Strength of Acids - Example from Lecture

[Shannon Asay 1C]

In the example from lecture Wednesday, Dr. Lavelle said that trichloroacetic acid, CCl3COOH, was stronger than acetic acid, CH3COOH. Could someone re-explain why that is?

[Mansi_1D]

I'm not completely sure but I think it's because trichloroacetic acid has a greater electronegativity since it has chlorine than acetic acid.

[William Chan 1D]

Trichloroacetic acid has 3 chlorine molecules, which pull harder on the electrons because chlorine has a higher electronegativity than hydrogen does.

The stability of the anion determines the strength of the acid. When either trichloroacetic acid or acetic acid loses a hydrogen ion, the oxygen is left with a negative charge. The chlorines do a better job than the hydrogens at pulling that negative charge (delocalizing it), and thus, stabilizing the ion. This makes trichloroacetic acid stronger.

[Hussain Chharawalla 1G]

To add on to this,

Yes because Chlorine has a greater electronegativity, it will be better in delocalizing electrons from the negative oxygen. He also mentioned that Fluorine would be an even stronger acid, because Fluorine is more electronegative and would delocalize electrons even more, giving more stability.

[KHowe_1D]

It is because chlorine has a higher electronegativity than Hydrogen.

[Shrayes Raman]

Draw the Lewis structure and see that the Cl form a ring around central carbon and then the lone pairs on the Cl pull on the Oxygen delocalizing the electrons which increases stability.

[Shail Avasthi 2C]

CCl3COOH and CH3COOH have the anions CCl3COO- and CH3COO- respectively. The former anion is more stable than the latter because the 3 chlorines delocalize the negative charge on the oxygen. Oxoacids will be more acidic if the resulting anion is stabilized by electronegative atoms which delocalize the negative charge. Therefore, since tricholoacetic acid has a more stable anion than acetic acid, it is more acidic.