This is another synthesis from "the Russian Hive" - hyperlab.org. It describes prepn of P2P from nothing else but
benzene, acetone and Mn(CH3COO)3. The latter is easily prepared from KMnO4(see below). As far as the search engine goes, it hasn't been covered here at all (xcept for one unanswered post in Aquisition where some stranger asks where to buy manganese triacetate
)
Here's the deal:
15 ml benzene, 15 ml acetone, 25 ml AcOH and 5 mmol(1,01 g) Mn(AcO)3 are boiled under N2 atmosphere until the color of the soln changes from dark brown Mn(AcO)3 to pink Mn(AcO)2 - approx. 1,5 h. The rxn mixtr is diluted w/40 ml ether, washed w/25 ml water and 2x25 ml 5% NaHCO3, the org layer is dried and evap'd to yield 40% P2P (134 mg)
Now, as you can see the yield is not that great - but, hey, who cares for acetone, what is more important the benzene/acetone to Mn(AcO)3 ratio is huge. Well, i can only say that the above procedure (as i have some good reasons to believe) bears rather analytic than preparative approach and the amt of Mn(AcO)3 undoubtedly can be scaled up significantly, but the exact answer is still to be found.
Although SWIM didn't succeed w/this rxn the 1st and the only one thus far time he tried it (see the experimental details below) there can be no doubt that it works as i've personally read two articles dedicated to studying its mechanism. It works even better w/substituted benzenes: for anisole the yield is 74% (in 45 min), unfortunately a mixture of isomers is formed of which ortho- predominates. Para-dimethoxybenzene is even more activated than anisole and completely symmetric, it seems to bee ideal for this rxn, don't you think so, bees?
The rxn also runs w/naphtalene (selectively forming 1-acetonylnaphtalene), furan, sylvan, pyridine, thiophene (all forming alpha-acetonyl compds), chloro- and cyano-benzene, toluene (forming a mxtr of isomers) and, beyond a shadow of a doubt, a whole lot of other aromatics which opens so many roads to new, untasted yet compounds - (which, coincidentally, are currently being discussed in Serious Discourse/Fluoroamph. thread) - that it is even scary. Just needs to be made to work
The mechanism of the rxn is as follows: first a ÑÍ2=Ñ(ÑH3)-Î-Ìn(3)-ÀãÍ complex is formed, which then falls apart w/simultaneous cleavage of Mn-O bond, acetonyl combines w/aromatic nucleus (the limiting step) and the resulting adduct radical is rapidly reduced w/another Mn(AcO)3 molecule.
Well, with that said let me finally get to the preparation of Mn(AcO)3 - i'll skip the abstract and just tell you guys what SWIM did, from the beginning to the end.
KMnO4 is reduced w/hexamine and HCl to MnCl2, precip'd as the carbonate, converted to Mn(AcO)2 and oxidized w/KMnO4 in boiling GAA to Mn(AcO)3.15 g KMnO4 was dissolved in some hot water and combined w/a soln of 15 g camping fuel (SWIM used hexamine cause he had it at hand - any ammonium salt will do just fine). Nothing happened. Then conc HCl was added in portions w/swirling until mixtr acidic. As he did it, the mxtr gradually turned completely clear and the stench of formaldehyde became almost unbearable
. Then SWIM put the soln in a 5 liter jar and mixed it w/a molar excess of saturated NaHCO3 (you can calculate it if you want - SWIM just took a large xcess). White precipitate (MnCO3) forms. The jar was filled w/water to wash it. DO NOT use NaOH for precip'ing manganese - Mn(OH)2 instantly oxidizes when exposed to air, and the carbonate is pretty stable.
When all settled, the water was decanted into another jar (to collect the still remaining suspended MnCO3 later) and the precip't washed in the same manner once again, MnCO3 in the other jar washed later too. Then all combined, water decanted off, precip't vac. filtered, DO NOT DRY IT - there's no need for that, and it WILL oxidize somewhat during drying. Just scrape it off the filter and dump into some GAA. Now, guess what, there was no fizzling and bubbling at this stage as SWIM expected, in fact, to dissolve all the MnCO3 it took a 2 hour reflux. At this stage the soln was a pleasant pink color, just as it should have been.
The GAA was boiled off overnight at 130 C in an oil bath and when SWIM woke up he found that the bottom of the flask was covered w/some
white (not pink) crystals - well, he thought, that must be unhydrous Mn(AcO)2 (the pink stuff is a tetrahydrate) - and so it turned out to be. SWIM dosn't remember the exact weight (uhhhh... 21 g?) but the yield was quantative.
Now SWIM went on to dissolving his salt in GAA, 250 ml (SWIM thought you'd have to 1st evap. GAA and then dissolve in it again as the former one has water in it - but he was wrong as you'll see. Well, he needed to weigh it anyway. Just skip this evap'n/dissolution step, it's probably not needed) -
the shit doesn't dissolve! even w/reflux! Probably, SWIM thought, the unhydrous stuff doesn't, so he added a theoretical amt of water, well, a little more in fact, about 7 ml to the mxtr and w/some boiling most of it went in the soln, some was still left at the bottom - it was OK, as it turned.
To this boiling soln SWIM added about 5,4 g (~1/4 molar equivalent) of KMnO4, in, say, 6 portions. During and after each addition the mxtr was vigorously stirred w/a glass rod. The KMnO4 must be prior to that ground as fine as possible - it's not hard at all. The mxtr turned dark and opaque. Boiling was continued for some 10 min, then the flask put into the fridge (16 C) and 3 ml water added to it to induce crystallization. The walls of the flask were periodically furiously scratched (on the in-side
) w/a glass rod and after like 10 hours - voila! - a heavy crop of dark brown, as they should be, crystals precipitated. (If it doesn't, you can add 3 ml more water to it and w/some scratching it'll happen in an hour).
The mxtr was filtered, the mother liquor still very dark (put 3 ml water into it and let stand for a week - all of your prouct will crystallize and the liquor will turn colorless, this time the crystals will be not dark brown, but of rust/cinnamon powder color, just like the dry stuff), crystals sucked as dry as possible and dried for ~3 days in a dessicator over CaO (SWIM doesn't have one so he designed one from a saucepan, a couple of plates, plastic bag and a heavy hammer
) Dry Mn(AcO)3 is a very-very fine rust colored powder, it's unbelieveable how much it increases in volume comparing to the initial KMnO4! Still the weight is consistent - SWIM got about 22 g from the 1st crop, and the 2nd one is still in the flask, probably will be ~5-7 g - the original article states the yield of 85%, fits w/SWIM's result perfectly.
OK bees i gotta go now, tomorrow i'll post the details of SWIM's P2P fuckup and maybe someone will tell me what was the reason (frankly speaking, i think it was his
fucken carelessness and
dirty reagents)
Hope this one will draw some attention
Is it that my posts are too long that no one answers them?
Eagerly awaitng your ideas and opinions,
Antoncho
