Strength of Acids - Example from Lecture

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Shannon Asay 1C
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Strength of Acids - Example from Lecture

Postby Shannon Asay 1C » Sun Dec 01, 2019 10:34 am

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
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Re: Strength of Acids - Example from Lecture

Postby Mansi_1D » Sun Dec 01, 2019 10:42 am

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
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Re: Strength of Acids - Example from Lecture

Postby William Chan 1D » Sun Dec 01, 2019 11:01 am

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
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Re: Strength of Acids - Example from Lecture

Postby Hussain Chharawalla 1G » Sun Dec 01, 2019 11:46 am

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
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Re: Strength of Acids - Example from Lecture

Postby KHowe_1D » Sun Dec 01, 2019 12:05 pm

It is because chlorine has a higher electronegativity than Hydrogen.

Shrayes Raman
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Re: Strength of Acids - Example from Lecture

Postby Shrayes Raman » Sun Dec 01, 2019 11:27 pm

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
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Re: Strength of Acids - Example from Lecture

Postby Shail Avasthi 2C » Mon Dec 02, 2019 10:23 am

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.


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