This paper presents a systematic computer aided molecular design (CAMD) framework for designing solvents for a reaction system. One of the functions of such solvents is to enhance the yield by product extraction. A number of solvent characteristics including biocompatibility, inertness, and ability to cause phase splitting, are considered for the reaction system. We employ the group contribution method to quantitatively represent the relationship between the structure and properties of the solvent molecule. The framework is modeled as a mixed integer nonlinear programming (MINLP) problem and the outer-approximation method with equality relaxation and augmented penalty (OA/ER/AP) is employed to solve it. We present two case studies on ethanol extractive fermentation to illustrate the proposed methodology.