[joanne]

hi i need explanation on why the lone pair of electron on nitrogen is in sp2 orbital for pyrdine but p orbital for pyrrole

THANKSS!!


also are the below underlined portions true (which i quoted from others)?

"Nitrogen as replacement heteroatom in benzene:
To formally replace a C atom of benzene, nitrogen must fulfill the same orbital and electronic criteria as the carbon it is to replace, i.e. it must be sp2-hybridised and have the same number of electrons (the principle of isoelectronic replacement).

Oxygen as replacement heteroatom in benzene:
For oxygen to achieve the same orbital and electronic requirements as a carbon in benzene it has to lose an electron becoming O+.

Sulphur as replacement heteroatom in benzene:
For sulphur to achieve the same orbital and electronic requirements as carbon it also has to lose an electron becoming S+. " 

what about thiopene then? it is S and not S+

[Yggdrasil]

hi i need explanation on why the lone pair of electron on nitrogen is in sp2 orbital for pyrdine but p orbital for pyrrole

Think about aromaticity.  Think about what orbitals are present on each atom in the ring.  Does pyridine have a p-orbital?  Is something already in it?

also are the below underlined portions true (which i quoted from others)?

"Nitrogen as replacement heteroatom in benzene:
To formally replace a C atom of benzene, nitrogen must fulfill the same orbital and electronic criteria as the carbon it is to replace, i.e. it must be sp2-hybridised and have the same number of electrons (the principle of isoelectronic replacement).

Oxygen as replacement heteroatom in benzene:
For oxygen to achieve the same orbital and electronic requirements as a carbon in benzene it has to lose an electron becoming O+.

Sulphur as replacement heteroatom in benzene:
For sulphur to achieve the same orbital and electronic requirements as carbon it also has to lose an electron becoming S+. " 

what about thiopene then? it is S and not S+

That sounds about right.  In the case of thiophene, thiophene is a five-membered ring, not a six-membered ring like benzene.