Chapter 14 - Chapter 14: Aromaticity, Reactions of Benzene...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 14: Aromaticity, Reactions of Benzene 14.1 AROMATIC COMPOUNDS ARE UNUSUALLY STABLE In Chapter 7, we saw that benzene is a planar, cyclic compound with a cyclic cloud of delocalized electrons above & below the ring. Benzene is a particularly stable compound due to delocalization energy. Compounds with unusually large resonance energies are aromatic compounds. Aromatic compounds are particularly stable. 14.2 THE TWO CRITERIA FOR AROMATICITY To be classified as aromatic, a compound must meet both of the following criteria: 1. It must have an uninterrupted cyclic cloud of electrons ( cloud) above π π and below the plane of the molecule. The molecule must be cyclic Every atom in the ring must have a p orbital The molecule must be planar 2. The cloud must contain an π odd number of pairs of electrons. π Huckel’s Rule ( 4n + 2 Rule) For a planar, cyclic compound to be aromatic, its uninterrupted cloud must π contain ( 4n + 2) electrons, where n is any whole number. π An aromatic compound must have 2 (n=0), 6 (n=1), 10 (n=2), 14 (n=3), 18 (n=4), etc. 14.3 APPLYING THE RULE FOR AROMATICITY Monocyclic hydrocarbons with alternating single and double bonds are called annulenes.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
[4]-annulene [6]-annulene Cyclobutadiene Benzene Cyclobutadiene is not aromatic because it has an even number of p electron pairs. Cyclopentadiene does not have a uninterrupted ring of p orbital-bearing atoms. Cyclopentadienyl cations have an even number of electron pairs. π However, the cyclopentadienyl anion has an uninterrupted ring of p orbital- bearing atoms and an odd number of electron pairs. π The resonance hybrid will show that the carbons in the cyclopentadienyl anion are equivalent. Each carbon has exactly one-fifth of the negative charge associated with the anion. These polycyclic hydrocarbons are also aromatic! Napthalene Prenanthrene
Background image of page 2
Chrysene 14.4 AROMATIC HETEROCYCLIC COMPOUNDS A compound does not have to be a hydrocarbon to be aromatic. A
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/10/2008 for the course CH 3412 taught by Professor Pohlmann during the Spring '08 term at Saint Mary's University Texas.

Page1 / 12

Chapter 14 - Chapter 14: Aromaticity, Reactions of Benzene...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online