Question

Write chemical equations for the following: 
(i) Kolbe reaction 
(ii) Reimer-Tiemann reaction 
(iii) Oxidation of Phenol 
(iv) Williamson synthesis 
(v) Industrial preparation of Methanol 
 

Hint:

Remember: Kolbe gives \textbf{salicylic acid}, Reimer–Tiemann gives \textbf{salicylaldehyde}, oxidation of phenol gives \textbf{quinones}, Williamson synthesis produces \textbf{ethers}, and industrial methanol is prepared by \textbf{CO + H$_2$ hydrogenation}.

Answer 1

(i) Kolbe Reaction:
Phenol reacts with sodium hydroxide to form sodium phenoxide, which further reacts with carbon dioxide under pressure, followed by acidification to give salicylic acid.
\[ C_6H_5OH + NaOH \; \longrightarrow \; C_6H_5ONa + H_2O \] \[ C_6H_5ONa + CO_2 \; \xrightarrow{373K, 4-7 atm} \; o\!-\!HOC_6H_4COONa \] \[ o\!-\!HOC_6H_4COONa + HCl \; \longrightarrow \; o\!-\!HOC_6H_4COOH \] (ii) Reimer-Tiemann Reaction:
Phenol reacts with chloroform in the presence of sodium hydroxide to give salicylaldehyde (ortho-hydroxybenzaldehyde).
\[ C_6H_5OH + CHCl_3 + 3NaOH \; \longrightarrow \; o\!-\!HOC_6H_4CHO + 3NaCl + 2H_2O \] (iii) Oxidation of Phenol:
Phenol undergoes oxidation with neutral ferric chloride (\(FeCl_3\)) or chromic acid to give para-benzoquinone.
\[ C_6H_5OH \; \xrightarrow{[O]} \; C_6H_4O_2 \; (p\!-\!benzoquinone) \] (iv) Williamson Synthesis:
An alkoxide reacts with an alkyl halide to form an ether.
\[ R\!-\!ONa + R'X \; \longrightarrow \; R\!-\!O\!-\!R' + NaX \] Example: \[ C_2H_5ONa + CH_3I \; \longrightarrow \; C_2H_5OCH_3 + NaI \] (v) Industrial Preparation of Methanol:
Methanol is prepared industrially by the catalytic hydrogenation of carbon monoxide.
\[ CO + 2H_2 \; \xrightarrow{ZnO-Cr_2O_3, \; 573K, \; 300 atm} \; CH_3OH \] Conclusion:
Each reaction illustrates a fundamental organic transformation—carboxylation, formylation, oxidation, ether synthesis, and catalytic hydrogenation—all central to industrial and laboratory organic chemistry.