Bextra, a COX-2 inhibitor used in the treatment of arthritis, contains an isoxazole ring. Why is

step 1 Solving Problem 43 of Chapter 15. So we need to explain why the ring present on this molecule ca

Bextra, a COX-2 inhibitor used in the treatment of...

Key Concepts

Aromaticity

Aromaticity is the concept that explains the unusually high stability of cyclic compounds that possess a conjugated system of electrons. These compounds are typically planar and allow for continuous overlap of p orbitals, which results in complete delocalization of pi electrons over the ring, lowering the overall energy of the molecule.

Hückel's Rule

Hückel's rule is a criterion used to determine whether a planar ring molecule will be aromatic. It states that a molecule will be aromatic if it has (4n + 2) pi electrons, where n is an integer. This electron count facilitates a fully delocalized electronic system, granting extra stability to the compound.

Conjugation and Planarity

For a molecule to exhibit aromaticity, it must have a completely conjugated system, which means that every atom in the ring must have a p orbital capable of overlapping with its neighbors. The molecule must also be planar, allowing for effective overlap of these orbitals and ensuring that the electrons are delocalized across the entire ring.

Heterocyclic Aromatic Compounds

Heterocyclic aromatic compounds are aromatic rings that include atoms other than carbon, such as nitrogen or oxygen. These heteroatoms can contribute lone pair electrons to the conjugated system, thereby helping to achieve the electron count required by Hückel's rule and ensuring that the overall ring maintains its aromatic character.

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