# What is the degree of unsaturation of oxalate anion? [closed]

I was practicing a DPP for JEE Mains & Advanced exam. There is a question in organic chemistry, a reaction sequence was given whose answer was oxalate anion. But the next question was what is the degree of unsaturation of the compound formed in the previous question . I simply did it 2 because there are 2 C=O bond but the answer was given 3. Please help me in making out, why it is so.

• Please be more specific how you have calculated the degree of unsaturation. in that way we can see your basis for the problem. – Martin - マーチン May 8 '20 at 17:16

• What is a pair of hydrogen atoms in this context? You can't really add three pairs of hydrogen atoms; to get the (theoretical) saturated compound $\ce{C2H6O4}$ two of the hydrogn atoms must be cations. That shouldn't count since those do not bring in electrons. Seems more realistic to require maintaining the charge, so the saturated species would be $\ce{C2H4O4^{2-}}$ and the degree of saturation would be two. – Oscar Lanzi May 11 '20 at 13:07