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Ramium
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Quote: Originally posted by gdflp  | | Did it ever heat up? What is your MEK source, I'm guessing that it may not be as pure as you originally thought, but it could be the bleach too. At
least there aren't too many possible culprits. |
the reaction dident seam to heat up. This is my MEK Source
http://www.tmkpackers.co.nz/index.php/site/gallery/category/...
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Ramium
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Had a closer look at the mixture and i saw a separite layer on the bottom!!!
It was hiden by the curve of the glass
Is there anyway to test the layer to see if its chloroform?
The layer looks cloudy
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Texium
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Remove the aqueous layer with either by decanting or using a separatory funnel. Then take the chloroform layer and set up a simple distillation. The
boiling point is 61.2 C, so the vapor should come over at close to that temperature. You can salt out any remaining water with anhydrous magnesium
sulfate if you wish. Otherwise, take the distilled product (which should be clear) and store it in an amber glass or otherwise dark bottle. Add a few
drops of ethanol to stabilize it (prevents decomposition to phosgene).
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blogfast25
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Dry it with CaCl2, then determine density. The 1.49 density is quite a lot higher than most organics.
Weighing accurately how much you've got can give a good idea of conversion of the reaction. Be careful with chloroform, though! Read up, if you
haven't already.
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Ramium
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thanks guys.
will distil it today 
[Edited on 10-4-2015 by Ramium]
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Ramium
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I added HCl to the rest of the mixture. then tried to salt out the propionic acid from the mixture but it didn't work. I then started thinking about
how to dispose of the mixture.
then i tested to with PH paper and it was alkaline. So I took it to a chemical disposal plant.
That stuff which i thought was chloroform isn't chloroform after all. Its turned white and viscous and i realised the strog smell was actully MEK.
I guess i failed. .
Anyone know any other feasible methods for making propionic acid?
[Edited on 16-4-2015 by Ramium]
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DraconicAcid
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If it was alkaline, then you hadn't added enough HCl. The stuff that you thought was chloroform might have been impure chloroform...who's to say?
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Ramium
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I guess. But sadly i have already disposed of the mixture.
I'll try the experiment again
I'm just worried because the first time it didn't seem to heat up at the start, which it was supposed to, so i am not sure if it is going to work the
second time
I'll try a differnt brand of bleach.
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Loptr
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| Quote: Originally posted by Ramium | I added HCl to the rest of the mixture. then tried to salt out the propionic acid from the mixture but it didn't work. I then started thinking about
how to dispose of the mixture.
then i tested to with PH paper and it was alkaline. So I took it to a chemical disposal plant.
That stuff which i thought was chloroform isn't chloroform after all. Its turned white and viscous and i realised the strog smell was actully MEK.
I guess i failed..
Anyone know any other feasible methods for making propionic acid?
[Edited on 16-4-2015 by Ramium] |
You could oxidize the alcohol to the carboxylic acid.
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Amos
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1-propanol can be reacted with an aqueous solution of potassium permanganate and sodium hydroxide, oxidizing the alcohol to propionic acid which is
neutralized immediately by the sodium hydroxide. The permanganate itself is reduced to manganese dioxide, which can be filtered out. The remaining
solution can be boiled down until it crystallizes, and the crystals of sodium propionate can be treated with sulfuric acid(or another acid if you
don't mind water) and a distillation of the propionic acid can then be carried out.
The 1-propanol can also be oxidized with potassium or sodium dichromate and sulfuric acid, but that's a little bit more messy. I would imagine that
the dead reaction mixture after the reaction(which is very, very exothermic) could be heavily salted with sodium chloride and the propionic acid could
be extracted with ether or chloroform.
[Edited on 4-16-2015 by Amos]
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DraconicAcid
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I would expect that acidic bleach would also oxidize 1-propanol to propionic acid, but one has to be careful to avoid chlorine formation. I've done
bleach oxidations of larger secondary alcohols to ketones, but not to acids.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Amos
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| Quote: Originally posted by DraconicAcid | | I would expect that acidic bleach would also oxidize 1-propanol to propionic acid, but one has to be careful to avoid chlorine formation. I've done
bleach oxidations of larger secondary alcohols to ketones, but not to acids. |
Do you have a link to such a process? I didn't know you could use hypochlorite/hypochlorous acid for those kinds of oxidations.
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DraconicAcid
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| Quote: Originally posted by Amos | | Quote: Originally posted by DraconicAcid | | I would expect that acidic bleach would also oxidize 1-propanol to propionic acid, but one has to be careful to avoid chlorine formation. I've done
bleach oxidations of larger secondary alcohols to ketones, but not to acids. |
Do you have a link to such a process? I didn't know you could use hypochlorite/hypochlorous acid for those kinds of oxidations.
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Not offhand, but I could probably scan that part from a lab manual and email it to you over the weekend.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Amos
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| Quote: Originally posted by DraconicAcid | | Quote: Originally posted by Amos | | Quote: Originally posted by DraconicAcid | | I would expect that acidic bleach would also oxidize 1-propanol to propionic acid, but one has to be careful to avoid chlorine formation. I've done
bleach oxidations of larger secondary alcohols to ketones, but not to acids. |
Do you have a link to such a process? I didn't know you could use hypochlorite/hypochlorous acid for those kinds of oxidations.
|
Not offhand, but I could probably scan that part from a lab manual and email it to you over the weekend. |
I would be interested in that, but I thought typically you would obtain a chloroalkane rather than a ketone or carboxylic acid.
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Loptr
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| Quote: Originally posted by Amos | 1-propanol can be reacted with an aqueous solution of potassium permanganate and sodium hydroxide, oxidizing the alcohol to propionic acid which is
neutralized immediately by the sodium hydroxide. The permanganate itself is reduced to manganese dioxide, which can be filtered out. The remaining
solution can be boiled down until it crystallizes, and the crystals of sodium propionate can be treated with sulfuric acid(or another acid if you
don't mind water) and a distillation of the propionic acid can then be carried out.
The 1-propanol can also be oxidized with potassium or sodium dichromate and sulfuric acid, but that's a little bit more messy. I would imagine that
the dead reaction mixture after the reaction(which is very, very exothermic) could be heavily salted with sodium chloride and the propionic acid could
be extracted with ether or chloroform.
[Edited on 4-16-2015 by Amos] |
The first procedure is actually the one I had in mind. It would be so much easier, as you end up with insoluble that you filter off, and a soluble,
which is the salt of your desired product.
You could also extract the propionic acid in the first procedure using an organic solvent, as is done in the second, if you don't want to have to run
a distillation.
Personally, I would start with calcium propionate that can be purchased here: http://www.ebay.com/itm/2-2-lbs-1kg-Calcium-Propionate-Food-...
[Edited on 16-4-2015 by Loptr]
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Ramium
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The 1- propanol method sounds much easyer. i think i'll try that
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Ramium
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I have worked this out so far
C3H8O + KMNO4 = C3H6O2 + ?
Could you please help complete and balance the equation?
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Amos
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| Quote: Originally posted by Ramium | I have worked this out so far
C3H8O + KMNO4 = C3H6O2 + ?
Could you please help complete and balance the equation?
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I believe the net reaction that takes place is this one:
4 KMnO4 + 3 CH3(CH2)2OH = 4 MnO2 + 3 CH3CH2COOK + 4 H2O + KOH
The solution is made alkaline because it increases the reaction speed and promotes selectivity, according to wikipedia. The base is not needed
necessarily, but otherwise it will take quite a long while. The reaction's yield is limited, as the decomposition of potassium permanganate in water
is catalyzed by acids, bases, or manganese dioxide, so an excess of permanganate is a must for complete oxidation of the alcohol.
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DraconicAcid
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| Quote: |
Not offhand, but I could probably scan that part from a lab manual and email it to you over the weekend. |
Scanner's down, but here: http://www.chemistry.mcmaster.ca/~chem2o6/labmanual/expt7/ex...
http://ochemonline.pbworks.com/f/03_bleach_oxidation_handout...
http://goose.ycp.edu/~khalliga/Courses/CHM%20236/Spring%2020...
http://www.brynmawr.edu/chemistry/Chem/mnerzsto/Labs/Experim...
When we did this in the lab (OT story ahead), it was as a lab exam. The students were supposed to come in, do the experiment without speaking, and
hand in their product. The alcohol was measured out for them in flasks at the front of the lab (this was explained to them at the beginning). One
student ("J") came in late.
About half an hour into the experiment, I noticed that there was still a flask of alcohol left on the cart, so I recounted the students, and wondered
why there was still a flask left- I was sure there was the right number of flasks at the beginning. Then J came up to me, complaining that their
reaction was smelling odd (it was full of green-yellow gas, too, but J hadn't noticed). Upon cross-examination, J explained that they had weighed out
the alcohol (pointing at the jar of sodium sulphate, there to be used as a drying agent), and followed the directions to the letter.
Aright, J, *here* is the real alcohol, now start over. J managed to oxidize the alcohol, and then needed to extract the ketone with dichloromethane,
and wash the extract with water, then with saturated sodium chloride.
So J pours in some solvent, sees it separate into two layers, keeps the lower layer, and then throws out the top layer. Right down the sink (you can
see what's going to happen, don't you?). Then J adds water, and....only one layer forms.
What happened? J is perplexed again. "I added the dichloromethane," J says, pointing at the bottle of saturated sodium chloride. This salted out
the ketone, which floated to the top, and was washed down the sink. Naturally.
So J now has about an hour left to write up the lab quiz and hand it in, while the other students are doing their distillation. "Can I have some more
alcohol to start over?"
NO!
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Amos
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Sounds like J was a handful. Those reactions are certainly interesting, and I'll probably end up utilizing them later on if I can't find a cheaper
oxidizer. I didn't see anything in the resources that described oxidizing primary alcohols, but there's no reason it can't at least be tried!
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DraconicAcid
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According to this: https://www.researchgate.net/publication/222458939_The_oxida...
Primary alcohols will be oxidized by bleach not to the acids, but to the esters....
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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blogfast25
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The solvent was acetonitrile:acetic acid (3:2), not for everyone, that. Reported yields were generally good. Wonder if this works also with the
straight alcohols. Or perhaps using acetone as a solvent?
Interesting find.
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Mesa
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| Quote: Originally posted by blogfast25 |
The solvent was acetonitrile:acetic acid (3:2), not for everyone, that. Reported yields were generally good. Wonder if this works also with the
straight alcohols. Or perhaps using acetone as a solvent?
Interesting find. |
The same paper is available in the rhodium archives, it was discussed for it's potential use in preparing benzaldehyde briefly.
I've always wanted to find more information about it, especially the properties needed in the co-solvent(acetonitrile) and what alternative solvent
systems were tried besides the one included.
I kinda thought the choice of solvents were to ensure it stopped at the aldehyde/ketone but I couldn't find any related info to confirm/deny.
Acetone would not work as a solvent as it will react readily with hypochlorites, it's one of the more popular methods of preparing chloroform.
[Edited on 22-4-2015 by Mesa]
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gdflp
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Yep, that was discussed very briefly here. Benzyl alcohol is more expensive than toluene in the States, so I'm looking for ways from toluene, if anyone has a good source of benzyl
alcohol though, let me know. I've got about 40ml left so I can do some more experimenting with this method.
I did some experimenting with this a few months back and I managed to get around a 70% yield of crude benzaldehyde I think, I'm not entirely sure
because I never measured it precisely. From memory, I didn't use any acetonitrile and I used significantly less acetic acid than a 5x scale up would
require based on the paper and it still seemed to work. Because of the relatively small scale, I couldn't distill the product due to the lack of
glassware small enough. I can dig up my notes on the exact molar ratios and procedure I used if anyone is interested.
EDIT : Nevermind, I actually used the amount of acetic acid called for.
[Edited on 4-22-2015 by gdflp]
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Mesa
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Sure. I assume you used a liquid bleach as the hypochlorite, the majority of solvent in the reaction consequently being mainly water. Do you know
what pH was prior to adding the benzyl alcohol?
Acetic acid is so polar that I'd think solvent extraction should be possible in some respect. If this is not the case, is there any reason NaI or
metabisulphate couldn't be used to isolate/purify as their adducts?
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