CHEM210organic chemistry

In order to predict aromaticity, a molecule must have the following characteristics:
●Cyclic 
total n4n+ 2 electrons 04(0)+2=214(1)+2=624(2)+2=1034(3)+2=14
●Planar 
Continuous array of p orbitals 
●4n+2electrons 
In most situations, atoms participating in an aromatic n-system will be sp hybridized; sp hybridized atoms also have p-orbitals that can participate in aromatic rings. However, sp hybridized atoms do not have p-orbitals; therefore, a ring containing an sp' hybridized atom will not be aromatic since it will not possess a continuous array of p-orbitals. So a ring containing a tetra-substituted carbon or nitrogen atom cannot be aromatic since there will not be a continuous array of p-orbitals 
HH H3C. CH3 N
H 
aromatic 
sp' hybridized, no p-orbital sp2 hybridized, p-orbital not aromatic 
Atoms surrounded by 4 electronic groups (atoms and lone pairs) are usually sp' hybridized Atoms surrounded by 3 electronic groups (atoms and lone pairs) are usually sp2 hybridized 
SOMETIMES A LONE PAIR DOES NOT RESIDE IN A HYBRIDIZED ORBITAL BUT WOULD RATHER BE INA p-ORBITAL. An atom with 4 electronic groups was considered to be sp, -hybridized. However, if an atom has one or more lone pairs, it may be sp-hybridized in order to make the molecule aromatic (contribute to a planar array of 4n+ 2 n-electrons) or contribute to an extended conjugated system. In this case, one lone pair will be in a p-orbital.
R—NR
RR—NR
sp' hybridized nitrogen 
sp2 hybridized nitrogen 
- lone pair in sp3-orbital 
- cannot participate in aromatic ring 
lone pair in p-orbital 
- may participate in aromatic ring