We perform molecular dynamics simulations on a system of hard annular sector particles (ASPs) to investigate the reaction-dynamics relationship. The dimerization reaction zone, mixing reaction zone including dimerization and n-merization (n > 2), and arrested region are observed successively as area fraction φA increases from low to high. In this work, we focus on the properties of the concentrated arrested region (φA≥ 0.400). The results show that for systems at φA≥ 0.400, the ratio of n-merization increases with φA and n-merization finally becomes the dominant reaction in the system; dynamic heterogeneity (DH) is observed and is demonstrated to originate from the divergent size of clusters consisting of high-mobility particles; the particles with a high translational or rotational mobility are found to have a high ability to react with other particles at φA > 0.400; more interestingly, binding reactions are found to correlate spatially with DH at φA > 0.400. Our work sheds new light on understanding the role of DH in binding reactions or specific-site recognition assembly in a crowded environment.