Terminal alkynes show acidic character due to:

Correct answer: A. Terminal carbon atoms are sp hybridized

  • A. Terminal carbon atoms are sp hybridized
  • B. Terminal carbon atoms are sp2 hybridized
  • C. Terminal carbon atoms are sp3 hybridized
  • D. Terminal carbon atoms show hydrogen bonding

Explanation

An sp hybrid orbital has 50 per cent s character, so it holds the bonding electrons closer to the carbon nucleus and the attached hydrogen is released more easily as a proton. This is why ethyne gives a precipitate with ammoniacal silver nitrate while ethene and ethane do not. Acidity therefore rises with s character in the order sp3 to sp2 to sp.

This question appeared on the UHS MDCAT 2025 paper, which you can sit online with every answer explained.

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About Alkynes

Alkynes are unsaturated hydrocarbons containing a carbon-carbon triple bond, with sp-hybridised carbon atoms and a linear arrangement around the bond. The content includes nomenclature, preparation, acidity of terminal alkynes, and addition reactions with hydrogen, halogens, hydrogen halides and water, as well as oxidation.

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