EXPERIMENTAL ENTHALPIES OF FORMATION AND STRAIN ENERGIES FOR THE CAGED C20H20 PAGODANE AND DODECAHEDRANE FRAMEWORKS

The enthalpies of formation (Delta H-f degrees(g)) and the strain ener gies (E(str)) have been determined from combustion calorimetry for [1. 1.1.1]pagodane 1 (47.9; 95.5 kcal/mol), its 4,9-bis(methoxycarbonyl) d erivative 3 (-107.3; 95.5 kcal/mol) and the 1,6-bis(methoxycarbonyl)do decahedrane 4 (-151.8; 61.4 kcal/mol). On the basis of these measureme nts Delta H-f degrees(g) = 22.4 +/- 1 kcal/mol (standard deviation) an d E(str) = 61.4 +/- 1 kcal/mol are reliable estimates for parent (CH)( 20) dodecahedrane 2, an ''evergreen'' for computational activities, in good agreement with the MM2 predictions.