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Author: Subject: Need help identifying a strange product...
Attondus
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[*] posted on 27-2-2018 at 17:11
Need help identifying a strange product...


I am an amateur self-teaching myself chemistry (have been doing so for a while), and I was doing an experiment and I am very puzzled about the formation of an unexpected substance...
A couple weeks ago, I bubbled NO2 gas through an alcohol to achieve the reaction ROH + 2NO2 --> RONO + HNO3. I used isopropanol (91%) as the alcohol. I ended up with a bright yellow product, with a fruity odor (from the isopropyl nitrite). I added a few drops onto copper and the surface corroded along with the formation of a few bubbles (from the HNO3). I was expecting the layers to separate, but I am guessing HNO3 is miscible in the nitrite. I left the mixture for a couple weeks, and the color turned orange. When I released the little bit of pressure that built up, I could smell a bit of nitrogen dioxide. This is probably due to the nitrite decomposing in the presence of the acid. So, I added sodium bicarbonate to neutralize the HNO3 and any dissolved NOx. I was left with a bright yellow liquid, and yellow-brown leftover bicarbonate, or other products on the bottom of the container. The liquid did not react with copper this time, and I put a small amount in a test tube of water and it separated into an organic layer on top. This, and the strong fruity odor confirms the presence of just the nitrite. So, I added water to the container to separate the rest of the nitrite, but instead, the entire mixture turned black after mixing, the nitrite layer didn't separate, and a little bit of odorless gas was released. I am guessing something in the leftover powder is reacting, but I have no clue what... Any ideas?

*Update: Mixture is pink when light is shone through it.

[Edited on 28-2-2018 by Attondus]
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Boffis
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[*] posted on 27-2-2018 at 22:12


I can't answer our question exactly but I read a paper once (its posted on this site somewhere) were the reactions of N2O4 were studied ith many compounds. In all but a few cases it is a messy reactant and it tends to function as an oxidizing agent as much as a proxy for nitrous and nitric acids. So your initial products probably contained acetone too. Under acid conditions this could react with the alkyl nitrite forming initially propanonal-3-oxime or with itself forming keto-alcohols and keto-olefin and so on. Eventually producing carboxylic acids and resins in a god awful mixture. I will see if I can find the paper, its on S somewhere.
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