scholarly journals On the Question of Mode-Specificity in Unimolecular Reaction Dynamics

1983 ◽  
Vol 2 (5-6) ◽  
pp. 243-252 ◽  
Author(s):  
William H. Miller
Keyword(s):  
Transition State ◽  
Coupled Oscillators ◽  
Laser Excitation ◽  
Model Problem ◽  
Significant Degree ◽  
Decay Rates ◽  
Unimolecular Reaction ◽  
Unimolecular Decomposition ◽  
Planar Transition ◽  
Mode Specificity

Unimolecular decomposition following state-specific laser excitation is considered. If the transition state for the unimolecular reaction possesses any geometrical symmetry, then it is shown that this can lead to mode-specificity in the decay rates (i.e., different states with essentially the same total energy and angular momentum react at significantly different rates). This is illustrated for a model problem of two coupled oscillators (the Henon–Heiles potential) and also for the unimolecular dissociation of formaldehyde, H2CO→H2+CO, which has a planar transition state. Dynamical calculations indicate that there may also be a significant degree of mode-specificity for the formaldehyde reaction beyond that due to symmetry.

Kinetics and mechanism of unimolecular decomposition of 3-methyl-1-p-tolyltriazene

1981 ◽  
Vol 59 (6) ◽  
pp. 923-926 ◽  
Author(s):  
Keith Vaughan ◽  
Michael T. H. Liu
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Kinetic Parameters ◽  
Kinetics And Mechanism ◽  
Unimolecular Decomposition ◽  
Mechanism Of Degradation

Kinetic parameters (Ea and ΔS≠) for the thermolysis of 3-methyl-1-p-tolyltriazene (1) in tetrachloroethylene have been determined. The near-zero value for ΔS≠ suggests a transition state with minimal stretching of the N—N bonds in tautomers 1a or 1b. The activation energy (Ea = 29.2 kcal/mol) and ΔS≠ for the decomposition of 1 are very similar to those of the azoarylalkanes (Ar—N=N—R), suggesting a similar mechanism of degradation. The major products of the thermolysis of 1 are p-toluidine, N-methyl-p-toluidine, and p-chlorotoluene, which are rationalized in terms of homolytic breakdown of both tautomers.

Mode specificity in the model unimolecular reaction H-C-C .fwdarw. H + C:C

1986 ◽  
Vol 90 (16) ◽  
pp. 3517-3524 ◽  
Author(s):  
Kandadai N. Swamy ◽  
William L. Hase ◽  
Bruce C. Garrett ◽  
C. William McCurdy ◽  
J. F. McNutt
Keyword(s):  
Unimolecular Reaction ◽  
Mode Specificity

On the Unimolecular Decomposition of the tert-Butoxy Radical

1973 ◽  
Vol 51 (13) ◽  
pp. 2138-2140 ◽  
Author(s):  
C. K. Yip ◽  
H. O. Pritchard
Keyword(s):  
Pressure Dependence ◽  
Unimolecular Reaction ◽  
Unimolecular Decomposition ◽  
Reaction Theory ◽  
Butoxy Radical

It is argued that a large apparent pressure dependence in the rate of decomposition of the tert-butoxy radical should not be interpreted in terms of unimolecular reaction theory; the effect is probably heterogeneous in origin.

scholarly journals Transition between [R]- and [S]-Stereoisomers without Bond Breaking

2020 ◽  
Author(s):  
Shampa Raghunathan ◽  
Komal Yadav ◽  
V. C. Rojisha ◽  
Tanashree Jaganade ◽  
V. Prathyusha ◽  
...  
Keyword(s):  
Transition State ◽  
Theoretical Calculations ◽  
Bond Breaking ◽  
Kinetic Properties ◽  
Intermediate Structure ◽  
Structure Dynamic ◽  
Planar Transition ◽  
First Time

We for the first time shown that transition between (R) and (S) stereoisomers via a planar transition state or an intermediate structure without having to break a bond is possible. Rigorous theoretical calculations have been used to study this novel phenomenon and to characterize the energetic, structure, dynamic and kinetic properties.

scholarly journals Local Mode Excitation for Time Resolved Unimolecular Decay Studies

1983 ◽  
Vol 2 (5-6) ◽  
pp. 321-333 ◽  
Author(s):  
T. R. Rizzo ◽  
B. D. Cannon ◽  
E. S. McGinley ◽  
F. F. Crim
Keyword(s):  
Hydrogen Peroxide ◽  
Laser Excitation ◽  
Local Mode ◽  
Unimolecular Reaction ◽  
Time Resolved ◽  
Mode Excitation ◽  
Excited Molecules

Laser excitation of overtone vibrations is a useful technique for selectively preparing molecules for state-selected unimolecular reaction studies. In addition, these studies provide new data on overtone vibration transitions in the excited molecules. Data obtained from state-selected unimolecular decay experiments and photoacoustic measurements provide local mode parameters for overtone vibrations in tetramethyldioxetane, t-butylalcohol, t-butylhydroperoxide, and hydrogen peroxide.

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