Define with equation/reaction :
a. Riemer-Tiemann reaction
b. Friedel-Crafts acetylation of anisole
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Answers
Explanation:
The Reimer–Tiemann reaction is a chemical reaction used for the ortho-formylation of phenols; with the simplest example being the conversion of phenol to salicylaldehyde. The reaction was discovered by Karl Reimer and Ferdinand Tiemann. The Reimer in question was Karl Reimer not the less known Carl Ludwig Reimer.
Answer:
a) Riemer-Tiemann reaction:
》treating phenol with chloroform in the presence of sodium hydroxide or potassiumhydroxide, a -CHO group is introduced at ortho position of benzene ring.
》in which salicylaldehyde forms, this reaction can also be called as formylation/carboxylation.
》The intermediate substituted benzal chloride is hydrolyzed in the presence of alkali to produce salicyaldehyde.
•mechanism is in the attachment.
b)Friedel-Crafts acetylation of anisole:
》this involves the addition of alkyl and acyl groups are treated at ortho and para positions of Anisole
》this reactions occur with alkyl hallide and acyl hallide in the presence of anhydrous aluminium chloride (act as Lewis acid) as catalyst.
•mechanism is in the attachment.
☆Note: we see that para-position is major product in both anisole reaction, because it has lesser crowding effect than ortho.
more the crowding,more it will hinder the electrophilic effect.
