Computational study on the mechanism and rate constant for the C6H5 + C6H5NO reaction

The reaction mechanism of C6H5 + C6H5NO involving four product channels on the doublet-state potential energy surface has been studied at the B3LYP/6-31+G(d, p) level of theory. The first reaction channel occurs by barrierless association forming (C6H5)2NO (biphenyl nitroxide), which can undergo isomerization and decomposition. The second channel takes place by substitution reaction producing C12H10 (biphenyl) and NO. The third and fourth channels involve direct hydrogen abstraction reactions producing C6H4NO + C6H6 and C6H5NOH + C6H4, respectively. Bimolecular rate constants of the above four product channels have been calculated in the temperature range 300-2000 K by the microcanonical Rice-Ramsperger-Kassel-Marcus theory and/or variational transition-state theory. The result shows the dominant reactions are channel 1 at lower temperatures (T < 800 K) and channel 3 at higher temperatures (T > 800 K). The total rate constant at 7 Torr He is predicted to be k(t) = 3.94 x 10(21) T(-3.09) exp(-699/T) for 300-500 K, 2.09 x 10(20) T(-3.56) exp(2315/T) for 500-1000 K, and 1.51 x 10(2) T(3.30) exp(-3043/T) for 1000-2000 K (in units of cm3 mol(-1) s(-1)), agreeing reasonably with the experimental data within their reported errors. The heats of formation of key products including biphenyl nitroxide, hydroxyl phenyl amino radical, and N-hydroxyl carbazole have been estimated.     

H2ClCS单分子分解反应机理的理论研究

用量子化学B3LYP/6 - 311+G(d,p)方法优化了H2ClCS单分子分解反应驻点物种的几何构型,并在相同水平上通过频率计算和内禀反应坐标(IRC)分析对过渡态结构及连接性进行了验证.用QCISD(T)/6-311++G(d,p)方法计算各物种的单点能,并对总能量进行了零点能校正.利用经典过渡态理论(TST)与...     

Ab initio chemical kinetics for the unimolecular decomposition of Si2H5 radical and related reverse bimolecular reactions

For plasma enhanced and catalytic chemical vapor deposition (PECVD and Cat‐CVD) processes using small silanes as precursors, disilanyl radical (Si₂H₅) is a potential reactive intermediate involved in various chemical reactions. For modeling and optimization of homogeneous a‐Si:H film growth on large‐area substrates, we have investigated the kinetics and mechanisms for the thermal decomposition of Si₂H₅ producing smaller silicon hydrides including SiH, SiH₂, SiH_3, and Si₂H₄, and the related reverse reactions involving these species by using ab initio molecular‐orbital calculations. The results show that the lowest energy path is the production of SiH + SiH₄ that proceeds via a transition state with a barrier of 33.4 kcal/mol relative to Si₂H₅. Additionally, the dissociation energies for breaking the Si? Si and H? SiH₂ bonds were predicted to be 53.4 and 61.4 kcal/mol, respectively. To validate the predicted enthalpies of reaction, we have evaluated the enthalpies of formation for SiH, SiH₂, HSiSiH₂, and Si₂H₄(C_2h) at 0 K by using the isodesmic reactions, such as ²HSiSiH₂ + ¹C₂H₆→¹Si₂H₆ + ²HCCH₂ and ¹Si₂H₄(C_2h) + ¹C₂H₆ → ¹Si₂H₆ + ¹C₂H₄. The results of SiH (87.2 kcal/mol), SiH₂ (64.9 kcal/mol), HSiSiH₂ (98.0 kcal/mol), and Si₂H₄ (68.9 kcal/mol) agree reasonably well previous published data. Furthermore, the rate constants for the decomposition of Si₂H₅ and the related bimolecular reverse reactions have been predicted and tabulated for different T, P‐conditions with variational Rice–Ramsperger–Kassel–Marcus (RRKM) theory by solving the master equation. The result indicates that the formation of SiH + SiH₄ product pair is most favored in the decomposition as well as in the bimolecular reactions of SiH₂ + SiH₃, HSiSiH₂ + H₂, and Si₂H₄(C_2h) + H under T, P‐conditions typically used in PECVD and Cat‐CVD. © 2013 Wiley Periodicals, Inc.     

Ab initio kinetics for the unimolecular reaction C6H5OH --> CO + C5H6

The unimolecular decomposition of C(6)H(5)OH on its singlet-state potential energy surface has been studied at the G2M//B3LYP/6-311G(d,p) level of theory. The result shows that the most favorable reaction channel involves the isomerization and decomposition of phenol via 2,4-cyclohexadienone and other low-lying isomers prior to the fragmentation process, producing cyclo-C(5)H(6) + CO as major products, supporting the earlier assumption of the important role of the 2,4-cyclohexadienone intermediate. The rate constant predicted by the microcanonical RRKM theory in the temperature range 800-2000 K at 1 Torr--100 atm of Ar pressure for CO production agrees very well with available experimental data in the temperature range studied. The rate constants for the production of CO and the H atom by O-H dissociation at atmospheric Ar pressure can be represented by k(CO) = 8.62 x 10(15) T(-0.61) exp(-37,300/T) s(-1) and k(H) = 1.01 x 10(71) T(-15.92) exp(-62,800/T) s(-1). The latter process is strongly P-dependent above 1000 K; its high- and low-pressure limits are given.     

A kinetics study on reactions of C6H5O with C6H5O and O3 at 298 k

Kinetics for reactions of phenoxy radical, C₆H₅O, with itself and with O₃ were examined at 298 K and low pressure (1 Torr) using discharge flow coupled with mass spectrometry (DF/MS). The rate constant for the phenoxy radical self‐reaction was determined to be k₁ = (1.49 ± 0.53) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ defined by d[C₆H₅O]/dt=−2 k₁[C₆H₅O]². The rate constant for the C₆H₅O reaction with O₃ was measured to be k₂ = (2.86 ± 0.35) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹, which may be a lower limit value. Because of much higher atmospheric abundance of ozone than that of both NO and phenoxy, the reaction of C₆H₅O with ozone may represent the principal fate of the phenoxy radical in the atmosphere. Products from reaction of C₆H₅O + C₆H₅O, NO, and NO₂ were also investigated, and (C₆H₅O)₂ (m/e = 186), C₆H₅O(NO) (m/e = 123), and C₆H₅O(NO₂) (m/e = 139) adducts were observed as products for the reactions of C₆H₅O with itself, NO, and NO₂, respectively. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 65–72, 1999     

Temperature-dependent kinetics studies of the reactions of C2H5O2 and n-C3H7O2 radicals with NO

The rate coefficients for the gas-phase reactions of C₂H₅O₂ and n-C₃H₇O₂ radicals with NO have been measured over the temperature range of (201–403) K using chemical ionization mass spectrometric detection of the peroxy radical. The alkyl peroxy radicals were generated by reacting alkyl radicals with O₂, where the alkyl radicals were produced through the pyrolysis of a larger alkyl nitrite. In some cases C₂H₅ radicals were generated through the dissociation of iodoethane in a low-power radio frequency discharge. The discharge source was also tested for the i-C₃H₇O₂ + NO reaction, yielding k_{298 K} = (9.1 ± 1.5) × 10⁻¹² cm³ molecule⁻¹ s⁻¹, in excellent agreement with our previous determination. The temperature dependent rate coefficients were found to be k(T) = (2.6 ± 0.4) × 10⁻¹² exp{(380 ± 70)/T} cm³ molecule⁻¹ s⁻¹ and k(T) = (2.9 ± 0.5) × 10⁻¹² exp{(350 ± 60)/T} cm³ molecule⁻¹ s⁻¹ for the reactions of C₂H₅O₂ and n-C₃H₇O₂ radicals with NO, respectively. The rate coefficients at 298 K derived from these Arrhenius expressions are k = (9.3 ± 1.6) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ for C₂H₅O₂ radicals and k = (9.4 ± 1.6) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ for n-C₃H₇O₂ radicals. © 1996 John Wiley & Sons, Inc.     

Theoretical study on the mechanism and kinetics for the self-reaction of C2H5O2 radicals

Oxygen-to-oxygen coupling, direct H-abstraction and oxygen-to-(α)carbon nucleophilic substitution processes have been investigated for both the singlet and triplet self-reaction of C(2)H(5)O(2) radicals at the CCSD(T)/cc-pVDZ//B3LYP/6-311G(2d,2p) level to evaluate the reaction mechanisms, possible products and rate constants. The calculated results show that the title reaction mainly occurs through the singlet oxygen-to-oxygen coupling mechanism with the formation of entrance tetroxide intermediates, and the most dominant product is C(2)H(5)O + HO(2) + CH(3)CHO (P5) generated in channel R5. Beginning from the radical products of P5 (C(2)H(5)O, HO(2)) and reactant (C(2)H(5)O(2)), five secondary reactions HO(2) + HO(2) (a), HO(2) + C(2)H(5)O (b), C(2)H(5)O + C(2)H(5)O (c), HO(2) + C(2)H(5)O(2) (d), and C(2)H(5)O + C(2)H(5)O(2) (e) mainly proceed on the triplet potential energy surface. Among these reactions, (a), (b), and (d) are kinetically favorable because of lower barrier heights. The calculated rate constants of channel R5 between 200 and 295 K are almost independent of the temperature, which is in agreement with the experimental report. With regard to the final products distribution, CH(3)CHO, C(2)H(5)OH, C(2)H(5)OOH, H(2)O(2), and (3)O(2) are predicted to be major, whereas C(2)H(5)OOC(2)H(5) should be in minor amount.     

Computational study on the kinetics and mechanisms for the unimolecular decomposition of formic and oxalic acids

The kinetics and mechanisms for the unimolecular decomposition reactions of formic acid and oxalic acid have been studied computationally by the high-level G2M(CC1) method and microcanonical RRKM theory. There are two reaction pathways in the decomposition of formic acid: The dehydration process starting from the Z conformer is found to be the dominant, whereas the decarboxylation reaction starting from the E conformer is less competitive. The predicted rate constants for the dehydration and decarboxylation reactions are in good agreement with the experimental data. The calculated CO/CO2 ratio, 13.6-13.9 between 1300 and 2000 K, is in close agreement with the ratio of 10 measured experimentally by Hsu et al. (In The 19th International Symposium on Combustion; The Combustion Institute: Pittsburgh, PA, 1983; p 89). For oxalic acid, its isomer with two intramolecular hydrogen bonds is the most stable structure, similar to earlier reports. Two primary decomposition channels of oxalic acid producing CO2+HOCOH with barriers of 33-36 kcal/mol and CO2+CO+H2O with a barrier of 39 kcal/mol were found. At high temperatures, the latter process becomes more competitive. The rate constant predicted for the formation of CO2 and HOCOH (the precursor of HCOOH) agrees well with available experimental data. The mechanism for the isomerization of HOCOH to HCOOH is also discussed.     

A computational study on the kinetics and mechanism for the unimolecular decomposition of o-nitrotoluene

The kinetics and mechanism for the unimolecular decomposition of o-nitrotoluene (o-CH(3)C(6)H(4)NO(2)) have been studied computationally at the G2M(RCC, MP2)//B3LYP/6-311G(d, p) level of theory in conjunction with rate constant predictions with RRKM and TST calculations. The results of the calculations reveal 10 decomposition channels for o-nitrotoluene and its six isomeric intermediates, among them four channels give major products: CH(3)C(6)H(4) + NO(2), C(6)H(4)C(H)ON (anthranil) + H(2)O, CH(3)C(6)H(4)O (o-methyl phenoxy) + NO, and C(6)H(4)C(H(2))NO + OH. The predicted rate constants in the 500-2000 K temperature range indicate that anthranil production, taking place initially by intramolecular H-abstraction from the CH(3) group by NO(2) followed by five-membered ring formation and dehydration, dominates at temperatures below 1000 K, whereas NO(2) elimination becomes predominant above 1100 K and CH(3)C(6)H(4)O formation by the nitro-nitrite isomerization/decomposition process accounts for only 5-11% of the total product yield in the middle temperature range 800-1300 K. The branching ratio for CH(2)C(6)H(4)NO formation by the decomposition process of CH(2)C(6)H(4)N(O)OH is negligible. The predicted high-pressure-limit rate constants with the rate expression of 4.10 x 10(17) exp[-37000/T] s(-1) for the NO(2) elimination channel and 9.09 x 10(12) exp[-25800/T] s(-1) for the H(2)O elimination channel generally agree reasonably with available experimental data. The predicted high-pressure-limit rate constants for the NO and OH elimination channels are represented as 1.49 x 10(14) exp[-30000/T] and 1.31 x 10(15) exp[-38000/T] s(-1), respectively.     

Computational studies on the mechanism and kinetics of Cl reaction with C2H5I

The dual‐level direct kinetics method has been used to investigate the multichannel reactions of C₂H₅I + Cl. Three hydrogen abstraction channels and one displacement process are found for the title reaction. The calculation indicates that the hydrogen abstraction from ? CH₂? group is the dominant reaction channel, and the displacement process may be negligible because of the high barrier. The rate constants for individual reaction channels are calculated by the improved canonical variational transition‐state theory with small‐curvature tunneling correction over the temperature range of 220–1500 K. Our results show that the tunneling correction plays an important role in the rate constant calculation in the low‐temperature range. Agreement between the calculated and experimental data available is good. The Arrhenius expression k(T) = 2.33 × 10^?16 T^1.83 exp(?185.01/T) over a wide temperature range is obtained. Furthermore, the kinetic isotope effects for the reaction C₂H₅I + Cl are estimated so as to provide theoretical estimation for future laboratory investigation. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Novel products from C6H5 + C6H6/C6H5 reactions

To date only one product, biphenyl, has been reported to be produced from C(6)H(5) + C(6)H(6)/C(6)H(5) reactions. In this study, we have investigated some unique products of C(6)H(5) + C(6)H(6)/C(6)H(5) reactions via both experimental observation and theoretical modeling. In the experimental study, gas-phase reaction products produced from the pyrolysis of selected aromatics and aromatic/acetylene mixtures were detected by an in situ technique, vacuum ultraviolet (VUV) single photon ionization (SPI) time-of-flight mass spectrometry (TOFMS). The mass spectra revealed a remarkable correlation in mass peaks at m/z = 154 {C(12)H(10) (biphenyl)} and m/z = 152 {C(12)H(8) (?)}. It also demonstrated an unexpected correlation among the HACA (hydrogen abstraction and acetylene addition) products at m/z = 78, 102, 128, 152, and 176. The analysis of formation routes of products suggested the contribution of some other isomers in addition to a well-known candidate, acenaphthylene, in the mass peak at m/z = 152 (C(12)H(8)). Considering the difficulties of identifying the contributing isomers from an observed mass number peak, quantum chemical calculations for the above-mentioned reactions were performed. As a result, cyclopenta[a]indene, as-indacene, s-indacene, biphenylene, acenaphthylene, and naphthalene appeared as novel products, produced from the possible channels of C(6)H(5) + C(6)H(6)/C(6)H(5) reactions rather than from their previously reported formation pathways. The most notable point is the production of acenaphthylene and naphthalene from C(6)H(5) + C(6)H(6)/C(6)H(5) reactions via the PAC (phenyl addition-cyclization) mechanism because, until now, both of them have been thought to be formed via the HACA routes. In this way, this study has paved the way for exploring alternative paths for other inefficient HACA routes using the PAC mechanism.     

A dual-level ab initio and hybrid density functional theory dynamics study on the unimolecular decomposition reaction C2H5O-->CH2O + CH3

We present a direct ab initio and hybrid density functional theory dynamics study of the thermal rate constants of the unimolecular decomposition reaction of C2H5O-->CH2O + CH3 at a high-pressure limit. MPW1K/6-31+G(d,p), MP2/6-31+G(d,p), and MP2(full)/6-31G(d) methods were employed to optimize the geometries of all stationary points and to calculate the minimum energy path (MEP). The energies of all the stationary points were refined at a series of multicoefficient and multilevel methods. Among all methods, the QCISD(T)/aug-cc-pVTZ energies are in good agreement with the available experimental data. The rate constants were evaluated based on the energetics from the QCISD(T)/aug-cc-pVTZ//MPW1K/6-31+G(d,p) level of theory using both microcanonical variational transition state theory (microVT) and RRKM theory with the Eckart tunneling correction in the temperature range of 300-2500 K. The calculated rate constants at the QCISD(T)/aug-cc-pVTZ/MPW1K/6-31+G(d,p) level of theory are in good consistent with experimental data. The fitted three-parameter Arrhenius expression from the microVT/Eckart rate constants in the temperature range 200-2500 K is k = 2.52 x 10(12)T(0.41)e(-8894.0/T) s(-1). The falloff curves of pressure-dependent rate constants are performed using master-equation method within the temperature range of 391-471 K. The calculated results are in good agreement with the available experimental data.     

Atmospheric chemistry of acetone: Kinetic study of the CH3C(O)CH2O2+NO/NO2 reactions and decomposition of CH3C(O)CH2O2NO2

Pulse radiolysis was used to study the kinetics of the reactions of CH₃C(O)CH₂O₂ radicals with NO and NO₂ at 295 K. By monitoring the rate of formation and decay of NO₂ using its absorption at 400 and 450 nm the rate constants k(CH₃C(O)CH₂O₂+NO)=(8±2)×10⁻¹² and k(CH₃C(O)CH₂O₂+NO₂)=(6.4±0.6)×10⁻¹² cm³ molecule⁻¹ s⁻¹ were determined. Long path length Fourier transform infrared spectrometers were used to investigate the IR spectrum and thermal stability of the peroxynitrate, CH₃C(O)CH₂O₂NO₂. A value of k₋₆≈3 s⁻¹ was determined for the rate of thermal decomposition of CH₃C(O)CH₂O₂NO₂ in 700 torr total pressure of O₂ diluent at 295 K. When combined with lower temperature studies (250–275 K) a decomposition rate of k₋₆=1.9×10¹⁶ exp (−10830/T) s⁻¹ is determined. Density functional theory was used to calculate the IR spectrum of CH₃C(O)CH₂O₂NO₂. Finally, the rate constants for reactions of the CH₃C(O)CH₂ radical with NO and NO₂ were determined to be k(CH₃C(O)CH₂+NO)=(2.6±0.3)×10⁻¹¹ and k(CH₃C(O)CH₂+NO₂)=(1.6±0.4)×10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The results are discussed in the context of the atmospheric chemistry of acetone and the long range atmospheric transport of NO_x. © John Wiley & Sons, Inc. Int J Chem Kinet: 30: 475–489, 1998     

Computational study on kinetics and mechanisms of unimolecular decomposition of succinic acid and its anhydride

The mechanisms and kinetics of unimolecular decomposition of succinic acid and its anhydride have been studied at the G2M(CC2) and microcanonical RRKM levels of theory. It was shown that the ZsgsZ conformer of succinic acid, with the Z-acid form and the gauche conformation around the central C-C bond, is its most stable conformer, whereas the lowest energy conformer with the E-acid form, ECGsZ, is only 3.1 kcal/mol higher in energy than the ZsgsZ. Three primary decomposition channels of succinic acid producing H2O + succinic anhydride with a barrier of 51.0 kcal/mol, H2O + OCC2H3COOH with a barrier of 75.7 kcal/mol and CO2 + C2H5COOH with a barrier of 71.9 kcal/mol were predicted. The dehydration process starting from the ECGCZ-conformer is found to be dominant, whereas the decarboxylation reaction starting from the ZsgsZ-conformer is only slightly less favorable. It was shown that the decomposition of succinic anhydride occurs via a concerted fragmentation mechanism (with a 69.6 kcal/mol barrier), leading to formation of CO + CO2 + C2H4 products. On the basis of the calculated potential energy surfaces of these reactions, the rate constants for unimolecular decomposition of succinic acid and its anhydride were predicted. In addition, the predicted rate constants for the unimolecular decomposition of C2H5COOH by decarboxylation (giving C2H6 + CO2) and dehydration (giving H3CCHCO + H2O) are in good agreement with available experimental data.     

Analysis of the unimolecular reaction N2O5 + M ⇌ NO2 + NO3 + M

Recent experimental results on the thermal decomposition of N₂O₅ in N₂ are evaluated in terms of unimolecular rate theory. A theoretically consistent set of fall-off curves is constructed which allows to identify experimental errors or misinterpretations. Limiting rate constants k₀ = [N₂] 2.2 × 10^?3 (T/300)^?4.4 exp(?11,080/T) cm³/molec·s over the range of 220–300 K, k_∞ = 9.7 × 10¹⁴ (T/300)^+0.1 exp(?11,080/T) s^?1 over the range of 220–300 K, and broadening factors of the fall-off curve F_cent = exp(-T/250) + exp(?1050/T) over the range of 220–520 K have been derived. NO₂ + NO₃ recombination rate constants over the range of 200–300 K are k_rec,0 = [N₂] 3.7 × 10^?30 (T/300)^?4.1 cm⁶/molec²·s and k_rec,∞ = 1.6 × 10^?12 (T/300)^+0.2 cm³/molec·s.     

A spectroscopic study of the equilibrium NO2 + NO3 + M 2 N2O5 + M and the kinetics of the O3/N2O5/NO3/NO2/ air system

The equilibrium constant, K_eq of the reaction NO₂ + NO₃ + M 2 N₂O₅ + M has been determined for a small range of temperatures around room temperature in air at 740 torr by direct spectroscopical measurements of NO₂, NO₃, and N₂O₅. At 298 K, K_eq was determined as (3.73 ± 0.61) × 10⁻¹¹ cm³ molecule⁻¹. Averaging this and 11 other independent evaluations of K_eq yields K_eq = (3.31 ± 0.82) × 10⁻¹¹ cm³ molecule⁻¹, where the uncertainty is given as one standard deviation. The kinetics of the O₃/NO₂/N₂O₅/NO₃/ air system was studied in a static chamber at room temperature and 740 torr total pressure. Evidence of a unimolecular decay reaction of NO₃, NO₃ → NO + O₂, was found and its rate coefficient was estimated as (1.6 ± 0.7) × 10⁻³ s⁻¹ at 295 ± 2 K.     

Thermal decomposition of ethanol. III. A computational study of the kinetics and mechanism for the CH3+C2H5OH reaction

The mechanism for the CH3+C2H5OH reaction has been investigated by the modified Gaussian-2 method based on the geometric parameters of the stationary points optimized at the B3LYP/6-311+G(d,p) level of theory. Five transition states have been identified for the production of CH4+CH3CHOH (TS1), CH4+CH3CH2O (TS2), CH4+CH2CH2OH (TS3), CH3OH+CH3CH2 (TS4), and CH3CH2OCH3+H (TS5) with the corresponding barriers 12.0, 13.2, 16.0, 44.7, and 49.9 kcal/mol, respectively. The predicted rate constants and branching ratios for the three lower-energy H-abstraction reactions were calculated using the conventional and variational transition state theory with quantum-mechanical tunneling corrections for the temperature range 300-3000 K. The predicted total rate constant, kt=8.36 x 10(-76) T(20.00) exp(5258/T) cm3 mol(-1) s(-1) (300-600 K) and 6.10 x 10(-25) T(4.10)exp(-4058/T) cm3 mol(-1) s(-1) (600-3000 K), agrees closely with existing experimental data in the temperature range 403-523 K. Similarly, the predicted rate constants for CH3+CH3CD2OH and CD3+C2H5OD are also in reasonable agreement with available low temperature kinetic data.     

Theoretical study on the rate constants for the C2H5 + HBr --> C2H6 + Br reaction

The reaction C(2)H(5) + HBr --> C(2)H(6) + Br has been theoretically studied over the temperature range from 200 to 1400 K. The electronic structure information is calculated at the BHLYP/6-311+G(d,p) and QCISD/6-31+G(d) levels. With the aid of intrinsic reaction coordinate theory, the minimum energy paths (MEPs) are obtained at the both levels, and the energies along the MEP are further refined by performing the single-point calculations at the PMP4(SDTQ)/6-311+G(3df,2p)//BHLYP and QCISD(T)/6-311++G(2df,2pd)//QCISD levels. The calculated ICVT/SCT rate constants are in good agreement with available experimental values, and the calculate results further indicate that the C(2)H(5) + HBr reaction has negative temperature dependence at T < 850 K, but clearly shows positive temperature dependence at T > 850 K. The current work predicts that the kinetic isotope effect for the title reaction is inverse in the temperature range from 200 to 482 K, i.e., k(HBr)/k(DBr) < 1.     

Kinetics and mechanism of the C2H5O2 + NO reaction: A temperature and pressure dependence study using chemical ionization mass spectrometry

The overall rate coefficient (k₁) for the reaction of C₂H₅O₂ + NO has been measured using the turbulent flow CIMS technique. The temperature dependence of the rate coefficient was investigated between 203 and 298 K. Across the temperature range, the experimentally determined rate coefficients showed good agreement with previous studies and were fitted using an Arrhenius type analysis to yield the expression k₁ = (1.75) × 10^?12 exp[(462 ± 19)/T] cm³ molecule^?1 s^?1. Experiments were carried out in the pressure range of 100–200 Torr within the stated temperature range, where the rate coefficients were shown to be invariant with pressure. The branching ratio of the reaction was also assessed as a function of temperature and was found to proceed 100 ± 5% via the C₂H₅O + NO₂ reactive channel. This work represents the first temperature and pressure study over which the branching ratio has been studied. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 253–260, 2005