Sciencemadness Discussion Board

(Diggers) toluene Inhibitors?

BenZeen - 22-6-2011 at 05:35

Hi everyone,
I have been playing around with the MAA cell (cycloknights variation) and have managed to get as far as generating the brown oxidative substance, after adding 100 - 150 mls of toluene i can smell a very faint amount of benzaldehyde, attempts to isolate anything meaningful has proved completely futile. (cell is 2 ltrs)

I have tried strong stirring, increase temp etc but to no avail, which has led me to believe there may be something in the toluene preventing it from becoming benz. I remember something about thiotoluenes inhibiting benzaldehyde formation, so simply i just would like to hear any ideas or comments regarding commercial toluene that may affect this reaction.

Thankyou very much

Panache - 25-6-2011 at 17:10

Do you have the msds of the product, this will let you know if anything is in the toluene, after that you can begin speculating, rather than speculating upon a speculation.

smuv - 25-6-2011 at 18:54

Is thiophene(s) even an impurity any more? Back in the day, sure, aromatics came from coal pyrolysis. Now, aromatics are petrochemicals, I have a hard time fathoming thiophene would make its way into even tech grade chemicals these days.

not_important - 25-6-2011 at 19:10

Not really, SFAIK most toluene is derived from petroleum (as you said). I believe the main impurity in commercial toluene is the corresponding methyl-cyclohexane and cyclohexenes, as their boiling points are close to that of toluene. Dilute KMnO4 or bromine water will test for non-aromatic unsaturates easy enough. Thioaromatics can be oxidised to sulfonones by H2O2 or other oxidisers, distillation would remove those.

BenZeen - 30-6-2011 at 10:57

Thanks guys, Always good to hear from more knowlegable chemists than I.
Perusing the interweb, I came across this pdf from the iupac detailing methods for purification of benzene and toluene.
I thought it might be worth posting incase this thread pops up at some future date in the FSE.
Cheers, Benzeen.

Sedit - 30-6-2011 at 11:19

Iv said it before, try dripping the oxidizer into warm toluene with good stirring. Else your just wasting your time.