"Buerste" wrote in message
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"DrollTroll" wrote in message
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"Buerste" wrote in message
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I seem to remember a machine that actually "cut" motor oil into shorter
HC chains to test motor oil longevity. Would it be possible to
mechanically crack HCs into fuel on a large scale? How about pressing
HCs through rollers so precise that they would actually crush molecules
to do the job? The trouble I see would be that people would start
disappearing into fuel tanks, chubby people would be the first to go.
You probably could, but, like fusion, the issue would likely be: can you
control the resulting products?
This is actually a very inneresting notion, and, perhaps, uh, cuts to the
core of chemical reactivity/bonding.
To mechanically cut organic molecules *within the molecule* (as opposed
to say, fracturing a crystal lattice, as in steel, or undoing much
simpler hydrogen bonds/protein interactions such as in cutting wood)
would actually involve a net chemical reaction, which may be difficult to
control after mechanical breaking.
Cutting something also raises the almost as dicey concept of what it
means to just touch, or even move something. Think London forces. 
But back to cutting:
If you were to actually "mechanically break" a hydrocarbon chain in half,
you would temporarily have two free-radical like carbons, highly
reactive. And the question would be, what would they then react with?
What you would want is a hydrogen atom replacing each half of the
previous C-C bond, but the now-unstable carbons might instead react with
the cutter itself, possibly something else, or likely just with each
other, simply recombining.
Reaction with the cutter itself would be very likely, because the
"cutting" is actually one set of molecular/atomic orbitals disrupting
another set of molecular orbitals. When orbitals become that intimate,
interaction is almost inevitable. Esp. when you visualize a "molecular
press/roller" situation.
This suggests that the "cutting" would have to occur on the surface of
some catalyst (think platinum, as what's in your car), and would involve
some very sophisticated solid-state chemistry.
The other way to mechanically cut a hydrocarbon chain would be to grab
(read: bond in some way) with the ends of the chain (like in a tug of
war), and just pull, until somewhere in the center breaks.
This then becomes its own conundrum, because then how would you
reversibly release the ends?
And, you would still have the reaction problem of an unstable middle.
The line between the mechanical and the chemical is always an inneresting
notion.
For example, in hydrocarbons, the transition from gas to liquids to
solids is a very nice mechanical continuum, from methane to asphalt, and
arises solely from the *length* of the hydrocarbon chain!
Methane is the way it is (a gas) because the chain is short -- just one
carbon; kerosene is about 8 carbons or so, forming a liquid; asphalt is
30-60 carbons, one chain literally knotted up with another (and maybe
even itself) like a a pile of strings, ie, a mess.
But, apparently a very useful mess.
Enzymes are what mother nature uses to "cut" molecules, and is akin to a
fixture on a BP, as opposed to a wielded ax:
Molecules are is held precisely (and reversibly) in place, as the
orbital surgery takes place, just as the fixture on a BP holds the
material, and the BP itself holds the fixture and the cutter.
Once the surgery is completed, the molecules are released -- like opening
a vise.
Pretty incredible, actually, yet so routine in living systems --
actually, the foundation.
In this scenario, you even have the literal concept of "tolerance", just
as you would, say, in a punch and die set.
An enzyme's effectiveness in catalyzing reactions (cutting/stitching) is
directly proportional to how well substrates "fit", and chemical
poisoning often proceeds by creating unworkable tolerances, especially in
metallo-based enzymes (which use copper, zinc, iron, magnesium, selenium,
etc).
Cadmium is one very elegant example of this poisoning, as it is orbitally
similar enough to zinc (iirc) to replace it in the enzyme system, but
dissimilar enough to disrupt the dimensions/tolerances of the enzyme that
depends on zinc to function in its molecular cutting/stitching.
Apropos of the above oh-so elegant transition from chemistry to
machining, most here would find the notion of "molecular motors" beyond
fascinating.
The biochem text by Voit and Voit shows pictures of some molecular motors
(eg, the rotating flagella of some bacteria), and your collective jaws
will hit the floor when you see nature's version of rotors, stators,
bearings, shafts, and the like.
It is *beyond uncanny* -- eerie, even -- and well worth a google search
to try and see these. Hard to imagine this not being on the web.
I doubt, however, if you will find a molecular IC engine, but who
knows.... Bomb beetles come close, tho...
Btw, not saying the raw mechanical cutting molecules can't be done, just
that there are bevies of details to what would ostensibly seem a trivial
process.
--
DT
Thanks for the wonderful chemistry lesson! I have this "Brain Candy"
notion that somebody will stumble on something stupid-simple that will
solve huge, complex problems...at least I hope!
Stupid simple: I just wish I had thought of registering wines.com... $10
mil, fast. Woulda solved a lot of huge problems.
Cupla extree thoughts:
The roller idea is inneresting, but likely fundamentally unfeasible, because
of the inherent "roughness" of orbital geometry in molecules.
iirc, if the nucleus of an atom were the sun, the electron orbitals would
resemble the planets -- or some such thing.
And it is, of course, the electrons/orbitals which are doing the
interacting.
Bottom line, the smooth carbon-backbone chain, or DNA for that matter, that
you see in pitchers, is far from smooth.
A "molecular roller" that is "flattening/tearing" other molecules would be
like two sheets of 24 grit sandpaper sandwiching strands of hair, trying to
slicing them.
If you made the roller out of a really small atom, say lithium, beryllium,
or boron, you might have a shot at flattening/tearing other molecules
"mechanically", but even that would proly be remote, and not controllable.
There are example of molecules snapping, however. Two examples I can think
of off-hand, involving ring strain.
But first, note that in carbon chains, the zero strain configuration for
*closed rings* is a hexagon, ie 6 carbons, of which cyclohexane (a liquid)
and benzene (also a liquid), are two classic examples, but in distinctly
different ways, having to do with hybridization.
Glucose is a classic example of a the cyclohexane type, which is actually a
"puckered" hexagonal ring. Benzene is a flat ring.
Pentagonal configurations are also pretty stable (fructose is a great
example), square is substantially strained, and triangles are very rare and
super strained.
1. The fragrance of the chrysanthemum flower has what's known as an "epoxide
ring", which is a very very unusual molecule, in that the ring is triangular
( a C-O-C, iirc), which means extremely high bond strain.
What is even more remarkable is that this compound is *natural*. It will,
on very little provocation, pop open to a linear open chain.
IOW, it "breaks".
Which may provide the fragrance, altho I'm not sure.
2. Penicillin acts via a square ring, C-C-C-S, iirc, and also substantially
strained. Its antibacterial action occurs when the ring pops open (breaks),
and the very reactive sulfur now attacks the bacterial membrane. Or so I
vaguely remember.
But anyway, these are the best examples I can remember of molecules just
"breaking". In these cases, the stress is internal, and the molecule
eventually gives way, but nevertheless it does set a kind of precedence for
the notion of "mechanical breaking".
But, proly not through rollers.
One poster pointed out that the rubbing of cylinders is a factor in altering
the structure of oil.
This is probably not the case, as explained above.
It is likely simply pressure and temperature effects (and time), both of
which are important factors in making reactions go or not. And, the metals
in the engine could act as catalysts, as well.
Unlikely that mechanical rubbing has anything to do with it, other than as a
source of very high pressure by which to make a reaction go.
Evidence for this would be that in used oil, the products are not cleaved
hydrocarbon chains (which are already pretty short to begin with), but
rather cyclic, heterocyclic and polycyclic aromatic rings -- ie, derivatives
of benzene, often with nitrogen.
Which happen to carcinogenic, or so they say.
Not all benzene derivatives are carcinogenic, and in fact many are common
moeities in biological systems. Benzoic acid, phenylalanine, many others.
Inyway, it is really intriguing how the nitty-gritty of atomic and molecular
orbitals, and all the quantum mechanical mumbo jumbo therein, can be
distilled into simple notions of mechanical "strain".
You can buy molecular modeling sets, which have all the standard bio-atoms
in their various hybridized geometries, and you can actually put together
"angularly accurate" models of molecules and literally "feel" the strain in
them, ergo their instability and "breakability".
Iow, as you put these models together, cyclohexane/glucose/benzene go
together very easily, while epoxides and penicillins have to be wrestled
with, to assemble them.
--
DT