Question

Alcohol forms a homologous series with general formula CnH2n+1 –OH and –OH group as functional group. Ethanol is commonly called alcohol and is used in alcoholic drinks. It is good solvent, used in medicines, cough syrups, tonics etc.

(a) Write structural formula and name of 4^th member of alcohol homologous series.    [1]

(b) What happens when ethanol is heated with alkaline KMnO₄? Write chemical equation involved.    [1]

(c) Write the chemical equation of reaction of ethanol with ethanoic acid in the presence of concentrated H₂SO₄. Write the name of this reaction.    [2]

OR

(c) What happens when ethanol is heated with excess concentrated sulphuric acid at 443 K? Write chemical equation involved. What is the role of concentrated sulphuric acid in this reaction?    [2]

Answer 1

(a) Name: Butanol

Structural Formula: \[\ce{CH3 - CH2 - CH2 - CH2OH}\]

(b) Ethanol is oxidised to ethanoic acid by alkaline potassium permanganate. KMnO₄ acts as an oxidising agent and converts alcohol into a carboxylic acid.

\[\ce{CH3CH2OH + [O] ->[KMnO4] CH3COOH + H2O}\]

(c) Ethanol reacts with ethanoic acid to form an ester (ethyl ethanoate) with a fruity smell. Esterification reaction takes place.

\[\ce{CH3CH2OH + C2H5OH ->[conc{.} H2SO4] CH3COOC2H5 + H2O}\]

OR

(c) When ethanol is heated with excess concentrated sulphuric acid at 443 K, ethanol gets dehydrated to form ethene.

\[\ce{C2H5OH ->[443 K, conc{.} H2SO4] C2H4 + H2O}\]

Role of Concentrated H₂SO₄:

• Acts as a dehydrating agent.
• Removes water from ethanol to form ethene.