killswitch
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Isomers & leaching
When I prepared mononitrotoluene, the product came in two forms: a pale-yellow solid and a dark green liquid. From what I can gather, the liquid is
o-MNT and the solid p-MNT, both with traces of m-MNT.
I didn't keep any MNT, using all of it for the dinitration, so my ability to observe its behavior was limited.
Unlike the standard TNT synthesis, I separated the DNT from the spent acid. I kept roughly half of it, melt-casting the waxy solid and pouring it into
a glass vial.
Over a period of several weeks, a layer of yellow liquid emerged as shown below:
Now, from what I can gather, 2,6-DNT, 2,4-DNT, 2,3-DNT, and 2,5-DNT all have melting points above 50ºC. So what is this impurity?
Later, I will extract the liquid with a syringe and melt-cast the DNT again. Will further leaching occur? What is the limit for this purification
method?
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DraconicAcid
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I'm not very familiar with the various isomers of DNT, but if you have a mixture of organic compounds (or isomers), the melting point of the mixture
will be below that of the pure material. That's why melting points are used to measure the purity of a sample.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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PHILOU Zrealone
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Each different molecular structure will interfere on eatch one its cristallization by lowering the mp...so you will get kind of overfusion.
What nitration process did you use?
Maybe you have some nitrobenzoic acid inside...
In the past I used once a long period nitration of toluene (100ml) in a closed vessel at ambiant T° with 69% HNO3 (200 ml)...
Normally aromatic nitrations are not supposed to occure in such dilluted HNO3 but still in a few seconds yellow tinge is visibile at the interface and
so I decided to persue and follow that experiment closely...
With days the color of the acid turns green and the upper toluene phase turns yellow; with weeks orange and finally brown-black.
With monthes you start to see pale yellow-orange cristals on the glass walls into the upper brown organic layer.
Finally you end up with all the organic layer cristallized with those yellow-orange cristals.
Into the mix I found, and it is a good discovery, because it goes in contradiction with what is learned in organic chem class, (after rough analysis):
- Ortho-nitrotoluene (oily minor)
- Para-nitrotoluene (solid major)
and
- Para-nitrobenzoic acid (solid major soluble into NaOH).
- Analysis was not performed further to see if there was m-NT inside or o-nitrobenzoic acid or m-nitrobenzoic acid.
This experiment shows that:
1°) Never stop to experimentate even if it goes against theories in books.
Nitration of aromatics can occure in dillute HNO3, there is no need for concentrated HNO3 nor concentrated H2SO4. You only need time. I used no
heating and heating would have speeden the things up.
2°) Toluen first reacts into the aromatic ring and some of the NOx generated apparently oxydises the methyl moeity what turns into carboxylic acid.
This is proven by the fact nitration of benzoic acid goes mainly into meta nitrobenzoic acid and not in para position.
3°) This is thus a simple one pot reaction to get 3 products in isolable yields!
I still have the all reaction product to make the work up and provide more quantitative details.
[Edited on 18-9-2013 by PHILOU Zrealone]
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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killswitch
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That... is very interesting. Verrrry interesting.
Is it possible to isolate nitrobenzaldehyde derivatives in this manner?
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