Sciencemadness Discussion Board - Purification of Toluene

Purification of Toluene

Magpie - 1-2-2012 at 10:49

I am presently purifying ~100 mL of Ace brand toluene. The label on the can says that it is "100% pure." I have reason to believe that is a reasonably correct statement.

My first step in purification was simple distillation. Wiki says that the azeotrope with water boils at 84.1C and that pure toluene boils at 110.6C. In my distillation the temperature shot right up to 109.8C without any hesitating around 84.1C. The temperature soon read 110.0C. At this point I discarded a foreun of ~20mL. The bp stayed at a steady 110.0C for the rest of the distillation. I left a few mLs in the pot.

My local weather station said the barometric pressure was 29.59"Hg, or 751.6mmHg. So, I thought that the lower barometric pressure vs the 760mmHg for the normal bp accounted for this difference.

I checked this against the Sigma-Aldrich nomograph but it gave me an obviously way too low value for the barometric pressure of 27.6"Hg (700mmHg), the upper limit of its scale.

So then I went to the Clausius-Clapeyron equation, which produced an expected bp of 110.24C. The Antoine equation produced a value of 110.23C.

So, even knowing that my thermometer is uncalibrated, I am satisfied with my bp and believe that it indicates toluene of high purity. It is also obvious that the Sigma-Aldrich nomograph has its limitations.

My distilled toluene has been sitting overnight on CaCl2 (per Vogel). Today I will transfer it to a bottle with activated 4A mole sieves for storage.

jamit - 1-2-2012 at 11:25

I have done simple distillation of ace brand toluene and got the same result. After getTing rid of the early distillate, the temp remained at a steady 110c for the rest. I also stopped the distillation before getting dry. The remaining liquid in the boiling flask was colorless like water. I collected about 450ml of toluene. I also added cacl2 and next day filtered and poured the toluene into a 500ml bottle for storage. I believe my toluene is very pure.

So I confirm your distillation of OTC toluene. Hope this helped.

turd - 1-2-2012 at 12:00

OK... You distilled toluene...?
No offense intended, but what is the point of this thread? I was somehow waiting for the punchline and it didn't come.

Unless your toluene is turbid or contains other solvents that increase water solubility (acetone?), no seizable water azeotrope is expected. All OTC toluene I bought was always quite dry. Unless you're doing metal organics all that drying is probably not even necessary. Distill through a column throw away a fem ml pre-run and it will be fine! Evidently: the larger the batch the less relative loss. 100 ml sounds a little bit on the low side.

And concerning the temperature: don't be more catholic than the pope! Distillation is an equilibrium thing - heat supply here, heat loss there, vaporization, condensation, diffusion, convection, etc. I'm sure there is more than one official boiling point. Organic chemistry is about cooking, not to act out your OCB.

Magpie - 1-2-2012 at 12:35

Thanks Jamit I appreciate you sharing your experience.

Turd, there was no real point other than a sharing of my experience in a purification. You may think I'm quibbling over the boiling point but what else do we home chemists have for establishing purity of toluene? If there would have been any water there it surely would have shown up at the azeotrope temperature.

Mostly I'm concerned with obtaining anhydrous toluene. I know this is no great challenge, I just thought my data and calculation results would be of interest to some. You even pitched in and gave some valuable opinions.

My next challenge is going to be preparing anhydrous ethanol from rectified spirit (95% ethanol, Everclear). I want to share my experience here also, as I think this is going to be much more of a challenge. I know there are time tested techniques in Vogel and elsewhere but I still think sharing our experiences as home chemists is both interesting and valuable.

Universities have sodium presses, Schlenk lines, glove boxes, Grubbs columns, and Karl Fischer analyzers. In fact a technician probably dries the solvents. They also start with purchased "anhydrous" ethanol which is probably no more than 0.5% water. It's a much tougher challenge for the home chemist who is likely starting with 5% water and has no fancy tools or grunts to do his work.

[Edited on 1-2-2012 by Magpie]

[Edited on 1-2-2012 by Magpie]

jamit - 1-2-2012 at 12:40

I think magpie just wanted to confirm his results. And I concur!

. And it seems like you concur too turd with most of magpie's results.

The point is... It's hard to believe that you can get really pure toluene from OTC solvent. But you can now, at least with toluene. Usually there's all kinds of junk... Ie denatured alcohol or 70% ethyl rubbing alcohol contains all kinds of mixed solvents.

I'm glad magpie posted his finding... Because I did my purification last year but didn't post my results...but I have been wondering about my results and it's good to know that someone has also tried the same thing.

S.C. Wack - 1-2-2012 at 14:14

The source is likely BTX, and there is no point in separation and purification of this without separating and purifying; no surprise then.

BTW I've mentioned here before the correction necessary for altitude from altitude-calibrated barometers. The internet says the pressure in Denver is currently higher than in Seattle.

Lambda-Eyde - 1-2-2012 at 14:59

I'd really recommend that you shake your toluene with conc. sulfuric acid before distilling next time - I didn't. (my image host is down right now, but when it comes back the pictures will speak for themselves...)

Magpie - 1-2-2012 at 15:45

Quote: Originally posted by S.C. Wack

BTW I've mentioned here before the correction necessary for altitude from altitude-calibrated barometers. The internet says the pressure in Denver is currently higher than in Seattle.

I am aware that airport weather stations report barometric pressure as "corrected to sea level." I was careful to ask about this and made sure the pressure I got (not from an airport) was "uncorrected," ie, a raw pressure uncorrected for altitude. I then checked with the local airport, and sure enough, their value was corrected 0.44" Hg higher (11 mmHg).

I've always been curious as to what effect my barometric pressure was having on the bp I would get during distillations, as compared to the normal bp. So yesterday when distilling the toluene I called and got the pressure, then made the comparisons.

I first tried to reconcile the data with the Sigma-Aldrich nomograph, but it was not useful here. The Clasius-Clapeyron and Antoine equations, which agreed to a remarkable degree, did give me reasonable results. Per these equations the lowering would be 0.36C from the normal bp. A 0.6C lowering was the actual differential per my uncalibrated thermometer.

[Edited on 2-2-2012 by Magpie]

[Edited on 2-2-2012 by Magpie]

benzylchloride1 - 1-2-2012 at 21:22

I use Ace Hardware toluene for all of my syntheses. I always distill about 25 mL of the solvent,the distillate is always milky due to a small amount of water present which would cause problems with much of the chemistry I do. I then reflux the toluene over sodium metal for several hours and then distill under helium. I have also run a sample of the purified toluene on a Gow-Mac 150 gas chromatograph of this purified toluene as an internal standard for another experiment that I was running and there appeared to be no extraneous peaks that would be attributed to any impurities.

[Edited on 2-2-2012 by benzylchloride1]

Magpie - 1-2-2012 at 23:09

Quote: Originally posted by benzylchloride1

I have also run a sample of the purified toluene on a Gow-Mac 150 gas chromatograph of this purified toluene as an internal standard for another experiment that I was running and there appeared to be no extraneous peaks that would be attributed to any impurities.

I take it from this that your purified Ace Hardware toluene has no sulfur compounds such as methylthiophene. Is that correct?

FYI:
http://www.iupac.org/publications/pac/1989/pdf/6110x1823.pdf

[Edited on 2-2-2012 by Magpie]

Magpie - 2-2-2012 at 13:27

My distilled Ace Hardware toluene has rested on activated 4A mole sieves overnight. Today I tested it for water using CaC2 and anhydrous CuSO4 (Brewster). Both tests were negative.

I also tested some 95% ethanol (rectified spirits), and some rectified spirit I had previously attempted to dry to <100ppm water using unactivated 3A mole sieves. Both tested positive for each test.

Edit: I just tested the toluene in the can: both tests were negative here also. This can is about 3/4's empty and is several years old.

[Edited on 2-2-2012 by Magpie]

Panache - 13-2-2012 at 00:23

I find distilling toluene from cacl2, using the maximum possible vacuum available to you yeilds better results cf/ distillation at atmospheric pressure. A couple of caveats herein though, firstly the commercial tolly here in australia still has the thio antioxidants added, they are neigh on impossible to remove via std distillation, vogel uses multiple sulphuric washes to remove them, which is horrendously expensive and time consuming, however i have reason to believe distillation under reduced pressure affects a separation, which forms the basis of the second caveat.
That being when an atmospherically dist. Toluene is treated with sodium a horrible orange gunky slop results, however with the vac dist. Toluene no colouration and little bubbling upon the sodium surface is observed. It is known that an effective way to crudely dry etoh fom the azeotropic 96% solution is under reduced pressure, this shifting the dynamics in favour of pure etoh, this was the basis for my trial regarding tolly and the annoying codistilling thiophenes.

starman - 13-2-2012 at 22:49

Quote: Originally posted by Panache

firstly the commercial tolly here in australia still has the thio antioxidants added

@Panacche I am interested on the basis of this statement.Reochem - Diggers brand that I make use of has the msds stating 100% Toluene.Though using atmospherically distilled tolly (went very smoothly at precise temp) has given me some unexpected problems in synthetic use (ie pTSA synthesis.)
I was going to repeat doing sulphuric washes but also have good vacuum capability now so may attempt to mirror your efforts.

Panache - 19-2-2012 at 19:25

Have you tried drying some wih sodium, post distillation?

scientician - 20-9-2012 at 16:51

After a few failed MPVO runs I tested my Ace brand toluene (which I had previously just dried over CaCl2.) While I don't have isatin to test with, adding conc. H2SO4 resulted in a lot of "white shit" precipitating out, which is the same thing I observed in my redox that ruined everything. Trust NO solvents, especially those made for purposes other than lab work.

MyNameIsUnnecessarilyLong - 23-9-2012 at 13:32

All the Ace Hardware stores in California where I live have permanently removed toluene, MEK, naptha, and xylene off the shelves a little less than 2 months ago. I really wish I had known ahead of time to stock up. So if anyone else here lives near the western United States or a state that has a tendency to mimic California, you should check to see if there are any impending bills that aim to do the same where you live.

kristofvagyok - 24-9-2012 at 10:24

Quote: Originally posted by Panache

Have you tried drying some wih sodium, post distillation?

Bingo, abs. Toluene is distilled from metallic sodium or from calcium hydride. The CaCl2 will dry it mostly, but it won't be truly waterfree, CaCl2 is not the best, because as we know CaCl2 pellets ar CaCl2.2H2O

But for the most reactions the CaCl2.2H2O, or MgSO4, Na2SO4, ect. dried toluene is good.

I use Sigma, but it's not that better than "Ace" brand.

starman - 24-9-2012 at 18:04

Quote: Originally posted by Panache

Have you tried drying some wih sodium, post distillation?

Unfortunately attempting tp procure sodium in W.A. invites unwarranted attention due to the the illicit drug trade.
(Seems to be running at about one explosion a week here in Perth,so I guess the authorities have a point.)
I've often looked at Len 1's set up for Na in a future project,time and money permitting...
So in short 'no'.

Texium - 7-11-2015 at 14:35

Sorry to dredge up this old thread, but I was curious: is the toluene that you have actually ACE brand, or just purchased from ACE? Because I bought some toluene at ACE earlier today and was looking to find out how pure it was, but it is KleanStrip brand.

I suppose it really doesn't matter as I can try distilling it like you did and see what results I get, but I thought it would still be good to know.

JJay - 7-11-2015 at 18:21

KleanStrip seems to be very much hit or miss... some of their products are low quality and some are high quality. I imagine their toluene is pretty good. Do we have any current ACS members who know what chemical tests to use to verify ACS quality? Maybe I should register....

Texium - 7-11-2015 at 19:05

I found another thread where gdflp mentions using isatin to test for thiophenes, which are the most frustrating and difficult to remove impurity (forms a blue color with isatin). Unfortunately I don't have any, so I may just have to try reacting it with sulfuric acid in a container I wouldn't mind mucking up with possible polymerization products. I want to use this toluene to make p-toluenesulfonic acid, so it can't have any thiophenes in it, though water wouldn't be a problem since I'll be using a Dean-Stark trap.

Oscilllator - 7-11-2015 at 22:29

Quote: Originally posted by zts16

I found another thread where gdflp mentions using isatin to test for thiophenes, which are the most frustrating and difficult to remove impurity (forms a blue color with isatin). Unfortunately I don't have any, so I may just have to try reacting it with sulfuric acid in a container I wouldn't mind mucking up with possible polymerization products. I want to use this toluene to make p-toluenesulfonic acid, so it can't have any thiophenes in it, though water wouldn't be a problem since I'll be using a Dean-Stark trap.

I'm not familiar with the ACE brand but I just looked it up and it seems like a hardware store. If that's the case then your toluene certainly contains thiophenes.
With regards to cleaning it with sulfuric acid, don't worry about the container. I've done this exact procedure also with the aim of making p-toluenesulfonic acid and although the sulfuric acid did get quite gunky on the first wash, it wasn't a problem to clean. I just added some water to the sulfuric acid once I had separated the toluene to get it nice and hot and it washed right out. I think I washed my toluene 2 or 3 times and that got out the vast majority of the thiophenes, but the resulting p-toluenesulfonic acid was an interesting pink colour.

CharlieA - 8-11-2015 at 19:39

http://www.kleanstrip.com/msds-cpsia I don't know how to make an attachment. On the link shown you can find the MSDS for Klean Strip Toluene; it shows the composition on page 3, as 100 % toluene.

On a side note, MSDS's can be find relatively easily, so why all the speculation about possible additives that one "thinks" might be in something?

Magpie: You like the results of correcting the bp for atmospheric pressure, but then give the caviat that your thermometer is un-calibrated. Therefore it is not correct to say your calculated bp was in good agreement with the observed bp. Why not just calibrate the thermometer? (please don't take this as a knock on your posts. I just think if you calibrated the thermometer, then your comparison of the observed and calculated bp's would be more meaningful.)

Magpie - 9-11-2015 at 08:41

Yes, I should have calibrated it. It has so often given expected results for mp's and azeotrope bp's that I have just assumed it to be sufficiently accurate.

I have also noted that Ace is now stocking more KleanStrip brands than offering these solvents under their own label. When it comes to trace amounts, like methylthiophene, I wouldn't trust an MSDS to list them.

[Edited on 9-11-2015 by Magpie]

CharlieA - 9-11-2015 at 12:52

I guess, really, there are probably few things that are 100% pure...there is always that next decimal place to be measured! I think it would do me good to see just what the requirements are for listing components/additives in the MSDS.

gdflp - 9-11-2015 at 14:41

My understanding is that the MSDS is required to list composition, NOT purity. For example, if they sell technical grade acetone which contains 5% water, but they don't add any water to the composition and the mixture simply contains it, then they can write 100% acetone. Similarly, the thiophenes are an impurity which arises from the production of the toluene and they may exceed 1%, but since they are impurities and not ingredients of the mixture they don't have to be listed on the MSDS. If they added 1% thiophenes to the mixture to improve some property of it though(this is just an example, there's no reason to do this), then they would need to list 1% methylthiophene(or a concentration range) on the MSDS.

JJay - 9-11-2015 at 21:55

I think it depends on whether the impurity exists in a significant quantity to cause a safety issue. If a detergent has 0.05% mercury impurity, it had better say so on the MSDS. On the other hand, if 2% sugar is added to it as an adhesive, it doesn't have to appear on the MSDS.

CharlieA - 10-11-2015 at 14:12

Here is a link to get the scoop on MSDS/SDS requirements:

https://www.osha.gov/Publications/OSHA3514.html

"Section 3: Composition/Information on Ingredients" starts out:
"This section identifies the ingredient(s) contained in the product indicated on the SDS, including impurities and stabilizing additives. This section includes information on substances, mixtures, and all chemicals where a trade secret is claimed. The required information consists of...:

This is only a 6-page printout.

Sniffity - 11-11-2015 at 20:35

This might seem like a fairly stupid question D: But could you explain what's this "corrected to sea level" means? And why is this correction necessary?

My way of understanding it was that the higher you take a barometre, the lower the pressure will be, and you didn't need to correct it?

Magpie - 11-11-2015 at 22:29

Air traffic controllers obtain the local tower pressure using a barometer, which, as you say gives the true atmospheric pressure regardless of the tower altitude. But this value is not usable by airplane pilots approaching the tower. They need a "corrected to sea level" value so they can dial it in on their altimeters. Their altimeter will then read the correct altitude when they are at that given tower.

This is my understanding and is subject to correction by someone who actually knows - please.

bobm4360 - 11-11-2015 at 23:06

An altimeter is just a barometer that reads funny. When you get tower pressure, and set that pressure in the altimeter, it will read field elevation if you are on the ground at that airport, or field elevation plus your height above ground if you are in the air. Knowing your altitude above local terrain is a Very Good Thing. Your altitude above sea level is worthless unless you are over the ocean.....
Above 18kft (mandatory instrument flight) everyone sets their altimeter to 29.92 in.Hg so they are on the same page and can maintain altitude separation. If pilot A reads 19000 ft in his aircraft and pilot B reads 20000 ft in his, they will not have a close encounter of the worst kind. If their altimeters were set at different fields, B could be at the same level as A or even below him.
The tower barometer is corrected for field elevation at standard temperature and pressure

[Edited on 12-11-2015 by bobm4360]

[Edited on 12-11-2015 by bobm4360]

JJay - 12-11-2015 at 01:06

Corrected to sea level means at a pressure of one atmosphere.

Magpie - 12-11-2015 at 09:50

I think I was incorrect in my explanation above about the "corrected to sea level" barometric pressure. This website gives the proper procedures:

http://www.skybrary.aero/index.php/Altimeter_Setting_Procedu...

Near the airfield the pilot wants to adjust his altimeter so that it reads his height (altitude) above the airfield (QFE).

Texium - 13-11-2015 at 15:28

To follow up, the KleanStrip toluene that I got at ACE seems to be very pure, as yesterday I synthesized tosylic acid with it and there was no polymerization whatsoever. The solution became slightly yellow during the reaction, but the product precipitated on cooling as nearly pure white crystals.

Fyndium - 15-9-2020 at 13:58

Barometric pressure gets me every time when I begin to suspect everything what I do when a distillation just keeps going over the limit even when every single factor seems to be on point. Then, I remember to check the local weather station, do a little math and pieces fall together. Toluene really keeps getting over at 113C when the barometer says 1020mbar.