Benzene is a clear, colourless liquid when pure. Its primary application is in the manufacture of polystyrene.Īlthough benzene is a naturally occurring substance produced by volcanoes and forest fires and found in many plants and animals, it is also a major industrial chemical derived from coal and oil. In nature, benzene is highly toxic and carcinogenic. It is a colourless liquid with a gasoline-like odour. Benzene is a basic petrochemical and a natural component of crude oil. In comparison to the meta intermediate, m-directing groups destabilise the intermediates for o,p substitution.īenzene is the most fundamental organic, aromatic hydrocarbon. In general, o,p-directing groups stabilise o,p substitution intermediates relative to the meta intermediate. O,p-substitution intermediates in relation to the meta intermediate. They are meta-directing not because they stabilise the intermediate for meta-substitution: far from it. Meta-directing deactivating groups are those that either do not donate electrons by resonance (sulfonic acid groups and ammonium ion groups) or actually withdraw electrons by resonance (carbonyl, nitrile, and nitro groups). Let's look at some phenol resonance forms where the -OH group is already attached to the benzene ring. The resonance theory explains why some substituents are ortho-para and others are meta-directing. What is Directive Effect? For Ortho-para Directors Example: Nitro group is a meta directing group. If the opposite is observed, the substituent is called a meta directing group. If the relative yield of the ortho product and that of the para product are higher than that of the meta product, the substituent on the benzene ring in the monosubstituted benzene is called an ortho, para directing group. Depending on their relative strengths, deactivating groups also determine the positions (relative to themselves) on the benzene ring where substitutions must take place this property is therefore important in processes of organic synthesis. In organic chemistry, a deactivating group (or electron withdrawing group) is a functional group attached to a benzene molecule that removes electron density from the benzene ring, making electrophilic aromatic substitution reactions slower and more complex relative to benzene.
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