Purification of Chloroform for
NMR Spectroscopy
In many respects chloroform is an ideal solvent for nmr spectrmcopy; being inexpensive, low boiling, and having gand solvation powers for a very wide range of compounds. Unfortunately, pure chloroform is very susceptible to oxidation and co&equently all commercial sources, including spectroscopic grades, are stabilized by the addition of 1-2% v/v ethanol. Although chloroform may be effectively freed from ethanol by standard techniques' the procedures are time consuming, significant losses2are encountered en route, and the purified solvent needs to bestored in the dark with rigorous exclusion of oxygen. We have recently found that chloroform can he rapidly and effectively purified by simply standing the solvent over activated molecular sieves. Thus, the figure shows the nmr spectrum of chloroform stabilized with 1.5%v/v ethanol before and after treatment4 with 5 A molecular sieves.5After treatment the small residual ethanol peak a t 6 1.23 is only just detectable, corresponding to an eths n d r m m
