Carboxylic Acids

Kolbe electrolysis is a method of preparing alkyl radicals from carboxylic acids by applying an electric current. When a carboxylate salt (usually sodium or potassium salt of a carboxylic acid) is electrolyzed, it undergoes decarboxylation, forming an alkane: For example, sodium acetate under Kolbe electrolysis gives ethane.
(ii) Aldol Condensation: % Solution
Solution:
Aldol condensation is a reaction where an aldehyde or a ketone with a hydrogen atom on the α-carbon reacts with another molecule of the same compound or a different one to form a β-hydroxy aldehyde or ketone. Upon heating, this product undergoes dehydration to form an α,β-unsaturated carbonyl compound. For example, acetaldehyde under basic conditions gives β-hydroxy aldehyde:
(iii) Rosenmund Reduction: % Solution
Solution:
Rosenmund reduction is a catalytic hydrogenation process that selectively reduces acyl chlorides to aldehydes. In this reaction, acyl chloride is treated with hydrogen gas in the presence of palladium on barium sulfate (Pd/BaSO ) and quinoline as a poison: For example, benzoyl chloride is reduced to benzaldehyde under these conditions.

(i) Aldol and Crossed Aldol Condensation in Aldehyde and Ketone:
Step 1: Aldol condensation.
When aldehydes or ketones containing at least one -hydrogen are treated with dilute alkali (NaOH, Ba(OH) ), they undergo
aldol condensation. The -hydrogen is removed to form an enolate ion which attacks another carbonyl group, producing -hydroxy aldehydes or ketones (aldols). On heating, they lose water to give -unsaturated compounds. Step 2: Crossed Aldol condensation.
When two different carbonyl compounds are used, the reaction is called
crossed aldol condensation. For example: Conclusion:
Aldol condensation gives -unsaturated aldehydes/ketones, while crossed aldol involves two different aldehydes/ketones.

Carboxylic acids can be prepared by several methods. The five important methods are: Method 1: Oxidation of Primary Alcohols.
Method 2: Oxidation of Aldehydes.
Method 3: Hydrolysis of Nitriles.
Method 4: Carbonation of Grignard Reagents.
Method 5: Hydrolysis of Esters.

Summary Table:
\begin{center} \begin{tabular}{|c|l|l|} \hline Method &
Reaction &
Product
\hline 1 & & From Primary Alcohol
\hline 2 & & From Aldehyde
\hline 3 & & From Nitrile
\hline 4 & & From Grignard Reagent
\hline 5 & & From Ester
\hline \end{tabular} \end{center} Conclusion:
Carboxylic acids can be synthesised by oxidation, hydrolysis, and carbonation reactions, making them versatile in both laboratory and industry.