DDNP, which stands for Diazodinitrophenol, has a reputation of being one of the best primaries out there when it comes to performance. Its synthesis is often disreguarded because few people have gotten it to work. It has a very high stability considering its a primary. The only downside to this is that some of the chemicals needed for the procedure are hard to find or must be synthesized. The synthesis actually has a lot of reactions going on throughout it. It is mainly two parts; preparation of sodium picramate, then diazotation of picramic acid. I have actually gotten this procedure to work, and I am satisfied with my product.
C6H3N3O7 + NaOH ---> C6H2N3O7Na + H2O (Picric acid neutralized to sodium picrate)
S + NaOH ----> Na2Sx (Sodium Polysulfide)
C6H2N3O7Na + Reducing compound ----> C6H4N3O5Na (Sodium picrate reduced to sodium picramate)
C6H4N3O5Na + H2SO4 ----> C6H5N3O5 + NaHSO4 (Sodium picramate acidified into picramic acid)
C6H5N3O5 + HNO2 ----> C6H3N4O5 (picramic acid diazotized)
|Picric Acid||2x 600ml Beakers|
|Sulfuric Acid||Ice bath and equipment|
|Sodium Nitrite||200ml evaporating dish|
Into a 600ml beaker, pour 100mls of water and heat up to ~70-80C. Add 9 grams of finely powdered picric acid to this and swirl it a little bit. It will not all dissolve however, so don't assume you're getting anywhere by swirling it for 24 hours. Now add 1.5 grams of sodium hydroxide to this. Swirl this mixture around until everything inside dissolves. Yes it will all dissolve just keep swirling. The solution will turn to an orangish color. This is a sodium picrate solution. Keep this on low heat and add water as it evaporates. In another beaker, pour 300mls of water and 8.0 grams of sodium hydroxide. Bring the solution to a rolling boil. Measure out 7.5 grams of pure sulfur, and crush it finely. Seive it into the boiling sodium hydroxide solution making sure to get as little sulfur on the sides of the beaker as possible. Let this boil for 60-120min (1 to 2 hours), adding water as neccesary. After this ammount of time, most if not all of the sulfur should be dissolved. If you sit and watch it the whole time, you will notice a color change from clear to green to blue, to puke green, to pea green, then to a very dark color and once all the sulfur dissolves it will be a very very dark red color. Set this on a towel or similar device and let it cool down until it stops boiling. The reason for the towel is so that it doesn't come in direct contact with any room temperature (or colder) surface. Once it stopped boiling (but is still hot) add it to the sodium picrate solution in the other beaker, in 4 portions. Once all of it is added, place the beaker in a refridgerator (about 4C) until its cold. There should be a healthy ammount of red crystals in the bottom of the beaker. Filter the whole solution into the 600ml beaker that was used in the last step. Discard the filtrate and clean that beaker out. Pour 300mls of water in it and bring it to a boil. Add the red crystals in the filter (and everything else) to the boiling water and boil it for 2-3 minutes. While it is still boiling clean out the other 600ml beaker which should be empty. Filter the boiling solution into the clean 600ml beaker. Discard the filter and its contents and let the filtrate cool to room temp. This is now a sodium picramate solution.
When the sodium picramate solution is at room temp, drip concentrated sulfuric acid in there with stirring. Keep dripping it in there until it just barely tests acidic on litmus paper. This will take 1-2ml. You will also notice that the color has changed from a deep red color to a sort of rusty color. There is also a precipitate in the beaker (and a lot of it). This is picramic acid. Measure out 7.5 grams of sulfuric acid and add it to this beaker. Mix the beaker up, then pour it into a 1000ml beaker. Add another 100ml of water to this. Place this beaker in an ice bath and bring the temperature down below 5C. In another 600ml beaker, pour 250ml of water and add 5.4 grams of sodium nitrite. Swirl it until its dissolved. Now, slowly add this solution to the picramic acid solution in the 1000ml beaker, keeping the temperature below 5C. Be sure to stir almost constantly during this part. You can stop stirring if you're not adding anything if you need a break though. Once all of it is added, continue stirring for a couple more minutes then remove it from the ice bath. Let it slowly warm up to room temperature. You will see a brown precipitate (the shade of brown varries sometimes).
Once it is up to room temperature, filter the solution out. There is a lot of DDNP crystals in here, so use two different filter papers. Try to even the ammounts of DDNP on each filter paper when filtering. Once all the crystals are filtered out, run 60ml of cold water through each filter to wash out some of the very soluble products. Remember, DDNP is slightly soluble in water so make sure its cold. Scrape the DDNP on the filter papers into a 250ml beaker. Add acetone to this, 100-150mls should be fine to dissolve all the DDNP. Swirl it around good to dissolve as much as possible. There will be a significant ammount of impurities that are undissolved which should be yellow; the solution should be brown. Filter this solution out into a 200ml evaporating dish. Discard the filter and the contents of it. Place the 200ml evaporating dish ontop of a 1000ml beaker with boiling water in the bottom of it. Keep boiling the water so that the steam boils away the acetone (do this outside or with good ventilation). Eventually you will be left with a brown crystal in your evaporating dish. This is pure DDNP. DO NOT SCRAPE THIS STUFF OFF THE EVAP DISH. Get as much as you can of the loose crystal, but don't scrape at the layer stuck to the evaporating dish because this compound is friction sensitive. The yeild I acheived was 3.7 grams. This is a poor yeild mainly because I lost a lot during purification because a filter paper ripped open (I know, I know; excuses excuses).