Preparation of Carboxylic Acids

Preparation of Carboxylic Acids from Alcohols and Aldehydes

Primary alcohols and aldehydes are oxidised to corresponding carboxylic acids with oxidising agents such as :

• KMnO₄ (neutral or acidic or alkaline )
• CrO₃-H₂SO₄ (Jones reagent)
• K₂Cr₂O₇ (acidic)

From aldehydes : Besides the above reagents, aldehydes are easily oxidised to carboxylic acids with mild oxidising agents such as Tollen's reagents.

Preparation of Carboxylic Acids from Alkylbenzene

Aromatic carboxylic acids are prepared by oxidation of alkylbenzenes with alkaline permangnate. The side chain of alkylbenzene is oxidised to -COOH irrespective of the length of the chain; the side products, however, are different depending upon the alkyl group. Take a close look at the following reactions :

Preparation of Carboxylic Acids from Nitriles

Hydrolysis of nitriles with H⁺ or OH⁻ as catalysts yields carboxylic acids.

Prepare ethanoic acid from methanol :

Possible answer :

Answer

One of the methods to prepare aryl nitrile is given below :

Preparation of Carboxylic Acids from amides

Amides on hydrolysis yield carboxylic acids.

Preparation of Carboxylic Acids from acid halides and anhydrides

Hydrolysis of acid chlorides yields carboxylic acids. It can be done in the following ways :

• Hydrolysis of acid chlorides with water gives carboxylic acids :
  
• Hydrolysis of acid chlorides with base followed by acidification gives carboxylic acids :
  

Similarly, hydrolysis of acid anhydrides yields carboxylic acids.

Preparation of Carboxylic Acids from Esters

Hydrolysis of esters either with mineral acids or alkalies gives carboxylic acid. Acidic hydrolysis of esters directly gives carboxylic acids while the basic one gives carboxylates, which upon acidification yield carboxylic acids.

Preparation of Carboxylic Acids from Grignard Reagents

The reaction of grignard reagents with crushed dry ice (solid carbon dioxide) followed by acidification with mineral acids gives carboxylic acids.

Conversions

Convert benzaldehyde to α-hydroxyphenylacetic acid.

Possible Answer

Convert benzene to phenylacetic acid.

Possible Answer

Convert bromobenzene to benzoic acid.

Possible Answer