Sciencemadness Discussion Board

Phthalic anhydride from naphthalene

CobaltChloride - 24-3-2018 at 12:42

I've recently found a moth repelling product which explicitly states that it is 80% naphthalene and 15% anti agglomeration agent. After recrystallization from ethanol, the product became crystalline. I've noticed that the science madness wiki lists "making phthalic anhydride" in the projects section of the naphthalene page. What is the process involved in this synthesis? It would be nice to not have to make it from gloves.

JJay - 24-3-2018 at 13:05

You can oxidize naphthalene to phthalic acid with permanganate. This is usually performed in an acid medium. There are several papers on this topic that you can easily locate. I don't know what the anti-agglomeration agent would be (talc, silicon dioxide, wax, ???).

battoussai114 - 24-3-2018 at 13:19

Industrially the oxidizer is oxygen over a transition metal oxide catalyst. I remember reading about it a while back and, IIRC, the better performing ones where Vanadium followed by Molybdenum oxide. I'm out of my house right now, as soon as I get back I'll try to upload some papers I probably have on my external HD.

CobaltChloride - 24-3-2018 at 13:32

Quote: Originally posted by JJay  
You can oxidize naphthalene to phthalic acid with permanganate. This is usually performed in an acid medium. There are several papers on this topic that you can easily locate. I don't know what the anti-agglomeration agent would be (talc, silicon dioxide, wax, ???).

I don't know what it is, but it doesn't seem to be soluble in boiling ethanol. Doing a hot filtration was enough to remove it. The recrystallization should've also removed the 5% which is unaccounted for because it is, most probably, composed of related hydrocarbons.

Magpie - 24-3-2018 at 14:37

Here's an easy way to make it from phthalic acid:

https://www.sciencemadness.org/whisper/viewthread.php?tid=25...

CobaltChloride - 24-3-2018 at 16:23

Quote: Originally posted by Magpie  
Here's an easy way to make it from phthalic acid:

https://www.sciencemadness.org/whisper/viewthread.php?tid=25...

I know the reaction conditions, but thank you for providing me with the exact procedure.

Foeskes - 24-3-2018 at 21:56

There are lots of videoes on making it from xylene. The procedure should be similar. I think making it from napthalene uses quite a lot of permanganate for a low amount. Maybe xylene is better(I haven't done any calculations yet.
Either way you need to be a bit careful permanganates are really strong oxidizers and if you're not careful it can oxidize your products to CO2 and H2O decreasing yield.

[Edited on 25-3-2018 by Foeskes]

CobaltChloride - 25-3-2018 at 03:36

I am quite new to the world of organic chemistry, so that's why I wanted an exact procedure (papers on the subject don't seem to give one). The stoichiometry is 1:4 naphthalene:permanganate according to this paper: https://jchps.com/issues/Volume%2010_Issue%201/40-0581116.pd... . For me, xylene isn't very easy to get (I need to do a fractional distillation of a paint thinner and a lot of azeotropes with xylene are formed, thus decreasing yield significantly).