Acids pyrolytic reactions

Another example of this is the loss of acetic acid when delphinine is heated in hydrogen at 200-215°. Just as aconitine is so converted into pyraconitine so delphinine yields pyrodelphinine, C3 H4 0,N, m.p. 208-212°, and similarly a-oxodelphinine, C33H430j qN, under like treatment loses acetic acid and yields pyro-a-oxodelphinine, C3 H3gOgN, which crystallises from methyl alcohol in needles, m.p. 248-250°, after sintering at 238°. This, on hydrogenation, forms a hexahydro-derivative, m.p. 183-5°, presumably by saturation of the benzoyl radical, which therefore leaves unexplained the mechanism by which acetic acid is lost in this pyrolytic reaction (c/. pyropseudaconitine, p. 683). 

Elimination reactions of fluorine compounds are not limited to the removal of simple molecules Frequently, large molecules or combination of smaller ones are formed as by-products, especially in pyrolytic reactions For example perhalo genated acid chlorides lose not only carbon monoxide but also chlorine fluoride [106, 107] (equations 74 and 75)... 

Both 1st- and 2nd-order rate expressions gave statistically good fits for the control samples, while the treated samples were statistically best analyzed by 2nd-order kinetics. The rate constants, lst-order activation parameters, and char/residue yields for the untreated samples were related to cellulose crystallinity. In addition, AS+ values for the control samples suggested that the pyrolytic reaction proceeds through an ordered transition state. The mass loss rates and activation parameters for the phosphoric acid-treated samples implied that the mass loss mechanism was different from that for the control untreated samples. The higher rates of mass loss and... 

Synthesis of (Z)-(lR)-tranH-Norchrysanthemic Acid by Pyrolytic Reaction of Chrysanthemum Dicaroboxylic Acid Monomethyl Ester with a New Catalyst... 

Although the majority of studies in this area involve five-membered ring cyclic anhydrides, a few pyrolytic reactions involving acyclic anhydrides have been reported. Thus, for example, FVP of 278 gives the alkylideneketene 279 with loss of trifluoroacetic acid142, while at 650 °C 280 loses both trifluoroacetic acid and cyclopentadiene to afford the indenylideneketene 281, which cyclizes by way of 282 to give 283143. FVP of... 

The major chemical changes in wood caused by fiberboard manufacture are secondary side reactions which are both beneficial and detrimental to the final properties achieved. Defibering is accomplished by hydrolytic breakdown of lignin and hemicelluloses under wet acidic conditions combined with high process temperatures. Board conversion and consolidation is attended by pyrolytic reactions which... 

Goodings [38] used ethylene dibenzoate as a model compound for pyrolysis studies on PET. His results indicated that an important pyrolytic reaction in molten PET is cleavage of an internal ester linkage to form a carboxylic acid end group and a vinyl ester end group... 

Pyrolytic reactions often occur in the gas phase, without the addition of another reagent. For example, heating carboxylate esters readily produces an alkene and a carboxylic acid. There is a requirement for a c/s-(3-hydrogen in order for this reaction pathway to proceed, because the reaction proceeds via a six-membered cyclic transition state. This cyclic pyrolytic elimination is labelled the Ei mechanism, which stands for intramolecular, or internal, elimination. In those versions of the Ei mechanism that involve a four- or five-membered cyclic transition state, there is a requirement that all the atoms are co-planar or virtually so. 

At high temperatures, pyrolytic reactions of lipids can yield fatty acid anhydrides, and fatty acids may eliminate carbon dioxide by decarboxylation. These reactions take place during food processing only at trace levels. 

F. derives de cyclodextrine Aim of derivatization is increased versatility by increasing the hydrophilic character of the outer surface area. This is accomplished with substituents such as sulfuric acid esters and alkyl, hydro-xyalkyl, carboxymethyl, aminoalkyl ethers formation of carboxyl groups by glycolic oxidation formation of branched c. with glucose or oligosaccharide side chains by pyrolytic reactions. Derivatization is mostly performed with P-cyclo-dextrin. Solubilities depend on DS as well as on the nature of the substituent groups levels up to 60% have been reached. In such cases, the viscos-... 

The derivative-forming process in pyrolytic alkylation involves two sequential reactions deprotonation of the acidic substrate in aqueous solution by the strongly basic tetra-alkylammonium ion and the thermal decomposition of the quaternary M-alkylammonium salt formed to give a tertiary amine and alkyl derivative. For some weak acids both processes may occur virtually simultaneously in the injector oven of the gas chromatograph. 

A third category of syn eliminations involves pyrolytic decomposition of esters with elimination of a carboxylic acid. The pyrolysis of acetate esters normally requires temperatures above 400° C and is usually a vapor phase reaction. In the laboratory this is done by using a glass tube in the heating zone of a small furnace. The vapors of the reactant are swept through the hot chamber by an inert gas and into a cold trap. Similar reactions occur with esters derived from long-chain acids. If the boiling point of the ester is above the decomposition temperature, the reaction can be carried out in the liquid phase, with distillation of the pyrolysis product. 

Retro-Diels-Alder reactions can be used to regenerate dienes or alkenes from Diels-Alder protected cyclohexene derivatives under pyrolytic conditions144. Most of the synthetic utility of this reaction comes from releasing the alkene by diene-deprotection. However, tetralin undergoes cycloreversion via the retro-Diels-Alder pathway to generate o-quinodimethane under laser photolysis (equation 89)145. A precursor of lysergic acid has been obtained by deprotection of the conjugated double bond and intramolecular Diels Alder reaction (equation 90)146. 

The first reaction step of thermal degradation is scission of an ester bond. Esters containing at least one ft-hydrogen atom decompose pyrolytically to give olefins and acids via a cyclic transition state (Figure 2.14). 

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