Chemistry - GOC Question with Solution | TestHub
Croconic acid is a diprotic acid with both protons more acidic than acetic acid. After losing both protons, all the C-C bonds of the ring are equal in length, and so are all the C-O bonds.
Which statement best explains these observations?
Options:
Answer:
Solution:
Croconic acid is 4,5-dihydroxycyclopent-4-ene-1,2,3-trione. Loss of the first proton gives an anion stabilised by resonance and by a strong intramolecular O-H...O hydrogen bond. Loss of the second gives a dianion with five equivalent resonance structures : the two negative charges are shared by all five oxygens, all C-C bonds are equal and all C-O bonds are equal - a quasi-aromatic, highly stabilised system. These very stable conjugate bases explain why both protons are so acidic and why the bond lengths average out.
