h a l f b a k e r yA few slices short of a loaf.
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
browse anonymously,
or get an account
and write.
register,
|
|
|
Even educated non-scientists know about fullerenes, the novel allotropes of elemental carbon resembling soccer balls or geodesic domes. C60, a spherical structure containing 60 carbon atoms, is the archetype. Each carbon atom in a classical fullerene is sp2 hybridized, meaning essentially that it is
bound to three other atoms arranged more-or-less in a plane with it. A carbon atom is said to be "saturated" if it has four bonds (sp3 hybridization), and any carbon with less than four--like those in fullerene structures--is said to be "unsaturated" because it could, at least in terms of classical valence bond theory, accept at least one more bond. These are the same "saturated" and "unsaturated" that give us the terms "saturated fat" and "unsaturated fat." The chemistry to take an unsaturated carbon to a saturated one is rudimentary and is practiced every day on vast industrial scales.
So I'm driving along the other day and it occurs to me that fullerenes are unsaturated--they're just carbon. Could we dump them in a reactor with hydrogen and a metal catalyst, just like we do with the vegetable oil that ends up in your oreo cookie filling, and produce the saturated hydrocarbon equivalents of fullerenes? Hydrofullerenes? So I went to the library and, per Hirsch and Brettreich's excellent book Fullerenes, found out that the short answer is "Yes, but not exhaustively." While partially-hydrogenated fullerenes like C60H36 can be produced and are relatively stable, exhaustive hydrogenation has not been achieved and is probably impossible, at least under practical conditions. This is believed to be a consequence of steric crowding on the exterior of the carbon shell; the more positively-charged protons you stick on to it, after a point, the less stable it gets.
The next-most intuitive question, at least for me, is "How about fluoridation?" The realization that flourine atoms can be treated analogously to hydrogen atoms in hydrocarbon chemistry gave us Teflon and the whole modern field of fluorocarbon chemistry. So if we can't make perhydrofullerenes, how about their perfluoro analogs? A sort of "Teflon sphere" idea? Turns out, again per Hirsch and Brettreich, that the answer is "No." Again, while partially-fluorinated fullerenes can be and have been produced, perfluorination turns out to be unfavorable for reasons which are analogous to those which disfavor perhydrogenation. The only difference is a sign change: While the surface of perhydrofullerene is too positively charged to be stable under practical conditions, the surface of perfluorofullerene is too negatively charged to be stable under practical conditions.
So my hare-brained idea is this: Try to fully saturate C60 using a "hetero-fluoro-hydro" strategy, so that the complimentary positive and negative partial charges of protons and fluorine atoms on the sphere's surface stabilize the structure. You could either hydrogenate and then fluoridate, or fluoridate and then hydrogenate. My intuition favors the latter, because while it's known that fluorine will displace hydrogen, the opposite reaction does not occur, to my knowledge.
I'm not an expert in the field by any means but I've done some rudimentary literature searches using phrases like "hydrofluorofullerene," "fluorohydrofullere," etc. and not found any precedent.
Chemists? Thoughts?
Fluorinated fullerenes : synthesis, structure, and properties
http://cat.inist.fr...cheN&cpsidt=4867896
[ldischler, Nov 27 2006]
Ionic properties of hydrogenated and fluorinated fullerenes
http://adsabs.harva...1994mrs..meet....4C
[ldischler, Nov 27 2006]
A google search
http://www.google.c...ated+fullerenes+%22
662 hits... [ldischler, Nov 27 2006]
Coated Diamond Coatings
Coated_20Diamond_20Coatings
[xaviergisz, Nov 27 2006]
Halfbakery: Poly-CO2
Poly-CO2
An annotation here mentions an "allotrope" of nitrogen, N4. This Idea mentions many others. [Vernon, Nov 29 2006]
[link]
|
| |
One of the key features as I recall of all elemental forms of carbon is that they are fully stabilized carbon structures, or put another way they are generally non reactive due to a highly stabilized atomic structure. The other point is that the atomic structure of fullerenes and nanotubes is their high electrical conductivity which is an artifact of their dispersed electric charge which would be destroyed with such a change. |
|
| |
Doping with impurities does not create different atomic structure but rather traps other atoms within the structure(Colored diamonds are still diamonds at an atomic level, but with other elements trapped in the lattice which change the optical properties. |
|
| |
I would wonder weather they would be amenable to this type of action. |
|
| |
Second what would be the benefit, Fullerenes are already fairly slippery and non reactive all on their own. What would you want this for? |
|
| |
Because it'd be nifty? [+] |
|
| |
[iamanangelchaser], you and Vernon would get along nicely (see link). |
|
| |
Two great talkers will not travel far together. (Spanish Proverb). |
|
| |
I'm just thinking - a lot of the useful properties of the fullerene stem from the fact that it's so regular; and when you, for example, fluoridate it, it will still be quite smooth (albeit somewhat less so), with all the protrusions being equally charged and mutually repelling. However, with a hydrogen/fluorine combination, it seems that the bonds for the surface atoms will be irregularly bent by mutual interaction, such that the properties of the result would likely be very sensitive to the bonding pattern, not just the empirical atom count. |
|
| |
As to benefit, who knows? My readings to date indicate that fully saturated fullerenes of any type have been produced only in trace quantities, if at all. It would be a significant achievement to produce saturated fullerene in significant yield. Then you study its properties and start to think applications. If nothing else, being the first to make lots of saturated C60 could be good for one's scientific career. |
|
| |
Also, jhomrighaus makes a good point that the fullerenes and fullerene type structures are highly stable. They are even more stable, in fact, than carbon in its adamantane geometry (i.e. diamond), because the sp2 hybridization of the carbon atoms in fullerenes allows for an enormous amount of resonance stabilization when the double bond electrons delocalize through the enormous pi-system. (Which is what makes them conductive.) This is something I glossed over earlier in discussing the energy costs of saturating fullerenes, when I only mentioned steric repulsion at the surface. If you saturate a fullerene, you're also breaking a very large resonance stabilization. This is why, per the material Vernon has provided, it appears to be feasible to exhaustively perfluoridate diamond surfaces--adamantane carbon is sp3. But it is not safe to assume that because diamond can be perfluoridated, so can fullerenes, again because diamond is not resonance stabilized and fullerenes are. |
|
| |
The hetero-fluoro-hydro strategy I propose might offset the steric costs of saturation with complimentary electrostatic interactions on the surface, but I don't think it'll help much with the resonance-breaking problem. However, because the studies I've seen suggest that it's really not too hard to at least partially saturate C60, my intuition is that the steric problem is much more significant than the resonance-breaking problem. After all, the first double bond should be the hardest to break, because it will have the most extended resonance and hence the most stabilization. And since they've already made it to C60H36 by conventional hydrogenation techniques, it follows that sterics are the limiting factor, not resonance. |
|
| |
Fluoridation of a fullerene will have an additional problem, besides mutual repulsion. The fluorine atoms are physically larger than the carbons. There may not be, literally, enough space surrounding a fullerne in which to physically put that many flourines. (Hydrogens are smaller than carbons, so they should physically fit fine --except for electric repulsion.) My intuition tells me that you might be able to do your combination fluoridation/hydrogenation, but it will tricky. If you do the fluoridation first, the fluorines may prevent the hyrdogens from getting access to the left-over bonding sites. If you do the hydrogenation first, then the fluoridation can be expected to steal many of the hydrogens from the carbons. |
|
| |
I might suggest "oxygenation". If an oxygen can latch onto two adjacent carbons, then for C-60 there would be only 30 surrounding oxygens, spaced farther apart than fluorines and having less electric repulsion (oxygen has lower electronegativity than fluorine) --and the carbons would be saturated. |
|
| |
As far as I can figure (with a bit of thinking and sketching), 30 oxygen atoms can't fit on a buckyball - the best I can get is 28, and that's not uniform anyway, so it probably wouldn't work either. It comes down to the 3 edges at each vertex, and the pentagonal faces. Odds and evens mess it all up.
On a similar note, has anyone tried making N60 - still three nice bonds to use, but with the extra electrons floating around, it may be even more conductive than C60. |
|
| |
Vernon, turns out your perepoxidation idea is workable. C.f. Chemical Physics Letters 384 (2004) 283-287. Tsukuda and co-workers demonstrate convincingly that they can produce C60On with n <= 30 by corona discharge ionization. Again, it hasn't been done in quantity, but Hirsch and Brettreich seem to think it could be. An impressive intuition on your part. neutrinos_shadow, check out the paper if you can; it includes a really cool figure showing C60O30. I would also note that traditional "wet" metal catalytic epoxidation has been tried many ways, and they can't seem to get more than 6 oxygen atoms installed. |
|
| |
[neutrinos_shadow], electrical conductivity depends on bonding-electrons that are not actually bonded. Nitrogen typically only has three, so N60 would use them all up. C60 and graphite and nanotubes are conductors because every carbon uses only 3 of its four bonding electrons, to make the substance. N60 may be possible, but I wouldn't expect it to be conductive. N60 might also be very-difficult-to-impossible, due to the bond-angles that nitrogen "prefers" relative to angles needed for that material. N4, a tetrahedral molecule, or N6, an octahedral molecule, or N8, a cubical molecule, are more likely possibilities. (Phosphorus, in the same column of the Periodic Table as Nitrogen, naturally forms P4 tetrahedral molecules.) |
|
| |
Nevertheless, your mention of nitrogen does bring to mind the possibility of saturating C60 with nitrogen instead of oxygen. That would be a C60N20 molecule, if each nitrogen could latch onto three adjacent carbons. |
|
| |
Wouldn't N4 be just about the most explosive thing ever? What with the very stable N2 gas as the logical breakdown product? |
|
| |
I think N8 would be more explosive than N4. And I think that Edward E. "Doc" Smith wrote a story back in the 1930s or so that mentioned using N20 as an explosive. I don't know if N20 is possible (bonding angles), just like I don't know about N60. But I do know that N20 would be a dodecahedral molecule. N12 may also be possible (an icosahedron). |
|
| |
--No, I take that back, about both N6 (octahedron) and N12 (icosahedron). The first shape requires 4 connections at each corner (nitrogen has 3 connectors), and the second shape requires 5 connections at each corner. However, tetrahedron, cube, and dodecahedron only need 3 connectors at each corner, so they continue to be possibilities for nitrogen molecules. |
|
| |
As a total aside: You explosives connoisseurs have probably already heard of octanitrocubane. If not, though, you should google it post haste. Wicked stuff. |
|
| |
C60 is incredibly expensive to manufacture, let alone fluorinating the bucky balls. even teflon is relatively expensive to manufacture. and what would be the purpose/use for this material, anyway? |
|
| |
[costellogroup], just be glad there's some indication that all the players on this page are at least aware of the existence of the paragraph break. |
|
| |
As for practicality, this is the Halfbakery. Two cubic centimeters is better than one gloomy sentiment. |
|
| |
As a drummer, I'd like to know, can you hit it with a stick? |
|
| |