Question

An alkene X is obtained by dehydration of an alcohol Y. X on ozonolysis gives two molecules of ethanol for every molecule of the alkene. X and Y are?
(A)X = 3-hexane, Y = hexanol
(B)X = 2-butene, Y = 2-butanolS
(C)X = 1-butene, Y = 1-butanol
(D)X = 1-hexane, Y = 1-hexanol

Answer 1

Hint: When alcohols are hated in a strong acidic medium they give alkenes. The alkene generated can be tested by cleavage of alkene by the ozonolysis reaction using ozone as a strong oxidizing agent.

Complete Answer:
According to the given data in the question the alkene X undergoes ozonolysis to give two molecules of ethanol. Ethanol is a two carbon alcohol with molecular formula ${{\text{C}}_{\text{2}}}{{\text{H}}_{\text{5}}}{\text{OH}}$, two molecules of ethanol thus contain four carbon atoms in total and the substrate must have four carbon atoms in it. As the reactant here is alkene the four carbon alkene must have the name butene because the root word ‘but means 4 carbon atoms’ and the unsaturation must be between 2 and 3 carbon atoms of butene to give two molecules of the same alcohol which is ethanol. So the alkene must be 2-butene$\left( {{\text{C}}{{\text{H}}_{\text{3}}}{\text{CH = CHC}}{{\text{H}}_{\text{3}}}} \right)$ and it can be obtained by dehydration of its corresponding alcohol which must be 2-butanol$\left( {{\text{C}}{{\text{H}}_{\text{3}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}\left( {{\text{OH}}} \right){\text{HC}}{{\text{H}}_{\text{3}}}} \right)$.

Therefore, the answer for the above question is option (B) X=2-butene, Y=2-butanol.

Note: Ozonolysis is a cleavage reaction for alkenes where the ozone reacts upon the unsaturation center and completely cleaves the alkene molecule to give two other molecules of different compounds as products.