Benzene Ring
<div>The first structure of benzene ring or structure was proposed by Friedrich Kekule in 1872 and this structure consisted of six membered ring with alternating single and double bonds with one hydrogen atoms attached to each of the carbon atoms. Although, Kekule proposal was consistent with many of the chemical properties of benzene but carried on with the controversy for many years.</div>
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<div>We also use the term arene to describe aromatic hydrocarbons. This is more so as we term an H removed from alkane as alkyl and hence a removing H from arene is called an aryl group. </div>
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<img title="Benzene Ring" src="https://images.tutorvista.com/cms/images/44/benzene-ring-1.png" alt="Benzene Ring" /></div>
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<div>The benzene rings or aromatic rings are common in all kinds of medications with frequent use of the structure. Benzene is the archetype aromatic compound and has the molecular formula C6H6 with the entire molecule being flat. The alternating double and single bonds in the ring is not exactly correct as the benzene ring shows resonance, which means the double bonds are actually delocalized around the entire six carbon atoms of the ring.</div>
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<h2 class="blocktitle">Benzene Ring Structure</h2>
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<div>The term aromatic hydrocarbon derives from the fact that many of the smaller molecules in this family have strong odours. The prototype of aromatic molecule is the benzene ring with a C6H6 arrangement. </div>
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<img title="Benzene Ring Structure" src="https://images.tutorvista.com/cms/images/44/benzene-ring-structure.png" alt="Benzene Ring Structure" /></div>
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<div>A benzene ring consists of 6 carbon atoms bonded to each other to form a regular hexagon. There is a carbon at each vertex of this hexagon and the C – C – C bond angle comes to about 120 degrees. There is a hydrogen atom attached to each carbon atom which finally gives the formula of C6H6. All of these benzene rings are planar.</div>
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<div>The circle or line inside the benzene ring represent some of the electrons involved in carbon – carbon bonding. These electrons are in orbitals that extend above and below the plane of the benzene ring. These electrons circulate around inside the benzene ring and are not part of any specific C – C bond. These electrons are delocalised and the C – C bond order in benzene rings is somewhere between the single bond of alkanes and double bonds of alkene.</div>
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<div>Hence the bonding between carbons of benzene rings can be also called as bonds and half. This unique bonding gives the aromatic rings unique structure, the specific chemistry and infrared spectra. There are variety of molecules that consist of the benzene ring and either one hydrogen or some hydrogens or even all of these hydrogens can be replaced by any number substituents. The arrangement of these substituents are also different which finally leads to the formation of many isomeric compounds.</div>
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<div>There are no isomers of mono substituted rings because putting together at any of these six positions on the ring gives six equivalent structures. These are formed by simply rotating the toluene molecule six times through 60 degree angle. There are three unique ways to arrange two substituents on a benzene ring. The bonds needs to be broken and then generate these isomers and cannot be generated by simply rotating the molecule. The structures of the three isomers of di-substituted benzene rings can give us the ortho isomer, meta isomer and finally the para isomer.</div>