Re: hyperconjugation, resonance

see answers below

[EMAIL PROTECTED] wrote:

>what is hyperconjugation?
>
First, conjugation is generally described as the sharing of electrons 
among three or more p-orbitals.  Hyperconjugation is almost the same 
thing, but uses one or more sigma molecular orbitals from neighboring 
sigma bonds.  The neighboring sigma bonds must be in the correct 
orientation, however, meaning approximately parallel with the p-orbital 
that they are conjugated with.

>how it affects the stability of carbocation and carboanion?
>
One simple answer is that conjugation, of any kind, offers extra 
stability by allowing more resonance structures.  In the case of 
carbocation/carboanion, there is added benefit of diffusing the charge, 
which also increases the stability.

>is resonance true or imaginary?
>  
>
<stepping on soapbox>  The answer depends on what you mean by resonance. 
 Individual resonance structures are imaginary.  They are a convenient 
way of describing a phenomenon that is hard to put down on paper.  There 
is only one structure, even though that structure is constantly changing 
as the molecule undergoes vibration and rotation in various directions. 
 Any drawing that we try to make concerning a molecule is imaginary. 
 There are no lines connecting atoms together.  There is no fixed 
interatomic distance between two atoms of a molecule.  Even though you 
will be able to obtain interatomic distances from X-ray analysis, these 
are only averages, as each atom is constantly in motion.  Also keep in 
mind that the atomic theory is still just that:  a theory.  It is no 
more a proven fact than the big bang.  Both of these just happen to be 
the theories that best fit the data available at the moment.  A hundred 
years down the road, the students of the time may laugh at us for 
believing such rubbish, just as we laugh at those who believed in 
phlogiston 200-300 years ago, or polywater 30 only years ago.  Regarding 
cold fusion, they may look at us in the same light as we now look at the 
establishment at the time of Galileo.  Always try to remember that 
chemistry is a science, not a religion.  Take EVERYTHING with a grain of 
salt.
</soapbox>

Dick
-- 
Paul J. Franklin(moderator - sci.chem.organic.synthesis) 
http://organicworldwide.net/sci.chem.organic.synthesis
Georgia State University <[EMAIL PROTECTED]>
Atlanta, GA