QRRK analysis

Other reactions, such as C-H bond scissions and Hj eliminations, although possible, have been shown to be unimportant under the conditions studied. In Table XIV, the parameters needed for the QRRK analysis of the recombination of CH2CI radicals are presented. The methods and sources used to obtain these data are the same as those noted in the discussion of the unimolecular QRRK method. In Fig. 22, the apparent rate coefficients for... 

Dean, A. M, and Westmoreland, P, R., Bimolecular QRRK analysis of methyl radical reactions, Int. J. Chem. Kinetics 19, 207 (1987). 

Fig. 10.5 Reaction pathways in the QRRK analysis of unimolecular reactions.

Fig. 10.7 QRRK analysis [207] of azomethane, CH3N2CH3, unimolecular decomposition at 603 K (solid curve), and comparison with experimental data (points) from Ramsperger [326].

For this QRRK analysis we will define the zero of energy as the ground-state energy of the stabilized C molecule. As in QRRK the analysis of unimolecular reactions, assume that the excited C molecule consists of s identical oscillators, each with vibrational frequency v. When we write C ( ), this indicates that the excited intermediate species has been formed with n quanta of vibrational energy thus, its total energy is E = nhv above the ground-state energy of C (which we have arbitrarily set to zero). 

Density functional theory was used to show that unimolecular formation of CO2 and dihydroxycarbene from oxalic acid has a barrier of 31 kcal mol-1.33 The barrier for H-migration in dihydroxycarbene to fonn fonnic acid was shown to be less than 37 kcal mol-1 if an exchange with oxalic acid was involved (23). QRRK analysis of the pyrolytic decomposition of 2-chloro-l,l,l,2-tetrafluoroethane (F3CCFCIH) indicated that the primary route is a-climination of HC1 to form singlet F3CFC .34... 

Using the results obtained on the phenyl system for the dibenzofuran + O2 system, kinetics of each path, as a function of temperature and pressure are determined using bimolecular chemical activation analysis. The high-pressure-limit kinetic parameters from the calculation results are again obtained with cannonical Transition State Theory. QRRK analysis is utilized to obtain k(E) and master analysis is used to evaluate the fall-off behaviour of this complex bimolecular chemical activation reaction [34]. 

Chemaster code is based on the quantum Rice-Ramsperger-Kassel (QRRK) analysis for k(E) and Master Equation analysis for fall off Chemaster will be employed to determine kinetic parameters in complex reaction systems, such as CeHs + O2. The source code for the QRRK... 

High Pressure limit kinetic parameters are obtained from canonical Transition State Theory calculations. Multifrequency Quantum Rice-Ramsperger-Kassel (QRRK) analysis is used to calculate k(E) data and master equation analysis is applied to evaluate fall-off in this chemically activated reaction system. 

Unimolecular dissociation and isomerization reactions of chemically activated and stabilized adduct resulting from addition or combination reactions are analyzed by constructing potential energy diagrams. Some high-pressure rate constants for each channel are obtained from literature or referenced estimation techniques. Kinetics parameters for uni-molecular and bimolecular (chemical activation) reactions are then calculated using multifrequency QRRK analysis iork(E) [199, 200, 63]. 

Scheme FI Input file for QRRK analysis with master equation analysis for Fall-off...

Karra, S. B., and Senkan, S. M., Analysis of the chemically activated CH2CI/CH2CI and CH3/CH2CI recombination reactions at elevated temperatures using the QRRK method, Ind. Eng. Chem. Research 27, 447 (1988b). 

Multifrequency Quantum Rice-Ramsperger-Kassel (QRRK) is a method used to predict temperature and pressure-dependent rate coefficients for complex bimolecular chemical activation and unimolecular dissociation reactions. Both the forward and reverse paths are included for adducts, but product formation is not reversible in the analysis. A three-frequency version of QRRK theory is developed coupled with a Master Equation model to account for collisional deactivation (fall-off). The QRRK/Master Equation analysis is described thoroughly by Chang et al. [62, 63]. 

Rate constant results from QRRK/Master Equation analysis are shown to accurately reproduce (model) experimental data on several complex systems. They also provide a reasonable method to estimate rate constants for numerical integration codes by which the effects of temperature and pressure can be evaluated in complex reaction systems. 

Multi channel, multi-frequency Quantum RRK calculations are performed for k(E) with master equation analysis for falloff on the chemical activated phenyl peroxy radical [PhOO ] and the intermediates (isomers) in this complex reaction system. This provides an evaluation of the rate constants for the formation of stabilized adducts or reaction products as a function of pressure and temperature. The bi-molecular chemical activated reaction of Phenyl + O2 system is carried out using the CHEMASTER program and incorporates all adducts and product channels illustrated. QRRK with Master equation analysis is used for unimolelcular dissociation of each adduct, but only isomeration to parallel, adjacent products / wells is included in the dissociation of stabilized intermediates. The input file for the phenyl + O2 reaction system is given in the appendix F. 

Table F2 Rate constants from chemical activation QRRK - Master Equation analysis Ph + O2 = [PhOO ] = Products...

CARRA CARRA, for chemically activated reaction rate analysis, calculates apparent rate constants for multi-well, multi-channel systems based on QRRK theory. It uses either the MSC (CAR-RA MSC) or the steady-state ME (CARRA ME) approach. The original concept was based on a single frequency representation of the active modes of each isomer [35,36]. Later, the code was updated to handle three representative frequencies. Descriptions of these earlier versions as well as applications can be found in Refs. [7,37]. CARRA is a modihed version of these older codes, which is currently still under development [38]. 

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