Disubstituted benzenes are named using the prefixes ortho (o), meta (m), or para (p). An ortho-disubstituted benzene has its two substituents in a 1,2 relationship on the ring, a meta-disubstituted benzene has its two substituents in a 1,3 relationship, and a para-disubstituted benzene has its substituents in a 1,4 relationship.
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ortho-Dichlorobenzene 1,2 disubstituted
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meta-Dimethylbenzene (meta-xylene) 1,3 disubstituted
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para-Chlorobenzaldehyde
1,4 disubstituted


CHAPTER CONTENTS - 15.1 Naming Aromatic Compounds

The ortho, meta, para system of nomenclature is also useful when discussing reactions. For example, we might describe the reaction of bromine with toluene by saying, "Reaction occurs at the para position," meaning at the position para to the methyl group already present on the ring.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0482.jpg?height=304&width=429&top_left_y=1252&top_left_x=574)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0482.jpg?height=262&width=394&top_left_y=1254&top_left_x=1099)


Toluene $\quad \boldsymbol{p}$-Bromotoluene
As with cycloalkanes (Section 4.1), benzenes with more than two substituents are named by choosing a point of attachment as carbon 1 and numbering the substituents on the ring so that the second substituent has as low a number as possible. If ambiguity still exists, number so that the third or fourth substituent has as low a number as possible, until a point of difference is found. The substituents are listed alphabetically when writing the name.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0482.jpg?height=334&width=1197&top_left_y=1817&top_left_x=464)


Note in the second and third examples shown that -phenol and -toluene are used as the parent names rather than -benzene. Any of the monosubstituted aromatic compounds shown in TABLE 15.1 can serve as a parent name, with the principal substituent ( -OH in phenol or $-\mathrm{CH}_{3}$ in toluene) attached to C 1 on the ring.


PROBLEM Draw structures corresponding to the following IUPAC names:
15-3 (a) $p$-Bromochlorobenzene (b) $p$-Bromotoluene (c) $m$-Chloroaniline
(d) 1-Chloro-3,5-dimethylbenzene


CHAPTER CONTENTS - 15.2 Structure and Stability of Benzene

Benzene $\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)$ has six fewer hydrogens than the six-carbon cycloalkane cyclohexane $\left(\mathrm{C}_{6} \mathrm{H}_{12}\right)$ and is clearly unsaturated, usually being represented as a six-membered ring with alternating double and single bonds. Yet it has been known since the mid-1800s that benzene is much less reactive than typical alkenes and fails to undergo typical alkene addition reactions. Cyclohexene, for instance, reacts rapidly with $\mathrm{Br}_{2}$ and gives the addition product 1,2-dibromocyclohexane, but benzene reacts slowly with $\mathrm{Br}_{2}$ and gives the substitution product $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{Br}$ rather than the addition product.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0483.jpg?height=331&width=1123&top_left_y=1195&top_left_x=504)


We can get a quantitative idea of benzene's stability by measuring heats of hydrogenation (Section 7.6). Cyclohexene, an isolated alkene, has $\Delta H_{\text {hydrog }}^{\circ}=-118 \mathrm{~kJ} / \mathrm{mol}(-28.2 \mathrm{kcal} / \mathrm{mol})$, and 1,3-cyclohexadiene, a conjugated diene, has $\Delta H^{\circ}{ }_{\text {hydrog }}=-230 \mathrm{~kJ} / \mathrm{mol}(-55.0 \mathrm{kcal} / \mathrm{mol})$. As noted in Section 14.1, this value for 1,3-cyclohexadiene is a bit less than twice that for cyclohexene because conjugated dienes are more stable than isolated dienes.

Carrying the process one step further, we might expect $\Delta H^{\circ}{ }_{\text {hydrog }}$ for "cyclohexatriene" (benzene) to be a bit less than $3 \times 118=354 \mathrm{~kJ} / \mathrm{mol}$, or three times the cyclohexene value. The actual value, however, is $-206 \mathrm{~kJ} /$ mol , some $148 \mathrm{~kJ} / \mathrm{mol}(35.4 \mathrm{kcal} / \mathrm{mol})$ less than expected. Because of this difference in actual and expected energy released during hydrogenation, benzene must have $148 \mathrm{~kJ} / \mathrm{mol}$ less energy to begin with. In other words, benzene is more stable than expected by $148 \mathrm{~kJ} / \mathrm{mol}$ (FIGURE 15.3).
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0484.jpg?height=657&width=1269&top_left_y=189&top_left_x=428)

FIGURE 15.3 A comparison of the heats of hydrogenation for cyclohexene, 1,3-cyclohexadiene, and benzene. Benzene is $148 \mathrm{~kJ} / \mathrm{mol}$ $(35.4 \mathrm{kcal} / \mathrm{mol})$ more stable than might be expected for "cyclohexatriene."


Further evidence for the unusual nature of benzene is that all its carbon-carbon bonds have the same length -139 pm , which is intermediate between typical single ( 154 pm ) and double ( 134 pm ) bonds. In addition, an electrostatic potential map shows that the electron density in all six $\mathrm{C}-\mathrm{C}$ bonds is identical. Thus, benzene is a planar molecule with the shape of a regular hexagon. All $\mathrm{C}-\mathrm{C}-\mathrm{C}$ bond angles are $120^{\circ}$, all six carbon atoms are $s p^{2}$-hybridized, and each carbon has a $p$ orbital perpendicular to the plane of the six-membered ring.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0484.jpg?height=329&width=627&top_left_y=1169&top_left_x=548)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0484.jpg?height=353&width=342&top_left_y=1187&top_left_x=1198)


Because all six carbon atoms and all six $p$ orbitals in benzene are equivalent, it's impossible to define three localized $\pi$ bonds in which a given $p$ orbital overlaps only one neighboring $p$ orbital. Rather, each $p$ orbital overlaps equally well with both neighboring $p$ orbitals, leading to a picture of benzene in which all six $\pi$ electrons are free to move about the entire ring (FIGURE 15.4b). In resonance terms (Section 2.4 and Section 2.5), benzene is a hybrid of two equivalent forms. Neither form is correct by itself; the true structure of benzene is somewhere in between the two resonance forms but is impossible to draw with our usual conventions. Because of this resonance, benzene is more stable and less reactive than a typical alkene.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0484.jpg?height=367&width=356&top_left_y=1909&top_left_x=364)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0484.jpg?height=272&width=356&top_left_y=1962&top_left_x=744)
(b)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0484.jpg?height=266&width=400&top_left_y=1965&top_left_x=1383)

FIGURE 15.4 (a) An electrostatic potential map of benzene and (b) an orbital picture. Each of the six carbon atoms has a $p$ orbital that can overlap equally well with neighboring $p$ orbitals on both sides. As a result, all $\mathrm{C}-\mathrm{C}$ bonds are equivalent and benzene must be represented as a hybrid of two resonance forms.


Chemists sometimes represent the two benzene resonance forms by using a circle to indicate the equivalence of the carbon-carbon bonds, but this representation has to be used carefully because it doesn't indicate the number of $\pi$ electrons in the ring. (How many electrons does a circle represent?) In this book, benzene and
other aromatic compounds will be represented by single line-bond structures. We'll be able to keep count of $\pi$ electrons this way but must be aware of the limitations of the drawings.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0485.jpg?height=155&width=1144&top_left_y=302&top_left_x=485)


Having just seen a resonance description of benzene, let's now look at the alternative molecular orbital description. We can construct $\pi$ molecular orbitals for benzene just as we did for 1,3-butadiene in Section 14.1. If six $p$ atomic orbitals combine in a cyclic manner, six benzene molecular orbitals result, as shown in FIGURE 15.5. The three low-energy molecular orbitals, denoted $\psi_{1}, \psi_{2}$, and $\psi_{3}$, are bonding combinations, and the three high-energy orbitals are antibonding.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0485.jpg?height=765&width=1403&top_left_y=696&top_left_x=361)

Six benzene molecular orbitals
FIGURE 15.5 The six benzene $\boldsymbol{\pi}$ molecular orbitals. The bonding orbitals $\psi_{2}$ and $\psi_{3}$ have the same energy and are said to be degenerate, as are the antibonding orbitals $\psi_{4}{ }^{*}$ and $\psi_{5}{ }^{*}$. The orbitals $\psi_{3}$ and $\psi_{4}{ }^{*}$ have no $\pi$ electron density on two carbons because of a node passing through these atoms.

Note that the two bonding orbitals $\psi_{2}$ and $\psi_{3}$ have the same energy, as do the two antibonding orbitals $\psi_{4}$ * and $\psi_{5}{ }^{*}$. Such orbitals with the same energy are said to be degenerate. Note also that the two orbitals $\psi_{3}$ and $\psi_{4} *$ have nodes passing through ring carbon atoms, thereby leaving no $\pi$ electron density on these carbons. The six $p$ electrons of benzene occupy the three bonding molecular orbitals and are delocalized over the entire conjugated system, leading to the observed $150 \mathrm{~kJ} / \mathrm{mol}$ stabilization of benzene.


PROBLEM Pyridine is a flat, hexagonal molecule with bond angles of $120^{\circ}$. It undergoes substitution rather
15-4 than addition and generally behaves like benzene. Draw a picture of the $\pi$ orbitals of pyridine to explain its properties. Check your answer by looking ahead to Section 15.5.
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Pyridine


CHAPTER CONTENTS - 15.3 Aromaticity and the Hückel $4 n+2$ Rule

Let's list what we've said thus far about benzene and, by extension, about other benzene-like aromatic molecules.


- Benzene is cyclic and conjugated.
- Benzene is unusually stable, having a heat of hydrogenation $150 \mathrm{~kJ} / \mathrm{mol}$ less negative than we might expect for a conjugated cyclic triene.
- Benzene is planar and has the shape of a regular hexagon. All bond angles are $120^{\circ}$, all carbon atoms are $s p^{2}$-hybridized, and all carbon-carbon bond lengths are 139 pm .
- Benzene undergoes substitution reactions that retain the cyclic conjugation rather than electrophilic addition reactions that would destroy it.
- Benzene can be described as a resonance hybrid whose structure is intermediate between two line-bond structures.


This list might seem to be a good description of benzene and other aromatic molecules, but it isn't enough. Something else, called the Hückel $4 \boldsymbol{n}+2$ rule, is needed to complete a description of aromaticity. According to a theory devised in 1931 by the German physicist Erich Hückel, a molecule is aromatic only if it has a planar, monocyclic system of conjugation and contains a total of $4 n+2 \pi$ electrons, where $n$ is an integer ( $n=0,1$, 2,3 ,). In other words, only molecules with $2,6,10,14,18, \pi$ electrons can be aromatic. Molecules with $4 n \pi$ electrons ( $4,8,12,16$,) can't be aromatic, even though they may be cyclic, planar, and apparently conjugated. In fact, planar, conjugated molecules with $4 n \pi$ electrons are said to be antiaromatic because delocalization of their $\pi$ electrons would lead to their destabilization.


Let's look at several examples to see how the Hückel $4 n+2$ rule works.


- Cyclobutadiene has four $\pi$ electrons and is antiaromatic. As indicated by the electrostatic potential map, the $\pi$ electrons are localized in two double bonds rather than delocalized around the ring.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0486.jpg?height=408&width=714&top_left_y=1021&top_left_x=722)


Cyclobutadiene is highly reactive and shows none of the properties associated with aromaticity. In fact, it was not even prepared until 1965, when Rowland Pettit at the University of Texas was able to make it at low temperature. Even at $-78^{\circ} \mathrm{C}$, however, cyclobutadiene is so reactive that it dimerizes by a Diels-Alder reaction. One molecule behaves as a diene and the other as a dienophile.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0486.jpg?height=93&width=755&top_left_y=1642&top_left_x=715)


Benzene -

Three double bonds; six $\pi$ electrons


Benzene -

- Cyclooctatetraene has eight $\pi$ electrons, but when it was first prepared in 1911 by the German chemist Richard Willstätter, it was found not to be particularly stable. In fact, its $\pi$ electrons are localized into four double bonds rather than delocalized around the ring, and the molecule is tub-shaped rather than planar. It has no cyclic conjugation because neighboring $p$ orbitals don't have the necessary parallel alignment for overlap, and it resembles an open-chain polyene in its reactivity.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0486.jpg?height=318&width=269&top_left_y=2177&top_left_x=684)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0486.jpg?height=354&width=484&top_left_y=2146&top_left_x=1013)


Benzene -

X-ray studies show that the $\mathrm{C}-\mathrm{C}$ single bonds in cyclooctatetraene are 147 pm long and the double bonds are 134 pm long. In addition, the ${ }^{1} \mathrm{H}$ NMR spectrum shows a single sharp resonance line at $5.78 \mathrm{\delta}$, a value characteristic of an alkene rather than an aromatic molecule.


Benzene -

What's so special about $4 n+2 \pi$ electrons? Why do $2,6,10,14 \pi$ electrons lead to aromatic stability, while other numbers of electrons do not? The answer comes from molecular orbital theory. When the energy levels of molecular orbitals for cyclic conjugated molecules are calculated, it turns out that there is always a single lowest-lying MO, above which the MOs come in degenerate pairs. Thus, when electrons fill the various molecular orbitals, it takes two electrons, or one pair, to fill the lowest-lying orbital and four electrons, or two pairs, to fill each of $n$ succeeding energy levels-a total of $4 n+2$. Any other number would leave an energy level partially filled.


Benzene -

The six $\pi$ molecular orbitals of benzene were shown previously in FIGURE 15.5, and their relative energies are shown again in FIGURE 15.6. The lowest-energy MO, $\psi_{1}$, occurs singly and contains two electrons. The next two lowest-energy orbitals, $\psi_{2}$ and $\psi_{3}$, are degenerate, and it therefore takes four electrons to fill both. The result is a stable six- $\pi$-electron aromatic molecule with filled bonding orbitals.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0487.jpg?height=476&width=895&top_left_y=868&top_left_x=615)

FIGURE 15.6 Energy levels of the six benzene $\boldsymbol{\pi}$ molecular orbitals. There is a single, lowest-energy orbital, above which the orbitals come in degenerate pairs.


Benzene -

PROBLEM To be aromatic, a molecule must have $4 n+2 \pi$ electrons and must have a planar, monocyclic system 15-5 of conjugation. Cyclodecapentaene fulfills one of these criteria but not the other and has resisted all attempts at synthesis. Explain.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0487.jpg?height=356&width=453&top_left_y=1576&top_left_x=413)


Benzene - 15.4 Aromatic lons

According to the Hückel criteria for aromaticity, a molecule must be cyclic, conjugated (nearly planar with a $p$ orbital on each atom), and have $4 n+2 \pi$ electrons. Nothing in this definition says that the number of $\pi$ electrons must be the same as the number of atoms in the ring or that the substance must be neutral. In fact, the numbers can differ and the substance can be an ion. Thus, both the cyclopentadienyl anion and the cycloheptatrienyl cation are aromatic even though both are ions and neither contains a six-membered ring.
<img class="imgSvg" id = "m6sn3nyln55vd57s1x" src="data:image/svg+xml;base64,PHN2ZyBpZD0ic21pbGVzLW02c24zbnlsbjU1dmQ1N3MxeCIgeG1sbnM9Imh0dHA6Ly93d3cudzMub3JnLzIwMDAvc3ZnIiB2aWV3Qm94PSIwIDAgMTQ3IDk2LjU1OTYyODcxMzAxMTk5IiBzdHlsZT0id2lkdGg6IDE0Ni45OTk5OTk5OTk5NzQ2NXB4OyBoZWlnaHQ6IDk2LjU1OTYyODcxMzAxMTk5cHg7IG92ZXJmbG93OiB2aXNpYmxlOyI+PGRlZnM+PGxpbmVhckdyYWRpZW50IGlkPSJsaW5lLW02c24zbnlsbjU1dmQ1N3MxeC0xIiBncmFkaWVudFVuaXRzPSJ1c2VyU3BhY2VPblVzZSIgeDE9Ijg5LjI0OTk3NTUxMzQ0NjY3IiB5MT0iNzUuNTU5NjI4NzEzMDExOTkiIHgyPSIxMDQuOTk5OTk5OTk5OTc0NjMiIHkyPSI0OC4yNzk4NDI2MzExMjAzNDYiPjxzdG9wIHN0b3AtY29sb3I9ImN1cnJlbnRDb2xvciIgb2Zmc2V0PSIyMCUiPjwvc3RvcD48c3RvcCBzdG9wLWNvbG9yPSJjdXJyZW50Q29sb3IiIG9mZnNldD0iMTAwJSI+PC9zdG9wPjwvbGluZWFyR3JhZGllbnQ+PGxpbmVhckdyYWRpZW50IGlkPSJsaW5lLW02c24zbnlsbjU1dmQ1N3MxeC0zIiBncmFkaWVudFVuaXRzPSJ1c2VyU3BhY2VPblVzZSIgeDE9Ijg5LjI1MDAyNDQ4NjUxNTI0IiB5MT0iMjEuMDAwMDI4Mjc0NjE0MzI2IiB4Mj0iMTA0Ljk5OTk5OTk5OTk3NDYzIiB5Mj0iNDguMjc5ODQyNjMxMTIwMzQ2Ij48c3RvcCBzdG9wLWNvbG9yPSJjdXJyZW50Q29sb3IiIG9mZnNldD0iMjAlIj48L3N0b3A+PHN0b3Agc3RvcC1jb2xvcj0iY3VycmVudENvbG9yIiBvZmZzZXQ9IjEwMCUiPjwvc3RvcD48L2xpbmVhckdyYWRpZW50PjxsaW5lYXJHcmFkaWVudCBpZD0ibGluZS1tNnNuM255bG41NXZkNTdzMXgtNSIgZ3JhZGllbnRVbml0cz0idXNlclNwYWNlT25Vc2UiIHgxPSI2MC44OTk5ODA2MDI4ODg2NzUiIHkxPSI2OS44ODk2MDMyNjU4NjEzNyIgeDI9Ijg2LjA5OTk4MDYwMjg3ODUzIiB5Mj0iNjkuODg5NjI1ODg1NTUyODUiPjxzdG9wIHN0b3AtY29sb3I9ImN1cnJlbnRDb2xvciIgb2Zmc2V0PSIyMCUiPjwvc3RvcD48c3RvcCBzdG9wLWNvbG9yPSJjdXJyZW50Q29sb3IiIG9mZnNldD0iMTAwJSI+PC9zdG9wPjwvbGluZWFyR3JhZGllbnQ+PGxpbmVhckdyYWRpZW50IGlkPSJsaW5lLW02c24zbnlsbjU1dmQ1N3MxeC03IiBncmFkaWVudFVuaXRzPSJ1c2VyU3BhY2VPblVzZSIgeDE9IjU3Ljc0OTk3NTUxMzQ1OTM2IiB5MT0iNzUuNTU5NjAwNDM4Mzk3NjUiIHgyPSI4OS4yNDk5NzU1MTM0NDY2NyIgeTI9Ijc1LjU1OTYyODcxMzAxMTk5Ij48c3RvcCBzdG9wLWNvbG9yPSJjdXJyZW50Q29sb3IiIG9mZnNldD0iMjAlIj48L3N0b3A+PHN0b3Agc3RvcC1jb2xvcj0iY3VycmVudENvbG9yIiBvZmZzZXQ9IjEwMCUiPjwvc3RvcD48L2xpbmVhckdyYWRpZW50PjxsaW5lYXJHcmFkaWVudCBpZD0ibGluZS1tNnNuM255bG41NXZkNTdzMXgtOSIgZ3JhZGllbnRVbml0cz0idXNlclNwYWNlT25Vc2UiIHgxPSI1Ny43NTAwMjQ0ODY1Mjc5NSIgeTE9IjIxIiB4Mj0iODkuMjUwMDI0NDg2NTE1MjQiIHkyPSIyMS4wMDAwMjgyNzQ2MTQzMjYiPjxzdG9wIHN0b3AtY29sb3I9ImN1cnJlbnRDb2xvciIgb2Zmc2V0PSIyMCUiPjwvc3RvcD48c3RvcCBzdG9wLWNvbG9yPSJjdXJyZW50Q29sb3IiIG9mZnNldD0iMTAwJSI+PC9zdG9wPjwvbGluZWFyR3JhZGllbnQ+PGxpbmVhckdyYWRpZW50IGlkPSJsaW5lLW02c24zbnlsbjU1dmQ1N3MxeC0xMSIgZ3JhZGllbnRVbml0cz0idXNlclNwYWNlT25Vc2UiIHgxPSI0MiIgeTE9IjQ4LjI3OTc4NjA4MTg5MTY2IiB4Mj0iNTcuNzQ5OTc1NTEzNDU5MzYiIHkyPSI3NS41NTk2MDA0MzgzOTc2NSI+PHN0b3Agc3RvcC1jb2xvcj0iY3VycmVudENvbG9yIiBvZmZzZXQ9IjIwJSI+PC9zdG9wPjxzdG9wIHN0b3AtY29sb3I9ImN1cnJlbnRDb2xvciIgb2Zmc2V0PSIxMDAlIj48L3N0b3A+PC9saW5lYXJHcmFkaWVudD48bGluZWFyR3JhZGllbnQgaWQ9ImxpbmUtbTZzbjNueWxuNTV2ZDU3czF4LTEzIiBncmFkaWVudFVuaXRzPSJ1c2VyU3BhY2VPblVzZSIgeDE9IjQ4LjQ4NTM2Mzk0MzM5MzI5NSIgeTE9IjQ4LjM4NjgxMTg4MTI3NzUyNCIgeDI9IjYxLjA4NTM4MzUzMjYxNTY1IiB5Mj0iMjYuNTYyOTgzMDE1NzY0MTkzIj48c3RvcCBzdG9wLWNvbG9yPSJjdXJyZW50Q29sb3IiIG9mZnNldD0iMjAlIj48L3N0b3A+PHN0b3Agc3RvcC1jb2xvcj0iY3VycmVudENvbG9yIiBvZmZzZXQ9IjEwMCUiPjwvc3RvcD48L2xpbmVhckdyYWRpZW50PjxsaW5lYXJHcmFkaWVudCBpZD0ibGluZS1tNnNuM255bG41NXZkNTdzMXgtMTUiIGdyYWRpZW50VW5pdHM9InVzZXJTcGFjZU9uVXNlIiB4MT0iNDIiIHkxPSI0OC4yNzk3ODYwODE4OTE2NiIgeDI9IjU3Ljc1MDAyNDQ4NjUyNzk1IiB5Mj0iMjEiPjxzdG9wIHN0b3AtY29sb3I9ImN1cnJlbnRDb2xvciIgb2Zmc2V0PSIyMCUiPjwvc3RvcD48c3RvcCBzdG9wLWNvbG9yPSJjdXJyZW50Q29sb3IiIG9mZnNldD0iMTAwJSI+PC9zdG9wPjwvbGluZWFyR3JhZGllbnQ+PC9kZWZzPjxtYXNrIGlkPSJ0ZXh0LW1hc2stbTZzbjNueWxuNTV2ZDU3czF4Ij48cmVjdCB4PSIwIiB5PSIwIiB3aWR0aD0iMTAwJSIgaGVpZ2h0PSIxMDAlIiBmaWxsPSJ3aGl0ZSI+PC9yZWN0PjwvbWFzaz48c3R5bGU+CiAgICAgICAgICAgICAgICAuZWxlbWVudC1tNnNuM255bG41NXZkNTdzMXggewogICAgICAgICAgICAgICAgICAgIGZvbnQ6IDE0cHggSGVsdmV0aWNhLCBBcmlhbCwgc2Fucy1zZXJpZjsKICAgICAgICAgICAgICAgICAgICBhbGlnbm1lbnQtYmFzZWxpbmU6ICdtaWRkbGUnOwogICAgICAgICAgICAgICAgfQogICAgICAgICAgICAgICAgLnN1Yi1tNnNuM255bG41NXZkNTdzMXggewogICAgICAgICAgICAgICAgICAgIGZvbnQ6IDguNHB4IEhlbHZldGljYSwgQXJpYWwsIHNhbnMtc2VyaWY7CiAgICAgICAgICAgICAgICB9CiAgICAgICAgICAgIDwvc3R5bGU+PGcgbWFzaz0idXJsKCN0ZXh0LW1hc2stbTZzbjNueWxuNTV2ZDU3czF4KSI+PGxpbmUgeDE9Ijg5LjI0OTk3NTUxMzQ0NjY3IiB5MT0iNzUuNTU5NjI4NzEzMDExOTkiIHgyPSIxMDQuOTk5OTk5OTk5OTc0NjMiIHkyPSI0OC4yNzk4NDI2MzExMjAzNDYiIHN0eWxlPSJzdHJva2UtbGluZWNhcDpyb3VuZDtzdHJva2UtZGFzaGFycmF5Om5vbmU7c3Ryb2tlLXdpZHRoOjEuMjYiIHN0cm9rZT0idXJsKCcjbGluZS1tNnNuM255bG41NXZkNTdzMXgtMScpIj48L2xpbmU+PGxpbmUgeDE9Ijg5LjI1MDAyNDQ4NjUxNTI0IiB5MT0iMjEuMDAwMDI4Mjc0NjE0MzI2IiB4Mj0iMTA0Ljk5OTk5OTk5OTk3NDYzIiB5Mj0iNDguMjc5ODQyNjMxMTIwMzQ2IiBzdHlsZT0ic3Ryb2tlLWxpbmVjYXA6cm91bmQ7c3Ryb2tlLWRhc2hhcnJheTpub25lO3N0cm9rZS13aWR0aDoxLjI2IiBzdHJva2U9InVybCgnI2xpbmUtbTZzbjNueWxuNTV2ZDU3czF4LTMnKSI+PC9saW5lPjxsaW5lIHgxPSI2MC44OTk5ODA2MDI4ODg2NzUiIHkxPSI2OS44ODk2MDMyNjU4NjEzNyIgeDI9Ijg2LjA5OTk4MDYwMjg3ODUzIiB5Mj0iNjkuODg5NjI1ODg1NTUyODUiIHN0eWxlPSJzdHJva2UtbGluZWNhcDpyb3VuZDtzdHJva2UtZGFzaGFycmF5Om5vbmU7c3Ryb2tlLXdpZHRoOjEuMjYiIHN0cm9rZT0idXJsKCcjbGluZS1tNnNuM255bG41NXZkNTdzMXgtNScpIj48L2xpbmU+PGxpbmUgeDE9IjU3Ljc0OTk3NTUxMzQ1OTM2IiB5MT0iNzUuNTU5NjAwNDM4Mzk3NjUiIHgyPSI4OS4yNDk5NzU1MTM0NDY2NyIgeTI9Ijc1LjU1OTYyODcxMzAxM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Benzene - 15.4 Aromatic lons


Benzene - 15.4 Aromatic lons

Cycloheptatrienyl cation


Benzene - 15.4 Aromatic lons

Six $\pi$ electrons; aromatic ions
To understand why the cyclopentadienyl anion and the cycloheptatrienyl cation are aromatic, imagine starting from the related neutral hydrocarbons, 1,3-cyclopentadiene and 1,3,5-cycloheptatriene, and removing one hydrogen from the saturated $\mathrm{CH}_{2}$ carbon in each. If that carbon then rehybridizes from $s p^{3}$ to $s p^{2}$, the resultant products would be fully conjugated, with a $p$ orbital on every carbon. There are three ways in which the hydrogen might be removed.


Benzene - 15.4 Aromatic lons

- The hydrogen can be removed with both electrons ( $\mathrm{H}:^{-}$) from the $\mathrm{C}-\mathrm{H}$ bond, leaving a carbocation as product.
- The hydrogen can be removed with one electron (H•) from the $\mathrm{C}-\mathrm{H}$ bond, leaving a carbon radical as product.
- The hydrogen can be removed with no electrons $\left(\mathrm{H}^{+}\right)$from the $\mathrm{C}-\mathrm{H}$ bond, leaving a carbanion as product.


Benzene - 15.4 Aromatic lons

All the potential products formed by removing a hydrogen from 1,3-cyclopentadiene and from 1,3,5-cycloheptatriene can be drawn with numerous resonance structures, but Hückel's rule predicts that only the six- $\pi$-electron cyclopentadienyl anion and cycloheptatrienyl cation can be aromatic. The other products are predicted by the $4 n+2$ rule to be unstable and antiaromatic (FIGURE 15.7).
<img class="imgSvg" id = "m6sn3nynvse4h7tk9w" src="data:image/svg+xml;base64,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Benzene - 15.4 Aromatic lons

1,3-Cyclopentadiene
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0488.jpg?height=150&width=104&top_left_y=1340&top_left_x=756)


Benzene - 15.4 Aromatic lons

Cycloheptatrienyl radical (seven $\pi$ electrons)
or

Cycloheptatrienyl anion
(eight $\pi$ electrons)


Benzene - 15.4 Aromatic lons

FIGURE 15.7 The aromatic six- $\pi$-electron cyclopentadienyl anion and the six- $\pi$-electron cycloheptatrienyl cation. The anion can be formed by removing a hydrogen ion $\left(\mathrm{H}^{+}\right)$from the $\mathrm{CH}_{2}$ group of 1,3-cyclopentadiene. The cation can be generated by removing a hydride ion $\left(\mathrm{H}:^{-}\right)$from the $\mathrm{CH}_{2}$ group of 1,3,5-cycloheptatriene.

In practice, both the four- $\pi$-electron cyclopentadienyl cation and the five- $\pi$-electron cyclopentadienyl radical are highly reactive and difficult to prepare. Neither shows any sign of the stability expected for an aromatic system. The six- $\pi$-electron cyclopentadienyl anion, by contrast, is easily prepared and remarkably stable (FIGURE 15.8a). In fact, the anion is so stable and easily formed that 1,3 -cyclopentadiene is one of the most acidic hydrocarbons known, with $\mathrm{p} K_{\mathrm{a}}=16$, a value comparable to that of water!

In the same way, the seven- $\pi$-electron cycloheptatrienyl radical and eight- $\pi$-electron anion are reactive and difficult to prepare, while the six- $\pi$-electron cycloheptatrienyl cation is extraordinarily stable (FIGURE 15.8b).


Benzene - 15.4 Aromatic lons

In fact, the cycloheptatrienyl cation was first prepared more than a century ago by reaction of 1,3,5-cycloheptatriene with $\mathrm{Br}_{2}$, although its structure was not recognized at the time.
(a)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0489.jpg?height=280&width=468&top_left_y=386&top_left_x=338)
$+\mathrm{H}_{2} \mathrm{O}$


Benzene - 15.4 Aromatic lons

1,3-Cyclo-
Cyclopentadienyl anion
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0489.jpg?height=291&width=413&top_left_y=321&top_left_x=956)

Aromatic cyclopentadienyl anion with six $\pi$ electrons
(b)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0489.jpg?height=342&width=600&top_left_y=783&top_left_x=329)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0489.jpg?height=337&width=892&top_left_y=750&top_left_x=933)


Benzene - 15.4 Aromatic lons

Cycloheptatrienyl cation six $\pi$ electrons


Benzene - 15.4 Aromatic lons

FIGURE 15.8 (a) The aromatic cyclopentadienyl anion, showing cyclic conjugation and six $\boldsymbol{\pi}$ electrons in five $\boldsymbol{p}$ orbitals, and (b) the aromatic cycloheptatrienyl cation, showing cyclic conjugation and six $\boldsymbol{\pi}$ electrons in seven $\boldsymbol{p}$ orbitals. Electrostatic potential maps indicate that both ions are symmetrical, with the charge equally shared among all atoms in each ring.


Benzene - 15.4 Aromatic lons

PROBLEM Draw the five resonance structures of the cyclopentadienyl anion. Are all carbon-carbon bonds
15-6 equivalent? How many absorption lines would you expect to see in the ${ }^{1} \mathrm{H}$ NMR and ${ }^{13} \mathrm{C}$ NMR spectra of the anion?


Benzene - 15.4 Aromatic lons

PROBLEM Cyclooctatetraene readily reacts with potassium metal to form the stable cyclooctatetraene dianion,
15-7 $\mathrm{C}_{8} \mathrm{H}_{8}{ }^{2-}$. Why do you suppose this reaction occurs so easily? What geometry do you expect for the cyclooctatetraene dianion?
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0489.jpg?height=177&width=614&top_left_y=1597&top_left_x=411)


Benzene - 15.4 Aromatic lons

PROBLEM The relative energy levels of the five $\pi$ molecular orbitals of the cyclopentadienyl system are similar
15-8 to those in benzene. That is, there is a single lowest-energy MO, above which the orbitals come in degenerate pairs. Draw a diagram like that in Figure 15.6, and tell which of the five orbitals are occupied in the cation, radical, and anion.


Benzene - 15.5 Aromatic Heterocycles: Pyridine and Pyrrole

Look back once again at the definition of aromaticity in Section 15.3: a cyclic, conjugated molecule containing $4 n+2 \pi$ electrons. Nothing in this definition says that the atoms in the ring must be carbon. In fact, heterocyclic compounds can also be aromatic. A heterocycle is a cyclic compound that contains atoms of more than one element in its ring, usually carbon along with nitrogen, oxygen, or sulfur. Pyridine and pyrimidine, for example, are six-membered heterocycles with carbon and nitrogen in their rings (FIGURE 15.9).


Pyridine


FIGURE 15.9 Pyridine and pyrimidine are nitrogen-containing aromatic heterocycles with $\pi$ electron arrangements like that of benzene. Both have a lone pair of electrons on nitrogen in an $s p^{2}$ orbital in the plane of the ring.
Pyridine is much like benzene in its $\pi$ electron structure. Each of the five $s p^{2}$-hybridized carbons has a $p$ orbital perpendicular to the plane of the ring, and each $p$ orbital contains one $\pi$ electron. The nitrogen atom is also $s p^{2}$-hybridized and has one electron in a $p$ orbital, bringing the total to six $\pi$ electrons. The nitrogen lone-pair electrons (red in an electrostatic potential map) are in a $s p^{2}$ orbital in the plane of the ring and are not part of the aromatic $\pi$ system. Pyrimidine, also shown in FIGURE 15.9), is a benzene analog that has two nitrogen atoms in a six-membered, unsaturated ring. Both nitrogens are $s p^{2}$-hybridized, and each contributes one electron to the aromatic $\pi$ system.


Pyrrole (spelled with two r's and one $I$ ) and imidazole are five-membered heterocycles, yet both have six $\pi$ electrons and are aromatic. In pyrrole, each of the four $s p^{2}$-hybridized carbons contributes one $\pi$ electron and the $s p^{2}$-hybridized nitrogen atom contributes the two from its lone pair, which occupies a $p$ orbital (FIGURE 15.10). Imidazole, also shown in (FIGURE 15.10, is an analog of pyrrole that has two nitrogen atoms in a fivemembered, unsaturated ring. Both nitrogens are $s p^{2}$-hybridized, but one is in a double bond and contributes only one electron to the aromatic $\pi$ system whereas the other is not in a double bond and contributes two from its lone pair.
<img class="imgSvg" id = "m6sn3nys8d6fpje0m3" 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Pyrrole


Imidazole
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0490.jpg?height=280&width=299&top_left_y=1652&top_left_x=677)
(Six $\pi$ electrons)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0490.jpg?height=806&width=452&top_left_y=1638&top_left_x=1187)


FIGURE 15.10 Pyrrole and imidazole are five-membered, nitrogen-containing heterocycles but have six- $\pi$-electron arrangements like that of the cyclopentadienyl anion. Both have a lone pair of electrons on nitrogen in a $p$ orbital perpendicular to the ring.

Note that nitrogen atoms have different roles depending on the structure of the molecule. The nitrogen atoms in pyridine and pyrimidine are both in double bonds and contribute only one $\pi$ electron to the aromatic sextet, just as a carbon atom in benzene does. The nitrogen atom in pyrrole, however, is not in a double bond and contributes two $\pi$ electrons (its lone pair) to the aromatic sextet. In imidazole, both kinds of nitrogen are present in the same molecule-a double-bonded "pyridine-like" nitrogen that contributes one $\pi$ electron and a "pyrrolelike" nitrogen that contributes two.