(John Michael Williams) wrote in message . com...
(Don Klipstein) wrote in message ...
In , Bill Sloman wrote
in part:

I had to work through the equations many years ago for an experiment
intended to monitor the process in which one of the "Dewar benzenes"
converted itself to normal - Kekule's - benzene, which is an
enormously energetic process, involving about an order of magnitude
more energy per molecule than you get out of TNT and PETN. I really
didn't want to blast my experimental apparatus to smithereens.

When I went through the calculations with my supervisor, he pulled a
very long face - the motivation for the experiment had been some
unexpected flashes of light seen when a dumb organic chemist had
released small drops of liquid "Dewar benzene" into a hot cell, and my
calculations made it clear that the flashes of light were just thermal
radiation from a hot plasma, rather than fluorsecence from from an
electronically excited state of Kekule benezene, which is what my
supervisor had been hoping for ...

For the difference between Dewar benzene and Kekule benzene see

http://www.chemsoc.org/exemplarchem/...enzenering.htm

If this produces anything near 10x the energy per weight of TNT or PETN,
then a version with controlled reaction rate would make one heck of a
rocket propellant.

Not really. The crucial feature of chemical explosives is that they
produce their energy fast, which is to say by intra-molecular
rearrangement. Burning a hydrocarbon in oxygen produces a lot more
energy per unit mass of fuel and oxidiser than does letting off TNT or
PETN where the oxygen comes from the nitro groups attached to the
hydrocarbon core, whence the popularity of fuel-air bombs, but you
don't get the same brissance.

I thought the ultimate energy per mass was magnesium and oxygen (or was
it beryllium and oxygen?), just a few times as much energy per mass as TNT
and not good like usual rocket propellants for producing gas to use as
rocket exhaust.

It depends on the electrochemical gradient, I think.
Hydrogen burning in fluorine probably produces more combustion
energy than anything else, per unit mass.

Atomic hydrogen recombining into molecular hydrogen would be better
(as a rocket fuel) but has never been reduced to practice. What I
remember from what I read on the subject - many years ago - was that
hydrogen-fluorine was the best possible fuel-oxidiser combination.
Nasty exhaust fumes ...

I am surely skeptical of changing one isomer of a molecule to another
producing even comparable energy to, let alone more energy than
decomposition of a similar or somewhat greater mass molecule of high
explosive.

Check out the published literature - that is all that I was doing at
the time.
Chemical explosives are relatively wimpy as far as energy per unit
mass goes - the rate of energy release is the crucial feature.

I share this skepticism. Burning TNT probably would produce 10x more
free energy than detonating it.

Trinitrotoluene is C7H5N3O6 and would burn to 7 CO2 molecules, 2.5 H2O
molecules and 1.5 N2 molecules - for which you'd need 10.5 extra
oxygen atoms, over and above the six oxygen atoms available in the
original TNT molecule.

Being simple-minded about it, 16.5/6 is 2.75, not ten, and that
exaggerates the advantage, because burning carbon to carbon monoxide
release quite a lot more energy than burning carbon monoxide to carbon
dioxide, which is where you use up seven of your extra 10.5 oxygen
atoms.

The exact amounts of energy involved are all available in the open
literature - that is where I found them, some thirty years ago, and
I'm sure that they are still available now.

-------
Bill Sloman, Nijmegen