Question

Acetic acid (CH3COOH) and trifluoroacetic acid (CF3COOH) are shown by these particulate models. The Ka for trifluoroacetic acid is 10⁴ times greater than acetic acid. Use the models to account for the differences in magnitude for the Ka constant. The yellow atoms are fluorine, the red atoms are oxygen, the black atoms are carbon, and the white atoms are hydrogen.

Part 1

Write the formulas for the conjugate bases for the two structures. 

The conjugate base of acetic acid 

 Part 2 

Which of the following item(s) explain the differences between the Ka values. Choose one or more: 

A. The oxidation state for oxygen in trifluoroacetate is more negative than the oxidation state for oxygen in acetate. 

B. The electron-withdrawing fluorine atoms pull electron density from the oxygen in trifluoroacetate. The negative charge is more stabilized in trifluoroacetate by this effect. 

C. The negative charge is on the more electronegative fluorine atom in trifluoroacetate. 

D. The trifluoroacetate molecule has more resonance structures than the acetate molecule.

Answer 1

−CF₃ is an electron withdrawing group, by the inductive effect. So our negative charge will be slightly drawn through the bonds toward the fluorines, thus it is further delocalized and thus more stable hence it is more acidic than acetic acid