Question

81. Identify the correct sequence of given steps for the conversion of calcium carbide to methyl alcohol.

(1) reaction with aqueous $\mathrm{KOH}$

(2) hydrolysis

(3) reaction with soda lime

(4) reaction with ${\mathrm{HgSO}}_4/{\mathrm{H}}_2{\mathrm{SO}}_4$

(5) reaction with ${\mathrm{HgSO}}_4$

(6) reaction with ${\mathrm{PCl}}_5$

• A. 2 4 5 3 6 1
• B. 2 4 3 1 6 5
• C. 2 6 4 5 1 3
• D. 4 2 3 5 6 1

Answer 1

The correct option is A

2 4 5 3 6 1

Step 1: Hydrolysis:

• Calcium Carbide $\left({\mathrm{CaC}}_2\right)$ undergoes hydrolysis when treated with water $\left({\mathrm{H}}_2\mathrm{O}\right)$ to form Ethyne $(\mathrm{CH}=\mathrm{CH})$ and Calcium Hydroxide $\left(\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\right)$.
• The reaction involved is: ${\mathrm{CaC}}_2+2{\mathrm{H}}_2\mathrm{O}\to \mathrm{HC}\equiv \mathrm{CH}+\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$

Step 2: Reaction with ${\mathrm{HgSO}}_4/{\mathrm{H}}_2{\mathrm{SO}}_4$:

• Ethyne reacts with Sulphuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$ and Mercury sulphate $\left({\mathrm{HgSO}}_4\right)$ to form Ethanal $\left({\mathrm{CH}}_3\mathrm{CHO}\right)$.
• The reaction involved is: $\mathrm{HC}\equiv \mathrm{CH}\underset{{\mathrm{HgSO}}_4}{\overset{{\mathrm{H}}_2{\mathrm{SO}}_4}{\to }}{\mathrm{CH}}_3\mathrm{CHO}$

Step 3: Reaction with ${\mathrm{HgSO}}_4$:

• Ethanal reacts with ${\mathrm{HgSO}}_4$ and oxidized to Ethanoic acid or Acetic acid $\left({\mathrm{CH}}_3\mathrm{COOH}\right)$.
• The reaction involved is: ${\mathrm{CH}}_3\mathrm{CHO}\stackrel{{\mathrm{HgSO}}_4}{\to }{\mathrm{CH}}_3\mathrm{COOH}$

Step 4: Reaction with soda lime:

• Ethanoic acid reacts with Soda lime $(\mathrm{NaOH}+\mathrm{CaO})$ to form Sodium acetate $\left({\mathrm{CH}}_3\mathrm{COONa}\right)$.
• The reaction involved is: ${\mathrm{CH}}_3\mathrm{COOH}+\mathrm{NaOH}\stackrel{\mathrm{CaO}}{\to }{\mathrm{CH}}_3\mathrm{COONa}+{\mathrm{H}}_2\mathrm{O}$

Step 5: Reaction with ${\mathrm{PCl}}_5$:

• Sodium acetate reacts with Phosphorus pentachloride $\left({\mathrm{PCl}}_5\right)$ to form Chloromethane $\left({\mathrm{CH}}_3\mathrm{Cl}\right)$.
• The reaction involved is: ${\mathrm{CH}}_3\mathrm{COONa}\stackrel{{\mathrm{PCl}}_5}{\to }{\mathrm{CH}}_3\mathrm{Cl}$

Step 6: Reaction with aqueous $\mathrm{KOH}$:

• Chloromethane reacts with aqueous Potassium hydroxide $\left(\mathrm{KOH}\right)$ to form Methyl alcohol or Methanol $\left({\mathrm{CH}}_3\mathrm{OH}\right)$ and Potassium chloride $\left(\mathrm{KCl}\right)$. This reaction is an example of substitution reaction.
• The reaction involved is: ${\mathrm{CH}}_3\mathrm{Cl}+\mathrm{KOH}\left(\mathrm{aqueous}\right)\to {\mathrm{CH}}_3\mathrm{OH}+\mathrm{KCl}$

The correct sequence for the conversion of Calcium carbide to Methyl alcohol is 2 4 5 3 6 1.

Hence, option (A) is the correct answer.