On Oct 12, 11:47*am, "Buerste" wrote:
"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!-

What huge problem???
http://en.wikipedia.org/wiki/Hydrocracking