Predict the products of these reactions and use them.
Predict the products of organometallic substitution and use them in synthesis.
Predict the products of oxidation and reduction of the aromatic ring.
For example, the aniline dye mauvine quickly replaced royal purple, but relatively few reactions that affect very expensive dye that was laboriously the bonds in the aromatic ring itself.
Most of the reactions are unique to sea snails.
Minor variations of aromatic substitution explain many reactions of benzene and its derivatives.
We will look at how substituents on the ring affect the reactivity of the ring and the regiochemistry of the products.
Other reactions of aromatic compounds include nucleophilic aromatic substitution, addition reactions, reactions of side chains, and special reactions of phenols.
benzene has clouds of pi electrons above and below its sigma bond framework.
Although benzene's pi electrons are in a stable aromatic system, they can be used to attack a strong electrophile to give a carbocation.
The aromatic substitution product can be created by either a reversal of the first step or the loss of the protons on the carbon atom.
A wide variety of reagents are used in this class of reactions.
The most important method for synthesis of substituted aromatic compounds is electrophilic aromatic substitution, because it enables us to introduce functional groups directly onto the aromatic ring.
The substitution product is given by the loss of a protons.
The substitution product is given by deprotonation.
We didn't consider the possibility of water acting as a nucleophile and attacking the carbocation in the step 2 of the iodination of benzene.
There is a general mechanism for aromatic substitution.
The formation of br+ is difficult because bromine is not sufficientlyphilic to react with benzene.
A strong Lewis acid such as FeBr3 makes the reaction happen by forming a complex with another acid.
Attack by benzene forms the sigma complexample Bromide ion from FeBr-4, which acts as a weak base to remove a proton from the sigma complex, giving the aromatic product and HBr, and regenerating the catalyst.
The products are given by the loss of a protons.
The transition state leading to the sigma complex occupies the highest energy point on the energy diagram.
The step is endothermic because it forms a carbocation.
The second step is exothermic because aromaticity is regained.
The reaction is exothermic by 45 kJ>mol.
Benzene is not as reactive as alkenes, which react rapidly with bromine at room temperature to give addition products.
The reaction is exothermic by 121 kJ>mol.
Under normal circumstances, the addition is not seen.
The substitution requires a Lewis acid catalyst to make bromine stronger.
Chlorination of benzene is similar to bromination, except that aluminum chloride is used as the Lewis acid catalyst.
There is a mechanism for the aluminum chloride-catalyzed reaction of benzene with chlorine.
Iodination of benzene requires an acidic oxidizer, such as carbon atoms ortho and nitric acid.
An oxidant site of substitution is where Nitric acid is consumed in the reaction.
Iodination probably involves a substitution of an aromatic with a cation.
Benzene reacts with hot, concentrated nitric acid.
A hot mixture of concentrated nitric acid with any oxidizable material could explode.
A safer and more convenient procedure uses a mixture of acids.
nitration can be done more quickly and at lower temperatures with the help of sphuric acid.
Next, the mechanism is shown.
The mechanism is similar to other dehydrations.
The hydroxy group of nitric acid can leave as water and form a nitronium ion.
The sigma complex is formed when the ion reacts with benzene.
Similar to the dehydration of an alcohol, nitric acid has a hydroxy group that can become protonated and leave as water.
The aromatic substitution by the ion gives it's name, nitrobenzene.
There is a loss of a protons.
Reduction followed by nitration is the best method for adding an aromatic ring.
The accelerated rate is explained by resonance forms of the sigma complex.
Strong acid catalysts are often used as nonpolar organic solvents.
Arylsulfonic acids can be synthesised using sulfonation of benzene derivatives and sulfur trioxide.
Benzene attacks sulfur trioxide, forming a sigma complexample loss of a protons on the carbon and oxygen gives benzenesulfonic acid.