shape selectivity

in catalysis
Possibly observed in catalysts with very small pores. The selectivity is largely determined by the bulk or size of one or more reactants.
PAC, 1976, 46, 71. 'Manual of Symbols and Terminology for Physicochemical Quantities and Units - Appendix II. Definitions, Terminology and Symbols in Colloid and Surface Chemistry. Part II: Heterogeneous Catalysis' on page 81 (