Solvents and chemicals

All chemicals and solvents used in inert atmosphere reactions must be dry. Most of these materials provided by suppliers are not dry enough, even solvents which you consider to be immiscible with water, and may contain enough moisture to hinder the reaction or reduce the yield of your product. Therefore you must ensure that all chemicals to be used in the process have been dried to the appropriate levels, as described below.

Solid chemicals
These should be dried by the methods outlined on. The most common approach is to dry the chemical in an oven and then allow it to cool in a vacuum desiccator. Techniques for extremely air-sensitive solids can be found in the specialist literature.

Liquid chemicals
All liquids should be dried by a method appropriate to the amount of water they may contain. Generally, the liquid should be dried with a solid drying agent which does not react with the chemical (consult the appropriate literature or your instructor), filtered, distilled, then stored over molecular sieves in a bottle capped by a septum and redistilled before use. Alternatively, the liquid can be dissolved in a solvent, the solution dried, the solvent removed by evaporation and the liquid distilled and stored as described above.

Solvents
The solvent will have the greatest volume in your reaction and it must be dry. Most laboratory-grade solvents, as supplied by manufacturers, contain varying amounts of water and therefore must be dried by the appropriate method before use. If you are required to dry the solvent, you should consult the literature (Errington, 1997; Harwood, et al., 2000; Furniss, et al., 1989).

Some manufacturers supply dry solvents in 2.5 L quantities for inert atmosphere reactions and HPLC. These solvents are relatively expensive but may be economic in terms of time and expense if one-off reactions are required. However, such solvents should be treated with suspicion if the containers are less than half-full, since air and moisture may have been allowed into the container by previous users. If you have any doubts, dry the solvent.