This chapter explores the intricate dynamics of bubble sonochemistry with an emphasis on reaction pathways during the maximum compression phase, commonly referred to as “the end first collapse.” We delve into the molar-time evolution of key species within the collapsing bubble, with a particular focus on reactive radicals and oxidants that significantly influence sonochemical processes, especially in micropollutant degradation. A detailed analysis is presented on the reaction-time sensitivity to various factors, including the nature of trapped gases, imposed oscillation conditions (frequency and acoustic intensity), and medium properties such as temperature. By leveraging literature findings and advanced dynamic models, predominantly developed by the authors of the book, we propose reaction schemes for specific reaction systems at specific bubble temperatures. These schemes identify the primary reactions governing the production and consumption of crucial species. This comprehensive discussion enhances our understanding of sonochemical processes, laying the groundwork for optimizing conditions for pollutant degradation and other applications.