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5-28-14: The "mono-" and "di-" hydrate both have the same number of oxygen atoms; why is the version with the ring considered a "dihydrate"?

This compound should be called ortho-phthaldialdehyde because it has two aldehyde functional groups. The name "phthalaldehyde" implies only one functional group, which is wrong, though often seen (incorrectly) in the environmental literature. Optimum functionality (of the Wikipedia entry) would be obtained by listing the term "phthalaldehyde" as a likely synonym and having searches for either term return an "ortho-phthaldialdehyde" entry198.137.20.95 (talk) 14:31, 8 June 2015 (UTC)[reply]

Common names for organic chemicals can be inconsistent and confusing (the reason that systematic nomenclature was developed). For a common name such as "phthalaldehyde" there is no reason to expect that a chemical structure could be unambiguously derived from the name. "Phthalaldehyde" and "phthaldialdehyde" are both synonyms for this compound. "Phthalaldehyde" seems to be the more commonly used one; therefore, per WP:COMMONNAME, it should remain the Wikipedia title. ChemNerd (talk) 20:03, 8 June 2015 (UTC)[reply]

​ Agreed, “o-phthaldialdehyde” would be wrong hypercorrection of a trivial name. In addition, "phthalaldehyde" is not just a trivial name, it's retained IUPAC name in the recent org. chem. nomenclature (2013), along with the preferred one, benzene-1,2-dicarbaldehyde. —Mykhal (talk) 07:50, 26 September 2020 (UTC)[reply]

Wikipedia editors might not fancy the nomenclature, but the real researchers at the front lines, who actually do the work, use ortho or o-. Check out the Org Syn and Chem Rev titles. I defer to those scholars. Just sayin'.--Smokefoot (talk) 12:28, 26 September 2020 (UTC)[reply]

​ If you pardon me using Google scholar quickly for now, searching for "phthalic", and limiting the search say from 2000, no title has that obsolete (o)rtho, in several first result pages. Just saying (& pinging). Regards, —Mykhal (talk) 13:28, 26 September 2020 (UTC)[reply]

Check out ref 2 and 5.--Smokefoot (talk) 13:38, 26 September 2020 (UTC)[reply]