Might tickle someones fancy...JohnWW - 4-2-2005 at 08:16
Cyclic O3 would be a very strained molecule. There is no N3 equivalent, and cyclopropane and its derivatives tend to be rather reactive with respect
to ring-opening. O3 is usually a bent molecule, with the central O being tetravalent and positively charged, and with the negative charge resonating
between being on either of he two outer Os.runlabrun - 4-2-2005 at 15:51
ahh but dont you see.... he is using laser beams.... that will make it work.....
I really have no idea, but it does sound impressive.... and if he does pull it off and get it to work, the applications would be very interesting.
I say, pretty cool.... provided it works.
-rlr
calculated energy
Quibbler - 15-7-2005 at 08:48
Well this thread nearly diappeared forever. My problem is that quantum mechanical calculations (I use GAMESS) make cyclic O3 much more stable than
bent. Of course QM does not care about all this valence bond shit - strain? what strain?So either the QM programs are wrong (there are some weasely
excuses out there why this is so) or there is a large energy barrier to form cyclic O3. Anyway good luck to the guy that got (presumably BIG) funds to
do this extremely speculative piece of work. Forget the lasers just blast some oxygen and try to separate out the 0.00001% cyclic O3 that may or may
not be formed12AX7 - 15-7-2005 at 13:10
Interesting.
Can you make polyperoxides? -O<sub>n</SUB>-, cyclic or linear? Why not?
Timchemoleo - 15-7-2005 at 13:35
For the reason that the normal peroxide bond is already quite unstable? How do you expect O-O-O to be stable as a result, except at -196 deg C or
soemthing?
Similarly, the N-N bond is more stable than the O-O bond, and this is topped once again by the C-C bond of course.
It's to do with the electro-negativity of the molecule; and presumably the denser electron shell that constrains and disfavours the bonding,
including the angles.
Quibbler- the strain is that the oxygen bonding is tetrahedral, i.e. 109 (?) deg. While in a triangular form (in case of cyclic O3), it is 60 deg.
Quite a difference eh?
That's obviously your energy barrier. Plus steric crowding and all that, already cyclopropane is quite constrained, and has a large energy
barrier to formation. Clearly this is much more a problem in cO3.
Personally I reckon these guys at DaRPA are wasting money.
They can't even use normal O3 in rockets, how do they expect to use cO3?
[Edited on 15-7-2005 by chemoleo]12AX7 - 15-7-2005 at 14:58
So electronegativity is as much a measure (of sorts) of bonding to other things as itself? But that doesn't really make sense since boranes and
silanes are less stable than carbanes (er.. alkanes) despite the lower electronegativity.
But yes N-N is more stable, they made poly-N at high pressures, and of course poly-C (of several forms) is made in the earth, and now the lab as well.
Timchemoleo - 15-7-2005 at 15:13
Uhmm. It doesn't make sense because you don't understand/know enough
It's electronegativity, steric and electronic crowding, bond angles, and type of orbitals etc. And of course whether an atom has a tendency to
gain or lose electrons, which is in part determined by the above. I am sure there are other additional factors I am not aware of.
You need to read a book to understand these things - I think there is a thread on the silicone man or something... where people argued (as usual) that
the silicone man should be possible... until someone pointed out, breathing SiO2 is hardly possible
So. Diboran. Not stable, because it cannot really achieve the old octett, while in carbon can, by sharing electrons. Even less for Be, or Mg, or Ca.
They are ionic, and tend to give away electrons, rather than accepting them (while Be and B are special cases anyhow). That's why metalloorganics
are very reactive.
Anyway. This is waaaaay off topic.
Really, read a book, on orbital theory, inorganic physical chemistry and such, it will explain this much better than I ever can, and probably much
more accurately, too.mykhal - 16-7-2005 at 03:11
Quote:
Originally posted by JohnWW
O3 is usually a bent molecule, with the central O being tetravalent and positively charged, and with the negative charge resonating between being on
either of he two outer Os.
In fact, oxygen cannot be teravalent. In each of two resonance structures, the middle oxygen is trivalent. And resonance is old concept, now we shuld
talk about conjugation, so we can say, that the middle oxygen has 1+ and each of the other oxygens have ½− charge.mykhal - 16-7-2005 at 03:24
Quote:
My problem is that quantum mechanical calculations (I use GAMESS) make cyclic O3 much more stable than bent. Of course QM does not care about all this
valence bond shit - strain? what strain?So either the QM programs are wrong (there are some weasely excuses out there why this is so) or there is a
large energy barrier to form cyclic O3.
What method and basis set did you use ? In J. Chem. Phys. 1977, 67, 2377 (Ab initio theoretical results on the stability of
cyclic ozone), people who probably knew what they were doing, report, that the cyclic state of ozone lays approx. about 28 kcal above
the linear state.Lambda - 17-7-2005 at 01:06
Quote:
Originally posted by Quibbler
Forget the lasers just blast some oxygen and try to separate out the 0.00001% cyclic O3 that may or may not be formed
The guy you are referring to, may be using a very powerfull UV LASER. Maybe cyclic O3 is short lived, which may allso be detected by LASER.unionised - 17-7-2005 at 01:51
Lasers aren't magic. Anyway, as has been pointed out, if the stuff is short lived (and I suspect it will be) then it's bugger-all use as a
rocket fuel. This looks like someone getting research money to play games (My laser's bigger than yours!) rather than to achieve any real
benefit.
Theoretical Chemists
Quibbler - 18-7-2005 at 04:30
The thing about theoretical chemists is they get good values when the answer is known. Cyclic O3 is (as far as I am aware) an unknown quantity. So the
current senario is whoa my program predicts that this molecule is stable yet nobody has made it. I know let's made some adjustments to the
calculation. Look at Can. J. Chem 51(1),139,(1973) there's probably some even predating this. So my problem is if the QM program has trouble with
O3 what of somthing more complex? Oh btw GAMESS can be downloaded for free and works on windows.
As for "Silicon Man" though Si is in the same group as C it can do many more things than form 4 bonds as it has access to d-orbitals, and
for you octet people just how does bent O3 make octets (oh I know dative bonds).
