PowerLabs PETN Synthesis!

2,2Bis[(Nitrooxy)-methyl]-1,3propanediol dinitrate (ester), Pentaerytritol Tetranitrate, 2,2-bisdihydroxymethyl-1,3-propanediol tetranitrate, nitropentaerytritol, penthrit, niperyt, Lentrat, Hasethrol, Perityl, Terpate, Subicard, Pentryate, Pentitrate, C₅H₈N₄O₁₂ or simply PETN(1), this compound finds both medicinal use as a coronary Vasodilator (often mixed with lactose to reduce sensitivity) and extensive use in the explosive industry, as a very high power booster in blasting caps and also as the filler in detonating fuse (DetCord, Primacord)*.

The ratios used for this synthesis are as follows:

34 ml of 65% HNO3
24,8 ml of 96% H2SO4
10,0 g of Pentaerythritol

All the chemicals used in this synthesis can be seen below:
From left to right: 65% Analytical Grade Nitric Acid, 98% Analytical Grade Sulphuric Acid, 99,5% Analytical Grade Acetone and 99.8% Extra Pure Pentaerythritol. The petri dish contains 10 grams of pentaerythritol.

1. A cold-water bath was prepared and used to chill A 200ml wide necked flask containing nitric acid. 24,8 ml of sulfuric acid were pipetted into the flask and the mixture was allowed to further cool by adding ice and salt to the cold water bath.

2. A second ice bath is prepared to be used for emergency cooling of the mixture should its temperature become too high.

3. With the mixed acids at or below -25�C, 10 g of pentaerythritol are added, 2 grams at a time. It is important to constantly stir the acid mixture during the addition as localized heating will occur during nitration. The mixture can be seen to thicken as nitration occurs and the temperature rises. At 5�C it became a thick slurry. A low starting temperature is key in this synthesis and should the temperature rise above 0C at any time, re-chilling will be necessary prior to further addition of the pentaerythritol. Should runaway nitration occur (evidenced by the evolution of brown N2O4 / NO2 gas) the mixture should be immediately poured into cool water.

After 10 minutes of mixing, the mixture is a white thick syrup:

4. Mixing is continued for 10 minutes after the last of the pentaerythritol is added. The mixture is then put in a hot water bath and heated to 45�C for 25 minutes. This will considerably increase yield by nitrating most sulfoesters into PETN. It is important to keep the temperature at or below 45C, maintain stirring and watch for any signs of runaway nitration. (This step is not needed, but will result in a much better yield).
5. The mixture is then diluted with 450 ml of ice cold water and excess water is decanted after the crystals settle so as to ease the filtering of the product. Care must be taken to slowly and evenly add the mixture to water, as the excess H2SO4 in the mixture will cause a temperature rise that can lead to decomposition of the final product.

6. The PETN is filtered and washed with cool water and then neutralized with hot sodium bicarbonate solution.

7. 200ml of acetone are heated to 50�C. And the PETN is stirred into it until all of it has dissolved (solubility: 58gr/100ml acetone at 50C). Excess acetone is needed, due to excess water in the PETN. Drying the PETN prior to this step will minimise the amount of acetone needed.

8.  The PETN / acetone mix is then filtered and poured into a beaker containing 600mL of ice cold water, causing the PETN to precipitate to the bottom as fine crystals.

9. After settling, excess water and acetone are decanted and the remaining PETN can be filtered out
After filtering, the PETN was put on a small petri plate and dried.

 The dry product weighted ~22 grams, which is a ~91% yield. Most losses seem to occur during filtering and during the acetone purification phase. Below a picture of the finished product can be seen:

Some Merck Data:
More sensitive to shock than TNT, practically insoluble in water, soluble in Acetone + Alcohol, melting point 140C.(1)

1-Merck Index 12th Edition (Entry #7149).

T. Urbanski (vol. IV.):

The maximal amount of water in the mix cannot exceed 30% due to nitric acid’s properties as a strong oxidizing agent between the 50-70% concentration range.
With added H2SO4, there must still be some water in the mix, or oxidation will occur. At the start of this procedure, the water content is 20%, at the end it rises to 30%. Increasing the amount of pentaerythritol will increase the water content at the end of the reaction, thus probably lowering the yields because of the oxidation of the end product.