Sciencemadness Discussion Board

lachrimatory effect of old iodine solution

Cloner - 15-11-2011 at 06:47

When using a solution of 0.1M iodine in ethanol that has been standing for a long time, I noticed a strong lachrimatory effect.

Is it possible some ethyl iodide has been produced?

bahamuth - 15-11-2011 at 07:03

Had this same effect on homemade iodine tincture (5% elemental iodine). I remember I used ketone denatured lab ethanol.

So I've always thought that the iodine formed something with the ketone, this since other solutions of iodine with acetone quite rapidly gained the lachrymatory effect.

AndersHoveland - 15-11-2011 at 13:25

Halogens slowly react with hydrocarbons through a radical cascade mechanism.
However, iodoalkanes are fairly reactive alkylating agents that would react with any alcohol (or water) present. These types of reactions are fairly complex, and there is no simple way to describe exactly what is happening.

Something similar to CH3CH2OCH(CH3)OCH2CH2I may likely be forming.

If acetone is used instead of alcohol, and you attempt to freeze such a mixture, you may likely notice heavy oily liquid droplets at the bottom, which are probably highly iodinated compounds.

[Edited on 15-11-2011 by AndersHoveland]