When a compound X is heated with concentrated tetraoxosulphate(VI)acid, it produces an alkene. X is an

Analyze the question: A compound X is heated with concentrated H₂SO₄ and an alkene forms. We need to identify the class of compound X.

Concept: Concentrated sulphuric acid is a strong dehydrating agent. When it is heated with an alcohol (alkanol), it removes a molecule of water (H and OH from adjacent carbons) to form an alkene. This is called dehydration, a type of elimination reaction.

Solution:

General reaction:

CₙH₂ₙ₊₁OH → CₙH₂ₙ + H₂O (conc. H₂SO₄, heat at about 170 °C)

Example with ethanol:

CH₃CH₂OH → CH₂=CH₂ + H₂O

Checking the other options:

• A. Alkane: Alkanes undergo substitution (e.g. with halogens) and combustion. Conc. H₂SO₄ does not convert them to alkenes.
• C. Alkanoate: Alkanoates are salts or esters of carboxylic acids. Heating with acid gives hydrolysis products (an alkanoic acid and an alkanol), not an alkene.
• D. Alkyne: An alkyne would need to be reduced (hydrogenated) to become an alkene. Conc. H₂SO₄ does not do that.

Tip: Remember "Alkanol + conc. H₂SO₄ + heat → Alkene + water". The acid acts as a dehydrating agent. Be careful about temperature: at about 140 °C with excess alcohol, you get an ether instead, and at about 170 °C you get the alkene.