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I think it was PsychoKittie's posts in this forum, and later Chem Guy's that elucidated this technique's possibilities.  Correct attributions will be aknowledged later.

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Chopper
Hive Bee
Posts: 72
Registered: Feb 2000
  posted 04-13-2000 03:45 AM           
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Dwarfer, you mentioned that you have experimented with microwave synth. I have had FREAKISH success with this using a 600W domestic microwave oven, and i tell ya, after you see the results of a successful microwave synthesis, you get your oil bath, bunsen burner, steamcone, etc...you go out onto the road, and throw them as far as you can, kicking and swearing as you make your way back inside.

Ive sucessfully done solventless reductive aminations using microwave in under 30min reaction time, with yields above 80%, but i am still optimising the reaction vessel itself. this is taking time.

I was wondering what sucess (or failure) you have had, as itd be good to hear from someone else who has tried such methods.

dwarfer
Hive Bee
Posts: 1416
Registered: Feb 99
  posted 04-13-2000 05:58 PM           
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In the large picture including my feet you will see a smaller white plastic gizmo which was "Gemini-I" my first microwave enhanced reaction vessel.

(See  KRZ machine thread...)

This next connection will refer you to the first page of a pictures group I started at visto com: the opening (and only) picture so far is Gemini III, the HORIZONTAL gemini (no comment ) which was my last one before launching into the microwave processing of l phenylalanine which i hope to make my life's project :< )

I had problems with Gemini III blowing off her (Its) end piece: but it will at least show you what I've been up to.

The Gemini series will be my next "novel" posting: with appropriate thanks to psychokitty for the turn-on.

I also was going to discuss ultra sound application to these constructs but frankly the results were not as good so I'll junk that dissertation........

Anyway i think this is the correct URL. I'll try it myself. by the way, that group is open to anyone who wishes to post pictures of common interest and intention.

which of course is cold fusion..... http://www41.visto.com/club@.html?uid=862628&club=/visto/groups/gp-amppics1.hivedwarfer 

 
Chopper
Hive Bee
Posts: 72
Registered: Feb 2000
  posted 04-14-2000 04:22 AM           
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I must say, i have considered the vessel idea and was planning on persuing it after finding the limitations of a microwave reflux setup. 2 ideas will be followed :
1) A chilled hexane filled liebig condenser (should be fine since rxn times are very short)
2) Liq Nitrogen vapour liebig condenser. (probably the better idea)
 
Chopper
Hive Bee
Posts: 72
Registered: Feb 2000
  posted 04-14-2000 04:31 AM           
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Results so far, all without any type of condenser, have been brilliant considering the amount of loss due to evaporation (despite many ideas to minimise this). Side products are generally nil.
 
dwarfer
Hive Bee
Posts: 1416
Registered: Feb 99
  posted 04-14-2000 11:17 AM           
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Why don't you start a thread on your microwave set up and details and I'll join in: my reactions have been essentially one pot short-time experiences: although I did come up with a "sub-containment " of the H2 reaction aluminum powder in a nifty piece of permeable plastic hose.

Chopper
Hive Bee
Posts: 72
Registered: Feb 2000
  posted 04-15-2000 03:02 AM           
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I used to have a microwave thread before everything got deleted. I started mentioning methods out of papers and asked if anyone had bothered trying them and the response was not real encouraging. So..ive started hacking through the published methods one by one (and YES!, a beaker of water in the microwave does sufficiently lower the power available to the reaction..or so the results suggest so far)and as soon as i come up with a satisfactory setup that is fuckup proof, and a useful and kick arse reaction sequence worthy of posting, ill start a thread.

Now..dont think im a piker, the reasons for hesitation in commentry on progress are that so far ive :-

- filled a lab with formic acid vapour (the already inefficient fumehood wasnt deep enough to fit the mic. in properly)

- melted the inside protective coating off half the microwave cavity

- almost blew the whole thing apart (decided to try the use of a solvent...for fuck sake, take the light OUT before trying that shit)
- and THEN bothered to test the microwave for radiation leakage, should have done it earlier..im glad i never stood in front of the thing while it was going. The formic acid vapour did some damage to the seals.

So unless i can get this reflux setup figured out, ill go with your (much more appropriate) enclosed reaction vessel.
(im trying to use what i have for now)

I cant really post any of my successful, yet potentially damaging, techniques as yet. Itd waste everyones time, money, and life expectancy.

dwarfer
Hive Bee
Posts: 1416
Registered: Feb 99
  posted 04-15-2000 04:11 PM           
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Yeah,Iknow what you mean. I was VERY concerned about release of H2 n th microwave cavity and sparking: I'd thought about a vent through the side wall: but discovered that it did not blow without a spark: an accident that had no explosive consequences gave rise to that observation.

Not the ideal test method, although as you may have seen from the Visto picture, the unit was outside and I never got within 35 feet when the AC power was on.

Note that you CAN use a sealed container witha pressure guage on it and read the pressure froma distance with binoculars: THE THREADED UNITS CAN BE USED SAFELY MORE THAN ONCE ONLY AT A PRESSURE NOT TO EXCEED 35 PSI!!!!!!!!

OTHERWISE THE THE threads WILL deform and allow the cap to blow off unexpectedly.

May I say that I was kept from a spray of hot acid only by the fortunate circumstance that the end cap "cocked" and wedged on it's way off the end at approx 55 PSI H2 once: the gap that occurred thereby was again fortunately on the UPPER side of the unit and hot GAS escaped: on the bottom it woulda been hot acid......

So as you said this maybe not the proper stage of evoulton for the complete discourse of the techniques we are discussing : but on the other hand it might be appropriate to at least post the cautionary warnings for others.
Hell, here I go posting the Gemini stuff in the KRZ thread......

OK I'll start the thread with this stuff.

dwrfr

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Pressure guages with plastic externals (except for the threaded part) are available for about $10.

If you use the PLASTIC GLUE SOLVENT WELDED
FULLY SEALED (except the hole in top) unit you can SAFELY run the unit (at least 10 times+) up to 60 PSI: use a set up that has a popett valve release at 70 PSI: watch the guage and shut off the power when the pressure gets to 60 PSI.

The reacting aluminum powder and acid will endogeneously elute H@ which will take it up to the pressure release point of the popettt valve: I put a heavey duty baloon over the popett valve just so that if it "pre blows" for some reason teh H2 will be contained.

You will wind up with a nice balloon of H2 to give to the kiddees  

two more "I learned from experience" suggestions:

1.  Use a steel pipe nipple in the top of the unit leading out of the cap: and GLUE IT IN>

      a.  The distortion of the sealed plastic container will otherwise spit it out when presurized.

      b.  The threads will be subject to a considerble amount of usage since this is the addition port.

2.  Look for a male adapter to comprise the end piece at the top which has a CONSTANTLY TAPERED SMOOTH inside: most of them have WEBBING reinfocement which become "pockets" to hold the material as you try to remove it after completion.

I'll try to make a picture which isolates the Gemini I bottle, although blowing up such a small area will undoubtedly degrade detail considerably.

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Considertion should be given to replicating the  unit in aluminum pipe (or electrical conduit)

The round sections of the proposed unit would not generate EMF point sources which would stimulate arcing. Obviously the unit must stay away from interior cavity walls.

  dwrfr

Oh yeah: ONE OTHER THING:

The branch of the pipe section leading to the popett valve blow off must be packed not loosely and not really tightly with fiberglass or equivalent to both:
      1.  keep the pressure from ENTIRELY venting when it release (otherwise the reseating time is such that you will lose most of the pressure)

      2.  keep the foamy instantly boiling liquid from ejecting aluminum powder into the valve seat thus keeping it from reseating at all.

This is a small picture (I think).  Blowing it up does not do much:

Note that this is a totally depreciated unit : the # 1: I had solvent welded in a plastic pipe nipple: it finally gave up the ghost and blew out the side thus rendering the whole unit shot.

Oh well: I think the unit cost about $4.59 or something.

(The popett valve is $11: the pressure guage about the same: they are more or less infinitely reusable. )