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The dendral computer program uses established rules of molecular fragmentation to help chemists solve complex structural problems from mass spectral data. This paper describes a computer program called Meta-DENDRAL, that can aid in the discovery of such rules from empirical data on known compounds. The program uses heuristic methods to search for common structural environments around those bonds that are found to fragment and abstracts plausible fragmentation rules. The program has been tested on the well-characterized, low-resolution mass spectra of aliphatic amines and the high-resolution mass spectra of estrogenic steroids. The program has also discovered new fragmentation rules for mono-, di-, and triketoandrostanes.

The thermal decomposition of normal alkanes and linear poly(α‐olefins) was found to occur predominately by random scissions, followed by volatilization into an open system. To show these processes the fragment distribution from high molecular weight linear polyethylene (fragments to C55), n‐alkanes, polypropylene, and polyisobutylene (fragments to C60) are reported and discussed in depth. Based on the results, a mechanism of random scissions followed by volatilization is postulated for polyethylene and n‐alkanes as well as for polyisobutylene and polypropylene. Polystyrene is shown not to follow the same mechanism, for little evidence for fragments above trimers was found. In addition, temperature rise–time measurements at the pyrolyzer probe are reported and explained.

Free-Radical Reactions of Pyrroles 1163 the reaction subsided and the system had reached room temperature. The reaction mixture was worked up by distillation and trituration with ligroin to give a crystalline solid. The recrystallized product, m.p. 69°, 3.1 g., was obtained in 28% yield. The infrared spectrum of the solid coincided with that of the prepared phenyl sulfoxide. Mixture melting technique gave no depression.

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