Chapter 4 - Solvent Selection

Abstract

Solvents are selected to increase reaction rates, to increase the reproducibility and ease of running reactions, and to ensure that the desired quality and yield of product is reached. Other important considerations are to decrease waste and allow for efficient solvent recovery and reuse. Each of these goals has a direct effect on productivity and product cost for a manufactured product. In early stages of development, providing material by any means is crucial, and solvents are selected to ensure that the desired product can be prepared within the timeline with minimal difficulty. This chapter concerns solvent classifications, solvation, and key physical parameters. Many of the characteristics of solvents are determined by functional groups. Many efforts have been made to quantitate and predict the ability of solvents to dissolve molecules. A parameter frequently used to assess the polarity of a solvent is the dielectric constant. Solvents are usually chosen based on compatibility with the selected reagents. Many solvents commonly used in academia are rarely used for scale-up in industry. Suitable solvents, which dissolve the desired materials, are liquid at the desired processing temperatures, and have the desired amount of water miscibility. Solvents should also allow for safe, convenient operations. There are three alternatives to solvents classically used by organic chemists. Water may be used in place of organic solvents, or no solvent may be added to a reaction. Alternative solvents are also being investigated.