$4.$ Provide a reasonable arrow$-$pushing mechanism for the reaction in Part II of the experiment.trapping experiments. For this experiment, $1,3,5-$cyclohepatriene will be heated in the presence of

maleic anhydride. If the $1,3,5-$cyclohepatriene behaves as a diene in a straightforward Diels$-$Alder reaction,

the product should be one or both of the top two products on the right in the scheme below. If$,$ on the other

hand, the $1,3,5-$cyclohepatriene undergoes a valence isomerization to norcaradiene and the norcaradience

behaves as a diene in a reaction with maleic anhydride, then one or both of the bottom two products should

be formed.

Assuming that one of the four possible products predominates in the reaction, the challenge after

running the reaction will be to determine which one of the isomers was formed. Fortunately, three of the four

possible products have been previously characterized. This means that if you are able to isolate a single

compound, you should be able to determine from melting points and NMR spectroscopy which product was

formed. If it is one of the bottom two, you will have provided evidence for the temporary formation of

norcaradiene during the course of the reaction.

norcaradiene

A

$+$

endo

exo