Assessing Acidity Qualitatively - All Four Factors - Exercise 27

Exercise 3.27 - Assessing Acidity Qualitatively - All Four Factors

Introduction

This video examines Exercise 3.27, focusing on why a particular molecule, known as one of the strongest acids in the world, exhibits such high acidity. The analysis incorporates the four key factors: Atom, Resonance, Induction, and Orbitals (REO).

Main Points

• Atom:

- The hydrogen in question is bonded to an oxygen atom, which is highly electronegative.

- In the periodic table, oxygen is far to the right, indicating strong electronegativity.

- When the hydrogen ion (H⁺) leaves, it leaves behind a lone pair on the oxygen atom, which stabilizes the negative charge.

• Resonance:

- The lone pair left behind on the oxygen is allylic to two places.

- The molecule exhibits a pattern of alternating single and double bonds (conjugation), allowing the negative charge to delocalize over the entire system.

- This extensive resonance stabilization greatly enhances the acidity.

• Induction:

- The presence of highly electronegative elements further stabilizes the negative charge through inductive effects.

- These electronegative atoms pull the negative charge away from the oxygen, distributing it over more bonds and increasing stability.

• Orbitals:

- Although the orbital factor is not emphasized in this example, it is noted that the molecule’s stability is primarily due to the other three factors.

Conclusion

The molecule's exceptional acidity is due to the combination of its highly electronegative atom (oxygen), extensive resonance stabilization, and strong inductive effects from neighboring electronegative atoms. These factors collectively stabilize the negative charge left behind when the hydrogen ion dissociates, making the molecule one of the strongest known acids.