Question

An organic compound ‘X’ which is sometimes used as an antifreeze, has the molecular formula ${\mathrm{C}}_2{\mathrm{H}}_6\mathrm{O}$. ‘X’ on oxidation gives a compound ‘Y’ which gives effervescence with Baking soda solution. What can ‘X’ and ‘Y’ be? Write the structural formulae.

Answer 1

Part 1:

• Carboxylic acid reacts with Sodium Hydrogen carbonate (Baking Soda) to form effervescence.
• It is given that, compound Y gives effervescence with Baking soda solution. So, Y must be a Carboxylic acid.
• So, X must be an alcohol. As the compound ${\mathrm{C}}_2{\mathrm{H}}_6\mathrm{O}$ has two Carbon atoms. So, X is Ethanol (${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}$). It is also used as an antifreeze.
• The oxidation of Ethanol in the presence of alkaline ${\mathrm{KMnO}}_4$ gives Ethanoic acid.

$$\begin{gathered} {\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{l}\right)+2\left[\mathrm{O}\right]\stackrel{\mathrm{Alk}.{\mathrm{KMnO}}_4}{\to }{\mathrm{CH}}_3\mathrm{COOH}\left(\mathrm{l}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Ethanol}\mathrm{Ethanoic}\mathrm{acid} \\ \mathrm{X}\mathrm{Y} \end{gathered}$$

• The reaction of Ethanoic acid with Baking soda produces Sodium Ethanoate, water and Carbon dioxide gas.

$$\begin{gathered} {\mathrm{CH}}_3\mathrm{COOH}\left(\mathrm{l}\right)+{\mathrm{NaHCO}}_3\left(\mathrm{aq}\right)\to {\mathrm{CH}}_3\mathrm{COONa}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right) \\ \mathrm{Ethanoic}\mathrm{Sodium}\mathrm{Sodium}\mathrm{acetate} \\ \mathrm{acid}\mathrm{Bicarbonate} \\ (\mathrm{Baking}\mathrm{soda}) \\ \mathbf{Y} \end{gathered}$$

Therefore, X is Ethanol (${\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{5}}\mathbf{OH}$) and Y is Ethanoic acid (${\mathbf{CH}}_{\mathbf{3}}\mathbf{COOH}$)

Part 2:

X is Ethanol (${\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{5}}\mathbf{OH}$)

Y is Ethanoic acid (${\mathbf{CH}}_{\mathbf{3}}\mathbf{COOH}$)