An idealized kinetic model and computer simulations of solid-state dimerization processes in stack-type crystal structures are reported. The expected concentration of isolated monomers, trapped between neighboring dimers, is 1/e2 ≈ 13.53% at the conclusion of dimerization. Expressions are derived for the concentration of monomers in environments with two, one, or zero monomeric nearest neighbors, as functions of conversion. Factors governing the quantum yield of photodimerizations and the rate of thermal dimerizations are analyzed. Deviations from the model due to reaction at defect sites, to solid-state diffusion, or to lattice distortions during the course of dimerization are considered.