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Strength of Acids - Example from Lecture

Posted: Sun Dec 01, 2019 10:34 am
by 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?

Re: Strength of Acids - Example from Lecture

Posted: Sun Dec 01, 2019 10:42 am
by 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.

Re: Strength of Acids - Example from Lecture

Posted: Sun Dec 01, 2019 11:01 am
by 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.

Re: Strength of Acids - Example from Lecture

Posted: Sun Dec 01, 2019 11:46 am
by 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.

Re: Strength of Acids - Example from Lecture

Posted: Sun Dec 01, 2019 12:05 pm
by KHowe_1D
It is because chlorine has a higher electronegativity than Hydrogen.

Re: Strength of Acids - Example from Lecture

Posted: Sun Dec 01, 2019 11:27 pm
by 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.

Re: Strength of Acids - Example from Lecture

Posted: Mon Dec 02, 2019 10:23 am
by 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.