Riniti
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Theoretical Molecules
First of all, I suppose, nice to meet you all. This is my first time here, after all. Anywho, I've always found theoretical molecules to be
intriguing. What would happen if they existed, could they exist, how could they apply in the modern-day world? This thread is for these. Post your own
theoretical molecules, and discuss the possibilities amongst each other.
I'll start with my most recent idea- the concept of an octagonal molecule, in the form of XeN8. It would consist of an atom of Xenon in the
middle, with eight atoms of Nitrogen around it. Each Nitrogen atom would be bonded once to the Xenon, and once to two of the other Nitrogen atoms, and
would also have one unbound electron pair.
What do you think? Could it exist? What molecular shape would it take? What would its properties be? What applications for it would there be?
I look forward to hearing your thoughts.
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blogfast25
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Conventional wisdom has it that Xe will only form fairly stable compounds with the most electronegative of elements like fluorine or oxygen and even
with these, the compounds remains powerful oxidisers. Nitrogen doesn't even come close in electronegativity. It's also a particularly sluggish reagent
due to that triple bond.
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Morkva
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http://www.sciencedirect.com/science/article/pii/S0022113900...
| Quote: | Evidence for the Synthesis of a "Stable" a-Bonded Xenon-Carbon Compound: Bis(trifluoromethy1)xenon
Sir:
A target of prime interest since the pioneering work of Bartlett in xenon chemistry' has been the synthesis of a compound in which carbon is sigma
bonded to xenon. Such a species is a definite possibility in view of the recent synthesis of FXeN(SO2F)2* and evidence from ion cyclotron resonance
experiments which estimate the strength of a xenon-carbon
bond to be in the range of 43 +/- 8 kcal/mol for Xe(CH3)+ The less stable species FXeCF3 has also been proposed as a reaction intermediate.
Previously in our laboratory we have developed a general synthesis for trifluoromethyl organometallic compounds employing reactions of plasma
generated radicals with metal halide
C2F6 - > 2CF3.
X = I, Br, CI
nCF3. + MX -> M(CF3), + 1/2X2
Considering the fact that xenon-fluorine bond strengths in XeF2 are on the order of 3 1 kcal/mol, i.e. weaker than many of the halogen-metal bonds
which have been broken in previous syntheses, synthesis of a xenon-carbon compound in this manner was thought to be a reasonable possibility. Crucial
factors for the success of such a synthesis are ( I ) that the electronic rearrangement lifetime of the radical FXe. be long with respect to the
collision frequency with an excess of trifluoromethyl radicals and (2) that, once formed in the free radical process, the molecular species Xe(CF3)z
be stable cnough to withstand collision and condensation.
By this synthetic method we were able to obtain a volatile, waxy, white solid which has a half-life of -30 min when contained in a Kel-F
container at room temperature. It has a much longer half-life (-2 weeks) at liquid nitrogen temperatures and decomposition is catalyzed by oxygen,
glass, and moisture. This new compound, believed to be Xe(CF3)2, sublimes under vacuum with a vapor pressure significantly greater than that of XeF2
and has very different physical properties. Thermal decomposition in the solid state while contained in a Kel-F tube gives xenon difluoride
and at least six (GLC evidence) fluorocarbon
products, presumably by a difluorocarbene elimination mechanism:
20 o c
Xe(CF3)2 - XeF2 + C,F,,
The XeF2 produced appears as a highly crystalline solid on the Kel-F tube in contrast to the original waxy solid and the fluorocarbon layer separates
over a 30-min period. Decomposition in the gas phase produces xenon and fluorocarbons including The synthetic procedure is identical with that
reported previously5 except that the entire plasma system is constructed of Teflon and other vacuum components are stainless steel and Kel-F.
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[Edited on 13-12-2014 by Morkva]
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Dan Vizine
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Morkva, This is the most fascinating noble gas compound I've ever heard of. It had never even crossed my mind that Xe--C sigma bonds could ever be
formed.
"All Your Children Are Poor Unfortunate Victims of Lies You Believe, a Plague Upon Your Ignorance that Keeps the Youth from the Truth They
Deserve"...F. Zappa
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dermolotov
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They do remain as highly reactive oxidisers, unfortunately. I belive these also have to be cooled with liquid helium when they do exist. That is true
with the molecules mentioned by blogfast25 in post no. 2.
I couldn't imagine what sort of stabilisers you would need for a Xe-N bond
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