Question

Acetylene hydrocarbons are acidic because

• A. acetylene contains least number of hydrogen atoms
• B. acetylene has only one hydrogen atom at each carbon atom
• C. acetylene belongs to the class of alkynes with formula $ {{C}_{n}}{{H}_{2n-2}} $
• D. sigma electron density of $ C-H $ bond in acetylene is nearer a carbon which has 50% $ s- $ character

Answer 1

Answer: (D)

In acetylene, carbon is in sp (50% 5, 50% p character) hybrid state. Due to very large $ s- $ character, the electrons in sp hybrid orbitals are held more tightly by the nucleus and consequently the electron pair of $ H-C= $ bond is displaced more towards the carbon atom and helps in release of $ {{H}^{+}} $ ion. Hence, terminal acetylene hydrocarbons are acidic in nature.