What is the systematic name for formaldehyde?

Formaldehyde is systematically named as methanal in the IUPAC nomenclature. Methanal is a simple aldehyde with the chemical formula CH₂O. This makes methanal the correct systematic name for formaldehyde.

In the context of the other options, ethyl alcohol refers to ethanol, which is a completely different compound with the formula C₂H₅OH. Propylene glycol is a type of alcohol, known as propane-1,2-diol, which consists of three carbon atoms and is used in food and pharmaceuticals. Phenol, on the other hand, is an aromatic compound with a hydroxyl group (-OH) attached to a benzene ring, represented as C₆H₅OH. None of these compounds share the same structure or classification as formaldehyde, which is why methanol, specifically methanal, is the correct answer.