[xshadow]

I don't undertand if bot the ring of saccharin are aromatic




Obviously the benzene ring is aromatic.
Than I have a substitued ""thiazole" ring

All atoms of the 5-membered ring can be sp2 with a p orbital perpendicular to the molecule plane
But what about the Huckel rule

Benzene has 3 electron pair
The ""thiazole"" ring in saccharin how many  pi-electron pairs  does it have?
N has a lone pair
Sulfur don't think has a lone pair  avaiable because it  has laready 6 bonds. All its pi-electrons (the two S=O  double bonds) are outside of the ring. I think they don't count.

SO I should have :
 3 pi-electron pair from benzene ring (3 C=C)
 1 pi-electron pair from thiazole ring ( lone pair on N)
But with 4 pairs...isn't aromatic

Thanks

[chenbeier]

No you have to calculate every ring seprately.
Benzen is aromatic. So the molecule is aromatoc.