determining aromaticity

[skylark]

---

Members don't see this ad.

to determine aromaticity...

with the 4n+2 equation, does the number of electrons include lone pairs in the same plane? how do you tell if its in the same plane?

and i do not understand the sp2 deal...because isnt the Nitrogen in Pyrrole an sp3? so why is that aromatic (according to Kaplan book)?

also, what makes a molecule anti-aromatic?

 

[trevnichols22]

It may or may not include the lone pairs of electrons. It depends on if the structure requires extra electrons to satisfy Huckle's rule (4N + 2 ).
If the electrons are used to satisfy the rule, they are NOT basic. If they are not needed the carbon is considered basic and may be reactive.

Basically with the sp2 sp3 deal, it cannot be sp3 and be aromatic, however, if the sp3 carbon includes a lone pair of electrons, the pair may be able to participate in the aromaticity and the overlapping of p orbitals. So, look for lone pairs. This is why pyrrole anion is aromatic. Pyrolle has 2 double bonds. 4N, but with the lone pair from the anion it is given 4N + 2 as the lone pair makes the sp2 and participates

Anti aromatic structres are those that contain the 4N number. Keep in mind thought that if the compound contains more that 8 carbons, because of the ability to occupy a non linear bending, the structure will be non aromatic.

Breakdown:

4N + 2 - Aromatic ( If more than 8 carbons must be linear)

4N - Antiaromatic with less than 8 carbons

More than 8 carbons will be non aromatic ONLY if non linear confirmation is existant.

Hope this clears it up at least a little..

You may see questions asking if a particular carbon