INFLUENCE OF SWELLING ON REACTION EFFICIENCY IN INTERCALATED CLAY-MINERALS .3. ION-DIPOLE REACTANT PAIRS

We continue our study of the influence of swelling on reaction efficie ncy in intercalated clay minerals. We consider ion-dipole reactant pai rs and recognize that when a smectite-type clay begins to swell, there will be a critical interlamellar spacing for which a dipolar molecule , previously constrained owing to the geometry of the host lattice, ca n begin to ''tumble''. The range of the potential function governing t he interaction of an ion-dipole reactant pair then switches from a 1/r (2) dependence, where an orientation angle theta must be specified, to a 1/r(4) dependence, where the angular dependence is washed out. We e xamine the consequences of this ''crossover'' by formulating a lattice -statistical model and studying in detail three cases where the effect s of angular orientation on the reaction efficiency can be thoroughly documented. Our principal conclusion is that the regions of theta-spac e where, statistically, the tumbling dipole spends the most time are t he regions characterized by the maximal (theta-specific) attractive in teractions between the ion-dipole reactant pair.