Sciencemadness Discussion Board - Toluene to Benzaldehyde with MnO2

Toluene to Benzaldehyde with MnO2

learningChem - 3-2-2013 at 21:35

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.

learningChem - 4-2-2013 at 15:53

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)

wireshark - 7-2-2013 at 10:30

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

learningChem - 7-2-2013 at 18:12

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 =/

Nicodem - 8-2-2013 at 00:54

Quote: Originally posted by learningChem

Thanks wireshark. In this case fractional distillation means to distill off the toluene, leaving behind the benzaldehyde, I imagine?

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.

learningChem - 8-2-2013 at 02:13

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:

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]

strawberryfieldsforever - 11-2-2013 at 19:42

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]

strawberryfieldsforever - 11-2-2013 at 19:52

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.

[Edited on 12-2-2013 by strawberryfieldsforever]

learningChem - 11-2-2013 at 22:10

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.

watson.fawkes - 12-2-2013 at 13:09

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.

learningChem - 13-2-2013 at 11:46

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]

watson.fawkes - 13-2-2013 at 16:18

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.

starman - 13-2-2013 at 21:05

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.

learningChem - 13-2-2013 at 23:18

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?

learningChem - 13-2-2013 at 23:19

>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.

watson.fawkes - 14-2-2013 at 04:27

Quote: Originally posted by learningChem

I mean, *what* is wrong with you? You know your position is absurd, yet you keep babbling?

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".

learningChem - 14-2-2013 at 10:18

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.

elementcollector1 - 14-2-2013 at 10:49

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.

learningChem - 14-2-2013 at 11:08

elementcollector,

Please don't post spam/trolling coments in this thread - Thank you.

watson.fawkes - 14-2-2013 at 11:17

Quote: Originally posted by elementcollector1

Amazing how you think watson really is a troll.

Oh, I doubt he actually thinks that. He's just too lazy to think up an insult that might possibly stick.

Quote: Originally posted by learningChem

elementcollector,

Please don't post spam/trolling coments in this thread - Thank you.

I surmise bullying has worked for you in the past. You don't seem to realize that it's not working for you here.

elementcollector1 - 14-2-2013 at 16:02

Quote: Originally posted by learningChem

elementcollector,

Please don't post spam/trolling coments in this thread - Thank you.

...
I don't even know how to reply to this level of arrogance.

Mailinmypocket - 14-2-2013 at 16:38

Quote: Originally posted by elementcollector1

Quote: Originally posted by learningChem

elementcollector,

Please don't post spam/trolling coments in this thread - Thank you.

...
I don't even know how to reply to this level of arrogance.

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]

learningChem - 14-2-2013 at 16:59

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.

learningChem - 14-2-2013 at 17:03

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.

Mailinmypocket - 14-2-2013 at 17:06

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.

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!

learningChem - 14-2-2013 at 17:14

Quote:

Okay, boss. However don't expect to get much help with your attitude.

God dammit. You don't get it sonny? None of the trolls here are or were interested in helping, to begin with.

They are interested in babbling their laughable moralistic nonsense.

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

ROFL

See, we have a 'scientist' who reads tea leaves...

elementcollector1 - 14-2-2013 at 19:45

Quote: Originally posted by learningChem

God dammit. You don't get it sonny? None of the trolls here are or were interested in helping, to begin with.

They are interested in babbling their laughable moralistic nonsense.

So, you come onto our board, with no provocation, call a few of the respectable members here "trolls" (an ironic accusation, considering your reputation for not being useful), and insult our procedures. Then, when called out for being one of the rudest k3wl's it has ever been my displeasure to meet online, you call us trolls, and what's worse, you might just actually believe it.

I'm calling bullshit on this entire topic, due to OP rudeness, unhelpfulness, and unwillingness to work with the rest of the board.

Go find a board that agrees with you if you want to be agreed with.

learningChem - 14-2-2013 at 20:02

Like I told you EC, please stop spamming this thread.

You made it clear you have nothing to say regarding the oxidation of toluene. And you made it clearly you are just a biased troll playing fawkes lapdog. You had your fun, now go troll somewhere else.

By the way, you piqued my interest with your dumb remark about fawkes post count, so I checked how many posts the learned, helpful fawkes made in the benz. sticky thread? You know how many? Right. Ze ro. Interesting, ne?

elementcollector1 - 14-2-2013 at 20:12

Quote: Originally posted by learningChem

Like I told you EC, please stop spamming this thread.

You made it clear you have nothing to say regarding the oxidation of toluene. And you made it clearly you are just a biased troll playing fawkes lapdog. You had your fun, now go troll somewhere else.

By the way, you piqued my interest with your dumb remark about fawkes post count, so I checked how many posts the learned, helpful fawkes made in the benz. sticky thread? You know how many? Right. Ze ro. Interesting, ne?

Alright, fine. You win, let's help you out a little. Even though I have the significant urge to "troll" by telling you how things work both in social life and on the internet, let's go with this:

On pages 2, 3, 6 and 19 of the toluene-> Benzaldehyde thread there are writeups far more comprehensive than yours, using a variety of OTC and specialized reagents, any one of which we can help you synthesize. Examples are manganese ammonium alum, sodium carbonate, sulfuric acid, and many others. For a better perspective, visit the pages mentioned above.

What exactly are you trying to achieve with your workup? Do you want a larger yield of benzaldehyde, less work time / reagents involved, what?

I don't like to come across as a troll. In fact, I make it my business to be generally honest and at least somewhat fair. But I consider most of the folks on here acquaintances, if not outright friends - and Nicodem and watson.fawkes are certainly not exceptions to that rule. So, when you came on here insulting them for criticizing you, naturally I wasn't happy about it. Sorry if things got a little rude, I just don't like to see a bunch of posts saying "You're a troll! No U!" and not contributing to the thread.

You're entirely right, by the way. I don't know anything about benzaldehyde, from preparations to uses. I'm more of an inorganic guy, and the MnO2 caught my eye first.

learningChem - 14-2-2013 at 20:49

EC,

Thanks for your message. I take back the name-calling.

I tried the electrolitical methods to prepare both manganese persulfate (divided cell), and manganese amonium sulfate. But since I didn't measure how much current was used, I wasn't sure about much oxidizer was created, and I wasn't sure about the rest of the stoichiometry either, etc.

Yes, there's more information on those oxidizers, but right now, I want to use MnO2.

Quote:

What exactly are you trying to achieve with your workup? Do you want a larger yield of benzaldehyde, less work time / reagents involved, what?

Well, the point of the work-up would be to isolate whatever benz. has been produced, I guess...? In this case I'm using 10g of toluene, so the max. theoretical yield would be 0.8g benzaldehyde, if my math is correct...

elementcollector1 - 15-2-2013 at 08:18

Quote: Originally posted by learningChem

After one hour the MnO2 had changed from brown-black to a pretty light brown.

That would very likely be MnO2 hydrate, a brown 'mud' of sorts that's impossible to airdry completely.
Also, did you happen to see any pink manganese sulfate anywhere? That sulfuric acid should do its job quickly if MnO2 hydrate is present and not the calcined, less reactive black powder. (Thought - reuse the MnO2 if you can, but just dry it, don't re-calcine it back to brown. It will be much more reactive this way, but will contain some amount of water.)

EDIT: As to your theoretical yield, almost no procedure ever gets 100% theoretical yield. I usually see figures in the area of 10-20% if the synthesis is difficult, and 50-80% if the synthesis is extremely well done.

If your goal is to isolate a reasonable quantity of benzaldehyde, I would suggest that you first calculate your % yield (actual/theoretical x 100%) and then scale that up to the amount you'd like to obtain (as a calculated actual yield, not the theoretical).

[Edited on 15-2-2013 by elementcollector1]

learningChem - 15-2-2013 at 13:51

Quote:

Also, did you happen to see any pink manganese sulfate anywhere?

After the reaction is done, all of the MnO2 is 'gone', and what's left is a light yellow precipitate. I'm guessing that is MnSO4. Also, part of the MnSO4 must be dissolved in the water/acid layer.

The yellow color comes at least partially from some kind of condensation product(s) from the organic layer.

I've seen (light) pink manganese sulfate in my bottle of manganese sulfate monohydrate (store bought) =P - That's what I'm using as starting point for the MnO2.

Quote:

If your goal is to isolate a reasonable quantity of benzaldehyde, I would suggest that you first calculate your % yield (actual/theoretical x 100%) and then scale that up to the amount you'd like to obtain (as a calculated actual yield, not the theoretical

.

Yes, but I still need to carry the reaction with a minimun of efficiency, which is something I apparently haven't managed to.

Also, I realize that the actual yield is going to be even smaller since the MnO2 is creating side products like benzoic acid, and whatever stuff is coloring the reaction yellow.

But it's also true that the reaction uses a rather large excess of toluene, so if yield is calculated based on toluene, it's pretty low to start with - and so perhaps it should be 'easy' to achieve' (though it doesn't seem to be...)

Anyway, all of the MnO2 is reacting in my tests, but it doesn't seem as if much benzaldehyde is being produced. I'm wondering now if it's possible for most of the MnO2 to be reacting with the H2SO4 'directly', without affecting the toluene?

Also, I took a look again at this thread

https://sciencemadness.org/talk/viewthread.php?tid=6882

and I can't help but notice that Hilski never said what his yields were. He said he was 'hopping' for ~80% but didn't provide any hard data...

[Edited on 15-2-2013 by learningChem]

elementcollector1 - 15-2-2013 at 13:57

The MnSO4 could be in the yellow precipitate, but the pure stuff is, as you said, pink - and some of it may as well be trapped in the water layer.
I think the MnO2 is reacting with the H2SO4, and is possibly used up before the toluene has a good chance to react.

learningChem - 15-2-2013 at 15:08

Actually, I have 'recycled' the yellow precipitate by dissolving it in water, and then adding Na2CO3 and precipitating a white non-water-soluble substance that can't be anything but MnCO3.

-----

I've cleaned glass that was stained with MnO2 using concentraded H2SO4 (~90%) at room temperature. The MnO2 disappears and the acid turns pink in a couple of minutes.

On the other hand, when I wanted to turn a couple of grams of MnO2 into MnSO4, I had to heat them in H2SO4 for hours - the acid was 90% and virtually boiling.

I guess I need to run a test with only 3g MnO2, 23g H2SO4 65% and no toluene. Stir it for a couple of hours at 50C and see what happens.