Thermolysis reactions, solution

All solvents for these solution thermolysis reactions were freshly distilled and all reactions were done in sealed glass tubes heated in a thermostatted oven. Over a wide range of solvents (DMF, naphthalene, diphenylmethane, benzene, toluene, and decalin) there was no significant variation in either isomerization rate or product composition. Reactions were done at 125°C, 155°C and 195°C and the only limitation was that DMF could not be used as the solvent in reactions at 195°C it led to substantial substrate destruction (polymer forming reactions of substrate with DMF ). Isomer compositions were ascertained both by HPLC and by NMR. 

Also the thermohydrolysis of the urea solution after the injection into the hot exhaust gas upstream of the SCR catalyst has been investigated at the diesel test rig. Urea solution was atomized about 3 m upstream of the SCR catalyst into the hot exhaust equivalent to a residence time in the pipe section of 0.1 s at 440°C. As expected for the thermolysis reaction, ammonia and isocyanic acid were found at the catalyst entrance at all temperatures (Figure 9.3). The 1 1 ratio of both components shows that only the thermolysis but not the hydrolysis is taking place in the gas phase. It can also be seen that the residence time of 0.1 s is not sufficient for the quantitative thermolysis of urea, as appreciable amounts of undecomposed urea were always found. The urea share even raises with lowering the flue gas temperature, although the residence time... 

We report here the results of our recent studies of poly(alkyl/arylphosphazenes) with particular emphasis on the following areas (1) the overall scope of, and recent improvements in, the condensation polymerization method (2) the characterization of a representative series of these polymers by dilute solution techniques (viscosity, membrane osmometry, light scattering, and size exclusion chromatography), thermal analysis (TGA and DSC), NMR spectroscopy, and X-ray diffraction (3) the preparation and preliminary thermolysis reactions of new, functionalized phosphoranimine monomers and (4) the mechanism of the polymerization reaction. 

The physical properties of the supercritical fluid differ from those of the bulk liquid. One of the most notable changes is the lower dielectric constant of polar solvents such as water which allows the accumulation of low-polarity solutes at this interface. This explains the crucial role of the hydro-phobicity of solutes during reactions in the solution. Thermolysis as well as radical abstraction reactions occur in this region. A temperature of approximately 800 K was determined for the interfacial region surrounding the... 

Azepines, or dibenzamils , are usually formed in minor quantities in the thermolysis reaction except in extremely dilute solutions, and no ring enlargement has been observed in systems where amines are absent or in photolyses in acetic acid it has been inferred that in these systems azacyclopropene is not formed. 

Solution thermolysis of [PtIV(Me)2H(K3-Tp )] also induces reductive elimination of methane. C-D bond activation occurs after methane elimination in benzene-, to yield [PtIV(Me)(C6D5)D(k 3-Tp )] (Fig. 2.128), that upon a second reductive elimina-tion/oxidative addition reaction forms isotopically labeled methane and [PtIV(C6D5)2D(K3-Tp )]. [Pt(Me)(NCCD3)(K2-Tp )] has been obtained upon elimination of methane from [PtIV(Me)2H(K3-Tp )]. The a-methane complex [Ptn(Me)(K2-Tp )(CH4)] has been indicated... 

Thermolysis of A(-(2-propynyl)dihydroisoindole at 500 °C provides another synthesis of 2H-isoindole <84AG(E)517, 87CZ349). The product can be obtained from the condensed (— 196°C) pyr-olyzate and used as a solution. The reaction presumably is a retroene process (Scheme 73). 

The first homogeneous catalytic HDS reaction reported involved the conversion of DBT to biphenyl plus H2S, together with some hydrogenolysis products by use of [(triphos)IrH], generated by thermolysis of [(triphos)IrH2(Et)] in THF solution. The reaction proceeds slowly at 170 °C. The catalytic cycle (Scheme 13) was established from the isolation of most of the intermediates involved and the independent study of the individual reactions implicated. ... 

These polymers are sensitive to thermolysis and decomposes rapidly and smoothly to bisphenol A, carbon dioxide, and volatile dienes when heated near 200 . For example polymer 8 affords only benzene, carbon dioxide, and bisphenol A upon heating. As in the case with t-butyl esters and carbonates, this thermolysis reaction is susceptible to acid catalysis and this property forms the basis of our resist design. The tertiary polycarbonate resist is formulated by casting a polymer film from a solution containing a few percent of substances which will produce strong acid upon photolysis. 

The main example of a category I indole synthesis is the Hemetsberger procedure for preparation of indole-2-carboxylate esters from ot-azidocinna-mates[l]. The procedure involves condensation of an aromatic aldehyde with an azidoacetate ester, followed by thermolysis of the resulting a-azidocinna-mate. The conditions used for the base-catalysed condensation are critical since the azidoacetate enolate can decompose by elimination of nitrogen. Conditions developed by Moody usually give good yields[2]. This involves slow addition of the aldehyde and 3-5 equiv. of the azide to a cold solution of sodium ethoxide. While the thermolysis might be viewed as a nitrene insertion reaction, it has been demonstrated that azirine intermediates can be isolated at intermediate temperatures[3]. 

Thermolysis of trithiane (69) or carbonate (70) at reduced pressure yields methylene-thiirane which is stable in cold, dilute solution (Scheme 152) (78JA7436, 78RTC214). A novel acenaphthylene episulfide is obtained by treatment of the six-membered sulfoxide (71) with acetic anhydride (Scheme 153) (68JA1676), and photolysis of (72) gives a low yield of episulfide (73 Scheme 154) (72JA521). Low yields may be due to the desulfurization of the thiiranes under the reaction conditions. 

The thermal behavior of A and B above 150°C has been studied. Both in the gas phase and in solution, each compound yields a 3 5 mixture of ,Z-l,5-cyclooctadiene (C) and Z,Z-l,5-cyclooctadiene (D). When hexachlorocyclopentadiene is present, compound E is found in place of C, but the amount of D formed is about the same as in its absence. Formulate a description of the thermolysis mechanism that is consistent with these facts and the general theory of thermal electrolytic reactions. 

The only known representative of this type of compound, 91, was prepared by 1,3-dipolar addition of mesityl nitrile oxide to telluroketone 85 (93JA7019 94MI1). The reaction proceeds smoothly on heating equimolar amounts of the reactants at 80°C, giving rise to 91 in 70% yield. The heterocycle is a thermally unstable and light-sensitive compound. Thermolysis of a deuterochloroform solution of 91 at 60-90°C in a sealed ampule affords 1,1,3,3-tetramethylindanone and mesityl isonitrile (94MI1). 

However, when MAIs are thermolyzed in solution, the role of the cage effect has to be taken into account. The thermolytically formed macroradicals can, due to their size, diffuse only slowly apart from each other. Therefore, the number of combination events will be much higher for MAIs than for low-molecular weight AIBN derivatives. As was shown by Smith [16], the tendency toward radical combination depends significantly on the rigidity and the bulkiness of the chain. Species such as cyclohexyl or diphenylmethyl incorporated into the MAI s main chain lead to the almost quantitative combination of the radicals formed upon thermolysis. In addition, combination chain transfer reactions may... 

Pioneering studies have shown that the yield of iV-phenyl-3//-azepin-2-amine (32, R = Ph) from the thermolysis of phenyl azide in aniline increases as the ratio of azide to aniline decreases, and in dilute solution with an azide to aniline ratio of 1 200 a 54% yield of the 3//-azepine can be achieved.34 The reaction is successful with other arylamines, but the procedure is of limited preparative value as large volumes of amine are required and only moderate yields of 3H-azepines are obtained. 

The thermolysis of aryl azides in alcoholic solution has been used to prepare 2-alkoxy-37f-azepines. Thermolysis of 3-azidophenyl methyl ketone in methanol in a sealed ampule furnishes a mixture of the 6-acetyl- (36a) and 4-acetyl-2-methoxy-3//-azepine (37a) in superior yields to those obtained in the corresponding photolytic reaction.78 Other 3-substituted azides behave similarly, with a preference for the 6-substituted isomers 36, as is observed for azide photolyses in amine solutions. 

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