Tackling TNAZ with pics

This particular energetic compound has been on my to-do list for a long time now.

TNAZ or 1,3,3 Trinitroazetidine is a four membered heterocycle with three nitro groups attached which was born into the world of energetics around 1990. It is an intriguing compound for two major reasons.

Firstly due to it's thermal stability, having a melting point of 101 degrees Celcius without decomposing. This property has resulted in research being conducted into new melt castable compositions for military use in the last decade or two in an attempt to find a replacement for TNT.

Secondly, TNAZ, due to its molecular structure, is a strained compound. Ideal sp3 hybridized bond angles sit at 109.5 degrees. Due to the square azetidine ring structure, these bond angles are approximately 90 degrees, imparting significant strain to the compound on a molecular level. This ring strain results in a more positive heat of formation and thus higher energy release upon detonation.

Despite the strained structure, the fact that this compound is thermally stable and only moderately sensitive is quite interesting. This could be due to the crystal packing, distribution of charge, the nitro groups, or all of these.
Anyway, here are the specs:

Molecular formula: C3H4N4O6
Molecular weight: 192.09 g/mol
Melting point: 101 .C
Oxygen balance: -16.66% (slightly underoxidized)
Density: 1.84 g/cm3
Heat of detonation: 6.30 KJ/g
Temperature of explosion: 4115 K
Moles of gas produced: 0.03644 mol/g
Avg molecular weight of gases: 32.01 g/mol
VOD: Using KJ method I get 9.69 Km/s but is too high, Klapotke states 8.86 Km/s.
Detonation pressure: I get 36.12 GPa, Klapotke states 34.25 GPa
Gurney velocity: 6 mm thick steel wall cylinder = 1.742 km/s (HMX = 1.646 Km.s). 19 mm thick steel wall cylinder =1.938 km/s (HMX = 1.842 Km/s)

I will be using the Coburn 5 step method for this synthesis. The reaction pathway is shown below.



[Edited on 20-11-2025 by greenlight]

[Edited on 20-11-2025 by greenlight]



[Edited on 20-11-2025 by greenlight]

Quote: Originally posted by Radiums Lab

but this seems to have almost similar yield compared to 3-step nitration of toluene.

Yes, Axt is correct, it seems the first and second step are high yielding then it becomes a challenge from there were the losses accumulate through the remaining steps. The cyclized azetidine ring formation for compound 4 has been described as highly problematic.

I think I have seen something once on using a nitroso intermediate and oxidation of the nitroso group.

And yes, Radium's Lab, the reagents are quite exotic and have taken a long time to acquire all 15 ready to go. I managed to get a couple of the harder ones and decided well I can't stop now

Step 1: 3-Tert-butyl-5-hydrpxymethyl-5-nitrotetrahydro-1,3-oxazine

Thankyou Radium's lab, i feel some luck will be needed.

The first reaction is a Mannich condensation between formaldehyde and nitromethane catalysed by sodium hydroxide. A second condensation is performed directly after in situ with butylamine to close the ring
Without further ado, here is step one.

Paraformaldehyde (81.06 g) was weighed out and dissolved in 300 ml of distilled water on a hotplate stirrer. A 40% solution of sodium hydroxide was prepared and cooled before 40 drops were pipetted into the above reaction mixture to act as a catalyst.
The reaction mixture was brought up to 40 degrees Celcius resulting in a clear colourless solution whereafter the dropwise addition of 32.40ml (36.62 g) was initiated from an overhead 100 ml dropping funnel. This step took over an hour as temperature control was challenging due to the exothermic nature of the reaction. At one point, the beaker had to be placed into a water bath as temperature climbed to 43 degree Celcius. After addition of the nitromethane, the solution became slightly cloudy and straw yellow in colour.
Temperature was now adjusted to 60 degrees Celcius and dropwise addition of 63.6 ml (44.30 g) tert-butylamine was begun. Only a small portion of the butylamine had been added before white precipitate began appearing rapidly in the reaction mixture. A short time later, the solution was so thick with the intermediate product that stirring was becoming increasingly difficult. Upon complete addition the stir bar was only just able to keep up and the top surface was barely being agitated around the edges of the beaker. Stirring and temperature was continued for one hour with some additional distilled water added to thin everything out to maintain stirring.
The reaction mixture was left to stir overnight and sure enough, the next morning, the stir bar was stuck.

The fine white precipitate was then vacuum filtered, rinsed with some cold water and placed on paper towel then into a vacuum desiccator with a vacuum pulled for complete drying. The wet product is extremely easy to handle and does not stick to the funnel or glass rods once the majority of the water is pulled through on the pump.

So far so good, the chemistry gods are happy with thy bidding and the first step is indeed high yielding


[Edited on 21-11-2025 by greenlight]

Step 2: 2-Tert-butylaminomethyl-2-nitro-1,3-propanediol hydrochloride

An aqueous acidic solution of 10.40 ml of 32% hydrochloric acid in 62.20 ml of distilled water was made up and placed on a stirrer/hotplate. To this solution was added 35.00 g of the product from step one and gentle heating applied to bring the mixture up to 40 C. Approximately a quarter of the product did not fully dissolve even when left for an hour at this temperature.

Slow addition of 13.68 ml 30% hydrogen peroxide solution was carried out before slowly bringing heat up to 58-60 C. The entirety of the step one product dissolved shortly after heating was increased. The solution began to take on an orange colour that became deeper as time under heat continued. Continuous bubble formation was observed and heating was continued at approximately 69 C for an hour.

The solution was then left to stir overnight at ambient temperature whereupon the next morning the bubbling activity has reduced to a minimal amount. The orange coloured solution was poured into a large evaporating dish and left at ambient temperature for three days to evaporate the water solvent. When approximately 2/3 of the water was removed, crystals began to form into a thin layer on the bottom of the dish.

The final product has yellow discolouration which could be due to the hydrochloric acid being hardware store grade and introducing iron contamination among other things or a need to recrystallise or wash the step one product.
Washing with isopropanol and then acetone has removed a large amount of the impurity leaving pale yellow crystals which are currently drying.
Maybe further washing of this diol is required as the literature states they are supposed to be off-white in colour.

Regardless, I only ran this on a small scale to identify issues so the process must be repeated with the remaining step one product.
I am quite sure the culprit is the hydrochloric acid and I think distillation will be required before using it for the next run.

[Edited on 7-12-2025 by greenlight]



[Edited on 7-12-2025 by greenlight]

Step 2 revision: 2-Tert-butylaminomethyl-2-nitro-1,3-propanediol hydrochloride

I have repeated the second step using hydrochloric acid that has been distilled. Upon addition of hydrogen peroxide to the distilled acid, there is no orange/red discolouration at all.
The azeotropic hydrochloric acid resulting from distillation is approximately ~20% compared to the original 32% so minor volumetric adjustments had to be made.

To start, 34.90 ml of distilled 20% hydrochloric acid was diluted in a beaker to a final volume of 140 ml with distilled water resulting in a ~5% solution. Thereafter, 67.00 g of the product from step 1 was added via spatula with stirring and heating brought to 40 degrees Celcius. Once again, all product did not go into solution. An additional 2.5 ml of 20% HCl was added to see if this would assist in dissolution but appeared to have no effect.

Hydrogen peroxide solution (30%, 26.30ml) was then pipette in slowly and heating increased to 59-60 degrees Celcius. This resulted in dissolution but once again the solution took on a light orange colour.

Heating was continued for an hour at 60 degrees Celcius and at one point a plastic like glob of orange solid with the consistency of chewed gum "polymerised" out of solution and was removed and discarded.

Stirring was continued for 15 hours at ambient temperature before pouring into a dish for evaporation. Orange coloured crystals resulted after 5 days that were washed three times with isopropanol and are now almost dry. The first wash was dark orange, second light orange, and final wash was straw yellow.

I am sure that adding the hydrogen peroxide before complete dissolution is causing issues. Maybe a much longer period in acidic medium is required for complete dissolution, but no real change was observed after 2 hours stirring at 40 degrees Celcius.

Product is stated in literature to be off white. A picture is uploaded below of it drying on cheap coffee filter as I am out of buchner filter paper.

[Edited on 24-12-2025 by greenlight]

Update on the dried yield is not so great coming in at 35% compared to the literatures 82%. I believe it is due to incomplete dissolution before hydrogen peroxide addition causing aggressive reaction resulting in a sort of polymer, plus the orange colour that reappears even with distilled HCl indicates that side reactions could be happening. The additional HCl added in an effort to dissolve all reagent could also have increased acidity to a point that damaged the formed diol.

Nevertheless, I have 25 g of purified diol to play around with.

This brings me to the next strange phenomenon on this adventure. For step 3, diisopropylazodicarboxylate is one of the required reagents. I purchased some a couple of years ago and immediately put it away ready for this moment without thinking too much on its form. Only problem is, I have now learned it is meant to be an orange liquid. I have 250 g of a fine white powder.

Has anyone heard of an exotic form of DIAD that is a salt instead of a liquid available anywhere before?