Sciencemadness Discussion Board

identifying an unknown substance

soma - 15-1-2019 at 10:06

I have a bottle that used to contain dipropylamine. It has decomposed and now the liquid distills at 95C (dpa bp is 109-111). I would like to find out what the substance has turned into and am wondering what tests would be used to do that.

Sigmatropic - 15-1-2019 at 10:34

Diisopropyl amine boils at 84 C according to my sources. Perhaps it comes over as a high boiling azeotrope with water? Have you tried distilling over KOH?

Edit: just read we weren't talking about isopropyl. Sorry. But then again have you dried it prior to distillation?

[Edited on 15-1-2019 by Sigmatropic]

Tsjerk - 15-1-2019 at 13:33

Dipropylamine forms a azeotrope with water at 60 mol% DPA boiling at 86 C. Maybe you have water saturated DPA.

Triethylamine is known to boil at around 75 C when saturated with water, normal bp is 89 C.

soma - 16-1-2019 at 04:05

This should be real dry. There was no way for water to get in other than from the air exposure which was minimal. Also I was distilling it over KOH and the pot temp was 95. (There was about 150 ml in a lL round bottom.)

AJKOER - 21-1-2019 at 11:13

Photolysis (from a light source, especially UV) or the presence of transition metal impurites and any O2 may lead to a chemical breakdown of the dipropylamine. Products could include a gas build up, which would be suggestive of this pathway, which leads to an assortment of products.