Question

98. How do you bring about the following conversions?

(b) ethyne to acetic acid

Answer 1

Step 1: Conversion of Ethyne to Acetaldehyde or Ethanal

Ethyne $(\mathrm{CH}\equiv \mathrm{CH})$ is oxidized in the presence of Sulphuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$ and mercuric ions $\left({\mathrm{Hg}}^{2+}\right)$ to form Acetaldehyde or Ethanal $\left({\mathrm{CH}}_3\mathrm{CHO}\right)$.

The reaction involved is:

$\underset{\mathrm{Ethyne}}{\mathrm{CH}\equiv \mathrm{CH}}\underset{{\mathrm{Hg}}^{2+}}{\overset{{\mathrm{H}}_2{\mathrm{SO}}_4}{\to }}\underset{\mathrm{Acetaldehyde}}{{\mathrm{CH}}_3\mathrm{CHO}}$

Step 2: Conversion of Acetaldehyde to Acetic acid

Ethanal is oxidized to Ethanoic acid or acetic acid $\left({\mathrm{CH}}_3\mathrm{COOH}\right)$ in the presence of Potassium dichromate $\left({\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7\right)$.

The reaction involved is:

$\underset{\mathrm{Acetaldehyde}}{{\mathrm{CH}}_3\mathrm{CHO}}\underset{\left[\mathrm{O}\right]}{\overset{{\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7}{\to }}\underset{\mathrm{Acetic}\mathrm{Acid}}{{\mathrm{CH}}_3\mathrm{COOH}}$