Sciencemadness Discussion Board

I Learned my LESSON!

smaerd - 17-10-2010 at 18:57

So I knew I was in over my ski's but I didn't think what I was doing was all that serious of an experiment.

I tried a prepare some p-toluenesulfonic acid following this procedure:
Quote:
Preparation of p-Toluenesulphonic Acid (SECTION 476).—
To 25 grams of toluene in a 200mL flask add 25mL of pure concentrated H2SO4, and place on the steam-bath. Allow the mixture to stand until the toluene has dissolved. This will require about 2hrs if the flask is shaken once in a while.

Let the solution cool; before it solidifies pour it, with stirring, into 100mL, of pure concentrated hydrochloric acid. Heat the mixture on the steam-bath until the solid dissolves.

Set aside to crystallize. Filter by suction, and wash the crystals with concentrated hydrochloric acid.

Press the crystals to remove as much of the mother-liquor as possible and dry them on a porous plate. Weigh the toluenesulphonic acid and calculate the
percentage yield from the toluene used.

p-Toluenesulphonic acid crystallizes from water, in which it is very soluble, in long colorless needles. It is less soluble in concentrated
hydrochloric acid. It melts at 104°-105°. The yield should be about 25 grams.


So here's what happened, instead of adding the solution to 100ml of HCl, I added 5mL of HCl to the solution. POOF clouds of Cl vapors? are emitted into my basement, thank god I could get a fan and a window running in time. So I'm sitting there for 20 minutes trying to figure out just what the hell I've done as the cloud clears.

I took it outside to just try again(stupid right?), and added maybe 15mL quickly to the round bottomed flask. I run behind a glass patio door, and the flask literally caught fire(excess toluene? I swear the two layers completely merged) and was pouring out Chlorine and what must have been water vapor? I'm nervous as shit at this point, goggles completely fogged up sweat dripping from my face . Hopefully I didn't just poison myself with those vapors. I didn't inhale much at all but :o.

I've learned my lessen here, don't fuck with things you don't completely understand. I knew the HCl was going too induce crystallization, but even the procedure mentions heating the solution afterwards. I did not get a solution, I got a fire and a flask full of what looks like yellow long needle crystals only using 1/5th the amount of HCl they used. I'm honestly too scared to even look at it right now...

Thank jeebus I don't have neighbors...

[Edited on 18-10-2010 by smaerd]

smuv - 17-10-2010 at 19:48

You have to watch out with things like this; its similar to quenching a friedel crafts or anything that involves adding HCl to dehydrating acids. If you add HCl to the acid, the drop of hydrochloric acid heats up and gets dehydrated causing lots of fuming and great chance of having a boil over. If you don't know any better don't try to change the procedure. If you follow this, things will stay under control; do it outside though, for your safety and also to protect all the metal in your basement from corroding.

Next time, cool a solution of hydrochloric acid in a big flask with an ice bath. Add the other solution portionwise with swirling too the freezing cold HCl. Feel the HCl flask from time to time; if it starts getting even perceptibly warm (say 20C) stop the addition and let the flask cool.

About the fire...Really?? Lots of fuming yes, but I would never expect that.

Some friendly advice though: hit the books (especially practical chemistry texts), read this forum and try to really understand whats going on and all the risks to everything. As I am sure you know, I think at the moment, you are in over your head here.

smaerd - 17-10-2010 at 19:54

Like I said I learned my lesson.

It wasn't like a big fire but I saw illumination in the flask. Thanks for the information but I'm not doing that one for a lonnnnnng time. I was pretty embarrassed to post this but I figure it's probably pretty important to get my lesson out here for any other dumbies like me to not go in over their head.

Hit the books indeed!

smuv - 17-10-2010 at 20:06

I didn't mean to rub it in. But I absolutely don't want anyone to get injured practicing this hobby.

Now that I re-read this procedure, I expect even with cooling a fair quantity of HCl gas to be released, but cool it anyways to minimize this, avoid boilover and uncontrolled exotherm.

[Edited on 10-18-2010 by smuv]

Magpie - 17-10-2010 at 20:36

Quote: Originally posted by smaerd  

... don't fuck with things you don't completely understand.


I think that is the key here. You changed (fucked with) the procedure. There is a reason why the procedure calls for adding the toluene sulfonate to the HCl instead of vice versa.

By all means do as much reading as possible beforehand and anticipate what can go wrong. But with proper ventilation and safety gear, and carefully following procedure, you can do this.

12AX7 - 17-10-2010 at 22:08

Do as you oughta, add acid to water!

Sedit - 18-10-2010 at 10:42

Sorry to hear about your problems smaerd but if its any consulation you have given me my next project I think. I have been thinking what to do with the few hundred ml of Toluene I have since making BnO got on my nerves sometime ago and this seems just a good a use as any.

I see that this is a non oxidising acid so I was woundering about the synthesis of HBr or HI from there salts without formation of the halogen. This should work well for that simular to H2PO4 correct?

smaerd - 19-10-2010 at 10:13

Alright so I redissolved the crystals in 20mL of H2O, tried to crystalize, no dice. So I tried slowly adding this new solution to 80mL of conc HCl. No dice, so I cooled it to about -30*C, nothing still.

So finally I said screw it I'm going to neutralize the HCl then evaporate the water. I added a few teaspoons of sodium bicarbonate(didn't want to use a strong base such as NaOH), it emitted CO2 was endothermic, seemed just like an HCl nuetralization reaction. Until I noticed the solution became nearly opaque, so I let it ride for a little bit. A precipitate formed. I then stirred the solution with a glass stirring rod, it did not go back into the solution. Could this be the TSoh, or did I nuetralize the TSoh? If it is TSoh than this is a pretty easy way to get it to precipitate without boiling off HCl.

I don't think it would be NaCl, I don't see why that wouldn't be water soluble at this point. I'm sorry to be uneducated on what I just did, I tried searching for "nuetralizing organic acids", and I'm at a stand still.

edit - okay so I just read that I nuetralized the TSoh, what did I nuetralize it too that would form a precipitate? I'm trying to figure this out, I'll report back when I do.

[Edited on 19-10-2010 by smaerd]

chemrox - 19-10-2010 at 11:01

"Real men add the acid to the water.." somebody here use(s)d this as a sig

smaerd - 19-10-2010 at 11:23

Alright I've added countless teaspoons of sodium bicarb and I've come to the conclusion that whatever the precipitate was/is is a result of the sodium bicarb, and not the TSoh. I read that you can neutralize TSoh with baking soda in a safety, pdf. I'm not really sure if its true at this point lol. I'm switching to sodium hydroxide, this is ridiculous. I just wanna be able to safely dispose the experiment at this point.

entropy51 - 19-10-2010 at 11:30

smaerd, please start over and use the prep in Vogel. By "use" I mean follow the directions as written. I have used it in the past to coax a little product out of this dog of a prep.


smaerd - 19-10-2010 at 11:44

I'm trying to start over right now, but I have used seriously a 100g+ of sodium bicarbonate and 50g of naoh and diluted to 10x the volume did a ph paper test and its still at ph 1. What should I do? This can't be safe to dispose of in the ground.

smaerd - 19-10-2010 at 12:04

edit - I just read it says to incinerate it, but that's not really an option. Damn this thing is still bubbling obviously the base did nothing but neutralize the HCl which is cool but I need to think of a way to decompose this stuff..

[Edited on 19-10-2010 by smaerd]

[Edited on 19-10-2010 by smaerd]

smaerd - 19-10-2010 at 13:07

Alright I guess I'm just gonna start a fire and throw it in there, seems like there's no other way out of it. Thanks for all the help as always, next time I won't get into a pickle like this.

zed - 20-10-2010 at 23:20

Hey! If they sell products containing H2SO4 or CuSO4 , to clean out your pipes. I see no problem with mixing your small amount of debris with a further box of bicarbonate, and flushing it down the crapper. Provided you aren't using a septic system, of course.

By the time it hits the sewage treatment plant, it will be so diluted that it won't be a problem.

It isn't Dioxin.

HydroCarbon - 21-10-2010 at 18:16

Great story, I probably would have shit my pants if this happened to me :P

Seems like a fun project to try, though, as long as it's done safely. I would also recommend trying to do it in smaller volumes first before scaling up.

Your neutralization precipitate very well could have been sodium chloride. I've had NaCl drop out of solution before when neutralizing conc. HCl and NaOH in large quantities, it's actually really cool when it happens.