Question

An organic compound ‘X’ when reacts with sodium liberates hydrogen. The same compound ‘X’ when heated at 443 K in the presence of concentrated sulphuric acid gives an unsaturated hydrocarbon.
(i) Identify ‘X’.

Hint:

Alcohol reacts with sodium to release hydrogen; conc. H$_2$SO$_4$ removes water to form alkenes.

Answer 1

(1) Reaction with sodium: \[ 2C_2H_5OH + 2Na \longrightarrow 2C_2H_5ONa + H_2 \uparrow \] Here, ethanol reacts with sodium metal to liberate hydrogen gas and forms sodium ethoxide. (2) Dehydration reaction: \[ C_2H_5OH \xrightarrow{\text{Conc. H}_2SO_4,\; 443 K} C_2H_4 + H_2O \] When heated with concentrated sulphuric acid at 443 K, ethanol gets dehydrated to form ethene (an unsaturated hydrocarbon). Role of Conc. H$_2$SO$_4$: It acts as a dehydrating agent and removes a molecule of water from ethanol.