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Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline.
*** Benzene is a carcinogen (cancer-causing agent). *** Very flammable. The pure material, and any solutions containing it, constitute a fire risk. Safe handling: Benzene should NOT be used at all unless no safer alternatives are available. If benzene must be used in an experiment, it should be handled at all stages in a fume cupboard.
[18] [19] The LDQ structure for benzene is shown below. [16] [24] The LDQ structure of benzene. The carbon nuclei are coloured brown and the hydrogen nuclei are coloured pink, while the electrons are coloured either purple or green to distinguish between the spin sets. Left: The dot-and-cross diagram of the LDQ structure of benzene.
In organic and physical organic chemistry, Clar's rule is an empirical rule that relates the chemical stability of a molecule to its aromaticity.It was introduced in 1972 by the Austrian organic chemist Erich Clar in his book The Aromatic Sextet.
In chemistry, chemical stability is the thermodynamic stability of a chemical system, in particular a chemical compound or a polymer. [ 1 ] Thermodynamic stability occurs when a system is in its lowest energy state , or in chemical equilibrium with its environment.
There are three main ortho effects in substituted benzene compounds: Steric hindrance forces cause substitution of a chemical group in the ortho position of benzoic acids become stronger acids. Steric inhibition of protonation caused by substitution of anilines to become weaker bases, compared to substitution of isomers in the meta and para ...
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The concept first appeared in 1899 in Johannes Thiele's "Partial Valence Hypothesis" to explain the unusual stability of benzene which would not be expected from August Kekulé's structure proposed in 1865 with alternating single and double bonds. [12] Benzene undergoes substitution reactions, rather than addition reactions as typical for ...