Hydrogen atoms in ethyne are attached to the sp hybirdised carbon atoms whereas they are attached to sp2 hybridized carbon atoms in ethene and sp3 hydridised carbons in ethane. Due to the maximum percentage of s – character (50%), the sp hybridized orbital’s of carbon atoms in ethyne molecules have highest etcetronegativity: Which attracts the shared pair of the C-H bond of ethyne to a greater extent than that of the sp2 hybridized orbital’s of carbon in ethene and the sp3 hybridized orbital of carbon in ethane. Thus in ethyne molecule, hydrogen atoms can be liberated as protons more easily as compared to ethene and ethane.
