02-01-02 18:11
No 263845
Was just sitting around doing a rearrangement of isosafrole epoxide using IPA and noticed that the end results were on top of the water layer. What causes this? IPA is miscible with water; ketone in example is denser. I would expect it to be in solution or at the bottom.
Real men cook naked.
(Pioneer Researcher)
02-01-02 19:55
No 263873
IPA is soluble in water, but if you add salt, it forms a different layer, it's not like methanol. May be ketone and the other organics form a different layer together with IPA, so it is on top.
(Junior Service Representative)
02-01-02 20:00
No 263874
Is this a viable method of obtaining anhydrous isopropyl (salt addition to overcome intermolecular attraction of isopropyl to H2O?)?
PB
(Chief Bee)
02-01-02 20:33
No 263883
Yes, you can probably use table salt to turn 90% IPA to 98-99% or so, and then you remove the last percent of water with MgSO4 or similar.
(Hive Addict)
02-01-02 22:08
No 263925
Basically, IPA isn't a very polar molecule. When you add ketone to IPA, to further decrease its polarity, it'll form its own layer. Ditto with adding something like salt or sulfuric acid to water, you'll increase the polarity of the water, and push the IPA into a non-polar layer. Same thing happens with n-propanol as well as isopropanol. Lower alcohols like EtOH and MeOH will not tend to do this, usually the lower alcohol will stick with the aqueous layer...
And higher alcohols, like n-butanol and n-pentanol aren't even fully miscible with water.