A central goal of chemical mechanism research is to provide a comprehensive interpretation of chemical reaction pathways to clarify the evolution patterns of reactions. In this work, we present an unprecedented comprehensive monitoring of the elementary reaction pathways of the SN1 solvolysis on an in-situ real-time single-molecule electrical detection platform. Through the precise control of an oriented external electric field, we capture two short-lived protonated intermediates at the single-molecule level and elucidate their roles in the solvolysis reaction. Both temperature- and isotope-dependent experiments, in combination with theoretical simulations, reveal crucial roles for the hydrogen-bonded acetic-acid-mediated triple-proton-transfer and the proton-tunneling effect in the interconversion of these two intermediates. This work highlights the precise manipulation of chemical reactions by electrostatic field and opens up a universal route to discover unknown intermediates or novel phenomena in the processes of material transformation and life activities.