Enthalpies of Hydrogenation of Phenylalkynes: Indirect Determination of the Enthalpy of Formation of Diphenylcyclopropenone

Article abstract of DOI:10.1021/jo00219a030

This paper gives the enthalpies of hydrogenation of some phenylalkynes, measured in hexane solution, which lead to their enthalpies of formation.Measured enthalpies of hydrogenation of phenylacetylene, 1-phenyl-1-propyne, 1-phenyl-1-butyne, 1-phenyl-1-hexyne, diphenylacetylene, and diphenylbutadiyne are -66.1 +/- 0.4, -62.2 +/- 0.5, -62.7 +/- 0.2, -62.6 +/- 0.3, -59.6 +/- 0.6, and -118.5 +/- 1.0 kcal mol^-1, respectively.Our experimental result for diphenylacetylene is not in agreement with group additivity calculations and, when combined with a recent value for the decarbonylation of 2,3-diphenylcycloprop-2-en-1-one, leads to a resonance stabilization for the compound of 22 kcal mol^-1, or about twice the estimate obtained by the group additivity method.