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Author: Subject: Reaction of sodium with DMF
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[*] posted on 19-2-2006 at 14:31
Reaction of sodium with DMF


In order to test out if dimethylformamide would be suitable as a liquid in which NaOH is soluble or reacts and which doesn't react with sodium (for use as a protective liquid in making Na/K alloy, mineral oil is not suitable because the metal tends to form small drops which won't unite again) I added a peasized piece of sodium to a test tube containing about 5ml of DMF.
Nothing happened at first, except for the (thin) NaOH crust on the Na to dissolve, and the sodium becoming shiny as intended.

As I then proceeded to heat the mix in order to melt the sodium, suddenly a very violent reaction occured. It hissed and boiled like crazy and spew out white smoke, it was scary as hell.

It formed a yellowish solid material in the tube, and the tube was extremely hot after the reaction had subsided.
I let it cool, added water and the solid dissolved. I poured the stuff away.

Now, this reaction was totally unexpected. I can't think of a reaction mechanism of sodium with DMF. I was under the impression that only NaOH would react with sodium, forming sodium formate and dimethylamine.
What could the reaction with sodium have produced? Does anyone have an idea?
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majdo
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[*] posted on 20-2-2006 at 10:08


1.strong bases like BuLi react w DMF,maybe Na mixed with something else may give stronly basic/nucleophilic medium that reacts with dmf
2.maybe something similar to acyloin condensation ocurred,but i'm not sure if amides can react so
3.but really i'm too stupid to know for sure what happened :),very interesting though
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[*] posted on 20-2-2006 at 11:15


Very interesting.
DMF seems to do a number of strange things, for instance with acetic anhydride it forms, after some time, a black solution - which still retains acetylating capability.

I tried to think of what could have happened but can't find a solution, and google is useless, all the MSDS says is 'Stable. Incompatible with strong oxidising agents, halogenated hydrocarbons, chloroformates, active halogen compounds, strong acids, strong reducing agents, rubber, leather.'. Also, DMF is known to undergo violent reactions with NaH, although this comb. is still used in org chem.

Are you prepared to do the experiment again, smaller amounts maybe?

I'd be very interested to see what gasses are evolved. Is it just heated DMF, or maybe some dimethylamine, or CO, methane, whatever? Siimple tests should allow you to determine the identity of it.
Also, that yellow residue could be identified further. I'm sure you could work it out that way.

Also, are you certain the DMF is pure, and doesn't contain water, or other things?




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[*] posted on 20-2-2006 at 12:16


I could repeat the reaction, and see if the evolving gases are, for example, flammable or have a special smell.
But the reaction looked as if only the DMF was boiling, and most of the white smoke stayed in the test tube.

I found the following two references, by searching on this site:

A study of the reaction of sodium metal with dimethylformamide

A study of the reaction of sodium with dimethylformamide

However, I cannot access them. Can somebody tell me how I could get them?
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[*] posted on 20-2-2006 at 13:01


Interesting! My first thought was acyloin-condensation, too. After searching some MSDS and Google I also just found the mentioned violent reaction of DMF with NaH. Later I found this abstract with SciFinder.

[color=darkgreen]Abstract

Alkali metal dimethylformamidyls, MCONMe2 (M = Li, Na and K) were prepd. by the reaction of alkali metals (Li, Na and K) with excess of DMF. These compounds are thermally unstable and lose CO gas in the initial stage (40-45°) of their decompn.


Bibliographic Information

Preparation and characterization of alkali metal dimethylformamidyls. Paul, R. C.; Anand, B. N.; Kapoor, R. Dep. Chem., Panjab Univ., Chandigarh, India. Indian Journal of Chemistry (1975), 13(12), 1338-40 [/color]

But what's the mechanism of this reaction? Maybe it’s a radical fragmentation with a followed polymerisation, which leads to the solid, but who knows. I hope someone can get that journal and/or the two studies.

However, it's astounding how difficult it is to find something about this reaction.




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S.C. Wack
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[*] posted on 20-2-2006 at 17:43


The article, and an earlier article that it references. The CA abstract mentioned is a mention of the second Maine paper, explanation of availability of this is on the "about" page.

Attachment: ijc.djvu (454kB)
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[*] posted on 21-2-2006 at 09:32


Thank you, S.C. Wack!

So the reaction produces dimethylformamidyl sodium (NaCON(CH3)2) first (at 0°C), under evolution of H2, and at 40- 50°C temperature this loses CO to form sodium dimethylamide.
Interesting, and also unexpected that the hydrogen atom of the formic group can react acidic when treated with metallic sodium.
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[*] posted on 21-2-2006 at 13:43


Thank you very much! I will read the articles during the weekend.

~Mephisto




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