# Why aren't primidone's lactam groups acidic?

I understand that 5,5-disubstituated derivates of barbituric acid only show lactam-lactim tautomerism opposed to the lactim-lactam and keto-enol tautomerism of barbituric acid, hence the 5-mono and 5,5-disubstituated derivates are less acidic.

Primidone differs from phenobarbital in a C2 oxo group, so it's lactam groups are not acidic and it is not soluble even in alkali-bases. Why aren't the lactam groups acidic exactly? The oxo groups should still present quite a bit of electron withdrawing effect, shouldn't they?

• Amides are not acidic and that is all these are – Waylander Dec 11 '18 at 21:27
• There's a carbonyl group missing (i.e., a barbituate is made from urea and this is made from diaminomethane). Compare the pKas of a ketone versus a $\beta-$keto ketone. – Zhe Dec 11 '18 at 21:27