Molecules: You'd better learn to live with them.
Sodium bisulfite is a decent reducing agent, but lots of synthetic chemists know it as a convenient (and positively ancient) reagent for forming derivatives of aldehydes, which are useful preparatively. When you treat an aldehyde with NaSO3H, an insoluble adduct often precipitates, leaving behind most of the non-aldehyde junk (assuming it was water-soluble in the first place). I like it because it's clean and old-timey. You don't see it used as often as you'd hope. It also has some utility in deaminating aromatic amines (and reaminating aromatic alcohols, given its reversibility).
Comments
Sodium bisulphite is also an important food preservative.
The reaction with aldehydes in one of the reasons that it is used in dried apricots and other dried fruit. The formation of the adduct prevents the formation non-enzymatic browning reaction products. Thus, the apricots stay orange. Unfortunately, in acid foods bisulphite turns into sulphur dioxide in the headspace which can cause asthma.
Posted by: Lab Cat | January 17, 2007 10:06 AM
Bisulfite addition products are also a convenient route to cyanohydrins in basic medium rather than using explicit HCN in acid medium,
http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0323
Note 1, in base
http://www.orgsyn.org/orgsyn/prep.asp?prep=cv2p0007
In acid
There's nothing quite like a hint of almond to convice the bench chemist (or his replacement) to try something else.
Posted by: Uncle Al | January 17, 2007 11:21 AM