• Acyl chlorides?are compounds with the functional group -COCl
• They look similar in structure to?carboxylic acids?but have a Cl atom instead of an -OH group attached to the carbonyl (C=O)
• Acyl chlorides are?more reactive?than their corresponding carboxylic acids and are therefore often used as?starting materials?in the production of organic compounds such as?esters
• They can be prepared from the reaction of carboxylic acids with:
  • Solid?phosphorus(V) chloride (PCl₅)
  • Liquid?phosphorus(III) chloride (PCl₃) and heat
  • Liquid?sulfur dichloride oxide (SOCl₂)
• For example, the acyl chloride?ethanoyl chloride?can be formed from?ethanoic acid?in the above reactions

Production of acyl chlorides from their corresponding carboxylic acids

• Carboxylic acids?can be formed from the?oxidation?of primary alcohols
• The primary alcohols are firstly oxidised to?aldehydes?and then further oxidised to?carboxylic acids
• Some carboxylic acids can get even?further oxidised

Methanoic acid

• Methanoic acid?is a?strong reducing agent?and gets?further oxidised?to?carbon dioxide?(CO₂)
• The oxidation of methanoic acid can occur by:
  • Warming methanoic acid with?mild?oxidising agents?such as?Fehling’s?or?Tollens’?reagent
    • In a Fehling’s solution, the Cu²⁺?ion is?reduced?to Cu⁺?ion which?precipitates?as?red?Cu₂O
    • With Tollens’ reagent, the Ag⁺?is?reduced?to Ag
  • Using?stronger?oxidising agents such as?acidified KMnO₄or?acidified K₂Cr₂O₇
    • The?purple?KMnO₄?solution turns?colourless?as Mn⁷⁺?ions are?reduced?to Mn²⁺?ions
    • The?orange?K₂Cr₂O₇?solution turns?green?as the Cr⁶⁺?ions are reduced to Cr³⁺?ions

Ethanedioic acid

• Another carboxylic acid that can get further oxidised is?ethanedioic acid
• A?strong oxidising agent?such as?warm acidified KMnO₄is required for the oxidation of ethanedioic acid to?carbon dioxide

Ethanedioic acid is a dicarboxylic acid that can get further oxidised to carbon dioxide