New hemicarcerands 1 and 2 were prepared in 2-10 and 25% shell closure yields from tetrol 3 and TsOCH(2)C=CCH(2)OTs, and tetrol 3 and cis-ClCH2CH=CHCH2Cl, respectively. One-to-one carceplexes 1.1,4-(CH3)(2)C6H4, 1.C6H5CF3, 1.C6H5OCF3, 1.CHCl3, 1.CH2Cl2.CH2Cl2, and 1.BrCH2CH(CH3)CH2CH3 were formed by heating empty 1 in guest as solvent and characterized. The decomplexation rates in CDCl3 of the first three complexes were measured at four temperatures to give Delta G(double dagger) values of 21.5, 21.9, and 23.3 kcal mol(-1), respectively, as well as Delta H-double dagger and Delta S-double dagger values. Hemicarceplexes 2.(CH3)(2)NCOCH3, 2.CH3CH2O2CCH3, 2.1,4-(CH3)(2)C6H4, and 2.CH3C6H5 were prepared by heating the mixture of complexes from shell closure in the desired guest as solvent. The new complexes were isolated and characterized, and their decomplexation rates were measured in CDCl3. The crystal structures of 1.CHCl2CHCl2 and 2.C6H5CH3 revealed that the hosts are untwisted and their interhemispheric bridges are oriented io maximize the cavity size. In the former, the guest occupies the torrid zones of the globe-shaped cavity, whereas the long axes of host and guest in the latter were roughly aligned. The O-C-C and C-C=C bond angles in the bridges of 1.CHCl2CHCl2 ranged from 99 degrees to 105 degrees and from 172 degrees to 175 degrees, respectively. Reduction of 1.CHCl2CHCl2 and 1.1,4-(CH3)(2)C6H4 With H-2-Pd/C gave 3.CHCl2CHCl2 and 3.1,4-(CH3)(2)C6H4, respectively.