Malonic acid has two acidic protons:

The pKa of the first proton (pK₁) is measured to be 2.8, while the pK_a of the second proton (pK₂) is measured to be 5.7.

(a) Explain why the first proton is more acidic than acetic acid (pK_a = 4.76).

(b) Explain why the second proton is less acidic than acetic acid.

(c) Draw the form of malonic acid that is expected to predominate at physiological pH.

(d) For succinic acid (HO₂CCH₂CH₂CO₂H), pK₁ = 4.2 (which is higher than pK₁ for malonic acid) and pK₂ = 5.6 (which is lower than pK₂ for malonic acid). In other words, the difference between pK₁ and pK₂ is not as large for succinic acid as it is for malonic acid. Explain this observation.

Transcribed Image Text:

НО ОН Malonic acid