Which of the following carboxylic acids is expected to have the highest pKa?Select answer from the options belowfluoroacetic aciddifluoroacetic acidtrifluoroacetic acidacetic acid
Question
Which of the following carboxylic acids is expected to have the highest pKa?Select answer from the options belowfluoroacetic aciddifluoroacetic acidtrifluoroacetic acidacetic acid
Solution
The pKa of a carboxylic acid is a measure of its acidity. The lower the pKa, the stronger the acid.
Fluorine atoms are highly electronegative, meaning they pull electron density away from the acidic hydrogen atom, making it easier for the hydrogen to be donated as a proton (H+). This increases the acidity of the carboxylic acid.
Therefore, the more fluorine atoms a carboxylic acid has, the stronger it is, and the lower its pKa.
So, the carboxylic acid expected to have the highest pKa (and therefore the weakest acid) from the options given is acetic acid, which has no fluorine atoms.
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