Cyclic alkyl carbonates, such as ethylene and vinylene carbonate (EC and VC), form solid electrolyte interphases (SEI) suppressing continuous solvent reduction at the graphite anode. There is a consensus that the choice of carbonate clearly affects SEI performance. VC has been observed to polymerize, forming poly(VC), but also to release major amounts of CO2,1,2 which are two seemingly contradictory processes. In this work, we present a detailed study of reaction pathways of EC and VC in typical Li-ion battery electrolytes. The rate of the decomposition reactions of these carbonates in presence of hydroxide is monitored using an injection cell coupled mass spectrometer at varying temperatures ranging from 30°C to 60°C. The activation energies from the Arrhenius relationship between the CO2 evolution rate and the cell temperature confirms that VC hydrolysis is autocatalytic rather than stoichiometric. Direct quantifications and comparisons of the solubilized reaction products will be done over varying times and temperatures with the help of in-situ nuclear magnetic resonance (NMR) and Raman spectroscopy that will help in clarifying the individual steps in the reaction process. The kinetic studies of EC and VC hydrolysis in model systems like this is an important step towards improving our understanding towards carbonates as there is always some trace amounts of hydroxides present in the cells. The complex interconversions and equilibria of these organic alkyl carbonates and oxides investigated herein, will add to the knowledge of interphase formation processes, and support the tailoring of electrolyte formulations in order to enhance performance of future Li-ion batteries.