found it to have a rate constant of k6 = (2.5 ± 0.5) × 10−10 cm3 s−1 independent of temperature. © John Wiley & Sons, Inc. Int J Chem Kinet 29: 421–429, 1997.

The UV absorption spectrum and kinetics of the self reaction of CH 3 OCH 2 O 2 at 298 K have been studied using both the modulated photolysis of Cl 2 /CH 3 OCH 3 /O 2 /N 2 mixtures and the pulse radiolysis of SF 6 /CH 3 OCH 3 /O 2 mixtures. The spectrum, characterized in the range 200-290 nm, is in good agreement with the single published determinations. The observed second-order removal kinetics of CH 3 OCH 2 O 2 , k 5obs , were found to be sensitive to both the variation of total pressure (17-760 Torr) and the composition of the reaction mixtures: 2CH 3 OCH 2 O 2 →2CH 3 OCH 2 O+O 2 (5a); →CH 3 OCHO+CH 3 OCH 2 OH+O 2 (5b)

Fourier transform infrared spectroscopy, was used to identify CH 3 OCHO and CH 3 OCH 2 OOH as products of the gas-phase reaction of CH 3 OCH 2 O 2 radicals with HO 2 radicals. At 700 Torr and 295 ± 2 K, branching ratios of k 1a / k 1 = 0.53 ± 0.08 and k 1b / k 1 = 0.40 ± 0.04 were established. Quoted errors are 2 standard deviations together with our estimate of systematic uncertainties. (CH 3 OCH 2 O 2 +HO 2 →CH 3 OCH 2 OOH+O 2 (1a), CH 3 OCH 2 O 2 +HO 2 →CH 3 OCHO+O 2 +H 2 O (1b).) This result is discussed with respect to previous literature data and to computer models of atmospheric chemistry. As part of this work, the rate constants for the reaction of Cl atoms with CH 3 OCH 2 OOH and CH 3 OCHO were determined to be (6.1 ± 0.3) × 10 −11 and (1.4 ± 0.1) × 10 −12 cm 3 molecule −1 s −1 , respectively.

The ultraviolet absorption spectrum of CH 2 FO 2 radicals and the kinetics and mechanism of their self-reaction have been studied in the gas phase at 298 K. Two techniques have been used: pulse radiolysis UV absorption to measure the spectrum and kinetics and long path length Fourier transform infrared spectroscopy (FTIR) to identify and quantify the reaction products. Absorption cross sections were quantified over the wavelenght range 220-300 nm

The atmospheric reactivity of diethyl sulfate (DES) has been investigated. Upper limits to the rate constants (in cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}) for the homogeneous gas-phase reactions of DES with O{sub 3}, NH{sub 3}, and H{sub 2}O have been determined by FTIR spectroscopy and are 12 years with respect to ozone. With the possible exception of its reaction with water, these results indicate that the atmospheric fate of DES within an urban air parcel is not determined by its homogeneous gas-phase reactions with any of the atmospheric species studied. No evidence has been found for the formation of DES or related compounds during the ozonolysis of olefins in the presence of SO{sub 2} and ethanol.

The relative rate technique has been used to measure rate constants for the reaction of chlorine atoms with peroxyacetylnitrate (PAN), peroxypropionylnitrate (PPN), methylhydroperoxide, formic acid, acetone and butanone. Decay rates of these organic species were measured relative to one or more of the following reference compounds; ethene, ethane, chloroethane, chloromethane, and methane. Using rate constants of 9.29×10−11, 5.7×10−11, 8.04×10−12, 4.9×10−13, and 1.0×10−13 cm3 molecule−1 sec−1 for the reaction of Cl atoms with ethene, ethane, chloroethane, chloromethane, and methane respectively, the following rate constants were derived, in units of cm3 molecule−1 s−1: PAN

Relative rate techniques were used to study the kinetics of the reactions of Cl atoms and OH radicals with ethylene glycol diacetate, CH3C(O)O(CH2)2OC(O)CH3, in 700 Torr of N2/O2 diluent at 296 K. The rate constants measured were k(Cl + CH3C(O)O(CH2)2OC(O)CH3) = (5.7 +/- 1.1) x 10(-12) and k(OH + CH3C(O)O(CH2)2OC(O)CH3) = (2.36 +/- 0.34) x 10(-12) cm3 molecule-1 s-1. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the absence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)CH2OC(O)CH3, CH3C(O)OC(O)H, and CH3C(O)OH. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the presence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)H and CH3C(O)OH. The CH3C(O)OCH2O* radical is formed during the Cl atom initiated oxidation of ethylene glycol diacetate, and two loss mechanisms were identified: reaction with O2 to give CH3C(O)OC(O)H and alpha-ester rearrangement to give CH3C(O)OH and HC(O) radicals. The reaction of CH3C(O)OCH2O2* with NO gives chemically activated CH3C(O)OCH2O* radicals which are more likely to undergo decomposition via the alpha-ester rearrangement than CH3C(O)OCH2O* radicals produced in the peroxy radical self-reaction.

Smog chamber/FTIR techniques were used to study the atmospheric fate of n-C(x)F(2)(x)(+1)C(O) (x = 1, 2, 3, 4) radicals in 700 Torr O(2)/N(2) diluent at 298 +/- 3 K. A competition is observed between reaction with O(2) to form n-C(x)()F(2)(x)()(+1)C(O)O(2) radicals and decomposition to form n-C(x)F(2)(x)(+1) radicals and CO. In 700 Torr O(2)/N(2) diluent at 298 +/- 3 K, the rate constant ratio, k(n-C(x)F(2)(x)(+1)C(O) + O(2) --> n-C(x)F(2)(x)(+1)C(O)O(2))/k(n-C(x)F(2)(x)(+1)C(O) --> n-C(x)F(2)(x)(+1) + CO) = (1.30 +/- 0.05) x 10(-17), (1.90 +/- 0.17) x 10(-19), (5.04 +/- 0.40) x 10(-20), and (2.67 +/- 0.42) x 10(-20) cm(3) molecule(-1) for x = 1, 2, 3, 4, respectively. In one atmosphere of air at 298 K, reaction with O(2) accounts for 99%, 50%, 21%, and 12% of the loss of n-C(x)F(2)(x)(+1)C(O) radicals for x = 1, 2, 3, 4, respectively. Results are discussed with respect to the atmospheric chemistry of n-C(x)F(2)(x)(+1)C(O) radicals and their possible role in contributing to the formation of perfluorocarboxylic acids in the environment.