Re: mech eng student with chem question


"wallace.k" <wallaceNOT.k@xxxxxxxxxxxxxxxxx> wrote in message
news:tO6dnR_O2M7F5t3ZRVn-qg@xxxxxxxxxxxxxx


The bonds in aromatics tend to be a little harder to break, because they
are resonating throughout the molecule and tend to protect themselves.

Typically, double bonds are a little easier to break than single bonds (I
think). We have a few problems with the double bonds in natural oils
reacting well before the rest of the molecule reacts. They are quite
happy to give up their high energy bond in favor of lower energy bonds.

As for why one bond would break rather than another, there can be several
reasons, most of which comes down to energy.

Michael

Can you explain what you mean by resonating? I know my mechanical
knowledge is not helping here, as in solid dynamics, if an object vibrates
at its resonant frequency, it tends to go into catastrophic failure-
basically can 'shake itself apart'. I assume this resonance is not the
same sort of thing, but what does it mean on an atomic or molecular level?

thanks,
Karinne


In a molecule, resonance means that electrons are being shared by several
atoms, each more or less in turn. In a benzene molecule, we sometimes think
of double bonds moving from one carbon pair to the next all the time. By
having many atoms share several electrons, it is possible to protect the
ring from breaking, as well as facilitate addition reactions. A good
chemical weenie could do a better job of explaining this than I can.

Michael


.

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