Isotope Effects as Probe ofConstrictiveandIntrinsicBinding in Hemicarceplexes

Kinetic isotope effects (KIE) of hemicarceplex dissociation for naphthalene and p-xylene hemicarceplexes with partially and fully deuterated guests have been measured. The KIEs are consistent with the absence of steric effects in the transition states of hemicarceplex dissociation, which supports an earlier interpretation of constrictive binding energy in hemicarceplexes as being primarily controlled by different forms of gating.