Lewis thermal analysis

Mos of the solid carbonaceous material available to industry is derived from the pyrolysis of petroleum residues, coal, and coal tar residues. Understanding the reactions occurring during pyrolysis would be beneficial in conducting materials research on the manufacture of carbonaceous products. The pyrolysis of aromatic hydrocarbons has been reported to involve condensation and polymerization reactions that produce complex carbonaceous materials (I). Interest in the mechanism of pyrolysis of aromatic compounds is evidenced in a recent study by Edstrom and Lewis (2) on the differential thermal analysis of 84 model aromatic hydrocarbons. The study demonstrated that carbon formation was related to the molecular size of the compound and to energetic factors that could be estimated from ionization potentials. 

The only way in which the inert gases could form compounds would be by the donation of electron pairs. Several attempts have accordingly been made to obtain evidence of reaction with strong Lewis acids. Booth and Willson (1935) made a thermal analysis of the system argon-boron trifluoride between —127 and —133 °C at pressures up to 40 atmospheres. They reported the existence of compounds Ar(BF3)j where x = 1, 2, 3, 6, 8 and 12, but Wiberg and Karbe (1948) failed to confirm this. 

Pentyl-4 -cyanobiphenyl and 4-octyl-4 -cyanobiphenyl liquid crystals (LCs) confined in molecular sieves of MCM-41 and cloverite types are studied in a wide temperature range by dielectric spectroscopy, thermal analysis and in-situ FTIR spectroscopy. The phase transitions of the bulk LCs cannot be detected when confined in MCM-41 sieve. A relaxational process occurs due to the molecular motions in the layer at the pore walls the temperature dependence of the characteristic frequency obeys a Vogel-Fulcher-Tamman law associated to a glassy state. In the cloverite cages, the LCs keep the phase transitions of the bulk but shifted. Interactions between Lewis and Brdnsted sites and the LC molecules are monitored by IR spectroscopy. DTA measurements put also in evidence strong guest-host interactions. 

The papers presented in the following chapters represent advances in pressure sensitive adhesives (ultraviolet light activated acrylate monomer - low Tg polyether formulations) photoinitiated cationic polymerization (light activated aryliodonium and arylsulfonium salts of lewis acids in epoxy resin formulations) polymer and formulation design criteria for radiation curable adhesives radiation curable composites (dynamic thermal analysis characterization of electron beam cured... 

VR Harwalkar, CY Ma, eds. Thermal Analysis of Foods, Elsevier, London, 1991. MJ Lewis. Physical Properties of Foods and Food Processing Systems, VCH, Weinheim, 1987. 

The thermal reaction produced 5 and 6 in a 3 2 ratio but the Lewis acid-catalyzed reaction gave a 1 1 ratio. We could not separate the two cycloadducts, but based the indicated constitution on analysis of the mass spectrum and lH NMR spectrum of the mixture of the two compounds. The stereochemistry was assigned on the basis that the Diels-Alder reaction is normally suprafacial-suprafacial18 and that for other cycloaddition reactions of levoglucosenone (2) the addition anti to the 1,6-anhydro bridge is favored.13 15... 

Norbomadiene reacted with diethylphosphonochloridite [ClP(OEt)2] to afford phosphinate ester 150 and it was characterized by single crystal diffraction analysis <1996JHC979> the Lewis acid, POCl3 accelerated the reaction. Reaction of bispyrrolylpropane 175 with PBr3 led to the formation of bromophosphine derivative, which proved to be thermally unstable and was further converted to phosphate 176 with water <1999CHE1383>. 

An alternate route to formation of alkyl monolayers is via Lewis acid catalyzed reactions of alkenes with the hydrogen terminated surface. In this approach, a catalyst such as ethyl aluminum dichloride is used to mediate the hydrosilylation reaction of an alkene (or alkyne), resulting in the same type of product as in the case of the photochemical or thermal reactions. This type of reaction is well known based on molecular organosilane chemistry and has also been used successfully to alkylate porous silicon [31]. Although this route has been shown to work on H/Si(lll), the resulting monolayers are found to have lower coverages than those achieved using the photochemical or thermal approach [29], Another concern with this approach is the possibility of trace metal residues from the catalyst that could adversely affect the electronic properties of these surfaces (even when present at levels below the detection limit of most common surface analysis techniques). 

The formulation of Section 9.5.1 has served to remove the chemistry from the field equations, replacing it by suitable jump conditions across the reaction sheet. The expansion for small S/l, subsequently serves to separate the problem further into near-field and far-field problems. The domains of the near-field problems extend over a characteristic distance of order S on each side of the reaction sheet. The domains of the far-field problems extend upstream and downstream from those of the near-field problems over characteristic distances of orders from to /. Thus the near-field problems pertain to the entire wrinkled flame, and the far-field problems pertain to the regions of hydrodynamic adjustment on each side of the flame in essentially constant-density turbulent flow. Either matched asymptotic expansions or multiple-scale techniques are employed to connect the near-field and far-field problems. The near-field analysis has been completed for a one-reactant system with allowance made for a constant Lewis number differing from unity (by an amount of order l/P) for ideal gases with constant specific heats and constant thermal conductivities and coefficients of viscosity [122], [124], [125] the results have been extended to ideal gases with constant specific heats and constant Lewis and Prandtl numbers but thermal conductivities that vary with temperature [126]. The far-field analysis has been... 

Pyridine adsorption at room temperature on activated cloverite evidences the presence of Lewis and Bronsted acid sites. Pyridinium species hardly persists after evacuation at 423 K, showing that the Bronsted acidity is not very strong. Spectra analysis confirms that pyridinium species occur from the interaction with P-OH groups since the 3673 cm- and 944 cm- bands are regenerated by heating at the expense of the pyridinium species. The 3700 cm- v(OH) band hardly reappears by thermal evacuation suggesting that an irreversible reaction occurs during this treatment. Note that pyridine adsorption on phosphated alumina leads to protonation (8) due to interaction with free POH hydroxyls. 

Maddock, J. Lewis, P.A. Woodward, A. Massey, P.R. Kennedy, S. Determination of isosorbide dinitrate and its mononitrate metabolites in human plasma by high-performance liquid chromatography-thermal energy analysis. J.Chromatogr., 1983, 272, 129-136... 

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