Propyl formate, pyrolysis

The pyrolysis of a mixture of the two stereoisomers of 5-methyl-5-(3-phenylpropyl)bicyclo[2.1.0]pentane leads to a mixture of three products. The two reactants equilibrate under the reaction conditions at a rate that exceeds product formation. When deuterium is introduced into the propyl side chain, there is no intermolecular deuterium scrambling. Write a mechanism for formation of each product and indicate how the deuterium results help to define the mechanism. What can be said about the lifetime of the intermediates in your mechanism ... 

Unsaturated compounds are obtained in good yield and often without isomerization by pyrolysis of esters of the requisite alcohol. These pyrolyses generally proceed with considerable stereoselectivity, yielding mostly the cis-olefin. A review of pyrolytic cw-eliminations has been provided by DePuy and King.23 The experimental technique is very simple the ester is heated as liquid or vapor at 300-500°. Working up of the product is also simple since neither a solvent nor another reactant is present. Pyrolysis of 1,2-dimethyl-propyl acetate at 500° gives pure 3-methyl-1-butene in 72% yield pyrolysis of 1,3-dimethylbutyl acetate also proceeds only in one direction, yielding 4-methyl-l-butene,24 and it is to be noted that in these cases olefin formation does not follow Saytzeff s rule ... 

To make the issue even more complex, two radicals can occasionally react with each other (dimerize) in a very exothermic formation of new hydrocarbons (dimers) that can reenter the reaction sequence and provide new species. For example, two propyl radicals might combine to form hexane (Fig. 11.8). Further pyrolysis of hexane would lead to many other products. 

---