Sciencemadness Discussion Board

Has anyone made sodamide?

thereelstory - 19-5-2010 at 18:56

by mixing na and anhydrous nh3?

also, what cool experiments could be done with this Sodamide?

Picric-A - 19-5-2010 at 23:12

You cant just 'mix' Sodium and anhydrous ammonia, the reaction must be conducted at high temp and probably pressure.
As for uses, do some research!

DJF90 - 20-5-2010 at 01:06

Whoa steady on... You CAN just mix sodium and anhydrous liquid ammonia; do YOUR research Picric-A! Initially you get the blue colour of solvated electrons but eventually this fades and what is left is a solution of NaNH2 in anhydrous liquid ammonia. Quoting Feiser:

Most laboratory procedures are based upon the discovery by Nieuwland and co-workers that the reaction between sodium and liquid ammonia is accelerated markedly by a black catalyst prepared originally by the reaction of a ferric salt with oxides of sodium in liquid ammonia. Liquid ammonia (500ml) was stirred at -33*C and treated with 0.3g Fe(NO3)3-6H2O and then with 1g of sodium. Air was bubbled through the mixture to discharge the initial blue colour and produce a black precipitate of catalyst. Additional sodium (25g), added portionwise was then consumed in about 20min. with discharge od the blue colour and production of a grey suspension of sodium amide. The solubility of sodium amide prepared in this way is 1 mole per liter of liquid ammonia at -33*C.

So perhaps you can familiarise yourself with the known literature before saying the reaction "must" but conducted at high temp and perhaps pressure. There is usually "more than one way to skin a cat", as it were...

As for uses, Feiser details 6 pages worth of material. I'm sure you could find some if you looked. I've been kind enough to attach the monograph from "Handbook of reagents for organic synthesis: Acidic and basic reagents".

[Edited on 20-5-2010 by DJF90]

Attachment: Acidic and Basic Reagents - Sodamide.pdf (327kB)
This file has been downloaded 2164 times

Picric-A - 20-5-2010 at 01:27

The sodium/ammonia complex takes a while to fade and so it is NOT the best method of preparing sodamide.
Brauer's prep outlines passing NH3 over heated Na then once fully reacted leave to cool in a steady stream of NH3, leaving pure white sodamide.
The Feiser prep leaves you with a solution of (1molar) sodamide to dispose of- i doubt anybody has the equiptment to safely deal with that or in an enviromently friendly manner.

DJF90 - 20-5-2010 at 01:59

Nobody said it was the best way to make it, but "best" is surely a matter of opinion depending on apparatus available and ease of preparation. If you can make liquid ammonia, then this is almost certainly the safest method, and gives material of adequte purity for all but the most demanding analytical uses. The Feiser prep gives sodium amide which has a solubility of 1 mole/liter of ammonia, but more than that is produced as it clearly states you obtain a grey suspension, i.e. there is more sodamide than can dissolve - however your comment about disposal of a 1M solution is minor as you would scale down suffuciently to make the amount of reagent needed for your synthesis; typically <10mmol.

panziandi - 20-5-2010 at 04:38

Firstly: I really think that this thread should be in the beginning section!

Secondly:The is nothing more anoying than reading the word "cool", in a context other than that relating to temperature, in the same sentence as sodamide! Sodamide is a particulrly strong base, it reacts violently with water releasing toxic and irritant fumes of ammonia. It also oxidises slowly on storage forming shock sensitive explosive peroxides! This is not really something to be made and experimented with by a k3wl!

Thirdly: I couldn't resist... Picric-A... Read before posting! DJF90 clearly states in the quote from Feiser that the sodium is consumed in 20mins with a precipitate of sodium amide, there is also some solvated sodium amide in the ammonia solvent. Indeed if you simply mixed sodium with liquid ammonia the solution is fairly stable for a time, that is why the ferric catalyst is added to reduce reaction time to 20mins, which, in all fairness, is a hell of a lot quicker than the method of heating sodium in a stream of ammonia. In addition the method of heating sodium in ammonia can also form sodium hydride which needs to be removed by adjusting the temperature in a second round of heating. So, why not do some research yourself before 1) posting uninformative remarks and 2) posting pseudo-knowledge.

Because of the sodium amide's tendancy to form explosive peroxides on storage, as well as with the fact that it is dangerous when wet and hygroscopic. Many university undergraduate labs prepare in situ by solvating sodium in liquid ammonia since this removes the storage and handling hazards of the solid material. Together with the fact that many students in a chemistry undergraduate lab are not chemists at heart, they often make handling errors when weighing etc, it wouldn't take a genious to envisage cross contamination into a jar of sodium amide something that would be incompatible...

In my honest opinion, if thereelstory is not a k3wl and is looking to do some interesting organic chemistry with this strong base rather than "cool" stuff, his best bet would be to form it in situ and not to isolate the sodium amide for storage.

Picric-A - 20-5-2010 at 04:55

I know some of the sodium amide precipitates however SOME also stays in solution and i would call a solution of sodium amide (corrosive, toxic) in liquid ammonia (toxic, corrosive, harmfull... etc...) a serious hazard to have around/ store/ destoy and i dont see why anybody would pick this method.

Of course there is virtually no means of us in the UK purchasing liquid ammonia however i hear it is fairly readily available in the USA for farms and so if it is readily avaiable then i guess i dont see why not use it! (liquid ammonia is used by meth cooks for Birch reduction in the USA)

Sedit - 20-5-2010 at 04:59

The complex also forms NaNH2 in the presence of Styrene and the references for this reaction can be found either in my Li[NH3]4 thread or others here on the board. There are a few catalyst that can perform this reaction to NaNH2 from the complex and if you do a search for inhibiters of the birch reaction you will find the government spent sometime trying to find things that quickly destroyed the Sodium or Lithium complexes to prevent its use in the manufacturing of Methamphetamines.

DJF90 - 20-5-2010 at 05:10

You don't have to buy liquid ammonia; -33*C is pretty mediocre and you can readily condense ammonia gas using dry ice/acetone or even a salt-ice mixture. Like I said before, the solution obtained is 1M which is fairly reasonable, and you would only make as much as you would need for the reaction in question. Both methods would involve decent ventilation but the high temperature route also has potential for explosion, as ammonia forms explosive mixtures with air (between 15 and 28% IIRC).

Panziandi is quite right when he says that this method is quick and reliable. Often you need a solvent for your reaction and selecting one for sodium amide can be tricky; when made in situ the liquid ammonia is the solvent and so this is not an issue, and the low temperature is generally required when deprotonating with a strong base anyway. You definately wouldnt *store* the solution as this would require a freezer suitable for purpose; it's easier to just make it as needed. If solid sodium amide is needed, one can allow the solvent to evaporate to leave the material behind as a slightly grey powder.

Picric-A - 20-5-2010 at 09:23

DJ- Both procedures have potential for explosion. In the high temp reaction it is true the temperature is off-putting however dont forget only pure NH3 is being tapped in and so no fuel/air mixtures are being produced-especially those as obscure as 15-28%.
The risks of the liquid NH3+Na method is well known as it is often a reason for meth labs 'random' explosion- runaway reaction.
I have to agree however, the latter would be better for producing <3g quantities.

DJF90 - 20-5-2010 at 11:36

You're missing the point Picric-A; when you're pumping the ammonia in to the apparatus, air is already in there. You may argue that with a tube this is not much of an issue and you're right, but for producing quantities via the hot method you typically use an oven as in "Inorganic Syntheses", in which the air might not be as readily displaced by the ammonia gas as you'd like.

Explosion from the liquid ammonia method is negligable; we're chemists here, not meth cooks, and so will know external cooling is required. Chances are you'll already have the flask in a (dry) ice bath anyway in order to help condense the ammonia and/or to minimise evaporative losses (this shouldnt be an issue with a dewar condenser though but some methods advocate allowing the ammonia to boil off during the preparation and topping up as required). Portionwise addition od sodium metal (also mentioned by Feiser) also helps with this issue.

I'm going to disagree with you again on your final point; for preparation of <3g quantities, especially if purity is an issue, the hot method would be more appropriate. 3g worth of material can be made readily from a quantity of sodium in a combustion boat in a tube. Again, this may not be the best method from a safety point of view if you have access to liquid ammonia (or if you condense it yourself), but on such a scale it is a minor problem (recall my comments about the tube above) readily overcome and gives a purer product (necessary if you're worried trace Fe compounds may interfere with your reaction).

The WiZard is In - 20-5-2010 at 13:01

Quote: Originally posted by thereelstory  
by mixing na and anhydrous nh3?

also, what cool experiments could be done with this Sodamide?

When thrown into water a most lively action occurs, just as if the
crystals had consisted of globules of red-hot metal, violent hissing
occurring without the evolution of any gas except water vapour.
The solution is found to contain only soda and ammonia.
Sodamide may be prepared in much larger quantities and in very
much less time by allowing .......

Didn't take a second or two to find this at
and a SL of other stuff.

panziandi - 20-5-2010 at 14:53

Also do not forget that with the method Picric-A suggests:

Na + NH3 => NaNH2 + 0.5H2

Some of this H2 is consumed forming NaH but some of it will escape. Note that both H2 and NH3 will form explosive mixtures with air. The reaction time is much longer, equipment is not the bog standard quickfit etc and will require a much larger amount of gaseous ammonia (in my opion but I haven't done the maths).

Reaction of sodium with liquid ammonia with a little ferric nitrate is the STANDARD method of preparing sodium amide for use in the lab. Liquid ammonia is both a reactant and later a solvent for the reaction. On work up the liquid ammonia is evaporated off and the follows standard work up. Much less hassle and much less time.

Liquid ammonia is easy. Simply pass ammonia into a flask cooled with a freezing mixture (normally dry ice-acetone) at first it's tricky to get it to condense but once a small amount has liquified the rest soon follows.

Sedit - 20-5-2010 at 16:46

Why all the talk of Liquid ammonia when it should work equally as well using a complex with Na using the gas form of ammonia. Then one would just have to bubble NH3 into Et2O and stir and the complex will rise to the surface for decanting. It would make the process even easier since ice and salt water bath is plety cold enough for this and since your going for NaNH2 cooling may not even be needed at all, just feed in NH3 until all the Na is consumed and precipitated as the amide.

In theory it should work rather well for the production on a small scale and Iv been planing it for sometime with LiNH2 but have had other focus everytime Iv made the Lithium complex such as studing its stablity and properties while also attempting to streamline the synthesis.

franklyn - 21-5-2010 at 04:32


ScienceSquirrel - 21-5-2010 at 06:43

I have made sodium amide by reacting sodium with liquid ammonia as described above.
Cylinders of ammonia gas are available quite readily in the UK and the gas can be condensed in a flask using a dry ice / acetone cooling mixture.
There is nothing about the reaction that a competent undergraduate could not achieve given the resources.

Barium - 21-5-2010 at 17:16

Quote: Originally posted by Picric-A  
Of course there is virtually no means of us in the UK purchasing liquid ammonia

Perhaps UK is the exception to this law of physics, but everywhere else in the world a commercial cylinder of compressed ammonia actually mostly contains liquid ammonia. Just get the right type of equipment to remove it in the liquid form.

Anders Hoveland - 6-7-2010 at 14:47

Quote: Originally posted by DJF90  

Most laboratory procedures are based upon the discovery by Nieuwland and co-workers that the reaction between sodium and liquid ammonia is accelerated markedly by a black catalyst prepared originally by the reaction of a ferric salt with oxides of sodium in liquid ammonia. Liquid ammonia (500ml) was stirred at -33*C and treated with 0.3g Fe(NO3)3-6H2O and then with 1g of sodium. Air was bubbled through the mixture to discharge the initial blue colour and produce a black precipitate of catalyst. Additional sodium (25g), added portionwise was then consumed in about 20min. with discharge od the blue colour and production of a grey suspension of sodium amide. The solubility of sodium amide prepared in this way is 1 mole per liter of liquid ammonia at -33*C.

[Edited on 20-5-2010 by DJF90]

This is an excellent reference. I am surprised. This should be very useful to make sodium azide. There are two main reactions for this. One is sodium nitrite warmed with hydrazine, the other is sodium amide and nitrous acid. If I can skip the hydrazine, this will be much easier.

Solvent for sodium amide

AndersHoveland - 13-4-2011 at 11:25

Is anyone aware of other solvents that can actually dissolve sodium amide, without reacting with it?

Anhydrous liquid ammonia is usually employed for such reactions, as this seems to be the only liquid which can dissolve sodium amide without reacting with it, but this solvent is extremely inconvenient for a variety of reasons.
Ammonia has a boiling point of minus 33 degrees Celsius, which means "dry ice" (frozen CO2) needs to be used to keep the ammonia cold. Liquid anhydrous ammonia is mildly corrossive and can cause severe chemical and cold burns on contact with skin. The liquid gives off of poisonous fumes, which can result in unconsciousness, or even death in high enough concentrations in air. Some reactions involving sodium amide require heat, which necessitates pressurizing the liquid ammonia. This requires the proper reaction vessel and is potentially dangerous.

Nearly all other solvents react with sodium amide. Alcohols, ethylene diamine, analine, hydrazine*, pyridine, and N,N-diisopropylethylamine all react with the amide ion.

Frequently, a dispersion of sodium amide in a hydrocarbon solvent is used for reactions. As the mixture is actually a suspension, the sodium amide is not actually dissolved.

The only thing I can think of that might work as a solvent is something like an alkyl zinc amide. CH3CH2CH2CH2ZnNH2

*Sodium hydrazide NaN2H3 is a pale yellow crystalline compound which is pyrophoric and can explode on exposure to air, and explodes violently when heated above 100 C. It can be produced by gradually addition of drops of hydrazine hydrate into a suspension of sodium in ether, then heating in the absence of oxygen. Otherwise hydrazine reacts very vigorously with sodium metal, producing only hydrogen and ammonia. For the reaction between sodium amide and anhydrous hydrazine, it was found necessary to use the sodium amide in finely divided form, as otherwise it will react only very slowly with the hydrazine because a protective coating of the sodium hydrazide forms on the surface.

[Edited on 13-4-2011 by AndersHoveland]

RiP057 - 15-4-2011 at 21:53

very true if you cool the cylinder down and then invert it and open up it usually comes out liquid or so Ive heard.... but this thread looks like it is chock full of people speaking out of there arse, but alas thats what the internet is for innit?

I did have a lecture bottle once of ammonia, and I actually had to keep heating it up so it would gas out the ammonia for when I was removing it from the cylinder (gas form) it kept cooling the remaining down to the boiling point which is quite cold....

Also try buying ammonia in the US and see what happens...... especially if you tell them you are dissolving sodium or a metal in it :)

However I like the use of ammonia hydroxide dripped over a bed of potassium hydroxide will gas ammonia right out.... best way to create ammonia gas in the lab....

and for small amount I like the sodium straight in anyhdrous liquid ammonia best.....straight forward

[Edited on 16-4-2011 by RiP057]

RiP057 - 15-4-2011 at 21:58

why not use benzene as a solvent??? I know it wouldnt solvate it very much, but it would a little

Eclectic - 16-4-2011 at 03:25

If you have good ventilation, delivering liquid anhydrous ammonia from tank bottom directly into a dewar works just fine. The heat of vaporization is high enough that boiling off a small amount cools the remainder. I've seen a sodamide prep done this way.

Azides from hydrazine and nitrite seems much less hazardous.

AndersHoveland - 16-4-2011 at 13:14

Sodium metal and dry ammonia gas, when heated to 320-350degC, react to form sodium amide and hydrogen. The reaction proceeds around 5 times faster by bubbling the anhydrous NH3 gas into the molten sodium (heated between 300-350degC) for two hours. Interestingly, below 250 degC, an unknown substance with a lower proportion of nitrogen is obtained. After complete reaction of the sodium, the unknown product did not produce hydrogen gas on reaction with water. With the reaction conducted at 200degC, the product contained 71.2% sodium by weight and 23.4% nitrogen. This possibly suggests formation of some Na2NH. However, this observation was published in the early part of the century (without modern analytical equipment) and there does not seem to be any other published detailed investigations into the unknown product of this reaction.

The "Concise encyclopedia chemistry", by Mary Eagleson, claims that, "sodium amide, m.p. 210C, sublimable in vacuum, decomposing above 500C to sodium imide, Na2NH, and then to sodium nitride, Na3N, and ammonia".*

It also says that sodium amide “is produced…by allowing the blue solution of sodium in liquid ammonia to stand. This slowly loses color and develops hydrogen (the reaction is more rapid in the presence of catalytic amounts of iron)…”

So apparently a catalyst is not absolutely required for sodium to react with cold liquid ammonia, the reaction is just very slow.

*However, I have severe doubts about the accuracy of the "sodium imide" and "sodium nitride".
A recent article (Synthesis and characterization of amide–borohydrides: New complex light hydrides for potential hydrogen storage, Philip A. Chater, 2007) claims that "Sodium imide is unknown". Sodium nitride is very unstable, decomposing into its elements at only 87 °C. Sodium metal cannot be made to react directly with nitrogen, and thermal decomposition of sodium azide only produces elemental sodium and N2.

Investigations by Titherly, C.A. Kraus, and William Argo showed that molten fused sodium amide, even when free from traces of sodium hydroxide, both very slowly dissolves metallic platinum, and catalyzes the partial decomposition of molten sodium amide. Using platinum black and fused sodium amide, the platinum slowly dissolved, and the color turned first red, then brown, and finally black, with apparent increased viscosity. The evolution of gas from the reaction was slow at 210C but increased rapidly with increased temperature. After heating for 14 hours at 300C, the gas evolved was almost entirely NH3. The solid product remaining was found to contain 1.658 moles of sodium for every mole of nitrogen present in the compound (sodium amide contains 1 mole of sodium for every 1 mole of nitrogen).

The fact that no nitrogen was evolved during the partial decomposition, and that the reaction product only produced NH3 when later reacted with water, suggested the formation of either some sodium imide and/or sodium nitride, although neither of these were isolated.

[Edited on 16-4-2011 by AndersHoveland]