I`ve put this in here as it maybe a little Newbish of a question.
as an experiment I put NaOH prills into a test tube containing 2ml of Toluene.
there was an almost instant color change to a grey/green and very noticable around the "White" prills.
after some time the color went to an orange/red and seems to have stabilised at this color.
I checked it this morning (24 hours later) and the liquid seems to be quite Viscous wilth gel like material in it.
have I made a sort of Soap perhaps?
I really don`t understand the mechanism behind this reaction, i just had a feeling it Would react.
my plan was to take this liquid and add Ammonium Chloride to it and hopefully replace and sodium with the Amine group.
I`ve looked in my books and also googled for Toluene NaOH even it`s proper name of methylbenzene, no real luck
the word Benzaldehyde crops up frequently, but I`m sure that`s Not what I`ve made.
edited to add:
the "liquid" still smells of toluene, and burns just the same with a sooty flame, but leaves a water soluble white powdery deposit.
if that helps any?
[Edited on 20-9-2006 by YT2095]chemoleo - 20-9-2006 at 06:24
Maybe you just formed some sort of Pi-stabilised complex, which is non-covalent and doesn't involve any bonds rearranged?
In all likelihood you simply 'dissolved' the NaOH. Interesting about the colour change though.not_important - 20-9-2006 at 06:55
The definition of saponification is the hydrolysis of an ester using base. While NaOH is a base, toluene is not an ester. A little reading whould
show that simple hydrocarbons, including simple alkylarenes such as toluene, don't react with pure NaOH, it's not strong enough of a base. This
suggests that one or both of the reagents are not pure.
Consider what reagents you have, C6H5CH3, NaOH, and from air O2, N2, CO2, and H2O. Toluene has been used as a protective liquid for metallic sodium,
sodium has been melted under toluene to make one big lump out of many hydroxide coated small bits, and I've read experiments where toluene solvent was
dried by refluxing over and distillation from molten sodium.
What is the source of the toluene? If it is industrial solvent stuff, did you try distilling it and noting the distillation range? Any part of it that
doesn't boil near 110 C isn't toluene itself. Same question for the NaOH, what was its source, how pure is it?
I suspect an ester, ketone, or even halocarbon in your toluene, off the top of my head. Strong bases cause ketones to condense to a mix of products.
A saponification will give you a soap, most properly when the acid is of the right size range and properties to give a hydrophobic 'tail' But
there's no way the reaction RCO2(-) Na(+) + NH4CL => NaCl + RNH2 + CO2
At the best you could form an ammonium soap RCO2NH4, best when run in an wet alcoholic solution so the NaCl mostly precipitates out while the 3 other
ompounds are more soluble.
Toluene can be oxidised by air, and is done so industrially; benzyl alcohol, benzaldehyde, benzoic acid, and benzoic acid esters being possible
products. However these oxidations are done using acid conditions and catalysts, thypically carboxylic acids such as acetic acid and a catalyst
containg cobalt and manganese acetates and a bromide, lithium bromide being popular. The reactions is run hot with air blown through it.YT2095 - 20-9-2006 at 07:38
well the Toluene is indeed industrial, it came in a huge metal can marked Toluene, still sealed and it was used in some sort of Printing press
company, beyond that I can`t comment any further other than to say, that I`ve used this to purify Sulphur in the past quite succesfully and the BP was
constant, I`ve also made a small quantity (about a gram) of TNT with it also.
the NaOH is B&Qs Finest
sold as Caustic Soda, and the ingrediant list says only that too (Sodium Hydroxide).
there are no Visible impurities either as a solid or in soln.
I also have used this for Many other things without issue.
I DO have, 99.9% pure KOH though, so maybe I`ll try with that also, it would at least elliminate ONE potential candidate for contamination.
Edit: I`ve just done the KOH + MB, there was a Slight turbidity of the MB and a 5c temp increase, no color change per se though, I put that slight
reaction down to air moisture present, as the KOH will stick to the spatula when you go back for a second lot, a peice left out will puddle before
your eyes.
Preliminary judgement says the NaOH is at fault
[Edited on 20-9-2006 by YT2095]not_important - 20-9-2006 at 08:00
Solvent grade stuff could function nicely as a solvent without even being what the label claims 8-) If there's something else in there that boils
higher that toluene, then even the boiling point isn't a good indication unless you're being very precise in measurement.
But it does sound as if something is going on with the NaOH. Other possibility is that there was one time contamination - did you run the reaction
more than once?Nerro - 20-9-2006 at 08:17
To Chemoleo;
With a metal like Na I wouldn't expect very much from complexing. Least of all with benzene or a simpel derivative like toluene. Maybe with a
transitionmetal like Fe, Co, Ni or Cu or something but not Na (nor Na+ which has no orbitals to complex with.)
It is probably just the impurities, it takes only a tiny amount of contaminants to colour a product.YT2095 - 20-9-2006 at 09:48
well after an hour or so, the KOH in MB shows no signs of Color change at all, there is some Loss of mass though, and as the MB evaporates it`s
forming tiny crystals about 1cm above the liquid layer.
it would seem it`s the NaOH at fault
with the Green and then orange/red, I guess maybe an Iron contamination, although Chrome will do this too, 1) it doesn`t seem very likely 2) there
would be a Purple at some stage with different light sources.
Thanks each for the good replys and advice, I feel a bit stupid now, the NaOH acted so Perfectly in all the other reactions I`ve used it for in the
past, Sorry about that!unionised - 20-9-2006 at 10:13
"well the Toluene is indeed industrial, it came in a huge metal can marked Toluene"
"with the Green and then orange/red, I guess maybe an Iron contamination"
Looks like a good bet to me, even if youu didn't get the same reaction with KOH. Impurities have a habit of coming an going without any clear reason.guy - 20-9-2006 at 13:13
The hydrogen on the methyl group of toluene can be deprotonated because it will increase resonance. So maybe the deprotonated verson is colored?not_important - 20-9-2006 at 22:46
Quote:
Originally posted by guy
The hydrogen on the methyl group of toluene can be deprotonated because it will increase resonance. So maybe the deprotonated verson is colored?
The pKa of a methyl hydrogen on phenylmethane is about 41, this is a thousand times more basic than NH2(-), a million times more basic than H(-) (from
NaH or such), and 25 orders of magnitude more basic than OH(-). That is, while the pH of a strong solution of NaOH is about 15 and a snudge, the pH of
C6H5CH2(-) would be 41.YT2095 - 21-9-2006 at 01:12
Quote:
Originally posted by unionised
even if youu didn't get the same reaction with KOH. Impurities have a habit of coming an going without any clear reason.
you`re actualy closer to the truth there than perhaps you realise, it gets worse!
I did the exact same thing again, but used 2 brand new test tube out the box, there was no color change with Either.
I have Woelen to thank for sugesting it maybe test tube contamination.
the only thing that remains constant between the new tests and the old one is that the AQ layer in NaOH test turned to a gel again also, the KOH
didn`t.
it looks like I`m going to have to give all these tubes a good long soak in Oxalic acid for a day or so.
