Kinetics of the reactions of the IO radical with dimethyl sulfide,methanethiol, ethylene,and propylene

The reactions of IO radicals with CH₃SCH₃, CH₃SH, C₂H₄, and C₃H₆ have been studied using the discharge flow method with direct detection of IO radicals by mass spectrometry. The absolute rate constants obtained at 298 K are the following: IO + CH₃SCH₃ → products (1): k₁ = (1.5 ± 0.2) × 10^?14; IO + CH₃SH → products (2): k₂ = (6.6 ± 1.3) × 10^?16; IO + C₂H₄ →products (3): k₃ < 2 × 10^?16; IO + C₃H₆ → products (4): k₄ < 2 × 10^?16 (units are cm³ molecule^?1 s^?1). CH₃S(O)CH₃ and HOI were found as products of reactions (1) and (2), respectively. The present lower value of k₁ compared to our previous determination is discussed.     

Kinetics of phenyl radical reactions with propane,n‐butane,n‐hexane,and n‐octane: Reactivity of C6H5 toward the secondary C?H bond of alkanes

The kinetics of C₆H₅ reactions with n‐C_nH_2n+2 (n = 3, 4, 6, 8) have been studied by the pulsed laser photolysis/mass spectrometric method using C₆H₅COCH₃ as the phenyl precursor at temperatures between 494 and 1051 K. The rate constants were determined by kinetic modeling of the absolute yields of C₆H₆ at each temperature. Another major product C₆H₅CH₃ formed by the recombination of C₆H₅ and CH₃ could also be quantitatively modeled using the known rate constant for the reaction. A weighted least‐squares analysis of the four sets of data gave k (C₃H₈) = (1.96 ± 0.15) × 10¹¹ exp[?(1938 ± 56)/T], and k (n‐C₄H₁₀) = (2.65 ± 0.23) × 10¹¹ exp[?(1950 ± 55)/T] k (n‐C₆H₁₄) = (4.56 ± 0.21) × 10¹¹ exp[?(1735 ± 55)/T], and k (n?C₈H₁₈) = (4.31 ± 0.39) × 10¹¹ exp[?(1415 ± 65)T] cm³ mol^?1 s^?1 for the temperature range studied. For the butane and hexane reactions, we have also applied the CRDS technique to extend our temperature range down to 297 K; the results obtained by the decay of C₆H₅ with CRDS agree fully with those determined by absolute product yield measurements with PLP/MS. Weighted least‐squares analyses of these two sets of data gave rise to k (n?C₄H₁₀) = (2.70 ± 0.15) × 10¹¹ exp[?(1880 ± 127)/T] and k (n?C₆H₁₄) = (4.81 ± 0.30) × 10¹¹ exp[?(1780 ± 133)/T] cm³ mol^?1 s^?1 for the temperature range 297‐‐1046 K. From the absolute rate constants for the two larger molecular reactions (C₆H₅ + n‐C₆H₁₄ and n‐C₈H₁₈), we derived the rate constant for H‐abstraction from a secondary C? H bond, k_s?CH = (4.19 ± 0.24) × 10¹⁰ exp[?(1770 ± 48)/T] cm³ mol^?1 s^?1. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 49–56, 2004     

The reactions of hydrogen atoms with bis(trifluoromethyl)disulfide

The reactions of hydrogen atoms produced by the mercury-photosensitized decomposition of H₂ with bis(trifluoromethyl)disulfide has been studied. The rate coefficient for the primary reaction, H + CF₃SSCF₃ → CF₃SH + CF₃S, was determined in competition with the reaction H + C₂H₄S → SH + C₂H₄ to have the value k = (3.0 ± 0.18) × 10¹⁴ exp[-(4560 ± 140)/RT] cm³ mol^?1 S^?1. The high A factor can be partially accounted for by assuming free rotation for the two CF₃ groups and the SCF₃ groups about the S—S bond in the transition state. The relatively high activation energy is attributed to inductive and orbital overlap effects. CH₃SH, H₂S, and CF₃SH all react with CF₃SSCF₃ to yield solid complexes which were not explored further.     

Selected rate constants for H,O, N,and Cl atoms with substrates at room temperatures

Rate constants for H + Cl₂, H + CH₃CHO, H + C₃H₄, O + C₃H₆, O + CH₃CHO, and Cl + CH₄ have been measured at room temperature by the discharge flow—resonance fluorescence technique. The results are (1.6 ± 0.1) × 10^?11, (9.8 ± 0.8) × 10 ^?14, (6.3 ± 0.4) × 10^{?13) (2.00 torr He), (3.95 ± 0.41) × 10?12, (4.9 ± 0.5) × 10|su?13} and (1.08 ± 0.07) × 10^?13, respectively, all in units of cm³ molecule^?1 s^?1. Also N atom reactions with C₂H₂, C₂H₄, C₃H₄, and C₃H₆ were studied but in no case was there an appreciable rate constant. These results are compared to previous studies.     

Reaction of hydrogen atoms with diethyldisulfide and ethylmethyldisulfide

H atoms react with C₂H₅SSC₂H₅ to give C₂H₅SH as the sole retrievable product with ? = 2.32 at 25°C and 2.84 at 145°C. The primary reaction is postulated to be H + C₂H₅SSC₂H₅ ← C₂H₅SH + C₂H₅S with k₁ = (4.73 ± 0.64) × 10¹³ exp [?(1710 ± 69)/RT] cm³/mol·s relative to the rate constant of the H + C₂H₄ ← C₂H₅ reaction. The high value of the entropy of activation suggests the presence of partial hydrogen bonding in diethyldisulfide which is broken in the transition state. Ethylmethyldisulfide reacts similarly: H + C₂H₅SSCH₃ ← C₂H₅SH + CH₃S or CH₃SH + C₂H₅S. The thiyl radicals propagate a chain of radical exchange reactions forming the symmetrical disulfides with exposure-time-dependent quantum yields. The overall kinetics conform to a 16-step mechanism from which the rate constants of the elementary reactions could be established by computer modeling. Thiyl radicals react considerably more slowly with disulfides than H atoms.     

Kinetics of the reactions of C2H5, n‐C3H7, and n‐C4H9 radicals with Cl2 at the temperature range 190–360 K

The kinetics of the C₂H₅ + Cl₂, n‐C₃H₇ + Cl₂, and n‐C₄H₉ + Cl₂ reactions has been studied at temperatures between 190 and 360 K using laser photolysis/photoionization mass spectrometry. Decays of radical concentrations have been monitored in time‐resolved measurements to obtain reaction rate coefficients under pseudo‐first‐order conditions. The bimolecular rate coefficients of all three reactions are independent of the helium bath gas pressure within the experimental range (0.5–5 Torr) and are found to depend on the temperature as follows (ranges are given in parenthesis): k(C₂H₅ + Cl₂) = (1.45 ± 0.04) × 10^?11 (T/300 K)^{?1.73 ± 0.09} cm³ molecule^?1 s^?1 (190–359 K), k(n‐C₃H₇ + Cl₂) = (1.88 ± 0.06) × 10^?11 (T/300 K)^{?1.57 ± 0.14} cm³ molecule^?1 s^?1 (204–363 K), and k(n‐C₄H₉ + Cl₂) = (2.21 ± 0.07) × 10^?11 (T/300 K)^{?2.38 ± 0.14} cm³ molecule^?1 s^?1 (202–359 K), with the uncertainties given as one‐standard deviations. Estimated overall uncertainties in the measured bimolecular reaction rate coefficients are ±20%. Current results are generally in good agreement with previous experiments. However, one former measurement for the bimolecular rate coefficient of C₂H₅ + Cl₂ reaction, derived at 298 K using the very low pressure reactor method, is significantly lower than obtained in this work and in previous determinations. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 614–619, 2007     

Kinetic study of reactions of C2H5O2 with NO at 298 K and 0.55 – 2 torr

The kinetics of C₂H₅O₂ and C₂H₅O₂ radicals with NO have been studied at 298 K using the discharge flow technique coupled to laser induced fluorescence (LIF) and mass spectrometry analysis. The temporal profiles of C₂H₅O were monitored by LIF. The rate constant for C₂H₅O + NO → Products (2), measured in the presence of helium, has been found to be pressure dependent: k₂ = (1.25±0.04) × 10^?11, (1.66±0.06) × 10^?11, (1.81±0.06) × 10^?11 at P (He) = 0.55, 1 and 2 torr, respectively (units are cm³ molecule^?1 s^?1). The Lindemann-Hinshelwood analysis of these rate constant data and previous high pressure measurements indicates competition between association and disproportionation channels: C₂H₅O + NO + M → C₂H₅ONO + M (2a), C₂H₅O + NO → CH₃CHO + HNO (2b). The following calculated average values were obtained for the low and high pressure limits of k_2a and for k_2b : k = (2.6±1.0) × 10^?28 cm⁶ molecule^?2 s^?1, k = (3.1±0.8) × 10^?11 cm³ molecule^?1 s^?1 and k_2b ca. 8 × 10^?12 cm³ molecule^?1 s^?1. The present value of k, obtained with He as the third body, is significantly lower than the value (2.0±1.0) × 10^?27 cm⁶ molecule^?2 s^?1 recommended in air. The rate constant for the reaction C₂H₅O₂ + NO → C₂H₅O + NO₂ (3) has been measured at 1 torr of He from the simulation of experimental C₂H₅O profiles. The value obtained for k₃ = (8.2±1.6) × 10^?12 cm³ molecule^?1 s^?1 is in good agreement with previous studies using complementary methods. © 1995 John Wiley & Sons, Inc.     

Kinetics of hydroxyl radical reactions with formaldehyde and 1,3,5-trioxane between 290 and 600 K

Absolute rate constants are measured for the reactions: OH + CH₂O, over the temperature range 296–576 K and for OH + 1,3,5-trioxane over the range 292–597 K. The technique employed is laser photolysis of H₂O₂ or HNO₃ to produce OH, and laser-induced fluorescence to directly monitor the relative OH concentration. The results fit the following Arrhenius equations: k (CH₂O) = (1.66 ± 0.20) × 10^?11 exp[?(170 ± 80)/RT] cm³ s^?1 and k(1,3,5-trioxane) = (1.36 ± 0.20) × 10^?11 exp[?(460 ± 100)/RT] cm³ s^?1. The transition-state theory is employed to model the OH + CH₂O reaction and extrapolate into the combustion regime. The calculated result covering 300 to 2500 K can be represented by the equation: k(CH₂O) = 1.2 × 10^?18 T^2.46 exp(970/RT) cm³ s^?1. An estimate of 91 ± 2 kcal/mol is obtained for the first C? H bond in 1,3,5-trioxane by using a correlation of C? H bond strength with measured activation energies.     

Kinetics of the reactions of atomic chlorine with H2S,D2S,CH3SH,and CD3SD

Time-resolved resonance fluorescence detection of atomic chlorine following 266-nm laser flash photolysis of Cl₂CO/RSR'/N₂ mixtures has been employed to study the kinetics of Cl reactions with H₂S(k₁), CH₃SH(k₂), D₂S(k₃), and CD₃SD(k₄) as a function of temperature (193–431 K) and pressure (25–600 torr). Arrhenius expressions which describe our results are (units are 10^?11 cm³molecule^?1s^?1; uncertainties are 2σ, precision only) k₁ = (3.69 ± 0.33) exp[(208 ± 24)/T], k₂ = (11.9 ± 1.7) exp[(151 ± 38)/T], and k₃ = (1.93 ± 0.32) exp[(168 ± 42)/T]. The Cl + CD₃SD reaction has been studied at 299 K and 396 K; values for k₄ at these two temperatures are essentially the same as those measured for k₂. Our results are compared with earlier studies and the mechanistic implications of observed negative activation energies and H? D kinetic isotope effects are discussed. © 1995 John Wiley & Sons, Inc.     

Gas‐phase reactions of Cl atoms with propane,n‐butane,and isobutane

Using the relative kinetic method, rate coefficients have been determined for the gas‐phase reactions of chlorine atoms with propane, n‐butane, and isobutane at total pressure of 100 Torr and the temperature range of 295–469 K. The Cl₂ photolysis (λ = 420 nm) was used to generate Cl atoms in the presence of ethane as the reference compound. The experiments have been carried out using GC product analysis and the following rate constant expressions (in cm³ molecule^?1 s^?1) have been derived: (7.4 ± 0.2) × 10^?11 exp [‐(70 ± 11)/ T], Cl + C₃H₈ → HCl + CH₃CH₂CH₂; (5.1 ± 0.5) × 10^?11 exp [(104 ± 32)/ T], Cl + C₃H₈ → HCl + CH₃CHCH₃; (7.3 ± 0.2) × 10^?11 exp[?(68 ± 10)/ T], Cl + n‐C₄H₁₀ → HCl + CH₃ CH₂CH₂CH₂; (9.9 ± 2.2) × 10^?11 exp[(106 ± 75)/ T], Cl + n‐C₄H₁₀ → HCl + CH₃CH₂CHCH₃; (13.0 ± 1.8) × 10^?11 exp[?(104 ± 50)/ T], Cl + i‐C₄H₁₀ → HCl + CH₃CHCH₃CH₂; (2.9 ± 0.5) × 10^?11 exp[(155 ± 58)/ T], Cl + i‐C₄H₁₀ → HCl + CH₃CCH₃CH₃ (all error bars are ± 2σ precision). These studies provide a set of reaction rate constants allowing to determine the contribution of competing hydrogen abstractions from primary, secondary, or tertiary carbon atom in alkane molecule. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 651–658, 2002     

The rate of the reactions of C2O radicals with H and H2

The rate constants for the reactions C₂O + H → products (1) and C₂O + H₂ → products (2) have been determined at room temperature by means of laser-induced fluorescence detection of C₂O radicals, generated either by the KrF excimer laser photolysis Of C₃O₂, or by the reaction of C₃O₂ with O atoms. Values of k₁ = (3.7 ± 1.0) × 10^?11 cm³ s^?1 and k₂ = (7 ± 3) × 10^?13 cm³ s^?1 were obtained.     

Rate constants for the elementary reactions between CN radicals and CH4, C2H6, C2H4, C3H6, and C2H2 in the range: 295 ⩽ T/K ⩽ 700

Pulsed laser photolysis, time-resolved laser-induced fluorescence experiments have been carried out on the reactions of CN radicals with CH₄, C₂H₆, C₂H₄, C₃H₆, and C₂H₂. They have yielded rate constants for these five reactions at temperatures between 295 and 700 K. The data for the reactions with methane and ethane have been combined with other recent results and fitted to modified Arrhenius expressions, k(T) = A′(298) (T/298)ⁿ exp(?θ/T), yielding: for CH₄, A′(298) = 7.0 × 10^?13 cm³ molecule^?1 s^?1, n = 2.3, and θ = ?16 K; and for C₂H₆, A′(298) = 5.6 × 10^?12 cm³ molecule^?1 s^?1, n = 1.8, and θ = ?500 K. The rate constants for the reactions with C₂H₄, C₃H₆, and C₂H₂ all decrease monotonically with temperature and have been fitted to expressions of the form, k(T) = k(298) (T/298)ⁿ with k(298) = 2.5 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.24 for CN + C₂H₄; k(298) = 3.4 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.19 for CN + C₃H₆; and k(298) = 2.9 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.53 for CN + C₂H₂. These reactions almost certainly proceed via addition-elimination yielding an unsaturated cyanide and an H-atom. Our kinetic results for reactions of CN are compared with those for reactions of the same hydrocarbons with other simple free radical species. © John Wiley & Sons, Inc.     

Equilibrium,kinetics, and mechanism of the malonic acid–iodine reaction

The equilibrium constant for the reaction CH₂(COOH)₂ + I₃^? ? CHI(COOH)₂ + 2I^? + H⁺, measured spectrophotometrically at 25°C and ionic strength 1.00M (NaClO₄), is (2.79 ± 0.48) × 10^?4M². Stopped-flow kinetic measurements at 25°C and ionic strength 1.00M with [H⁺] = (2.09-95.0) × 10^?3M and [I^?] = (1.23-26.1) × 10^?3M indicate that the rate of the forward reaction is given by (k₁[I₂] + k₃[I₃^?]) [HOOCCH₂COO^?] + (k₂[I₂] + k₄[I₃^?]) [CH(COOH)₂] + k₅[H⁺] [I₃^?] [CH₂(COOH)₂]. The values of the rate constants k₁-k₅ are (1.21 ± 0.31) × 10², (2.41 ± 0.15) × 10¹, (1.16 ± 0.33) × 10¹, (8.7 ± 4.5) × 10^?1M^?1·sec^?1, and (3.20 ± 0.56) × 10¹M^?2·sec^?1, respectively. The rate of enolization of malonic acid, measured by the bromine scavenging technique, is given by k_en[CH₂(COOH)₂], with k_en = 2.0 × 10^?3 + 1.0 × 10^?2 [CH₂(COOH)₂]. An intramolecular mechanism, featuring a six-member cyclic transition state, is postulated to account for the results on the enolization of malonic acid. The reactions of the enol, enolate ion, and protonated enol with iodine and/or triodide ion are proposed to account for the various rate terms.     

Kinetic study of the reaction of IO with CH3SCH3

The reaction IO + CH₃SCH₃ → products (3) was studied at room temperature and near 1 Torr pressure of He, using the discharge flow mass spectrometric technique. The rate constant was found to be k₃ = (1.5 ± 0.5) × 10^?11 cm³ molecule^?1 s^?1. CH₃S(O)CH₃ was detected as a product suggesting the following channel: IO + CH₃SCH₃ → CH₃S(O)CH₃ + I. The rate constant of the reaction IO + IO → products (1) was also measured: k₁ = (3 ± 0.5) × 10^?11 at 298 K and 1 Torr pressure. The atmospheric implication of reaction (3) is discussed. The results indicate that this reaction could be a potential important sink of CH₃SCH₃ in marine atmosphere.     

Kinetics of the reactions of fluorine and chlorine atoms with ethylene oxide (oxirane)

The kinetics of the reactions of F and C1 atoms with ethylene oxide have been studied using relative rate techniques in 10–700 Torr of either nitrogen or air diluent at 295 ± 2 K; k(F + C₂H₄O) = (9.4 ± 1.6) × 10^?11 and k(C1 + C₂H₄O) = (5.0 ± 0.9) × 10^?12 cm³ molecule^?1 s^?1. The result for k(F + C₂H₄O) is in good agreement with the literature data. The result for k(C1 + C₂H₄O) is a factor of 5.6 lower than that reported previously. It seems likely that in the previous study most of the loss of C₂H₄O attributed to reaction with C1 atoms was actually caused by unwanted secondary reactions leading to an overestimate of k(C1 + C₂H₄O). © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 122–125, 2002     

Rate constant and RRKM product study for the reaction between CH3 and C2H3 at T = 298 K

The total rate constant k₁ has been determined at P = 1 Torr nominal pressure (He) and at T = 298 K for the vinyl‐methyl cross‐radical reaction: (1) CH₃ + C₂H₃ → Products. The measurements were performed in a discharge flow system coupled with collision‐free sampling to a mass spectrometer operated at low electron energies. Vinyl and methyl radicals were generated by the reactions of F with C₂H₄ and CH₄, respectively. The kinetic studies were performed by monitoring the decay of C₂H₃ with methyl in excess, 6 < [CH₃]₀/ [C₂H₃]₀ < 21. The overall rate coefficient was determined to be k₁(298 K) = (1.02 ± 0.53) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ with the quoted uncertainty representing total errors. Numerical modeling was required to correct for secondary vinyl consumption by reactions such as C₂H₃ + H and C₂H₃ + C₂H₃. The present result for k₁ at T = 298 K is compared to two previous studies at high pressure (100–300 Torr He) and to a very recent study at low pressure (0.9–3.7 Torr He). Comparison is also made with the rate constant for the similar reaction CH₃ + C₂H₅ and with a value for k₁ estimated by the geometric mean rule employing values for k(CH₃ + CH₃) and k(C₂H₃ + C₂H₃). Qualitative product studies at T = 298 K and 200 K indicated formation of C₃H₆, C₂H₂, and C₃H₅ as products of the combination‐stabilization, disproportionation, and combination‐decomposition channels, respectively, of the CH₃ + C₂H₃ reaction. We also observed the secondary C₄H₈ product of the subsequent reaction of C₃H₅ with excess CH₃; this observation provides convincing evidence for the combination‐decomposition channel yielding C₃H₅ + H. RRKM calculations with helium as the deactivator support the present and very recent experimental observations that allylic C‐H bond rupture is an important path in the combination reaction. The pressure and temperature dependencies of the branching fractions are also predicted. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 304–316, 2000     

Does the HO2 radical react with H2S,CH3SH,and CH3SCH3?

The kinetics of the title reactions were investigated in a discharge flow tube by using laser magnetic resonance detection of HO₂. The upper limits for the bimolecular rate constants for the reactions of HO₂ with H₂S (k₁), CH₃SH (k₂), and CH₃SCH₃ (k₃) are <3 × 10^?15, <4 × 10^?15, and <5 × 10^?15 cm³ molecule^?1 s^?1, respectively, at 298 K. Our upper limit for k₁ is three orders of magnitude lower than the previously reported value. Measurements at higher temperatures also yield similar upper limits. Our results suggest that HO₂ is not an important oxidant for these reduced compounds in the atmosphere. © 1994 John Wiley & Sons, Inc.     

Kinetics and mechanism associated with the reactions of hydroxyl radicals and of chlorine atoms with 1‐propanol under near‐tropospheric conditions between 273 and 343 K

Rate constants for the reactions of OH radicals and Cl atoms with 1‐propanol (1‐C₃H₇OH) have been determined over the temperature range 273–343 K by the use of a relative rate technique. The value of k(Cl + 1‐C₃H₇OH) = (1.69 ± 0.19) × 10^?12 cm³ molecule^?1 s^?1 at 298 K and shows a small increase of 10% between 273 and 342 K. The value of k(OH + 1‐C₃H₇OH) increases by 14% between 273 and 343 K with a value of (5.50 ± 0.55) × 10^?12 cm³ molecule^?1 s^?1 at 298 K, and further when combined with a single independent experimentally determined value at 753 K gives k(OH + 1‐C₃H₇OH) = 4.69 × 10^?17T^1.8 exp(422/T) cm³ molecule^?1 s^?1, which fits each data point to better than 2%. Two well‐established structure–activity relationships for H abstraction by OH radicals give accurate predictions of the rate constant for OH + 1‐C₃H₇OH, provided the β‐CH₂ group is given an increased reactivity of a factor of about 2 over that for the structurally equivalent CH₂ group in alkanes at 298 K. A quantitative product analysis was carried out at 298 K for the Cl‐initiated photooxidation of 1‐C₃H₇OH, using both FTIR and gas chromatography. HCHO, CH₃CHO, and C₂H₅CHO were the only major organic primary products observed, although HCOOH was found in much smaller amounts as a secondary product. A key characteristic of the analysis was that the initial values of the product ratio [CH₃CHO]/[C₂H₅CHO] were effectively constant for NO pressures between 0.15 and 0.3 Torr, but fell by about 35% as the pressure fell to 0.0375 Torr. From a detailed consideration of the mechanism for the oxidation, it is suggested that C₂H₅CHO, CH₃CHO (+HCHO), and 3 molecules of HCHO are formed uniquely from CH₃CH₂CHOH, CH₃CHCH₂OH, and CH₂CH₂CH₂OH radicals, respectively. On this basis, use of the product yields gives the branching ratios of 56, 30, and 14% for Cl atom reaction at the α‐, β‐, and γ‐C? H positions in 1‐C₃H₇OH at 298 K. Given the very low temperature coefficients involved, little change will occur over tropospheric temperature ranges. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 110–121, 2002     

Kinetic study of the reaction of chlorine atoms with CF3I and the reactions of CF3 radicals with O2, Cl2 and NO at 296 K

The kinetics of the gas-phase reaction of Cl atoms with CF₃I have been studied relative to the reaction of Cl atoms with CH₄ over the temperature range 271–363 K. Using k(Cl + CH₄) = 9.6 × 10^?12 exp(?2680/RT) cm³ molecule^?1 s^?1, we derive k(Cl + CF₃I) = 6.25 × 10^?11 exp(?2970/RT) in which E_a has units of cal mol^?1. CF₃ radicals are produced from the reaction of Cl with CF₃I in a yield which was indistinguishable from 100%. Other relative rate constant ratios measured at 296 K during these experiments were k(Cl + C₂F₅I)/k(Cl + CF₃I) = 11.0 ± 0.6 and k(Cl + C₂F₅I)/k(Cl + C₂H₅Cl) = 0.49 ± 0.02. The reaction of CF₃ radicals with Cl₂ was studied relative to that with O₂ at pressures from 4 to 700 torr of N₂ diluent. By using the published absolute rate constants for k(CF₃ + O₂) at 1–10 torr to calibrate the pressure dependence of these relative rate constants, values of the low- and high-pressure limiting rate constants have been determined at 296 K using a Troe expression: k₀(CF₃ + O₂) = (4.8 ± 1.2) × 10^?29 cm⁶ molecule^?2 s^?1; k_∞(CF₃ + O₂) = (3.95 ± 0.25) × 10^?12 cm³ molecule^?1 s^?1; F_c = 0.46. The value of the rate constant k(CF₃ + Cl₂) was determined to be (3.5 ± 0.4) × 10^?14 cm³ molecule^?1 s^?1 at 296 K. The reaction of Cl atoms with CF₃I is a convenient way to prepare CF₃ radicals for laboratory study. © 1995 John Wiley & Sons, Inc.     

An ftir study of the reaction between nitrogen dioxide and alcohols

The reaction 2NO₂ + ROH = RONO + HNO₃ (R = CH₃ or C₂H₅) has been studied using the FTIR method at reactant pressures from 0.1 to 1.0 torr at 25°C. The termolecular rate constant for the forward reaction was determined to be (5.7 ± 0.6) × 10^?37 cm⁶/molec²·s for CH₃OH and (5.7 ± 0.8) × 10^?37 cm⁶/molec²·s for C₂H₅OH, that is, d[RONO]/dt = k[NO₂]²[ROH]. The corresponding equilibrium constants were measured as 1.36 ± 0.06 and 0.550 ± 0.025 torr^?1, respectively. These results are consistent with those of a previous study based on the NO₂ decay measurements at reactant pressures from 1 to 10 torr.