4.5 Activation and Deactivation

4.5 Activation and Deactivation

• Make sure you can draw a mechanism for the sulfonation of benzene on a separate piece of paper.
• There will be three steps, the first of which is the transfer of protons.
• Don't forget to draw the resonance structures of the intermediate sigma complexample if you want to draw the mechanism.

• The process will be the same as when you drew it.
• The SO H group will be removed, H+ will come on the ring, and SO will leave the ring.

• Make sure your mechanism involves an intermediate sigma complex.

• In order to make a reaction happen, we introduced a Lewis acid into the mixture, which created a better electrophile.

• We will consider the effect that a substituent will have on the reactivity of the ring when we answer this question.
• Benzene has no substituents.

• An OH group is one of the substituents in the aromatic ring.

• An OH group has an effect on the electron density of the aromatic ring.
• Let's start with something.
• In the first semester, the relative electronegativity of the atoms can be compared.
• The OH group is connected to the ring by the C--O bond.

• The oxygen atom is leaving the ring.
• We need to think about resonance.

• There is a negative charge spread throughout the ring.

• There is a partial negative charge spread throughout the ring.
• We have a competition.

• There are exceptions.
• We will soon see one of these exceptions, but in general resonance wins.

• Let's apply this rule to our case.

• Experiments show that phenol is more nucleophilic than benzene.
• The ring is said to be being activated by the OH group.
• An effect called hyperconjugation is what causes alkyl groups to be electron donating.
• The nitro group is an excellent example.