A question asks whether C4 in 3-butyne-2-one can act as a nucleophile, electrophile, or acid (it can be more than one). The answer is that it can be both electrophilic and acidic.
The acidity makes sense, it's a terminal alkyne, sp orbitals stabilize the negative charge on the conjugate base.
The electrophilicity I don't quite understand. I can write a resonance structure that puts some positive charge on C4, analogous to an alpha-beta unsaturated carbonyl compound, but it looks bizarre. I know ketenes are a real thing, but is this resonance structure a real contributor? Is there another explanation for the electrophilicity?
Google searches for alkynone, ynones, etc. yielded mostly peer-reviewed literature that's above my understanding.