Vigorous pyrolysis

Intact bacteria were first introduced into a mass spectrometer for analysis of molecular biomarkers without processing and fractionation around 1975.6 The ionization techniques available at the time limited analysis to secondary metabolites that could be volatilized, such as quinines and diglycerides, and vigorous pyrolysis of bacteria was explored as an alternative.7 Although biomarkers were destroyed in pyrolysis strategies, computer-supported cluster analysis was developed to characterize pure samples. 

Experiments, based on the hypothesis that the behaviour of suitably chosen (our italics) aromatic molecules on vigorous pyrolysis should closely or even exactly parallel the fragmentations of the corresponding molecular ions in the mass spectrometer , have led to an improved synthesis of biphenylene (R. F. C. Brown and Solly, 1966). The mass spectra of polycarbonyl compounds (29-31) were used as a guide to the selection of suitable precursors of biphenylene and its derivatives by... 

The pyrolytic reactions usually take place at temperatures higher than 250-300° C, commonly between 500° C and 800° C. The chemical transformations taking place under the influence of heat at a temperature between 100° C and 300° C are commonly called thermal degradations [4] and not pyrolysis. Mild pyrolysis is considered to take place between 300° C and 500° C and vigorous pyrolysis above 800° C. 

Vigorous Pyrolysis. Occurs at temperatures between 800 and 1100°C. The end results is the breaking of carbon-carbon bonds and cleaving organic molecules into smaller fragments. 

The alkanes have low reactivities as compared to other hydrocarbons. Much alkane chemistry involves free-radical chain reactions that occur under vigorous conditions, eg, combustion and pyrolysis. Isobutane exhibits a different chemical behavior than / -butane, owing in part to the presence of a tertiary carbon atom and to the stability of the associated free radical. 

This structure rationalizes (a) the formation of mono- and, under more vigorous conditions, tetra-acetyl derivatives, (b) the methyla-tion to a dimethyl derivative still containing two active hydrogens, (c) the pyrolysis back to monomeric indole, (d) the formation of a benzylidene derivative containing the Ph CH=N— Ar ehromophore, (e) the failure to form a simple nitroso derivative, (f) the Zn/AcOH reduction of the dimethyl trimer to base C18H20N2, shown to be identical with the dihydro derivative of (26). 

Synthesis of benzo[c]furans and isoindoles (181) is also possible by the addition of benzyne to the respective monocycles (178), followed by reduction (179 — 180) and pyrolysis. In an alternative procedure, (179) is reacted with 3,6-bis(2-pyridyl)-l,2,4,5-tetrazine, which affords (181) under far less vigorous conditions via a retro Diels-Alder reaction of the intermediate (182). 4-Phenyl-1,2,4-triazoles pyrolyze to form isoindoles (Section 3.4.3.12.2). 

The reactors for the basic propane and n-butane pyrolysis were of monolithic annular quartz construction (Type I reactor). The reaction space was kept virtually isothermal by a surrounding bath of Ottawa sand fluidized vigorously by a stream of nitrogen. Temperature profiles were measured by calibrated Pt-Rh couples in a central thermowell. A description of this type of reactor has been given elsewhere (6). 

Much of the chemistry of alkanes involves free-radical chain reactions, which take place under vigorous conditions and usually yield mixtures of products. A reactive particle—typically an atom or free radical—is needed to begin the attack on an alkane molecule. It is the generation of this reactive particle that requires the vigorous conditions the dissociation of a halogen molecule into atoms, for example, or even (as in pyrolysis) dissociation of the alkane molecule itself. 

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