Experiments and Previous Theoretical Investigations

The pyrolysis of substituted cyclopropane leads to three types of unimolecular isomerizations (see Fig. 3). The first kinetic study of the conversion of cyclopropane into propylene (reaction a) was undertaken by Trautz and Winkler in 1922  

The geometrical isomerization (reaction b) was discovered by Rabinovitch, Schlag, and Wiberg in 1958 reaction b is faster than structural isomerization in propylene (a). Finally, the optical isomerization was observed, independently by Crawford and Lynch by Berson and Balquist by Bergmann and Carter and by Willcott and Cargle their common conclusion states that geometrical (b) and optical (c) isomerizations are competitive reaction processes. If only the sub- 

These reactions have aroused a great deal of interest among theoretical chemists. Indeed, they lie within the simplest reactions in organic chemistry formally, they require only a rotation of 180° in one or both methylene groups. Hoffmann, in his 

I) For a more recent experimental work on the mechanism of this reaction, see Ref. For.later studies on cis-trans isomerization in substituted cyclopropanes, see 

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