drone 342
Member posted 10-23-98 10:45 AM
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We currently use MH as well; but the mercury vapor lamps are readily available. Say, do you think you might be able to find a comparative spectral-output-diagram-thingie for the various types of bulbs? I've just gotten done with about four days of mad library strip-mining, and if I have to look up another thing today, I swear I will go nuts.
Speaking of which, I need to make a correction or two. m-DCB is not as good a catalyst as p-DCB, and the energy needed to excite the electrons in a cyano group is 10.14 eV -- which if I remeber correctly is pretty high (meaning a rather short wavelength.) This number can be readily converted into the wavelength of light required somehow, but I can remember exactly the formula. I want to say DeBroglie, but I could be wrong. Its been a while since I studied quantum mechanics, so if you could be so kind, Lr, I'm sure you've studied it as well -- you just have that aura about you.
The way I forsee separation is quite simple -- acid-base extraction. DCB and TPB are both very hydrophobic, and MDMA is quite hydrophilic in the right circumstances. Simply strip off the acetonitrile in vacuo, then extract the residue with DCM, and extract the DCM solution with a few washings of diluted HCl. From there, the DCB and TPB can be purified by fractional distillation under reduced pressure, and the MDMA by means of acid-base extraction and subsequent distillation. I've never used the term before, but I think its safe enough to use in this case: badda-bing, badda boom.
Sure, TPB has a high bp, but its not too unmanagably high at, say, 30 torr. You're absolutely right in saying its a stable compound. If you want, I can send you a Beistein review of all the basic chemical properties of all the components avaiable. Actually, if you visit my web page, I'm workingon an informational page about this reaction.
Let me know if you have any more good thoughts on this stuff, and how I might be able to help out. I think this is one of the most exciting discoveries by any Hive bee yet (if I do say so myself), and I think that I'd be great if its developement was an international effort.
-drone #342
drone 342
Member posted 10-23-98 10:49 AM
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< A HREF = "
http://www.geocities.com/CapeCanaveral/Hall/1399/p-DCB.html
" > This is a break-down of some useful data on p-DCB.< /A > If the link I tried to insert didn't work, the url is:
http://www.geocities.com/CapeCanaveral/Hall/1399/p-DCB.html
Enjoy,
-drone #342
drone 342
Member posted 10-23-98 02:11 PM
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I did the calculations, and I came up with a wavelength of around 123 nm from that 10.14eV, which puts it squarely into the far end of the UV spectrum (if that's not an oxymoron.) Here's how I came up with it:
If E = 10.14 eV,
and
1 eV = 1.6022 E(-19) J
h = 6.62608 E(-34) J s
c = 2.99792 E( m/s
E = h v (that should be a "nu", but I think you get the idea)
c = l v (that should read "lambda nu", but again, y'know what I mean; the speed of light equals the frequency times the wavelength)
v = E / h
l = c / v
implies:
l = c h / E
...Which I got to be 123 nm, which is right in the ballpark for a quantum transition of bonding electrons (what's happeining in our little reaction.)
Anywho, gettin' back to the matter at hand, aside from being really confusing, this really doesn't mean a whole lot (though I'm sure everybody figured that out for themselves.) Other frequencies should work, including frequencies a little lower and a little higher than 123 nm (this due to the Doppler effect, etc.), not to mention frequencies that might activate it to other equally useful excited states.
What this *does* tell us is a confirmation of what I said before. For maximum results, we want a light source with a spectrum on the high-end of energy -- more blue than red. Acordinf to waht you said, mercury vapor lamps may be more preferable to sodium, but what of other light sources? And what of the whole heat vs. intensity of useable photons deal? I'll leave the rest up to you.
-drone #342
icculus
Junior Member posted 10-23-98 03:47 PM
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Alright! For the past couple of months I have been researching methods for direct amination of alkenes. I found a bunch of promising routes. The one that seems most promising is... photoamination (in my humble opinion)!
Most first exposure to the process came in the form of US patents #4483757 and 4459191. They used actinic light(UV) and a photococatalyst, an amine and an alkene. Their yields were only 20% and I kind of last faith in the possibility of photoamination of isosafrole. But in steps the Japenese researchers and their amazing advances in photoamination.
Now regarding the source of light...Drone you calcaulated around 128nm. I don't think this is right, it wouldn't make it through the glass. The patent the discuss the ideal types of lamps and glass to conduct the reactions in. It seems that conventional quartz glass(Pyrex) has a cut off around 180nm. Silica glass lets +160nm through.
I wonder what the absorbing properties of plastic are? I think that the absorb short-wave length radiation very well.
Of course the wavelength that is required to excite the catalysts we are talking about is different. It seems that is a higher wavelength since mercury lamps are used very effectively.
Anyway, deuterium lamps, low pressure mercury argon lamps, and high energy xenon flash lamps emit in the range of 160-200nm. High pressure mercury lamps produce emissions in the higher spectrum, 200 to 1400nm.
I feel that this reaction has a huge potential to scale up. One would have to have a lot more catalyst, longer stirring times (who cares!) and possibily a stronger output (more watts).
Oh,by the way, there have been aminations of methylene dioxy derivatives. See JOC vol 57, no 5, 1992, p. 1351. The yields for these compunds sucked (20%). But, the improvements in Tet, vol 50, no 31 pp.9275 using better catalysts,to similar compounds were up to 65-91% I would expect our friend to be around 65%. What do you think Drone?
Now where can I get that m-DCB and some yummy TPB?
Icculus
Labrat
Member posted 10-24-98 08:48 AM
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You want a spectral energy distribution of the lamps? I could only find one for the sodium lamp. It's in "Marihuana binnen" by Jorge Cervantes (Dutch version, how do you like that for a ref?!). I can send it to ya if you like.
The separation of m-DCB and TPB you're giving looks good and is certainly workable. You're composing a whole web-page on this subject? I'll go check it out as soon as it's ready!
The calculation you did was correct, but I agree with Icculus that normal glass will absorb all of the light in the frequency you gave. Maybe we need the ionisation potential
of yet another transition. I reread the TET article and found the authors found 300 nm important, since they did measuremeants in at this wavelength. This seems more logical to me, since the high-pressure mercury lamp will emit in this range. Lr/
drone 342
Member posted 10-24-98 11:08 AM
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...And that's the confusing part! Obviusly, there's something missing here.
The amount of energy required for electron dissociation from DCB (photoionization) has been measured at 10.14 eV by several different ref's. Doing all the caluculations as shown, you get 123 nm, which I agree is a very high-energy wave, and if borosilicate (Pyrex(tm)) glass (which incidentally is a different animal than quartz), will absorb that frequency, then how is is that this reaction takes place with pyrex-filtered light? What's going on, and can anyone explain why 300nm works?
300 nm is a number I could come to believe; its still pairly short, but why would it work? How does this work? According to the Japanese research aforementioned, the mechanism for this clearly involves photoionization, but 300 nm, in theory, *shouldn't* do it.
Icculus, many thanks for the new ref's and the added background. What are the conditions used in those ref's you described? What catalysts have worked/failed for this?
Obviosly, you've done some homework in this subject. Have you any comparative literature with hard data on the spectral energy distribution of various possibly useful lamps?
DCB is used extensively, I am told, in semiconductors and other electronics. The stuf is cheap and readily available -- Acros sells the stuff for around 77 USD/kg. TPB is a little harder to come by; the stuff is rather carcinogenic, though still it ain't too pricey. Many other (cheaper) sources exist for both, but that the only one to come to mind right now.
-drone #342
drone 342
Member posted 10-26-98 05:44 PM
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Icculus,
I looked up those ref's, but one of them was one of the original articles I cited.
The other one was more interesting though. In JOC vol 57, no 5, 1992, p. 1351, they do indeed describe the use of a methyledioxy-containing material, and they do get bad yeilds, but there are some discrepancies here. First, they use the same catalyst here as they did in the Tetrahedron article, so that isn't what accounts for the low yield. Secondly, they use stilbenes instead of methylstyrenes, getting lower yields consistantly, with a couple exceptions. The thing that seems to be a big factor in that reaction is the solvent ratios; they got the best yeilds with a 7:2:1 ratio of acetonitrile, benzene, and water ( actually, a mixture of 9:0:1 seemed to work well too.)
Anyways, what we really need some hard data on spectral output of incandescent lights.
-drone #342
icculus
Junior Member posted 10-30-98 02:22 PM
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Photoamination of Isosafrole:
Mechanism of reaction : The photoamination of isosafrole is initiated by electron transfer from the excited singlet state of isosafrole to DCB. The Isosafrole (I) is excited by the light much more than the DCB; the molar excitation coefficient at 300 nm for the styrene derivative is 7x10^3 versus 43 for p-DCB. So, this forms cation radicals of I and anion radicals of DCB. Addition of RNH2 to I gives the aminated radical after deprotonation. The one electron reduction of the I aminated radical with the DCB anion radical followed by protonation gives the aminated products.
The wavelength calculated for exciting DCB was right, but we aren't trying to excite the DCB. Photocatalysis is so effective because molecules are excited at different wavelengths. Using light filters (like Pyrex, which lets 90% of 360nm, 50% of 300nm and 20% of 290 nm light through) allows one to selectively excite certain molecules.
Light Source:
In the original articles (see above) a high pressure mercury lamp is used because it has a high discharge around 300nm through about 450 nm. By using Pyrex and acetonitrile as the solvent ( which transmits 100% of 313nm and 10% 190nm) the light that reaches the solution is high in 300nm radiation, which effectively excites our molecule.
Metal Halide lights are the same as Mercury lamps except that they also conatin a halide (of course!), This broadens the specturm of light to make it more like sunlight. Therefore a Metal Halide would work just as well, if not better. Most hardware stores sell mercury lamps and metal halides.
Methodology for Photoamination:
Degassing of Solvent:
It is very important that the solvent is free of impurities such as air and peroxides. This is easily accomplished by bubbling an inert gas, such as nitrogen, argon or helium through the solvent. Nitrogen is readily available but still contains some water and oxygen. Helium is readily available and is the best choice.
Aparatus for Reaction.
In classical organic photchemistry, an immersion well is used, where the reaction solution surrounds the lamp or an external radiation method where the reaction solution is surrounded by a battery of lamps.
To see an imersion well click here:
http://www.promote-it.co.uk/photo/chemical.htm
An immersion well would be ideal, they can range in size from 100ml to a few litres. It may be possible to obtain one but the exteranl-irradiation method is more applicable:
The solution is in a Pyrex flask and placed in the center of a battery of lamps. Typically a quartz flask is used, which allows 200 nm and above through. For our purposes, the flask itself acts as the filter. Fans can be used to control the temperature. One lamp with mirrors surrounding the flask may be sufficient for
our purposes.
Amine source:
Ammonia or methylamie can be bubbled into the acetonitrile. Or methylamine gas can be produced and liquified by venting into a flask in a ice/salt bath. This can then be directly added to the solution.
Procedure:
Into a Pyrex vessel is introduced an MeCN (70 ml) solution containing isosafrole (3.5 mmol) , m-DCB(3.5 mmol), TPB(0.75 mol), bubbled with helium gas, and then an amine (17.5 mmol) was added to the solution. Solution is irradiated for an appropriate time (18 hr) with a high-pressure mercury lamp or metal halide (300W or more). Solvent is evaporated and products are seperated by column chromatography or most likely extracted with HCL solution, washed with DCM, basified and extracted with DCM.
This reaction can be scaled up, the key is getting sufficient irradiation of the solution.
I hope this information is helpful in answering some questions reagarding this amazing reaction.
Information on the spectrum of lights and techniques of photocatalysis can be found in the book Best Synthetic Methods: Photochemical Synthesis by I. Ninomiya and T.Naito.,1989
Other good reading:
W.M. Horspool , Synthetic Organic Photochemistry, 1984
A.Schonberg, Preparative Oranic Photochemistry, 1968
drone 342
Member posted 11-03-98 09:42 AM
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Icculus,
Many thanks for the in-depth information on this reaction. However, I do still have a couple questions. What is meant by "pyrex and actenitrile transmits 100% at 313 nm, and 10% at 190nm"? The 100% I can understand, but how does this 10% number fit in with Beer's law, where transmission is dictated by A=Ebc?
Another question is regarding procedure. If one looks at the molar concentration, one has to think that this must be boostable, but to what degree? If it could be raised by an order of magnitude, this would be an extremely amazing procedure.
This is obviously a minor question, since you've really done a swell job of collecting a ungodly amount of good, hard data. This really looks like a winner. Great job, Icculus!
-drone #342
icculus
Junior Member posted 11-03-98 05:21 PM
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Thanks. I'm trying my hardest to perfect this reaction. Maybe I should call those original researchers; we could all do lunch and talk about the miracles of photoinduced electron transfer.
When light hits an object/surface/liquid/gas it can do a number of things. Scattered, defracted, absroberd, transmitted,etc. So light can be transmitted at varying degrees, like most things, nothing is always a hundred percent. So when 290nm hits pyrex only 20% of it makes it through. The rest is abosrbed or reflected.
Early you said that p-DCB was a better catalyst than m-DCB. Why? I don't think so, from what I've read.
Scaling. That is the biggest question right now. The problem with using external irradiation, like we are proposing, is that light isn't transmitted as well as using an immersion-well. I thnik that using a large flask, with a large surface area and possibly multiple lights, it can easliy be scaled up to industrial quantities.
I found a reference on scaling photocatalized reactions, but we don't have the book at my library. It is in Ullmann's Encylopedia of Industrial Chemistry. There is a section on photoreactions, reactos and such. Should be very helpful. Maybe you can find it. I think we would all appreciate it in the long run!
Oh yeah, I also found an old article: J. Assoc. Off. Anal. Chem, vol.61, no. 4, 1978 , p.951. They were analyzing a horrible, naughty illegal manufacturing lab. Anyway, the max UV absorbance of isosafrole is 260-304nm. What a coincidence! And we have a readily avalible source of light with great output in that range. In fact I think I'll go buy one at the Depot, right now>
Icculus
Osmium
Member posted 11-04-98 05:24 AM
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Give me that Ullmann ref. I think I can get it.
icculus
Junior Member posted 11-04-98 09:04 AM
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Go to the Wiley-Vch web site:www.wiley-vch.de/contents/ullmann/ and look under photochemistry and reactor types.
It has the entire table of contents but that's it.
The full title is Ullmann's Encylopedia of Industrial Chemistry, 6th Ed., 1998, Electronic Release. The whole thing is on CDRom now. My library doesn't have a copy. Earlier paper editions may have the info, but I don't know.
drone 342
Member posted 11-04-98 03:31 PM
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I'm sitting here with a copy of Ullmann's Encyclopedia of Industrial Chemistry, volume A 19 in front of me. Nice. Very nice. The photochemistry section is 24 pages of rockem'-sockem' chemistry excitement, complete with schematics of industrial-scale reactors. Have no fear, oh less-priveledged chemists; drone #342 will scan a copy of everything onto his website soon.
-drone #342