Shock-tube studies of the reactions of NO2 with NO2, SO2, and CO

The thermal decomposition of NO₂ and its atom-transfer reactions with SO₂ and CO have been studied behind incident shock waves using photometric detection methods. From the decomposition study it is possible to obtain information on the rate of the reaction 2NO₂ → antisymmetric-NO₃ + NO. The results on the reaction, NO₂ + SO₂ → NO + SO₃ extend the earlier work of Armitage and Cullis to about 2000°K. The reaction with CO [NO₂ +] [CO NO + CO₂] at shock temperatures is somewhat faster than predicted from available low-temperature data and provides a modification of the rate-constant expression that is applicable over a wide temperature range.     

Thermal decomposition of trifluoromethoxycarbonyl peroxy nitrate,CF3OC(O)O2NO2

The thermal decomposition of trifluoromethoxycarbonyl peroxy nitrate, CF₃OC(O)O₂NO₂, has been studied between 278 and 306 K at 270 mbar total pressure using He as a diluent gas. The pressure dependence of the reaction was also studied at 292 K between 1.2 and 270 mbar total pressure. The rate constant reaches its high‐pressure limit at 70 mbar. The first step of the decomposition leads to CF₃OC(O)O₂ and NO₂ formation, that is, CF₃OC(O)O₂NO₂ + M ? CF₃OC(O)O₂ + NO₂ + M (k₁, k_?1). Reaction (?1) was prevented by adding an excess of NO that reacts with the peroxy radical intermediate and leads to carbonyl fluoride (CF₂O), carbon dioxide (CO₂), nitrogen dioxide (NO₂), and small quantities of CF₃OC(O)O₂C(O)OCF₃. The kinetics of reaction (1) was determined by following the loss of CF₃OC(O)O₂NO₂ via IR spectroscopy. The temperature dependence of the decomposition follows the equation k₁(T) = 1.0 × 10¹⁶ e^{?((111±3)/(RT))} for the exponential term expressed in kJ mol^?1. The values obtained for the kinetic parameters such as k₁ at 298 K, the activation energy (E_a), and the preexponential factor (A) are compared with literature data for other acyl peroxy nitrates. The atmospheric thermal stability of CF₃OC(O)O₂NO₂ and its dependence with altitude is discussed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 831–838, 2008     

Theoretical study of the mechanism for the ClOO + NO reaction on the singlet potential energy surface

A detailed quantum chemical study is performed on the mechanism of ClOO + NO reaction at the B3LYP/6-311+G (2d) level of theory combined with CCSD (T) single point energy calculation. The possible product channels for the reaction are obtained and discussed on the basis of the singlet [ClNO₃] potential energy surface. The calculation indicates that the dominant product for the title reaction is ClO + NO₂ by the direct dissociation of the initial adduct, and the formation of the other products is much less likely since they are unfavorable kinetically. A comparison is also made between the title reaction and the analogous reaction of FO₂ + NO to gain a deeper insight into the mechanism of the XO₂ + NO reactions.     

Hemoglobin as a nitrite anhydrase: modeling methemoglobin-mediated N2O3 formation

Nitrite has recently been recognized as a storage form of NO in blood and as playing a key role in hypoxic vasodilation. The nitrite ion is readily reduced to NO by hemoglobin in red blood cells, which, as it happens, also presents a conundrum. Given NO’s enormous affinity for ferrous heme, a key question concerns how it escapes capture by hemoglobin as it diffuses out of the red cells and to the endothelium, where vasodilation takes place. Dinitrogen trioxide (N₂O₃) has been proposed as a vehicle that transports NO to the endothelium, where it dissociates to NO and NO₂. Although N₂O₃ formation might be readily explained by the reaction Hb‐Fe³⁺+NO₂^?+NO?Hb‐Fe²⁺+N₂O₃, the exact manner in which methemoglobin (Hb‐Fe³⁺), nitrite and NO interact with one another is unclear. Both an “Hb‐Fe³⁺‐NO₂^?+NO” pathway and an “Hb‐Fe³⁺‐NO+NO₂^?” pathway have been proposed. Neither pathway has been established experimentally. Nor has there been any attempt until now to theoretically model N₂O₃ formation, the so‐called nitrite anhydrase reaction. Both pathways have been examined here in a detailed density functional theory (DFT, B3LYP/TZP) study and both have been found to be feasible based on energetics criteria. Modeling the “Hb‐Fe³⁺‐NO₂^?+NO” pathway proved complex. Not only are multiple linkage‐isomeric (N‐ and O‐coordinated) structures conceivable for methemoglobin–nitrite, multiple isomeric forms are also possible for N₂O₃ (the lowest‐energy state has an N? N‐bonded nitronitrosyl structure, O₂N? NO). We considered multiple spin states of methemoglobin–nitrite as well as ferromagnetic and antiferromagnetic coupling of the Fe³⁺ and NO spins. Together, the isomerism and spin variables result in a diabolically complex combinatorial space of reaction pathways. Fortunately, transition states could be successfully calculated for the vast majority of these reaction channels, both M_S=0 and M_S=1. For a six‐coordinate Fe³⁺‐O‐nitrito starting geometry, which is plausible for methemoglobin–nitrite, we found that N₂O₃ formation entails barriers of about 17–20 kcal mol^?1, which is reasonable for a physiologically relevant reaction. For the “Hb‐Fe³⁺‐NO+NO₂^?” pathway, which was also found to be energetically reasonable, our calculations indicate a two‐step mechanism. The first step involves transfer of an electron from NO₂^? to the Fe³⁺–heme–NO center ({FeNO}⁶) , resulting in formation of nitrogen dioxide and an Fe²⁺–heme–NO center ({FeNO}⁷). Subsequent formation of N₂O₃ entails a barrier of only 8.1 kcal mol^?1. From an energetics point of view, the nitrite anhydrase reaction thus is a reasonable proposition. Although it is tempting to interpret our results as favoring the “{FeNO}⁶+NO₂^?” pathway over the “Fe³⁺‐nitrite+NO” pathway, both pathways should be considered energetically reasonable for a biological reaction and it seems inadvisable to favor a unique reaction channel based solely on quantum chemical modeling.     

Theoretical Study on the Formation of H‐ and O‐Atoms,HONO, OH,NO, and NO2 from the Lowest Lying Singlet and Triplet States in Ortho‐Nitrophenol Photolysis

The photolysis of nitrophenols was proposed as a source of reactive radicals and NOx compounds in polluted air. The S₀ singlet ground state and T₁ first excited triplet state of nitrophenol were investigated to assess the energy dependence of the photofragmentation product distribution as a function of the reaction conditions, based on quantum chemical calculations at the G3SX//M06–2X/aug‐cc‐pVTZ level of theory combined with RRKM master equation calculations. On both potential energy surfaces, we find rapid isomerization with the aci‐nitrophenol isomer, as well as pathways forming NO, NO₂, OH, HONO, and H‐, and O‐atoms, extending earlier studies on the T₁ state and in agreement with available work on other nitroaromatics. We find that accessing the lowest photofragmentation channel from the S₀ ground state requires only 268 kJ/mol of activation energy, but at a pressure of 1 atm collisional energy loss dominates such that significant fragmentation only occurs at internal energies exceeding 550 kJ/mol, making this surface unimportant for atmospheric photolysis. Intersystem crossing to the T₁ triplet state leads more readily to fragmentation, with dissociation occurring at energies of ～450 kJ/mol above the singlet ground state even at 1 atm. The main product is found to be OH + nitrosophenoxy, followed by formation of hydroxyphenoxy + NO and phenyloxyl + HONO. The predictions are compared against available experimental data.     

Kinetic modeling of the CO/H2O/O2/NO/SO2 system: Implications for high‐pressure fall‐off in the SO2 + O(+M) = SO3(+M) reaction

Flow reactor experiments were performed to study moist CO oxidation in the presence of trace quantities of NO (0–400 ppm) and SO₂ (0–1300 ppm) at pressures and temperatures ranging from 0.5–10.0 atm and 950–1040 K, respectively. Reaction profile measurements of CO, CO₂, O₂, NO, NO₂, SO₂, and temperature were used to further develop and validate a detailed chemical kinetic reaction mechanism in a manner consistent with previous studies of the CO/H₂/O₂/NO_X and CO/H₂O/N₂O systems. In particular, the experimental data indicate that the spin‐forbidden dissociation‐recombination reaction between SO₂ and O‐atoms is in the fall‐off regime at pressures above 1 atm. The inclusion of a pressure‐dependent rate constant for this reaction, using a high‐pressure limit determined from modeling the consumption of SO₂ in a N₂O/SO₂/N₂ mixture at 10.0 atm and 1000 K, brings model predictions into much better agreement with experimentally measured CO profiles over the entire pressure range. Kinetic coupling of NO_X and SO_X chemistry via the radical pool significantly reduces the ability of SO₂ to inhibit oxidative processes. Measurements of SO₂ indicate fractional conversions of SO₂ to SO₃ on the order of a few percent, in good agreement with previous measurements at atmospheric pressure. Modeling results suggest that, at low pressures, SO₃ formation occurs primarily through SO₂ + O(+M) = SO₃(+M), but at higher pressures where the fractional conversion of NO to NO₂ increases, SO₃ formation via SO₂ + NO₂ = SO₃ + NO becomes important. For the conditions explored in this study, the primary consumption pathways for SO₃ appear to be SO₃ + HO₂ = HOSO₂ + O₂ and SO₃ + H = SO₂ + OH. Further study of these reactions would increase the confidence with which model predictions of SO₃ can be viewed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 317–339, 2000     

Theoretical study on the mechanism of OH + HCNO reaction

A detailed mechanistic study of the OH + HCNO reaction, in which the products P _i with i=1, 2, . . . ,7 are involved, is carried out by means of CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p)+ZPVE computatio-nal method to determine a set of reasonable pathways. It is shown that P ₆ (CO + H₂NO) and P ₃ (HNO +HCO) are the major product channels with a minor contribution from P ₅ (NO + H₂CO), whereas the other channels for P ₁ (H₂O + NCO), P ₂ (NH₂ + CO₂), P ₄ (HCN + HO₂) and P ₇(CO + H₂ + NO) are less favorable. All these theoretical results are in harmony with experimental facts.     

Study of the HNO + HNO and HNO + NO reactions by intracavity laser spectroscopy

Flash photolysis of CH₃CHO and H₂CO in the presence of NO has been investigated by the intracavity laser spectroscopy technique. The decay of HNO formed by the reaction HCO + NO → HNO + CO was studied at NO pressures of 6.8–380 torr. At low NO pressure HNO was found to decay by the reaction HNO + HNO → N₂O + H₂O. The rate constant of this reaction was determined to be k₁ = (1.5 ± 0.8) × 10^?15 cm³/s. At high NO pressure the reaction HNO + NO → products was more important, and its rate constant was measured to be k₂ = (5 ± 1.5) × 10^?19 cm³/s. NO₂ was detected as one of the products of this reaction. Alternative mechanisms for this reaction are discussed.     

Proton‐Transfer Reaction Dynamics and Energetics in Calcification and Decalcification

CaCO₃‐saturated saline waters at pH values below 8.5 are characterized by two stationary equilibrium states: reversible chemical calcification/decalcification associated with acid dissociation, Ca²⁺+HCO₃^??CaCO₃+H⁺; and reversible static physical precipitation/dissolution, Ca²⁺+CO₃^2??CaCO₃. The former reversible reaction was determined using a strong base and acid titration. The saturation state described by the pH/P_CO2‐independent solubility product, [Ca²⁺][CO₃^2?], may not be observed at pH below 8.5 because [Ca²⁺][CO₃^2?]/([Ca²⁺][HCO₃^?]) ?1. Since proton transfer dynamics controls all reversible acid dissociation reactions in saline waters, the concentrations of calcium ion and dissolved inorganic carbon (DIC) were expressed as a function of dual variables, pH and P_CO2. The negative impact of ocean acidification on marine calcifying organisms was confirmed by applying the experimental culture data of each P_CO2/pH‐dependent coral polyp skeleton weight (Wskel) to the proton transfer idea. The skeleton formation of each coral polyp was performed in microspaces beneath its aboral ectoderm. This resulted in a decalcification of 14 weight %, a normalized CaCO₃ saturation state Λ of 1.3 at P_CO2 ≈400 ppm and pH ≈8.0, and serious decalcification of 45 % and Λ 2.5 at P_CO2 ≈1000 ppm and pH ≈7.8.     

Radical–molecule reaction CH<Subscript>2</Subscript>Cl + NO<Subscript>2</Subscript>: a mechanistic study

The radical–molecule reaction mechanism of CH₂Cl with NO₂ has been explored theoretically at the B3LYP/6–311G(d,p) and MC–QCISD (single-point) levels of theory. Our results indicate that the title reaction proceeds mostly through singlet pathways, less go through triplet pathways. The initial association between CH₂Cl and NO₂ is found to be the carbon-to-nitrogen attack forming the adduct a H₂ClCNO₂ with no barrier, followed by isomerization to b ₁ H₂ClCONO-trans which can easily convert to b ₂ H₂ClCONO-cis. Subsequently, the most feasible pathway is the C–Cl and O–N bonds cleavage along with the N–Cl bond formation of b (b ₁ , b ₂ ) leading to product P ₁ CH₂O + ClNO, which can further dissociate to give P ₅ CH₂O + Cl + NO. The second competitive pathway is the 1,3-H-shift associated with O–N bond rupture of b ₁ to form P ₂ CHClO + HNO. Because the intermediates and transition states involved in the above two favorable channels all lie below the reactants, the CH₂Cl+NO₂ reaction is expected to be rapid, as is confirmed by experiment. The present results can lead us to understand deeply the mechanism of the title reaction and may be helpful for further experimental investigation of the reaction.     

An FTIR product study of the reaction between HCO and NO2

The product distribution of the reaction (1a) $$\rm\longrightarrow OH+NO+CO$$ (1b) $$\rm\longrightarrow HNO+CO_{2}$$ (1c) $$\rm\longrightarrow H+NO+CO_{2}$$ (1d) $$\rm\longrightarrow HCO_{2}+NO$$ (1e) (1f) (1g) was investigated at room temperature in the gas phase in Ar buffer gas at 570 mbar pressure by Fourier transform infrared (FTIR) spectroscopy. Mixtures of NO₂/H₂CO/Ar were photolyzed under stationary conditions using a high‐pressure Hg lamp at λ = 300–340 nm. NO, CO, CO₂, HONO, and H₂O were found as major reaction products. A small amount of N₂O was detected at long reaction times. From the yields of CO and CO₂, branching ratios were found to be (k_1a + k_1b)/k₁ = (0.66 ± 0.10) and (k_1c + k_1d + k_1e)/k₁ = (0.34 ± 0.10). The formation of HONO was attributed to reaction ( 1a ) and/or reaction ( 1c ) followed by the reaction HNO + NO₂ → NO + HONO with a combined branching ratio of (k_1a + k_1c)/k₁ = (0.28 ± 0.10). © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 136–145, 2000     

Thermal reaction of CH2O with NO2 in the temperature range of 393–476 K: FTIR product measurement and kinetic modeling

The thermal reaction of CH₂O with NO₂ has been investigated in the temperature range of 393–476 K by means of FTIR product analysis. Kinetic modeling of the measured CH₂O, NO, CO, and CO₂ concentration time profiles under varying reaction conditions gave rise to the rate constants for the following key reactions: (1) and (2) The error limits shown represent only the scatter (±1 σ) of the modeled values. In the modeling, the total rate constant for the CHO + NO₂ reaction, k₂ + k₃, was not varied and the value reported by Gutman and co-workers (ref. [8]) was used for the whole temperature range investigated here. The proposed reaction mechanism, employing these newly established rate constants, can quantitively account for nearly all measured product yields, including the [CO]/([CO] + [CO₂]) ratios reported by earlier workers.     

15N Chemically Induced Dynamic Nuclear Polarization (15N‐CIDNP) Investigations of the Peroxynitrite Decay and Nitration of N‐Acetyl‐L‐tyrosine

During the decay of (¹⁵N)peroxynitrite (O?¹⁵NOO ^? ) in the presence of N‐acetyl‐L ‐tyrosine (Tyrac) in neutral solution and at 268 K, the ¹⁵N‐NMR signals of ¹⁵NO and ¹⁵NO show emission (E) and enhanced absorption (A) as it has already been observed by Butler and co‐workers in the presence of L ‐tyrosine (Tyr). The effects are built up in radical pairs [CO , ¹⁵NO ]^S formed by O? O bond scission of the (¹⁵N)peroxynitrite? CO₂ adduct (O?¹⁵NO? OCO ). In the absence of Tyrac and Tyr, the peroxynitrite decay rate is enhanced, and ¹⁵N‐CIDNP does not occur. This is explained by a chain reaction during the peroxynitrite decay involving N₂O₃ and radicals NO ^. and NO . The interpretation is supported by ¹⁵N‐CIDNP observed with (¹⁵N)peroxynitrite generated in situ during reaction of H₂O₂ with N‐acetyl‐N‐(¹⁵N)nitroso‐dl ‐tryptophan ((¹⁵N)NANT) at 298 K and pH 7.5. In the presence of Na¹⁵NO₂ at pH 7.5 and in acidic solution, ¹⁵N‐CIDNP appears in the nitration products of Tyrac, 1‐(¹⁵N)nitro‐N‐acetyl‐L ‐tyrosine (1‐¹⁵NO₂‐Tyrac) and 3‐(¹⁵N)nitro‐N‐acetyl‐L ‐tyrosine (3‐¹⁵NO₂‐Tyrac). The effects are built up in radical pairs [Tyrac ^. , ¹⁵NO ]^F formed by encounters of independently generated radicals Tyrac ^. and ¹⁵NO . Quantitative ¹⁵N‐CIDNP studies show that nitrogen dioxide dependent reactions are the main if not the only pathways for yielding both nitrate and nitrated products.     

Kinetics of HCCl + NOx reactions

The kinetics of reactions of HCCl with NO and NO₂ were investigated over the temperature ranges 298–572 k and 298–476 k, respectively, using laser‐induced fluorescence spectroscopy to measure total rate constants and time‐resolved infrared diode laser absorption spectroscopy to probe reaction products. Both reactions are fast, with k(HCCl + NO) = (2.75 ± 0.2) × 10^?11 cm³ molecule^?1 s^?1 and k(HCCl + NO₂) = (1.10 ± 0.2) × 10^?10 cm³ molecule^?1 s^?1 at 296 K. Both rate constants displayed only a slight temperature dependence. Detection of products in the HCCl + NO reaction at 296 K indicates that HCNO + Cl is the major product with a branching ratio of ? = 0.68 ± 0.06, and NCO + HCl is a minor channel with ? = 0.24 ± 0.04. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 12–17, 2002     

Theoretical study on the reaction of CN radicals with ClO radicals by density functional theory

The reaction mechanism of CN radicals with ClO radicals has been studied theoretically using ab initio and density functional theory (DFT). The result shows that the main reaction path is the O atom in radical ClO attacks the C atom in radical CN to compose the intermediate 1 ClOCN. Three thermodynamically accessible prodncts, P₁ (CO+ClN), P₃ (NO+CCl), and P₄ (ClNCO), were obtained from intermediate 1 through isomerization and decomposition reactions. P₄ is the primary product, and P₁ and P₃ are the secondary product. Compared with the singlet potential energy surface, the contribution of the triplet potential energy surface can be ignored.     

Catalytic NO Reduction by NO Pre-Adsorbed RhCeO2NO− Clusters

A fundamental understanding on the dynamically structural evolution of catalysts induced by reactant gases under working conditions is challenging but pivotal in catalyst design. Herein, in combination with state-of-the-art mass spectrometry for cluster reactions, cryogenic photoelectron imaging spectroscopy, and quantum-chemical calculations, we identified that NO adsorption on rhodium-cerium bimetallic oxide cluster RhCeO₂⁻ can create a Ce³⁺ ion in product RhCeO₂NO⁻ that serves as the starting point to trigger the catalysis of NO reduction by CO. Theoretical calculations substantiated that the reduction of another two NO molecules into N₂O takes place exclusively on the Ce³⁺ ion while Rh behaves like a promoter to buffer electrons and cooperates with Ce³⁺ to drive NO reduction. Our finding demonstrates the importance of NO in regulating the catalytic behavior of Rh under reaction conditions and provides much-needed insights into the essence of NO reduction over Rh/CeO₂, one of the most efficient components in three-way catalysts for NO_x removal.     

Substituent Effect on the Electronic Properties and Nature of the W≡C Bond in trans‐Cl(OC)(H3P)3W(≡C‐para‐C6H4X) (X = H,F, SiH3, CN,NO2, SiMe3, CMe3, NH2, NMe2) Complexes: A Computational Quantum Chemistry Study

In this investigation, we describe substituent effect on the dipole moment, ionization potential, electron affinity, structure, frontier orbitals energy, in the trans‐Cl(OC)(H₃P)₃W(≡C‐para‐C₆H₄X) (X = H, F, SiH₃, CN, NO₂, SiMe₃, CMe₃, NH₂, NMe₂) complexes using MPW1PW91 quantum chemical calculations. The nature of chemical bond between the [Cl(OC)(H₃P)₃W]⁻ and [C‐para‐C₆H₄X]⁺ fragments was illustrated with energy decomposition analysis (EDA). Percentage composition in terms of the defined groups of frontier orbitals for these complexes was inspected to investigate the character in metal–ligand bonds. Quantum theory of atoms in molecules (QTAIM) was used for illustration of metal–ligand bonds in these complexes.     

Theoretical study on reaction mechanism of the fluoromethylene radical with nitrogen dioxide

The complex doublet potential energy surface for the reaction of 1CHF with NO2, including 14 minimum isomers and 30 transition states, is explored theoretically at the B3LYP/6-311G(d,p) and CCSD(T)/6-311G(d,p) (single-point) levels of theory. The initial association between 1CHF and NO2 is found to be the carbon-to-middle-nitrogen attack forming an energy-rich adduct a (HFCNO2) with no barrier, followed by concerted O-shift and C--N bond rupture leading to product P2 (NO + HFCO), which is the most abundant. In addition, a can take a 1,3-H-shift to isomer b (FCN(O)OH) followed by the dissociation to form the second feasible product P4 (OH + FCNO). The least favorable pathway is that b undergoes a concerted OH-shift to form d (HO(F)CNO), which will dissociate to product P5 (HF+OCNO) via side HF-elimination. The secondary dissociation of P5 may form product P7 (HF+NO+CO) easily. Furthermore, the 1CHF attack at the end-O of NO2 is a barrier-consumed process, and thus may only be of significance at high temperatures. The comparison with the analogous reactions 1CHCl + NO2 is discussed. The present study may be helpful for probing the mechanism of the title reaction and understanding the halogenated carbine chemistry.     

Economizing on Precious Metals in Three‐Way Catalysts: Thermally Stable and Highly Active Single‐Atom Rhodium on Ceria for NO Abatement under Dry and Industrially Relevant Conditions**

We show for the first time that atomically dispersed Rh cations on ceria, prepared by a high‐temperature atom‐trapping synthesis, are the active species for the (CO+NO) reaction. This provides a direct link with the organometallic homogeneous Rh^I complexes capable of catalyzing the dry (CO+NO) reaction. The thermally stable Rh cations in 0.1 wt % Rh₁/CeO₂ achieve full NO conversion with a turn‐over‐frequency (TOF) of around 330 h^?1 per Rh atom at 120 °C. Under dry conditions, the main product above 100 °C is N₂ with N₂O being the minor product. The presence of water promotes low‐temperature activity of 0.1 wt % Rh₁/CeO₂. In the wet stream, ammonia and nitrogen are the main products above 120 °C. The uniformity of Rh ions on the support, allows us to detect the intermediates of (CO+NO) reaction via IR measurements on Rh cations on zeolite and ceria. We also show that NH₃ formation correlates with the water gas shift (WGS) activity of the material and detect the formation of Rh hydride species spectroscopically.     

Atmospheric chemistry of HFC-134a: Kinetics of the decomposition of the alkoxy radical CF3CFHO

Decomposition of the CF₃CFHO radical formed in the reaction of CF₃CFHO₂ radicals with NO was studied at 296 and 393 K using a pulse radiolysis transient VIS-UV absorption absolute rate technique. At room temperature in 1 atmosphere of SF₆ diluent it was found that the majority (79 ± 20)% of CF₃CFHO radicals formed in the CF₃CFHO₂ + NO reaction decompose within 3 μs via C(SINGLE BOND)C bond scission. This result is discussed with respect to the current understanding of the atmospheric degradation of HFC-134a. As a part of the present work the rate constant ratio k_CF3CFH+02/k_CF3CFH+NO was determined to be 0.144 ± 0.029 in one atmosphere of SF₆ diluent at 296 K. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 209–217, 1997.