Sciencemadness Discussion Board

Picric Acid without Sulfuric Acid or Benzene

APO - 28-2-2013 at 22:21

I was looking here and I wanted to do it, but I don't want to work with sulfuric acid or any carcinogens like benzene any substitute for these in the synthesis?

caterpillar - 28-2-2013 at 22:42

One wise boy wanted to prepare sweets without sugar, honey, fruits. He has only flour, salt and water.

Motherload - 1-3-2013 at 07:22

You don't actually use benzene unless you are going the catalytic route.
For a regular nitration synt ... You will need phenol or aspirin etc.
if you are uncomfortable safely handling H2SO4 ..... Then you shouldn't be handling energetics.

497 - 1-3-2013 at 08:41

Heh, picric acid is ok but sulfuric isn't? Might want to rethink your plans...

That said, somewhere in the massive thread called something like "unconventional picric acid synthesis" I posted a reference that indicated that you could get picric acid (along with variable amounts of less nitrated products) by simply boiling various substituted phenols in ~%50 nitric acid for a long time. They were actually using tyrosine, and a vanadium salt to catalyze the oxidation of the side chain, but everything pointed toward 4-hydroxybenzoic acid and probably salicylic acid (formed from aspirin in situ), being usable with straight nitric. The yield wasn't as good as the usual procedure, and it would be less convenient in many ways, but no sulfuric needed... Not that the nitric acid would really be a whole lot easier to get or safer to handle than sulfuric.

APO - 1-3-2013 at 11:29

I'm not comfortable with sulfuric because it's a liquid, meaning a spill could result in much more danger. Not to mention that Picric Acid is not very sensitive when wet.

caterpillar - 1-3-2013 at 13:44

I can tell you just what @Motherload told: compared with another reagents, sulfur acid is one of the most harmless reagents. I made experiment- put some drops on my hand. I spent some seconds, waiting for noticeable pain. But an accidental contact with RFNA clearly demonstrated me, which acid is more dangerous- I lost few square cm of my skin in a heartbeat.

APO - 1-3-2013 at 15:34

Thanks, but what kind of safety should be used for WFNA?

Bot0nist - 1-3-2013 at 16:36

Independent research should be done on the safe handling of all your reagents. If that is not already habit, then you need to leave energetic materials alone, IMO.

I would hardly call sulfur acid harmless, but it is a very common reagent in so, so much chemistry. Especially energetic chemistry. Follow lab safety protocols and you will be fine. Sounds to me like you have a lot of reading to do before attempting to make TNP.

Sure, its not to sensitive to initiation, but it is a highly toxic, high explosive compound, and it has some serious compatibility issues that could prove catastrophic to the uninformed.

A proper nitration all the way to TNP is not trivial to pull off, even when using established procedures.

Best of luck to you, APO. Keep safety at the forefront, always.

neptunium - 1-3-2013 at 17:11

common sense and knowledge saves lives

APO - 1-3-2013 at 18:11

Thanks, I'm just curious, I won't do this until I know every bit of this reaction and have the proper equipment. When ever I'm doing something potentially dangerous I build up to it incrementally, especially with reactions. Sometimes I'm a bit vague.

caterpillar - 1-3-2013 at 22:52

I never told that sulfur acid is harmless- only RELATIVELY harmless. RFNA is more dangerous out of questions, vapor of HN3 may kill you as well as HCN. I read, that late Saddam has a bath with sulfur acid. May be, it was rumor, spread out by its enemies. Well, to work with such reagents one must have lot of baking soda in a hand reach, water with snow or crushed ice, protective gloves, goggles and ventilation. And it would be better do not inform your neighbors about such kind of activity. Yeah, start with small amount- 10 gr of phenol would be enough for beginning. As for me, my usual portion was 250 gr of phenol, 1 kg of KNO3 and 2.5 bottles of sulfur acid (92-94%, 800 gr per a bottle). I got a runaway, when I had tried to replace KNO3 with NH4NO3.

kristofvagyok - 2-3-2013 at 17:46

Quote: Originally posted by APO  
I wanted to do it, but I don't want to work with sulfuric acid or any carcinogens like benzene any substitute for these in the synthesis?


I laughed loud while reading this.

You want to make an almost mineral acid strength highly toxic, flammable and explosive salt forming material, but you are afraid from sulfuric acid? Have you ever thought about this?

There are several ways to make picric acid, and some of them doesn't require as much H2SO4, but you will need it... There is a really "friendly" way, the only problem, that you have to start from 4-aminobenzenesulfonic acid.

There is a recipe in "Praktikum der organisch-präparativen pharmazeutischen Chemie" where first they diazotate the sulfanilic acid sodium-nitrite (beware, if you eat it, it could cause serious problems :D). First dissolve the sulfanilic acid in NaOH, then add the NaNO2 in a dilute soln. with water at 5C, then acidify it with 20-30% H2SO4 on an icebath. The participated diazonium salt should be filtered and immediately used in the next reaction. If it's dried, it could explode, so as I said, use it in the next reaction before something funny happens...

The next step is the nitration of the previously prepared compound. Just add it to COOL 65% HNO3 and het it up SLOWLYto 65-70C and keep it there. Wait an bit, use TLC to know that where is your reaction and when it's ready, pour it on ice and be happy. 60% yield.

-this recipe is way less than anyone could reproduce it well. If you want to make such things, read a bit from this and get the original articles.

Some lead picrate, cheers :D

APO - 2-3-2013 at 19:23

I've learned more about H2SO4 and I'm fine with the thought of it now.