A Comprehensive Study of the Reaction NH2+ NO → Products:  Reaction Rate Coefficients, Product Branching Fractions, andab InitioCalculations

1997 ◽  
Vol 101 (35) ◽  
pp. 6243-6251 ◽  
Author(s):  
M. Wolf ◽  
D. L. Yang ◽  
J. L. Durant
Keyword(s):  
Reaction Rate ◽  
Branching Fractions ◽  
Rate Coefficients ◽  
Product Branching ◽  
Comprehensive Study

Spreadsheet Method for Evaluation of Biochemical Reaction Rate Coefficients and Their Uncertainties by Weighted Nonlinear Least-Squares Analysis of the Integrated Monod Equation

1998 ◽  
Vol 64 (6) ◽  
pp. 2044-2050 ◽  
Author(s):  
Laurence H. Smith ◽  
Perry L. McCarty ◽  
Peter K. Kitanidis
Keyword(s):  
Least Squares ◽  
Mixed Culture ◽  
Substrate Concentration ◽  
Reaction Rate ◽  
Initial Rate ◽  
Weighted Least Squares ◽  
Nonlinear Least Squares ◽  
Rate Coefficients ◽  
Monod Equation ◽  
Best Fit

ABSTRACT A convenient method for evaluation of biochemical reaction rate coefficients and their uncertainties is described. The motivation for developing this method was the complexity of existing statistical methods for analysis of biochemical rate equations, as well as the shortcomings of linear approaches, such as Lineweaver-Burk plots. The nonlinear least-squares method provides accurate estimates of the rate coefficients and their uncertainties from experimental data. Linearized methods that involve inversion of data are unreliable since several important assumptions of linear regression are violated. Furthermore, when linearized methods are used, there is no basis for calculation of the uncertainties in the rate coefficients. Uncertainty estimates are crucial to studies involving comparisons of rates for different organisms or environmental conditions. The spreadsheet method uses weighted least-squares analysis to determine the best-fit values of the rate coefficients for the integrated Monod equation. Although the integrated Monod equation is an implicit expression of substrate concentration, weighted least-squares analysis can be employed to calculate approximate differences in substrate concentration between model predictions and data. An iterative search routine in a spreadsheet program is utilized to search for the best-fit values of the coefficients by minimizing the sum of squared weighted errors. The uncertainties in the best-fit values of the rate coefficients are calculated by an approximate method that can also be implemented in a spreadsheet. The uncertainty method can be used to calculate single-parameter (coefficient) confidence intervals, degrees of correlation between parameters, and joint confidence regions for two or more parameters. Example sets of calculations are presented for acetate utilization by a methanogenic mixed culture and trichloroethylene cometabolism by a methane-oxidizing mixed culture. An additional advantage of application of this method to the integrated Monod equation compared with application of linearized methods is the economy of obtaining rate coefficients from a single batch experiment or a few batch experiments rather than having to obtain large numbers of initial rate measurements. However, when initial rate measurements are used, this method can still be used with greater reliability than linearized approaches.

Dissociative recombination of the deuterated acetaldehyde ion, CD3CDO+: product branching fractions, absolute cross sections and thermal rate coefficient

2007 ◽  
Vol 9 (22) ◽  
pp. 2856-2861 ◽  
Author(s):  
Erik Vigren ◽  
Magdalena Kamińska ◽  
Mathias Hamberg ◽  
Vitali Zhaunerchyk ◽  
Richard D. Thomas ◽  
...  
Keyword(s):  
Cross Sections ◽  
Rate Coefficient ◽  
Branching Fractions ◽  
Dissociative Recombination ◽  
Product Branching

Rate Constants and Product Branching Fractions for the Reactions of H3O+and NO+with C2−C12Alkanes

1998 ◽  
Vol 102 (45) ◽  
pp. 8881-8887 ◽  
Author(s):  
Susan T. Arnold ◽  
A. A. Viggiano ◽  
Robert A. Morris
Keyword(s):  
Rate Constants ◽  
Branching Fractions ◽  
Product Branching

Barrierless Reactions of Three Benzonitrile Radical Cations with Ethylene

2020 ◽  
Vol 73 (8) ◽  
pp. 705
Author(s):  
Oisin J. Shiels ◽  
P. D. Kelly ◽  
Stephen J. Blanksby ◽  
Gabriel da Silva ◽  
Adam J. Trevitt
Keyword(s):  
Ion Trap ◽  
Radical Cations ◽  
Branching Ratios ◽  
Ring Closure ◽  
Van Der Waals Complexes ◽  
Rate Coefficients ◽  
Ion Trap Mass Spectrometry ◽  
Closure Mechanism ◽  
Product Ions ◽  
Product Branching

Reactions of three protonated benzonitrile radical cations with ethylene are investigated. Product branching ratios and reaction kinetics, measured using ion-trap mass spectrometry, are reported and mechanisms are developed with support from quantum chemical calculations. Reactions proceed via pre-reactive van der Waals complexes with no energy barrier (above the reactant energy) and form radical addition and addition–elimination product ions. Rate coefficients are 4-dehydrobenzonitrilium: 1.72±0.01×10−11 cm3 molecule−1 s−1, 3-dehydrobenzonitrilium: 1.85±0.01×10−11 cm3 molecule−1 s−1, and 2-dehydrobenzonitrilium: 5.96±0.06×10−11 cm3 molecule−1 s−1 (with±50% absolute uncertainty). A ring-closure mechanism involving the protonated nitrile substituent is proposed for the 2-dehydrobenzonitrilium case and suggests favourable formation of the protonated indenimine cation.

Sign in / Sign up

Export Citation Format

Share Document