 The compound has nevertheless considerable strain energy and reverts to benzene with a chemical half-life of two days.This thermal conversion is relatively slow because it is symmetry forbidden based on orbital symmetry arguments.The compound itself was first synthesized in 1962 as a "tert"-butyl derivative and then as the unsubstituted compound by Eugene van Tamelen in 1963 by photolysis of the "cis"-1,2-dihydro derivative of phthalic anhydride followed by oxidation with lead tetraacetate.