madscientist
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Preparing alkali amides
Everyone knows about the standard process for preparing sodium amide: passing anhydrous ammonia over sodium metal at 350C in the absence of oxygen.
That process is a little difficult. After some thought, I have devised an alternative.
CH3CONH2 + Na2O ----> NaCH3COO + NaNH2
A classic example of an acid anhydride reacting with a base anhydride.
This should also be able to be done with other carboxyl amines.
I weep at the sight of flaming acetic anhydride.
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kingspaz
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what about reduction of KNO2 with Na2Sx?
KNO2 + Na2S +H2O ---> Na2SO3 + KNH2
thats probably balls....nooooo....i just realised it is wrong because reduction on picramic acid is is NO2 -> NH2
this would be ONO- -> NH2....ONO- may not work...i dunno..i'm not thinkin straight...
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Rhadon
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I don't have acetamide, but it can be prepared by heating ammonium acetate.
I like the idea of making NaNH2 at home, since this would finally enable me to make sodium azide. But Na2O seems to be a problem to me. It would have
to be bought, wouldn't it?
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Rhadon
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OrgSyn.org also shows a method for making acetamide. It works after the same scheme as the way I mentioned above. Here is some copy & paste:
1. Procedure
In a 5-l. flask is placed 3 kg. (2860 cc., 50.0 moles) of glacial acetic acid and to this is added a weight of ammonium carbonate corresponding to 400
g. (23.5 moles) of ammonia (Note 1). The flask is fitted with a one-hole stopper holding an efficient fractionating column 90 cm. long with condenser
and receiver. An air condenser 150–200 cm. long may be employed. The mixture in the flask is heated to gentle boiling and the flame so regulated
that the rate of distillation does not exceed 180 cc. per hour. The distillation is continued in this way for eight to ten hours, until the
temperature at the head of the column reaches 110°. The distillate, which is a mixture of water and acetic acid, amounts to 1400–1500 cc. The
receiver is changed, the flame under the flask is gradually increased, and the distillation is continued at about the same rate until the temperature
at the head of the column rises to 140°. The distillate, which amounts to 500–700 cc., is largely acetic acid and may be used in the next run. The
contents of the flask are transferred to a 2-l. flask for fractional distillation (p. 130), having a column 40–50 cm. long, and distilled under
atmospheric pressure, using an air condenser. The fraction boiling below 210°, amounting to 250–300 cc., is collected separately. The material
remaining in the flask is nearly pure acetamide and may all be distilled, 1150–1200 g. passing over at 210–216°. By redistilling the fraction
boiling below 210°, the yield may be increased to 1200–1250 g. (87–90 per cent of the theoretical amount). The acetamide thus obtained is pure
enough for most purposes, but if a purer product is desired it may be recrystallized from a mixture of benzene and ethyl acetate; 1 l. of benzene and
300 cc. of ethyl acetate are used for 1 kg. of acetamide (Note 2). Colorless needles melting at 81° are thus obtained (Note 3). The solvent and the
acetamide it contains may be recovered by distillation.
2. Notes
1. Ammonium carbonate of commerce is often extremely impure, and care must be taken to obtain a representative sample for the determination of the
ammonia content by titration with standard acid. The ammonium carbonate used in this preparation contained 27.2 per cent of ammonia, and 1470 g. was
used in each run. 2. Crystallization of acetamide, by solution in hot methyl alcohol (0.8 cc. per g.) and dilution with ether (8–10 cc. per g.), has
been recommended as the best method of purification.1 3. As acetamide is somewhat hygroscopic, it cannot be exposed to the air unless precautions are
taken to have the air dry.
3. Discussion
Acetamide can be prepared by the rapid distillation of ammonium acetate;2 by heating ammonium acetate in a sealed tube and distilling the product;3 by
treating acetic anhydride with ammonia;4 by heating a mixture of ammonium chloride and sodium acetate to 240°;5 by the action of cold aqueous ammonia
on ethyl acetate;6 by boiling a mixture of glacial acetic acid and ammonium thiocyanate for four days;7 by saturating glacial acetic acid with dry
ammonia and then refluxing;8 by distillation of ammonium acetate through a reflux condenser filled first with glacial acetic acid and then with
aniline until the temperature of the mixture reaches 220°;9 by passing a stream of ammonia through heated acetic acid;10 and from formamide and
hydrogen at 200–500°.11 The procedure described is based on the method of Noyes and Goebel,12 in which equimolecular proportions of ammonium
acetate and acetic acid are heated together, the acetic acid having been shown to accelerate both the dehydration of ammonium acetate and the
hydrolysis of acetamide.
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Polverone
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Sodium amide is something that you try to use *only* if there's absolutely nothing else that will serve. It's one of the most difficult to handle,
hazardous compounds you'll encounter in a lab. If you want sodium azide, the preparations using hydrazine and isopropyl nitrites are far more easily
realized for the home experimenter. Of course it would be cool to have a little sodium amide, just as a trophy compound, but it's not something you
want to keep around for very long.
Oh, and Kingspaz, your method won't work because sodium amide is very water sensitive.
For preparing Na2O you could probably attempt NaOH electrolysis. Just don't bother with any sort of protection for the sodium metal. After a while
you'll have a mix of NaOH and Na2O. You'll need to be careful to shield the vessel from carbon dioxide (if using a combustion heat source). Or maybe
if you heat NaNO3 very strongly (so that nitrate and nitrite break down) in a clean crucible, you might get Na2O. All in all it strikes me as a very
dubious proposition, but NaNH2 is never going to be easy to make.
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Rhadon
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Thanks for your help, Polverone. The NaOH electrolysis might be worth a try. But I don't understand why NaNH2 is that hazardous - because it reacts
very strongly with water and forms NaOH?
Anyway, the hydrazine + isopropyl nitrite method seems harder to me if you also have to synthesize both the N2H4 and C3H7NO2 yourself.
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Polverone
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NaNH2 is corrosive, flammable, air sensitive, and water sensitive. It forms peroxides on extended exposure to air/oxygen and the resulting mixture of
amide and peroxide is explosive and shock-sensitive. So, assuming this reaction does work, you'd need to add your Na2O to acetamide (both perfectly
anhydrous) and evaporate the excess acetamide under anhydrous inert gas. Then you've got to dissolve it in anhydrous liquid ammonia and add a nitrate
or expose it to anhydrous nitrous oxide to form the azide. Does it still sound easier than the hydrazine route?
Also, do you ever buy chemicals from real dealers? It is not hard for me to buy hydrazine sulfate (100 g pharmaceutical grade for $25), although I
would still have to make my own isopropyl nitrite. I could also just buy the sodium azide but I am too nervous to place an order for it in the current
political climate. But I do not know what your chemical supply situation is like.
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Rhadon
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You may be right that making sodium azide that way will also be hard. But I still like it more than the hydrazine route.
And, yes, I buy chemicals from "real dealers", but only those ones which are totally unsuspicious. The chemical supply situation in Germany seems to
be pretty bad... there are resellers which do only sell "harmless" chemicals to private persons. And there are others who give you everything you want
but inform the police if they doubt that their stuff is used for legal purposes only. That's my experience, so I won't dare ordering sodium azide.
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madscientist
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I would think that it would be possible to prepare NaN3 from NaNH2 and NaNO2 using CH3COCH3 as a solvent.
I weep at the sight of flaming acetic anhydride.
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Polverone
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NaNO2 doesn't dissolve in acetone to any appreciable degree.
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PrimoPyro
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Nope
Cant reduce nitrites to amides. Reduction involves producing byproducts like water or alcohol, and amides react with these entities to form
oxides/alkoxides/hydroxides and ammonia.
Na2O reacts with liquid ammonia by the way to form a mixture of solid NaOH and NaNH2.
Im not sure if Na2O will react with acetamide.
Acetamide is easily made by several reactions including ethyl acetate + ammonia, acetic acid + urea, and dehydrating ammonium acetate by distilling
it.
PrimoPyro
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rikkitikkitavi
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In "chemistry of the elements" by Greenwood , p525 the following reaction is listed
Na2O + NH3 => NaNH2 + NaOH (in liquid NH3 )
the risks involved by handling liquid NH3 should not be taken lightly , however preparing Na2O is much easier than Na.
/rickard
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chochu3
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K20
KI + O3 = K2O + O2 + I2
Introduction to Chemical Science, by R.P. Williams, A.M., Chapter 26 sections 127 -128
 madhatter
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unionised
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I think sodamide would react with acetone. It also wouldn't dissolve the NaNO2.
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blip
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2NH<sub>3</sub>(l) + 2Na(s)
<sup><u> Fe2O3 </u></sup><s>></s> 2NaNH<sub>2</sub>(s) +
H<sub>2</sub>(g)
Another route if you happen to have Na around, but more difficult than what rickard presented as a result.
http://chemmovies.unl.edu/chemistry/redoxlp/b22.html
Main page:
http://chemmovies.unl.edu/chemistry/redoxlp/redox000.html
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