Sciencemadness Discussion Board

Toluene and KNO3

tom haggen - 23-3-2010 at 13:17

Will toluene react with potassium nitrate at room temperature?

woelen - 23-3-2010 at 13:46

No, it will not. KNO3 is rather inert at room temperature.

mnick12 - 23-3-2010 at 14:51

React in what way? I dont think KNO3 would react with toluene even at an elevated tempurature.

hissingnoise - 24-3-2010 at 07:39

Presumably toluene would react in a KNO3/H2SO4 mixture but I don't know to what extent.
Some MNT is probable, DNT possible but to get TNT this way would be very difficult and wasteful of acid, I think.

ScienceSquirrel - 24-3-2010 at 09:05

I reckon you could reflux potassium nitrate in toluene and nothing would happen.

Mumbles - 24-3-2010 at 22:52

I speak from experience that you can make MNT at least with some DNT impurity from KNO3/sulfuric acid.

2bestyle - 31-3-2010 at 00:56

Do you want to nitrify Toluene to Monnitrotoluene or do you want do oxidize it to Benzoic Acid? For the First one you could use a mixture of KNO3 and Sulfuric Acid. For the second one you have to use Potassium permanganate.

rrkss - 2-4-2010 at 11:04

Nitration of Toluene is very tough and will require some very harsh conditions if that is what you are after. Mono-Nitro-Toluene can be made by refluxing toluene in a mixture of Nitric Acid/Sulfuric acid or KNO3 in concentrated H2SO4. You might get some DNT but Nitro-groups are very deactivating which means that the more Nitro groups you attach to the toluene, the more difficult it is to attach another one.

mnick12 - 2-4-2010 at 15:19

Quote: Originally posted by rrkss  
Nitration of Toluene is very tough and will require some very harsh conditions if that is what you are after. Mono-Nitro-Toluene can be made by refluxing toluene in a mixture of Nitric Acid/Sulfuric acid or KNO3 in concentrated H2SO4. You might get some DNT but Nitro-groups are very deactivating which means that the more Nitro groups you attach to the toluene, the more difficult it is to attach another one.


I sorta disagree,
Toluene is generally very easy to mono- nitrate and even di- nitrate, as long as your reagents are not complety full of water. It is usually tri- nitration that tends to be a problem, but if you are simply after a MNT then there is no need to reflux, and if you want DNT then just nitrate your MNT at an elevated tempurature.
rrkss, mabe you are thinking of benzene? Benzene is quite a bit harder to nitrate, though I do not think you need to reflux just react for a longer time.

rrkss - 2-4-2010 at 20:50

Well thinking about it more, you are right. The methyl group on toluene would slightly activate the ring making the first nitro easy to put on. TNT seems like it would need very harsh conditions to make with two deactivating nitro groups and would most likely need heat + oleum to be a possibility.

DJF90 - 3-4-2010 at 01:19

I disagree, even benzene is not that tough to mono-nitrate, requiring only a mixture of concentrated sulfuric and nitric acids, and temperature regulation at about 55*C (in the procedures I've seen)... toluene is even more reactive and I would probably try the nitration at 0*C; methyl m-nitrobenzoate is formed by nitration of methyl benzoate (in which the ring is deactivated by the ester group) at 5-10*C. Trinitration is however pretty tough, although doesn't require oleum if you're willing to reflux for a longer period; chlorobenzene (in which the chlorine substituent is a deactivating ortho/para directing group) can be trinitrated using fuming nitric acid (easy to make by distillation of 68% HNO3 from equal volume of conc. sulfuric acid) and concentrated sulfuric acid at reflux for 35h, with replacement of the acid at the 17h mark... toluene would be much easier than this, and I suspect that using the same nitrating mixture would have the reaction over in about 5-10hrs.

densest - 5-4-2010 at 09:36

"The Chemistry of Powder and Explosives", Tenney L. Davis, 1941-1943 on pp 141-153 shows the 3-step process for nitrating toluene. Each additional NO2 requires stronger acid. There is a one-step procedure using a mercury catalyst which I don't have a reference handy. Both have approximately the same yield. There are a number of side reactions which limit yield and reaction rate/temperature.

hissingnoise - 5-4-2010 at 10:50

Densest, was the mercury-catalysed nitration not the one which produced picric acid by refluxing 68% HNO3/benzene?

Formatik - 5-4-2010 at 12:37

Wilbrand's synthesis of TNT (Ann. 128 [1863], 178) consisted of heating toluene with mixed fuming sulfuric and fuming nitric acids for several days at gentle boiling. Then adding water, washing obtained precipitate with water and drying, recryst. from alcohol.

densest - 5-4-2010 at 13:28

@hissingnoise - you're quite right! It's even in the same book a few pages down. I'll see if I can remember where I saw the 1-step TNT synthesis...

hissingnoise - 5-4-2010 at 13:30

The preparation of TNB by direct nitration is so difficult, it was found more economical to remove the methyl group of TNT by oxidation. . .
Densest, sure you're not mixing up TNT with PA?


[Edited on 5-4-2010 by hissingnoise]