Benzene and the C6H6 isomers

This aromatic time-honoured species, first prepared by Faraday in 1825, is of course a highly symmetric stable molecule, C6H6, featuring six equivalent protons, yielding an uninteresting single NMR line. The term aromatic implies presence of enhanced diamagnetic currents provided by electrons in the species.75 6 

In the gas-phase, benzene shows a single line,77 78 and can yield useful information regarding the diffusion/transport properties. Benzene trapped within pores in glasses and silica gels too yields results, about pore size and adsorbed versus liquid-phase conditions.79 Chemisorption on alumina-supported platinum catalysts leads to disclosure as to how and where the benzene molecules are located, via FT NMR.80 

Benzene was the first molecule studied by NMR within liquid crystals, that is oriented in nematic liquids.81 This opened up much research, using benzene,82 leading to information about the chemical-shift anisotropy and selected spin-spin couplings. Isotope substitution too played a major role for example see Ref. 83. The 1H NMR powder spectrum at ca. 225 K gave principal values of the proton-shift parameter matrix.84 Various isotopically labelled versions of benzene 

In the table below are given the valence isomers of benzene (for definition and explanation see the article, benzene and its isomers, resonance, vol. 6, no. 5, pp. 74-78, 2001). A few properties that are listed here give an idea of how different and interesting such isomers could be. These structures can be found among the 217 structures given in this poster.  

0-0 Benzene Petroleum, coal tar, trimerization of acetylene, natural products, etc. Colourless liquid, b.p.80°C m.p.5.5°C. stable. Has relatively pleasant odour, (carcinogenic). Industrially a very important compound). 

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