Coumarins have attracted intense interest in recent years because of their diverse pharmacological properties. Among these properties, their cytotoxic effects were most extensively examined, their broad range of effects on the tumors as shown by various in vitro and in vivo experiments. Coumarins have important effects in plant biochemistry and physiology, acting as antioxidants, enzyme inhibitors. In addition, these compounds are involved in the actions of plant growth hormones, growth regulators, the control of respiration and photosynthesis. Coumarin derivatives have also found applications as fluorescent dyes, anti-inflammatory agents, antineoplastic agents, antifungals, anticoagulants, antibacterial, antimicrobial, insecticides, hepatoprotective and anti HIV activity. Therefore, the kinetics of the base hydrolysis of some coumarin derivatives were studied in aqueous solution and aqueous-co organic media at different temperatures.Moreover, the transfer chemical potentials of the investigated compounds were calculated from solubility data to give an overall idea of solvent effects on reactivity.