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Give short notes on the following : (a) Kolbe’s reaction (b) Riemer Tiemann reaction (c) Coupling reaction |
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Answer» Solution :(a) Kolbe's reaction: In this reaction, phenol is first converted into SODIUM phenoxide which is more reactive than phenol towards electrophilic substitution reaction with `CO_(2)`. TREATMENT of sodium phenoxide with `CO_(2)` at 400 K, 4-7 bar pressure followed by ACID hydrolysis gives salicylic acid.  (ii) Riemer- Tiemann reaction: On treating phenol with `CHCl_(3)//NaOH`, a-CHO groupis introduced at ortho position. This reaction proceeds through the formation of substituted benzal chloride INTERMEDIATE.
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