Question

Bring out the following conversions: Acetic acid to Malonic acid.

Answer 1

Conversion of Acetic acid to Malonic acid:

• The conversion of acetic acid to malonic acid takes place in two steps:

Step 1: Hell-Volhard-Zelinsky reaction

• In this reaction, acetic acid $\left({\mathrm{CH}}_3\mathrm{COOH}\right)$is treated with chlorine, and an alpha chloro-acetic acid is obtained. this reaction is known as the Hell-Volhard-Zelinsky reaction.
• This reaction takes place in the presence of red phosphorus which helps in the formation of necessary intermediates.
• The chemical reaction can be depicted as:

$$\begin{gathered} {\mathrm{CH}}_3\mathrm{COOH}+{\mathrm{Cl}}_2\stackrel{\mathrm{Red}\mathrm{P}}{\to }{\mathrm{CH}}_2\left(\mathrm{Cl}\right)\mathrm{COOH}+{\mathrm{POCl}}_3+\mathrm{HCl} \\ (\mathrm{Acetic}\mathrm{acid})\left(\mathrm{Chlorine}\right)(\mathrm{Chloro}-\mathrm{acetic}\mathrm{acid})(\mathrm{Phosphorus}\mathrm{ocychloride})(\mathrm{Hydrochloric}\mathrm{acid}) \end{gathered}$$

Step 2: Conversion of alpha chloroacetic acid to malonic acid

• An alpha chloroacetic acid is treated with potassium cyanide in the presence of ethanol which results in the formation of malonic acid$\left(\mathrm{COOH}-{\mathrm{CH}}_2-\mathrm{COOH}\right)$
• The reaction can be depicted as:

$$\begin{gathered} {\mathrm{CH}}_2\left(\mathrm{Cl}\right)\mathrm{COOH}+\mathrm{KCN}\to {\mathrm{CH}}_2\left(\mathrm{CN}\right)\mathrm{COOH}+\mathrm{KCl} \\ (\mathrm{Chloro}-\mathrm{acetic}\mathrm{acid})(\mathrm{Potassium}\mathrm{cyanide})(\mathrm{Cyanoacetic}\mathrm{acid})(\mathrm{Potassium}\mathrm{chloride}) \\ {\mathrm{CH}}_2\left(\mathrm{CN}\right)\mathrm{COOH}\stackrel{{\mathrm{H}}_3{\mathrm{O}}^{+}/{\mathrm{H}}^{+}}{\to }\mathrm{COOH}-{\mathrm{CH}}_2-\mathrm{COOH} \\ (\mathrm{Cyanoacetic}\mathrm{acid})(\mathrm{Malonic}\mathrm{acid}) \end{gathered}$$