Experimental details are given for the preparation of large self-complementary molecules capable of assembly into pseudospherical capsules. These structures exist as hydrogen bended diners in organic solvents, and they form and dissipate on a time scale that permits direct NMR observation of the reversible encapsulation of smaller molecules. The cavity is roomy enough to accommodate more than one molecule, and two solvent molecules such as benzene appear to occupy the resting state of the capsules. Liberation of these solvent molecules is responsible for the unexpected thermodynamic parameters of the encapsulation process. A bimolecular reaction-the Diels-Alder reaction-is shown to be accelerated by the capsule as both reactants can occupy the capsule concurrently. Size selectivity, saturation kinetics, and product inhibition studies point to a reaction that takes place within the capsule.