Chlorination

Overview

PCl5 converts carboxylic acids into acyl chlorides.

Transformation

Carboxylic acids → Acyl chlorides

Equation

R-CO2H + PCl5 -> R-COCl + POCl3 + HCl

Reagents

PCl5

Environment

room temperature

Reaction class

substitution

Mechanism

acyl chloride formation

Evidence level

textbook core

Scope and limitations

Scope

Carboxylic acids can be converted into acyl chlorides using phosphorus(V) chloride.

Limitations

This route records the PCl5 conversion; other chlorinating reagents such as SOCl2 are not merged into this record.

Related reactions

• Oxidation: Alcohols → Carboxylic acids

  Full oxidation of a primary alcohol gives a carboxylic acid.

• Complete oxidation: Primary alcohols → Carboxylic acids

  Full oxidation of a primary alcohol gives a carboxylic acid.

• Reduction: Carboxylic acids → Primary alcohols

  Reduction of a carboxylic acid gives a primary alcohol.

• Oxidation: Aldehydes → Carboxylic acids

  Oxidation of an aldehyde gives a carboxylic acid.

• Hydrolysis: Nitriles → Carboxylic acids

  Nitriles can be hydrolysed to carboxylic acids, splitting the old aggregate nitrile-to-amide route into a single functional-group conversion.

• Activation for amide formation: Carboxylic acids → Amide chemistry

  Carboxylic acids or activated acid derivatives connect to amide-bond formation.

• Esterification: Carboxylic acids → Esters

  Carboxylic acids react with alcohols to form esters.

• Hydrolysis: Esters → Carboxylic acids

  Hydrolysis converts esters back into carboxylic acid products.

• Chlorination with thionyl chloride: Carboxylic acids → Acyl chlorides

  Thionyl chloride converts carboxylic acids into acyl chlorides with sulfur dioxide and hydrogen chloride as by-products.

• Hydrolysis: Acyl chlorides → Carboxylic acids

  Water hydrolyses acyl chlorides to carboxylic acids, releasing hydrogen chloride.

• Acylation: Acyl chlorides → Esters

  Alcohol acylation converts acyl chlorides into esters.

• Acylation: Acyl chlorides → Amides

  Ammonia acylation converts acyl chlorides into amides.

• Acylation: Acyl chlorides → N-substituted amides

  Amine acylation converts acyl chlorides into N-substituted amides.

• Carboxylation: Grignard reagents → Carboxylic acids

  Grignard carboxylation gives carboxylic acids after acidic work-up.

• Grignard carboxylation co reactant: Carbon dioxide → Carboxylic acids

  Carbon dioxide plus a Grignard reagent gives a carboxylic acid after acidic work-up.

• Salt formation: Carboxylic acids → Carboxylate salts

  Carboxylic acids react with bases, carbonates and reactive metals to form carboxylate salts.

References

1. Pearson Edexcel Level 3 Advanced GCE in Chemistry specificationPearson Education Limited · Pearson qualifications · 2024

   Supports the textbook-core organic reaction routes used for displayed route and mechanism content.