Editing Aromatic compound (section)

== Benzene and derivatives of benzene ==
[[File:Ortho_meta_para.png|thumb|170x170px|class=skin-invert-image|Substitution nomenclature of benzene<ref name=":43" />]]
Benzene derivatives have from one to six [[substituent]]s attached to the central benzene core.<ref name=":0" /> Examples of benzene compounds with just one substituent are [[phenol]], which carries a [[hydroxyl]] group, and [[toluene]] with a [[methyl]] group. When there is more than one substituent present on the ring, their spatial relationship becomes important for which the [[arene substitution patterns]] ''ortho'', ''meta'', and ''para'' are devised.<ref name=":02">{{Cite web |date=2015-05-03 |title=16.5: An Explanation of Substituent Effects |url=https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_(Morsch_et_al.)/16%3A_Chemistry_of_Benzene_-_Electrophilic_Aromatic_Substitution/16.05%3A_An_Explanation_of_Substituent_Effects |access-date=2023-12-03 |website=Chemistry LibreTexts |language=en}}</ref> When reacting to form more complex benzene derivatives, the substituents on a benzene ring can be described as either [[Activating group|activated]] or [[Deactivating group|deactivated]], which are electron donating and electron withdrawing respectively.<ref name=":02" /> Activators are known as ortho-para directors, and deactivators are known as meta directors.<ref name=":02" /> Upon reacting, substituents will be added at the ortho, para or meta positions, depending on the directivity of the current substituents to make more complex benzene derivatives, often with several isomers. Electron flow leading to re-aromatization is key in ensuring the stability of such products.<ref name=":02" />

For example, three [[isomer]]s exist for [[cresol]] because the methyl group and the hydroxyl group (both ortho para directors) can be placed next to each other (''ortho''), one position removed from each other (''meta''), or two positions removed from each other (''para'').<ref name=":14">{{cite book |doi=10.1016/B978-0-12-386454-3.00296-7 |chapter=Cresols |title=Encyclopedia of Toxicology |date=2014 |last1=Badanthadka |first1=M. |last2=Mehendale |first2=H.M. |pages=1061–1065 |isbn=978-0-12-386455-0 }}</ref> Given that both the methyl and hydroxyl group are ortho-para directors, the ortho and para isomers are typically favoured.<ref name=":14" /> [[Xylenol]] has two methyl groups in addition to the hydroxyl group, and, for this structure, 6 isomers exist.{{citation needed|date=December 2023}}

Arene rings can stabilize charges, as seen in, for example, phenol (C<sub>6</sub>H<sub>5</sub>–OH), which is [[acidic]] at the hydroxyl (OH), as charge on the oxygen (alkoxide –O<sup>−</sup>) is partially delocalized into the benzene ring.

<gallery perrow="5" caption="Representative arene compounds">
File:Benzene circle.svg|[[Benzene]]
File:Toluene.svg|[[Toluene]]
File:Ethylbenzene-2D-structure.svg|[[Ethylbenzene]]
File:Para-Xylol - para-xylene.svg|[[Xylene|''p''-Xylene]]
File:Meta-Xylol - meta-xylene.svg|[[Xylene|''m''-Xylene]]
File:Ortho-Xylol - ortho-xylene.svg|[[Xylene|''o''-Xylene]]
File:1,3,5-Trimethylbenzene.svg|[[Mesitylene]]
File:Durene.png|[[Durene]]
File:Biphenyl.svg|[[Biphenyl]]
File:Phenol.svg|[[Phenol]]
File:Aniline.svg|[[Aniline]]
File:Benzaldehyde.svg|[[Benzaldehyde]]
File:Benzoic acid.svg|[[Benzoic acid]]
File:Benzamide.svg|[[Benzamide]]
File:Acetophenone structure.svg|[[Acetophenone]]
</gallery>