Which of the following statements is true for cthanc, cthenc...

Which of the following statements is true for cthanc, cthenc and acetylene? (1) \Lambdacetylcne is the weakest acid and has the longest C II bond distance. (2) \Lambdacetylene is the strongest acid and has the strongest $\mathrm{C}$ II bond distance. (3) Ethanc is the strongest acid and has the longest C II bond distance. (4) Ethene is the strongest acid and has the shortest C II bond distance.

Which of the following statements is true for cthanc, cthenc and acetylene?
(1) \Lambdacetylcne is the weakest acid and has the longest C II bond distance.
(2) \Lambdacetylene is the strongest acid and has the strongest $\mathrm{C}$ II bond distance.
(3) Ethanc is the strongest acid and has the longest C II bond distance.
(4) Ethene is the strongest acid and has the shortest C II bond distance.

Key Concepts

Carbon–Carbon Bond Length and Order

The bond length between carbon atoms varies with the bond order; triple bonds (as in acetylene) have shorter bond distances than double bonds or single bonds due to the greater electron sharing and stronger orbital overlap. This trend coincides with increasing bond strength, meaning that the molecule with a triple bond not only exhibits a shorter carbon-carbon bond length but also a stronger bond compared to molecules with lower bond orders.

Acid Strength in Hydrocarbons

Acidity in hydrocarbons is largely determined by the stability of the conjugate base after deprotonation and can be indirectly assessed by pKa values. Due to the higher s-character and greater electronegativity of sp-hybridized carbons, molecules such as acetylene (ethyne) exhibit lower pKa values (stronger acidity) compared to compounds with sp² (ethene) or sp³ (ethane) carbons.

Hybridization Effects

The type of hybridization in carbon atoms (sp, sp², sp³) significantly influences both acidity and bond lengths. In molecules like acetylene, the carbon atoms are sp?hybridized, which incorporates 50% s-character, drawing electrons closer to the nucleus. This increased electron density near the nucleus stabilizes the negative charge of the conjugate base and results in a shorter and stronger bond, in contrast to sp² or sp³ carbons that have lower s-character.

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