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Unformatted text preview: means there is no direct interaction. The nonbonding electrons are localized on the nitrogen. N : The pyridine ! " electrons are stabilized, as in benzene, because they reside in a closed shell structure. N . . pyridine In, pyrrole , furan and thiophene , the four ring carbons contribute four electrons to the ! " electronic structure while the heteroatom (N,O,S) contributes a nonbonding pair to give a sextet of ! " electrons . The "aromaticity" of these five-membered ring heterocycles results from a closed shell electronic structure as is found in the cyclopentadiene anion. Note again the heteroatom is sp 2 hybridized. N H N-H . . pyrrole O : O . . : furan S : S . . : thiophene six ! " electron systems These heterocyclic aromatic compounds are widely found in biological structures....
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This note was uploaded on 10/20/2009 for the course CHEM 322BL at USC.
- Organic chemistry