Stereochemical nonrigidity in solid zirconium and hafnium tetrakistetrahydroborates. Evidence for two dynamic intramolecular rearrangement processes in covalent tridentate tetrahydroborates

1977 ◽  
Vol 99 (23) ◽  
pp. 7539-7545 ◽  
Author(s):  
I-Ssuer Chuang ◽  
Tobin J. Marks ◽  
William J. Kennelly ◽  
John R. Kolb
Keyword(s):  
Intramolecular Rearrangement ◽  
Stereochemical Nonrigidity ◽  
Rearrangement Processes

Derivation of a Master Equation for Intramolecular Relaxation Using Projection Operator Techniques in Liouville Space

1972 ◽  
Vol 27 (3) ◽  
pp. 526-533
Author(s):  
Notker Rösch
Keyword(s):  
Master Equation ◽  
Coarse Graining ◽  
Relevant Information ◽  
Coarse Grained ◽  
Inhomogeneous Equation ◽  
Intramolecular Rearrangement ◽  
Von Neumann ◽  
Liouville Space ◽  
Space Formalism ◽  
Rearrangement Processes

Abstract A generalized master equation is derived to describe intramolecular rearrangement processes. It is an inhomogeneous equation, including memory effects. The derivation is based on the Liouville space formalism. Because chemically relevant information is contained in the off-diagonal elements of the density matrix, a non-diagonal coarse-graining projector is used. All necessary assumptions are stated explicitly. By making further approximations, the master equation can be reduced to an inhomogeneous von Neumann equation with an effective Liouville operator the imaginary part of which is responsible for relaxation-like coarse-grained solutions. All neglected terms are given in closed form. The character of the solutions of the master equation is discussed in "coordinate-free" manner, i.e. without referring to the underlying Hilbert space.

Thermo-Oxidative Decomposition of Lovage (Levisticum officinale) and Davana (Artemisia pallens) Essential Oils under Simulated Tobacco Heating Product Conditions

2020 ◽  
Vol 29 (1) ◽  
pp. 27-43
Author(s):  
Emma Jakab ◽  
Zoltán Sebestyén ◽  
Bence Babinszki ◽  
Eszter Barta-Rajnai ◽  
Zsuzsanna Czégény ◽  
...  
Keyword(s):  
Low Temperature ◽  
Essential Oils ◽  
Relative Yield ◽  
Gas Chromatography Mass Spectrometry ◽  
Intramolecular Rearrangement ◽  
Oxidation Reactions ◽  
Pyrolysis Gas ◽  
Oxidative Decomposition ◽  
Oxidative Pyrolysis ◽  
Artemisia Pallens

SummaryThe thermo-oxidative decomposition of lovage (Levisticum officinale) and davana (Artemisia pallens) essential oils has been studied by pyrolysis-gas chromatography/mass spectrometry in 9% oxygen and 91% nitrogen atmosphere at 300 °C to simulate low-temperature tobacco heating conditions. Both lovage and davana oils contain numerous chemical substances; the main components of both oils are various oxygen-containing compounds. Isobenzofuranones are the most important constituents of lovage oil, and their relative intensity changed significantly during oxidative pyrolysis. (Z)-ligustilide underwent two kinds of decomposition reactions: an aromatization reaction resulting in the formation of butylidenephthalide and the scission of the lactone ring with the elimination of carbon dioxide or carbon monoxide. Davanone is the main component of davana oil, which did not decompose considerably during low-temperature oxidative pyrolysis. However, the relative yield of the second most intensive component, bicyclogermacrene, reduced markedly due to bond rearrangement reactions. Davana ether underwent oxidation reactions leading to the formation of various furanic compounds. The changes in the composition of both essential oils could be interpreted in terms of bond splitting, intramolecular rearrangement mechanisms and oxidation reactions of several constituents during low-temperature oxidative pyrolysis. The applied thermo-oxidative method was found to be suitable to study the stability of the essential oils and monitor the decomposition products under simulated tobacco heating conditions. In spite of the complicated composition of the essential oils, no evidence for interaction between the oil components was found. [Beitr. Tabakforsch. Int. 29 (2020) 27–43]

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