While the chemistry of amines has been extensively studied on the Si(100)-2x1 surface, relatively little is known about their reactivity with the Ge(100)-2x1 surface. In this study, the reactions of pyrrole and multiple pyrrole derivatives, including methylpyrrole, pyrrolidine, and methylpyrrolidine, with the Ge(100)-2x1 and Si(100)-2x1 surface were investigated via multiple internal reflection infrared spectroscopy and ab initio quantum chemistry calculations. This series of compounds comprises a model system for examining the competition of multiple functionalities on Ge(100) and Si(100) and the role kinetics and thermodynamics play on selectively controlling growth of organics on semiconductor surfaces. Although these compounds are structurally similar, they each follow different reaction mechanisms on the Si surface, including dative bonding, N-H dissociation, cycloaddition, and electrophilic aromatic substitution. We have also found that the adsorption of pyrrole and its derivatives on the Ge surface is surprisingly different from the Si surface. While the reaction of organics on Si is typically under kinetic control, the experimental and theoretical results show that thermodynamical considerations are also necessary to explain the reaction of organics on Ge. Additionally, aromaticity and charge transfer to the surface are found to have significant effects on the adsorption behavior of these compounds.