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learningChem
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Toluene to Benzaldehyde with MnO2
I'm trying my hand at the procedure in this patent
US613460
They use
300 kg toluene - 3260 mols
700 kg h2so4 65% - 4640 mols acid
90 kg Mn02 - 530 mols
Apparently this is how the reaction goes
2MnO2 + 2H2SO4 + PhCH3 --> PhCHO + 2MnSO4 + 3H2O
174______196______92
So, they are using enough MnO2 to oxidize 530/2 mols of toluene - or 24.4 kilos. That's only 8% of all the available toluene being converted. They
use stirring and the reaction temperature should be 40C.
--------
I put 3g MnO2, ~24g 65% H2SO4 and 10g toluene in the bottle shown in the picture. The bottle was capped. I used magnetic stirring and an oil bath
maintened at 45C.
After one hour the MnO2 had changed from brown-black to a pretty light brown. I let the thing run two more hours, which probably was a mistake.
The picture shows the reaction after 3 hours. "B" is the H2SO4-toluene interface. And in the toluene layer there a second layer of 'fluffy' looking
stuff which I'm guessing is benzoic acid.
I'm going to try again with a shorter reaction time and lower temperature.
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learningChem
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Second try. Same quantities. I stirred the thing for ~3 hours at 38C. Picture included. The toluene layer is clear. Nothing seems to be floating in
it.
At the end of the three hours I cut off the power (and went to sleep). So the reaction was left standing at room temperature (~27C) for ~14 hours. I'm
stirring it again at RT and it seems that almost all the MnO2 has reacted now.
I got a couple of questions...Assuming there's any benzaldehyde, where is it? Dissolved in the toluene layer? Or is there benzaldehyde in both the
toluene layer and the water/acid layer? (The water layer is cloudy). And second question : what's a practical way to extract it?
(picture of the MnO2 I used attached)
 
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wireshark
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Quote: Originally posted by learningChem  | | Assuming there's any benzaldehyde, where is it? Dissolved in the toluene layer? Or is there benzaldehyde in both the toluene layer and the water/acid
layer? (The water layer is cloudy). And second question : what's a practical way to extract it? |
1. It would be in the toluene layer. 2. fractional distillation
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learningChem
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Thanks wireshark. In this case fractional distillation means to distill off the toluene, leaving behind the benzaldehyde, I imagine? If it's anything
more complex than that, I don't think I have the propper glassware =/
What I tried meanwhile is the bisulfite adduct. Picture attached (sorry about the focus, the autofocus locked onto the wall...)
I separated the toluene layer and shacked it with a bisulfite solution. Filtering the adduct was messy. The amount of adduct was small (~0.3g maybe
but I forgot to weight it). I dried it, then dissolved it in water (~5ml), and added some Na2CO3. Got a cloudy solution that had the right smell, but
there was no benzaldehyde to be seen.
I distilled that solution and got a few small drops of benzaldehyde (not exactly steam distillation, but similar?) Anyway, the yield was...horrible
=/
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Nicodem
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| Quote: Originally posted by learningChem | | Thanks wireshark. In this case fractional distillation means to distill off the toluene, leaving behind the benzaldehyde, I imagine?
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No. Not at all. Fractional distillation means just what the name implies. How about reading a book about laboratory techniques before posting such
questions on an internet forum?
| Quote: | | If it's anything more complex than that, I don't think I have the propper glassware =/ |
Then chose experiments suitable to the glasware you have. How do you think you will ever be able to learn anything, if you start the practice without
having the tools to complete?
| Quote: | | I separated the toluene layer and shacked it with a bisulfite solution. Filtering the adduct was messy. The amount of adduct was small (~0.3g maybe
but I forgot to weight it). I dried it, then dissolved it in water (~5ml), and added some Na2CO3. Got a cloudy solution that had the right smell, but
there was no benzaldehyde to be seen. |
The bisulfite adduct based purification of aldehydes is a process and thus has a procedure! What was the point of such an experiment where you did not
following the procedure, yet expected equal results?
To make a more understandable comparison: You can't complain ending dead, if you go parachuting without a parachute. The reason is not only in that
dead people don't complain. It is also because parachuting is a process that needs to be done by the instructions, step by step, in the right order,
and with the right equipment (you need to follow an exact procedure!). Same goes with the bisulfite adduct purification process for aldehydes.
The bottom line is that preparative chemistry is based on science and until you acknowledge this fact, you won't succeed in it.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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learningChem
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| Quote: | | Fractional distillation means just what the name implies. |
No it doesn't. And yes, I know what it is because I've read more than one basic introduction to chemistry. In this case, assuming there's a mixture of
toluene (bp 110) and benzaldehyde (bp 178), distillation would 'create' two fractions. And actualy, since the boiling points of the two compounds are
not that close, I didn't expect that something like a fractioning column would be needed.
| Quote: | | The bisulfite adduct based purification of aldehydes is a process and thus has a procedure! What was the point of such an experiment where you did not
following the procedure, yet expected equal results? |
I have a basic idea of how the method should work and I was, get this, experimenting with it. It's amazing that you can ask such a dumb question.
------
Now, since you (wrongly) think you can lecture me, let me give you a taste of your own medicine.
You are not helpful. Of course, you are under no obligation to be helpful. But since you bothered to post a bunch of un-helpful and dumb comments,
I'll reply.
Your obsession with 'literature' and following procedures to the letter is almost laughable. And you seem to be clueless about how people can learn
things.
Also, did you read the sticky "toluene to benzaldehyde" thread? 95% of it is off topic garbage. And what is on topic is incomplete.
So, how about you Mr. "Super Moderator" manage to have threads were there's pertinent and concise information as opposed to hundreds of posts of
useless crap?
[Edited on 8-2-2013 by learningChem]
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strawberryfieldsforever
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I second that fully lol. I like seeing the failed experiments and attempts. You didn't hurt anyone or yourself at all in the process, so no harm done.
I mean look at your name lol and Beginnings. Sure everyone needs to read more.. That's a given lol and i'm sure he's tired of saying it lol or does
he like to say it. Could be.
[Edited on 12-2-2013 by strawberryfieldsforever]
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strawberryfieldsforever
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| Quote: | Preparation of gamma-Manganese Dioxide Manganese (II)
sulphate monohydrate (140 g) was dissolved in 2.66 liters of water and heated to 60°C. Potassium permanganate (97.3 g) in 1.85 liter of water was
added over a period of 15 minutes and stirred at 60°C for 1 hour, until manganese dioxide precipitated out. The reaction mixture was filtered and the
residue was washed with deionised water until no sulphate ion was present. The solid was dried under suction for 2 hours followed by drying at 70°C
under vacuum to a constant weight (about 8 days) to give 115 g of a dark brown powder.
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[Edited on 12-2-2013 by strawberryfieldsforever]
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learningChem
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Thanks StrawberryFields =]
Too bad KMnO4 can't be had OTC here, thanks to the local nazis following orders from the amerian nazis.
I've prepared MnO2 starting with the sulfate, (1) precipitating MnCO3 and then heating it, (2) precipitating MnO(OH) and then drying it, and (3)
precipitating MnO2 directly with NaOCl.
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watson.fawkes
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| Quote: Originally posted by learningChem | | So, how about you Mr. "Super Moderator" manage to have threads were there's pertinent and concise information as opposed to hundreds of posts of
useless crap? |
I'm sorry, but have you posted "pertinent and concise information" in this thread yet? All
I've seen are a couple of sloppy experimental reports that aren't complete, as they're missing work-up, characterization, and yield, at the very
least.
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learningChem
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| Quote: | | as they're missing work-up, |
That's perhaps because work-up is exactly the topic I was seeking help with? Perhaps you didn't even bother to read the thread?
Surely now you realize that your post is as absurd and unhelpful as that of Mr. Super Moderator's? Have a nice day.
edit :
not to mention, I did post a work-up in message 7-2-2013 at 18:12
[Edited on 13-2-2013 by learningChem]
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watson.fawkes
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| Quote: Originally posted by learningChem | That's perhaps because work-up is exactly the topic I was seeking help with? Perhaps you didn't even bother to read the thread?
[...]
not to mention, I did post a work-up in message 7-2-2013 at 18:12 |
Oh, I've read the whole thread, twice or
more, seeking this pertinent and concise information from you that you yourself were seeking elsewhere.
You then cite your own message containing a mostly-failed workup with abysmal yields, which seems to me not all that pertinent, because it does not
illustrate a practical technique, particularly when there's literature you might have read before that could have led to a more successful outcome.
And it certainly isn't concise, since to be concise it would have had to have appeared with the original message. And it's nowhere near even a proper
workup report, since you are missing both the concentration of the bisulfite solution and the ratio of that solution to what came out of your boiling
flask.
I will be merely blunt, so that I can avoid being insulting. Everything you've said in this thread marks your behavior as heedless, impatient, and
lazy. Heedless because you apparently didn't think much about workup before you started, much less consider that the oxidizer could also oxidize
benzaldehyde. Impatient because, just to pick one example, you couldn't be bothered to take a second photo to share that was in focus. Lazy because
you have bristled at suggestions that you help yourself (by reading) before expecting help here.
From the evidence here, my odds are that you're not all that interested in the science of this but are rather looking for one piece in some
get-rich-quick scheme that involves learning as little chemistry as possible and purchasing less than the minimum necessary equipment. It surprises me
not at all that folks here aren't jumping in to help you, which speaks well of the membership here in my estimation.
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starman
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| Quote: Originally posted by watson.fawkes |
From the evidence here, my odds are that you're not all that interested in the science of this but are rather looking for one piece in some
get-rich-quick scheme that involves learning as little chemistry as possible and purchasing less than the minimum necessary equipment. It surprises me
not at all that folks here aren't jumping in to help you, which speaks well of the membership here in my estimation.
|
I would have to agree with this.Also it is difficult to believe you cannot extract what you require from the twenty page sticky on the
subject,complete with links and reference papers.
One last piece of advice in the unlikely event that you last on this board.Mods like Nicodem can be a fantastic source if you actually want to learn
something,best not to alienate members that can help the most if you are prepared to put the work in.
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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learningChem
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Hey "watson fawkes"
I'm really surprised by your message. I mean, *what* is wrong with you? You know your position is absurd, yet you keep babbling?
See, I am here because I lack knowledge about subject or technique X. And what do you do?
Provide help? No.
Shut up and get lost as you should? No.
What you do is accuse me of not knowing X. Well, that is the whole point isn't it?
| Quote: | | From the evidence here, my odds are that you're not all that interested in the science of this but are rather looking for one piece in some
get-rich-quick scheme |
The fuck are you talking about, sonny?
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learningChem
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>Also it is difficult to believe you cannot extract what you require from the twenty page sticky on the subject,complete with links and reference
papers.
As I said, that thread is mostly garbage. You probably didn't read it.
Kindly get lost as well. Thank you.
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watson.fawkes
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I suggest you
ask that first question again, this time replacing the pronoun "you" with "me".
If it were the case that members here were jumping in to help you, perhaps your assertion of my absurdity would have merit. Since you haven't figured
it out yourself, apparently, you should know that people here seem to be avoiding you.
As the saying goes, you catch more flies with honey than vinegar. Because you haven't figured it out yourself yet, here "honey" means "science".
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learningChem
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Just for giggles, I reviewed the sticky thread again.
Three people (frogfot, organikum, garage chemist) actually tried the reaction as opposed to the endless, useless, pseudo-theoretical babbling that's
so common here.
All of them posted descriptions which are less detailed than my descriptions, and none of them posted a single picture. None of them even posted the
equation for the reaction...
Oh, all of them failed, of course. In some of those failures, they didn't even get the MnO2 to react (not my case =) )
You were saying, Dr, Watson?
Hey I've got an idea for you and the other troll in this thread. Go to preach to a church. That's where you belong.
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elementcollector1
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Amazing how you think watson really is a troll.
Simple and obvious evidence that anyone, member or not could figure out:
Watson's post count: 2,353 posts, registered 8/16/08
Your post count: 62 posts, registered 7/21/11
He's been here longer than you, contributed more than you, and is overall more helpful to the board than someone who thinks a sloppy write-up is
anything to take note of.
If you think you'll get help from us by blatantly insulting one of our most-contributive members when he calls you out for sloppy work, you've got
another think coming.
To give you a personal perspective, I used to be precisely as sloppy as the above. Then I actually started learning how to do the math, and doing it,
and my work improved considerably. Chemistry is 10% experiment and 90% math, research and planning, in my opinion.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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learningChem
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elementcollector,
Please don't post spam/trolling coments in this thread - Thank you.
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watson.fawkes
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Oh, I doubt he actually thinks that. He's just too lazy to
think up an insult that might possibly stick. I surmise bullying has worked for you in
the past. You don't seem to realize that it's not working for you here.
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elementcollector1
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...
I don't even know how to reply to this level of arrogance.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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Mailinmypocket
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Just don't...
Let him/her toil away with their mucky bottles of smelly and dirty organic cocktails, shooting rude comments and posting poor experimentals.
Eventually they'll realize how proper communication and experimentation can benefit them (hence the name "learning chem" i suppose).
[Edited on 15-2-2013 by Mailinmypocket]
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learningChem
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Mailinmypocket
Please don't post spam and trolling comments in this thread.
Same for the rest of people who have already shown that they have nothing to contribute, chemistry-wise.
You are just trolls, and not even funny after the second message.
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learningChem
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Just in case some of the trolls here don't get it yet, let me rub it in again.
The benzaldehyde sticky tread is garbage as far as the MnO2 method is concerned.
Even my 'sloppy' experiments here are better than what's been posted there.
Oddly enough, none of you dumb trolls bothered to troll that thread...
Cute double standard, eh.
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Mailinmypocket
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| Quote: Originally posted by learningChem | Mailinmypocket
Please don't post spam and trolling comments in this thread.
Same for the rest of people who have already shown that they have nothing to contribute, chemistry-wise.
You are just trolls, and not even funny after the second message.
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Okay, boss. However don't expect to get much help with your attitude. I wouldn't talk down in such a manner to a community of people who are
potentially able to help me. Just sayin'
Now, unless you yourself have something to contribute chemistry-wise, please, go back to the drawing board and google for your benzaldehyde wishes
in-lieu of posting sloppy work and asking for the old spoon. Seeing as my own comment is not related to the topic at hand I will not post again in
this thread, good luck with your project though!
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