2,4,6-TriNitroResorcinol, 2,4-dihydroxy-1,3,5-trinitrobenzene. C6H3N3O8. Molar Weight; 245.11. Percentage composition; C: 29.40%, H: 1.23%, N: 17.14%, O: 52.22%. Styphnic Acid is a dibasic acid which forms into hexagonal yellow crystals from dilute acid, but becomes almost colorless on vacuum sublimation. It becomes deep yellow on contact with air. Anhydrous, it melts at 175.5C. One gram dissolves in 156mL water at 14C, 88mL water at 62C. Freely soluble in alcohol and ether. Acid to litmus. It deflagrates on rapid heating. Styphnic acid is used in the manufacture of dyes, pigments, inks, medicines, and explosives. It deflagrates on rapid heating. (Source: Merck Index 12th edition).
I have been interested in manufacturing this acid for quite a while now, for experimentation purposes. However, I have never been able to find a detailed article on its synthesis. Thanks to my lab skills, and some pointers from Merck, which outlined the industrial synthesis as being similar to that of Picric Acid (2,4,6-TriNitroPhenol), I have been able to devise the synthesis below which is an adaptation of that to make Picric Acid. It seems to work safely and with good yield. Since the Internet as a whole lacks such a document, I am making it available here. Please do not copy this synthesis as it is a product of my individual work. Instead, link back to this site.
As with any other nitration, this procedure is hazardous and involves the use of highly corrosive acids. The final product is toxic and dangerous. This should only be attempted by experienced chemists!
150mL Glass beaker.
|Ethanol (C2H6O(l))||Funnel/filter paper|
|Distilled Water (H2O(l))||Ice bath|
Here all the chemicals used in the synthesis are seen, from left to right, back to front: Absolute Ethanol, Resorcinol, Sulphuric Acid (98%), Nitric Acid (68%), Distilled water. In front of the picture a tall measuring tube is seen holding 8 grams of powdered Resorcinol, and it sits next to a beaker holding 10mL of concentrated Sulphuric Acid.
A note on proportions: 0.8grams of resorcinol are reacted for every 1.5ml of Nitric acid and 1ml of sulfuric acid.
C6H6O2(s) + H2SO4(l) => C6H7O5S + HNO3(aq) => C6H3N3O8
8grams of powdered resorcinol are weighted and added to the 150ml beaker containing the 10ml (18.5g) of concentrated sulfuric acid. The mixture is stirred for several minutes untill the resorcinol dissolves and forms into a yellow liquid. It is than heated on a hotplate set for 100C for 30 minutes, during which it quickly solidifies into a pink cream (Resorcinol Sulphate). Stirring is continued untill the 30 minutes are over and the resultant product is than chilled to -5C on a water bath with salt added, becoming a solid pink mass to which 15ml of nitric acid are added inside a fume cupboard.
Shortly after the Resorcinol Sulphate and the Nitric Acid are stirred, a reaction takes place which produces Nitrogen Dioxide (NO2) in large amounts. The red colored gas is highly toxic and corrosive and should therefore be avoided. The mixture is allowed to stand for a few minutes until the reaction subsides, and the beaker is once again put in a hot plate at 100C for 1 and a half hours, so as to complete the reaction. The liquid is stirred occasionally and the mixture gives off some more NO2 fumes.
Once the heating is complete 100mL of distilled water are added to the mixture, causing the Styphnic acid to precipitate as small crystals in the bottom of an orange liquid. The mixture is cooled to 5C so as to precipitate most of the remaining Styphnic acid, and than is quickly filtered and washed with 450mL of cold distilled water so as to remove any traces of the nitration acids.
The filtrate appears as the fine yellowish mass of crystals seen to the left. Yield is approximately 10grams for the 8 grams of resorcinol started out with. These crystals are high purity and have all of the properties attributed to reagent grade Styphnic Acid. However, they can be purified:
Making use of Resorcinol’s high water solubility, and the higher solubility of lower nitration portions of resorcinol, the Styphnic Acid can be purified to near analytical grade by re-crystallization from a solvent mixture of 1 volume ethanol and 2 volumes water, roughly 8ml of solvent being required per gram of Styphnic Acid.
The final product: The crystals are than removed by vacuum filtering, are vacuum dried in a dissector, and form into a nearly yellow mass of mp 175,5C.
It is advisable to store Styphnic acid wet with at least 30% water and in rubber stoppered flasks.
This filter paper is witness to Styphnic acid’s incredible staining power: With only a small amount the entire paper became bright yellow; almost fluorescent!
The melting point and the deflagration show that the result of this synthesis is indeed Styphnic Acid. The picture to the right shows a fireball produced by 300mG of the product as it is heated over an alcohol lamp. Clicking on it downloads the 157kb .mpg movie that shows how the product deflagrates from flame.
This acid may be used for many other syntheses. The one of greatest importance is its heavy metal salt Lead Styphnate:
Lead Styphnate Synthesis