MHTCET 18 Apr 2026 Shift 2 Paper

Concept:A terminal alkyne has the triple bond at the end of the carbon chain, forming the terminal group $\mathrm{-C \equiv CH}$.Explanation:To identify a terminal alkyne, check whether a hydrogen atom is directly attached to a triple-bonded carbon.Ethyne: $\mathrm{HC \equiv CH}$. Both triple-bonded carbons carry hydrogen atoms, so it is a terminal alkyne.Propyne: $\mathrm{CH_3{-}C \equiv CH}$. The triple bond is between carbon 1 and carbon 2, with a terminal hydrogen, so it is terminal.But-1-yne: $\mathrm{CH_3{-}CH_2{-}C \equiv CH}$. The triple bond starts from carbon 1, so it is terminal.But-2-yne: $\mathrm{CH_3{-}C \equiv C{-}CH_3}$. The triple bond lies in the middle of the chain, and no triple-bonded carbon carries a hydrogen atom.Hence, But-2-yne lacks the terminal $\mathrm{-C \equiv CH}$ group, so it is NOT a terminal alkyne.Answer:Option D: But-2-yne