11.71 Explain the following with an example. (i) Kolbe’s reaction. (ii) Reimer-Tiemann reaction. (iii) Williamson ether synthesis. (iv) Unsymmetrical ether.

<p><strong>11.71&nbsp;</strong></p><p><strong>Kolbe's Reaction:&nbsp;</strong>it is a carboxylation chemical reaction that proceeds by heating sodium phenoxide (the sodium salt of phenol)with carbon dioxide under pressure (100 atm,125°C), then treating the product with a sulphuric acid. The final product is salicylic acid (the precursor to aspirin).</p><p>The reaction is given as:</p><p>The mechanism is given below:</p><p><strong><u>Reimer-Tiemann reaction:</u> </strong>The Reimer Tiemann reaction is a chemical reaction used for the ortho-formylation of phenols, with the simplest example being the conversion</p><p>of phenol to salicylaldehyde.</p><p>When phenol is treated at 340K with chloroform and alkali, it forms salicylaldehyde.</p><p><strong>Williamson ether synthesis: </strong>It is an organic reaction forming ether from an organohalide and a deprotonated alcohol (alkoxide). Typically it involves the reaction of an alkoxide ion with primary alkyl halide via S_N2 reaction.</p><p>During this reaction, the main bonds broken is the C-Br bond and the new bonds formed are “C- O” bond.</p><p><strong>Unsymmetrical ether: </strong>It is an ether in the molecule of which the two ligands on the ether group are different.</p><p>Eg.</p>

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