How to Compare the Acidities of Organic Molecules – Part 1

A conjugate base (cB) is what remains after an acid has donated a proton (H+) during a chemical reaction.


Acidity is pronounced if the cB is stabilized.

Resonance or delocalization of electrons (aka mesomeric (M) effect) typically happens through π─bonds in compounds with conjugation while inductive (I) effect happens through σ─bonds. Both effects may withdraw (─M, ─I effects) or donate (+M, +I effects) electrons depending on situations.

Question:

Acrylic acid should be less acidic than Acetic acid due to resonance by the vinyl group, but on the contrary, the former is more acidic. Explain.

Solution infographic:



Click/tap to enlarge the image

EN = Electronegativity

Awed by acidity❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

References:

(1)    Brown, C.; Ford, M. Higher Level Chemistry, 2nd ed.; Pearson Education: Harlow, Essex, 2014.

(2)    Ncert. Chemistry : Textbook for Class XII - Part.II; National Council Of Educational Research And Training: New Delhi.

(3)    Graham, T. W.; Fryhle, C. B.; Snyder, S. A. Organic Chemistry.; Hoboken, Nj John Wiley Et Sons, Inc, 2016.

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