Search results for "composition"

Periodic Classification of Local Anaesthetics (Procaine Analogues)

2006

Algorithms for classification are proposed based on criteria (information entropyand its production). The feasibility of replacing a given anaesthetic by similar ones in thecomposition of a complex drug is studied. Some local anaesthetics currently in use areclassified using characteristic chemical properties of different portions of their molecules.Many classification algorithms are based on information entropy. When applying theseprocedures to sets of moderate size, an excessive number of results appear compatible withdata, and this number suffers a combinatorial explosion. However, after the equipartitionconjecture, one has a selection criterion between different variants resulting fromc…

Reactive species formed upon interaction of water with fine particulate matter from remote forest and polluted urban air

2020

Interaction of water with fine particulate matter leads to the formation of reactive species (RS) that may influence the aging, properties, and health effects of atmospheric aerosols. In this study, we explore the RS yields of fine PM from remote forest (Hyytiälä, Finland) and polluted urban air (Mainz, Germany and Beijing, China) and relate these yields to different chemical constituents and reaction mechanisms. Ultrahigh-resolution mass spectrometry was used to characterize organic aerosol composition, electron paramagnetic resonance (EPR) spectroscopy with a spin-trapping technique was used to determine the concentrations •OH, O2•−, and carbon- or oxygen-centered organic radicals, …

Theoretical Study of the Gas Phase Decomposition of Glycolic, Lactic, and 2-Hydroxyisobutyric Acids

1997

The reaction mechanism associated with the decomposition of three α-hydroxycarboxylic acids (glycolic, lactic, and 2-hydroxyisobutyric) in the gas phase to form carbon monoxide, water, and the corresponding carbonyl compounds has been theoretically characterized by using ab initio analytical gradients at the MP2 level of theory with the 6-31G** and 6-31++G** basis sets. A detailed characterization of the potential energy surface points out the existence of three competitive reaction pathways for the decomposition process. The first pathway describes a two-step mechanism, with water elimination and formation of an α-lactone intermediate, achieved by the nucleophilic attack of the carbonylic …

Study of the thermal decomposition of bromazepan complexes with Co(II), Ni(II), Cu(II) and Zn(II)

1984

Abstract The thermal behaviour of complexes of bromazepan with Co(II), Ni(II), Cu(II) and Zn(II) was studied by thermogravimetry (TG) and differential thermal analysis (DTA). The complexes decompose in two steps: dehydration and decomposition. A correlation between the dehydration temperatures of MB2Xn and the coordinating ability of X is observed.

Pd-catalyzed hydrodehalogenation of chlorinated olefins: Theoretical insights to the reaction mechanism

2012

Abstract Density functional theory calculations are applied to study energetics of trichloroethene (TCE) hydrodechlorination over pure Pd(1 1 1), chlorine-covered Pd(1 1 1), and Pd island supported by Au(1 1 1). Our results show that in all cases C Cl bond breakings take place more readily than C H bond formations and that TCE dechlorinates fully producing CCH precursors for the hydrogenations. The reaction pathway through radical-like species provides a possible explanation to the experimental product distributions that show a nominal amount of lesser chlorinated species in the presence of excess hydrogen. The surface chlorine resulted from the TCE decomposition weakens the binding of the …

A theoretical study on the decomposition mechanism of β-propiolactone and β-butyrolactone

1998

Abstract The reaction mechanism associated with the decomposition of β-propiolactone and β-butyrolactone in the gas phase to form carbon dioxide and ethylene or propene, respectively, has been theoretically characterized by using analytical gradients at the B3LYP/6-31G**, B3LYP/6-31++G**, MP2/6-31G** and MP2/6-31++G** calculation levels, as well as by single point calculations at QCISD(T)/6-31++G**//MP2/6-31++G**. A detailed analysis of the results points out that the reaction pathway can be described as an asynchronous concerted process. The geometrical parameters and the components of the transition vector are weakly dependent on the computational method. By applying transition state theo…

Initial reaction steps in the condensed-phase decomposition of propellants

2002

Understanding the reaction mechanisms for the decomposition of NO2-containing energetic materialsin the condensed phase is critical to our development of detailed kinetic models of these energetic materials in propellant combustion. To date, the reaction mechanisms in the condensed phase have been represented by global reactions. The detailed elementary reactions subsequent to the initial NO2 bond scissioning are not known. Using quantum chemical calculations, we have investigated the possible early steps in the decomposition of energetic materials that can occur in the condensed phase. We have used methylnitrate, methylnitramine, and nitroethane as prototypes for O−NO2, N−NO2 and C−NO2 nit…

Effect of catalyst composition on chain-end-group of polyethylene produced by salen-type complexes of titanium, zirconium, and vanadium

2010

Synthesis of Nanoferroics

2013

The Chapter covers the technological aspects of many chemical and physico-chemical nanofabrication methods relevant to making nanoferroic materials and composites. First, the classification of relevant synthesis methods of nanoferroics has been presented. Synthesis of particular nanoferroics with different chemical bonding like metallic, oxide and non-oxide compounds is considered in details. Among the methods, the mechanochemical, sonochemical, hydrothermal, co-precipitation, emulsion, thermal decomposition of unstable precursors have been analyzed. The competition between new phase nucleation and nuclei growth has been revealed to be controlled using feedback between reaction rate and tem…

The Performance Gap in Priority-Education and Non-Priority Education French Public Schools: Are we fighting inequality or reinforcing it?

2016

International audience