Some Common Solvent Purification Methods


1.  Riddick, J. A.; Bunger, W. B.;  Sakano, T. K. (1986) Organic Solvents (4th ed.), John Wiley & Sons, New York.
2.  Gordon, A. J. and Ford, R. A. (1972) The Chemist’s Companion, John Wiley & Sons, New York, pp 431-436.

I have also included a few procedures which I have found to be superior to methods suggested by the above references.

Acetone  (BP 56.2)

Dry over Molec sieves or K2CO3.  Removal of aldehydes by KMnO4.  High purity:  saturate w/ dry NaI,  then chill to -10 C, filter off NaI crystals.  Distill and dry over sieves.

Acetonitrile  (BP 81.6)

Predry if wet, reflux & stir w/ CaH until gas evolution ceases.  Distill and store over sieves.

Benzene  (BP 80.1)

Stir w/ H2SO4 (.1l/l benzene) and separate acid.  Repeat until no darkening occurs, then distill.

Chloroform (BP 61.2)

Shake w/ con H2SO4, wash w/ water, dry and distill from K2CO3.  Alternatively, pass through column of Grade I activated alumina (50g/L solvent).

Diethyl ether (BP 34.5)

Check for peroxides.  Pretreat with Na wire, then add LAH (or CaH) and distill.

Diglyme (BP 161)

Heat over Na, then distill.

DMF (BP 152)

Stir w/ KOH, filter and distill from CaO or BaO.

DMSO (BP 189)

Dry overnite w/ Drierite, BaO, CaO, or NaOH.  Distill from BaO, CaO, or NaOH (2-3mm, 50 C).

p-Dioxane (BP 102)

Reflux over Na until the metal remains shiny then distill, store in dark under N2.  To remove acetal impurities, reflux a mixture of 300 ml H2O, 40 ml HCl, and 3 L dioxane for 12 h under N2.  Cool, add KOH until no more dissolves, then decant the dioxane layer and dry w/ KOH.  Distlill as above.

Ethanol (BP 78.3)

For anhydrous from abs:  Reflux 60 ml EtOH, 5 g Mg, and a few drops of CHCl3 or EtBr (catalyst) until all Mg converted to the oxide.  Add 900 ml EtOH, reflux 1 h, then distill, store over sieves.  Abs EtOH can be prepared from 95% if benzene must be excluded (no denaturants if USP grade) by refluxing over CaO for several hours, then distilling.

Ethyl Acetate (BP 77.1)

Wash with 5% Aq Na2CO3, then sat. CaCl2;  dry over K2CO3 and distill from P2O5.

Hexane (BP 68.7) See Saturated Hydrocarbons

Methanol (BP 64.5)

Most water removed by storage over CaO then distillation from CaO.  Storage over sieves (NO DRIERITE!!).  Ultrapure:  50 ml MeOH, 5 g Mg and 0.5g I2;  reflux until I2 color disappears, then add 1 L MeOH and return to reflux 1 h.  Distill slowly.

Methylene Chloride (BP 40.8)

Wash with con H2SO4, sat. Na2CO3, and water.  Dry over CaCl2 and distill from P2O5.  Alternatively, distillation from anhydrous K2CO3 and storage over 3A sieves gives pretty good product.

Pyridine (BP 115.3)

Dry over KOH for ~24 h, then distill from BaO or CaO.  Store over sieves.

Saturated Hydrocarbons

Most contain small amounts of olefin/aromatic.  For removal, shake with a mixture of H2SO4 and HNO3 3-4 times, wash water, dry CaCl2, and distill.

Tetrahydrofuran (BP 66)

Store over iron powder to inhibit peroxide formation, filter before purification.  Remove peroxides by refluxing with 0.5% (w/v) CuCl for 30 min., then distill.  Predry from KOH, reflux over Na for several hours, then cool to ~40* and add benzophenone;  distill when deep blue color is obtained.

Toluene  (BP 110.6)

Dry over CaCl2 (only if very wet) then distill.

The preceding information is intended for use by experienced chemists only.  If you are not famialiar with the reagents listed, do not attempt to use this information.