Chemistry · Hydrocarbons

Ethyne (C2H2), an unsaturated hydrocarbon, consists of two sp-hybridized carbon atoms bonded via a triple bond. This bond includes one sigma (σ) and two pi (π) bonds formed by the sideways overlap of unhybridized p orbitals. The molecule exhibits linear geometry with an H–C≡C–H bond angle of 180°. Ethyne undergoes electrophilic addition reactions due to the presence of loosely held π electrons, and it also shows mild acidity, forming salts with reactive metals like sodium or calcium carbide. However, unlike alkenes, ethyne and other alkynes do not exhibit geometrical isomerism, despite having multiple bonds. Which of the following statements are correct based on the passage? (A) The acidity of ethyne is due to the high % s-character of the sp hybrid orbitals. (B) Geometrical isomerism in alkynes is not possible due to restricted rotation about triple bonds. (C) Triple bonds allow free rotation around the C≡C axis, enabling isomerism. (D) Benzene can be formed by cyclic trimerization of ethyne.