unionised
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unusual/ unexpected reactions
OK, I realise thats not a very helpful title.
I got some paladium wire the other day and thought it would be intersting to see if a reaction that I heard about ages ago really worked.
If you take a centimetre or so of about 0.5 mm diameter Pd wire and wrap it with Al foil then heat it until the Al melts the Pd reacts with the Al and
the mixture sudenly gets very hot. I can't measure temperatures in that range but this stuff lit up almost as brightly as burning magnesium.
Pd isn't very reactive so most people wouldn't expect this reaction to happen at all.
I just wondered what were the least expected reaction that you have met .
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The_Davster
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Accidently made nitrogen trichloride and it detonated multiple times in solution.
http://www.sciencemadness.org/talk/viewthread.php?tid=2044
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unionised
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Thanks, but tht's not quite what I had in mind. You expect NCl3 to be unstable (even if you don't plan to make it) but who expects 2 metals
to react violently?
The Pd/Al is just a weird reaction.
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Nick F
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Did you collect the residue from the reaction? CsAu is a salt-like compound, I wonder if anything similar may have formed? Or perhaps the Pd catalysed
the fission of the oxygen molecules, allowing them to react with the Al more readily?
Whatever happened, that is very interesting!
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unionised
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I did collect the residue and it's currently disolving in NaOH. I'm not sure whether I will get the Pd back in a state that I can re do the
experiment. Even if I don't, I should have the Pd equivalent of Raney Ni.
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chemoleo
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Hasn't this reaction been discussed before?
See http://www.sciencemadness.org/talk/viewthread.php?tid=2202
It's an intermetallic reaction that occurs with many metals.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Axt
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I found the reaction involved on rec.pyrotechnics, and it seems to be available in a commercial product known as "pyrofuse" Pt/Al, Pd/Al,
Ni/Al with varying properties. searching rec.pyro for "pyrofuse" will yield quite a few results. I suggest you get the intermetallic
reaction tables from FTP2 its very interesting.
| Quote: | Originally posted by Norman L. Reitzel on rec.pyrotechnics
Well, there are more sources of energy than transferring electrons. The
particular reaction of which you are speaking forms an intermetallic
compound (Nickel Aluminide) where the nickel and aluminum are covalently
bonded. However, the crystal lattice for nickel aluminide is quite a bit
more compact and regular than for either aluminum or nickel alone. The
energy you are seeing is called the lattice energy, and comes from the
increased bonding that occurs when the dense nickel-aluminum crystals are
formed.
Incidentally, the reason that aluminum is so great in pyrotechnics is
because aluminum oxide has -extremely- high lattice energy. Think about
the product, aluminum oxide, and you will find that it is -really- hard,
and used for abrasives. This hardness (and density) come from the same
place, the density and bonding energy of the aluminum-oxygen lattice.
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Raney Ni (NiAl) is pyrophoric, so that may explain PdAl exploding into sparks if allowed to fall onto concrete.
[Edited on 5-7-2004 by Axt]
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chemoleo
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Well, one that happened was this:
Mix NaClO3, Sugar, Fe powder, Sulphur, and KMnO4 with polystyrene dissolved in trichloroethylene.. and make a paste of it. Let it evaporate, and
choose whatever shape you want, for you make a solid fast burning.
Store in a container... and oh joy, after a few days (hours) you will notice the lovely smell of chlorine.
Now take this away from the house/burnable things, and put this container into the sun (more heat, faster reaction). After 1-2 hours, you have
autoignition, and the whole thing bursts & burns in a big burst of flame.
What was unexpected about this? Well my dad was gardening nearby, and he nearly got his ass burned... so I got a rather unexpected reaction... from
him  (one of my youthly tales that is  )
Later I found out it is becuase KMnO4 and trichloroethylene are incompatible. Do the same thing without it, and without the Fe powder, and there
won't be a problem.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Marvin
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chemleo, chlorates and sulphur are also incompatable. As are sulphur and permanganates.
I can think of a lot of weird reactions. Ozone from aq electrolysis, acetylene from aq electrolysis. Ketones and aldehydes by pyrolysis of salts.
Furfural from bran. Formation of the ammonia complex of nitrogen triiodide instead of the expected ammonium iodate...
Most of these things can be easily explained after you know they happen, but very hard to predict before hand.
I think a favorate would have to be the acetone + sulphuric acid -> trimethyl benzene (25% yeild or up to 50% with HCl in sealed tubes). Stage
magic for chem students, "ta da, aromatic ring".
[Edited on 6-7-2004 by Marvin]
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PHILOU Zrealone
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Henry's condensation of ceton on active H...here it is also crotonisation in acidic media....yield can go as high as 60% for mesytilene (1,3,5
trimethylbenzen from aceton and H2SO4 and heat).
Chemoleo,
"Mix NaClO3, Sugar, Fe powder, Sulphur, and KMnO4 with polystyrene dissolved in trichloroethylene.."
-KMnO4/suggar moderately compatible
-TCE/Fe moderately compatible
-Fe/S idem
-Fe/KMnO4 idem
-KMnO4/S idem
-NaClO3/S inadvisable
...many of the above are moisture sensitive or heat sensitive Fe/S reaction starts with moisture arround 100°C this gives more heat.
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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Marvin
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Henry condensation is actually specific to nitro compounds on ketones but I see what you are saying, aldol. Its probably a multistep aldol
reaction/dehydration to phorone and then a cyclisation.
Do you have the procidure for the 60% yeild, or a reference?
The org synthesis method produces about 18% yeild at the high end (1940's probably) up from 13-15% a difference they explain with the quality of
the acetone.
Urbanski gives it as 25% (mid 1950's I think), but goes on to say that with dry HCl under pressure the yeild is improved and with sealed tubes up
to 50% is possible.
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