organic chemistry - Does a double bond or a triple bond have a higher priority in nomenclature?

I have this structural formula:

Should it be named pent-1-en-4-yne or pent-1-yn-4-ene?

Answer

The relevant section in the 2013 IUPAC Recommendations (Blue Book) reads:

P-31.1.1 [...] Locants as low as possible are given to multiple bonds as a set, even though this may at times give 'yne' endings lower locants than 'ene' endings. If a choice remains, preference for low locants is given to the double bonds. [...]

In this case, the two possible numbering schemes lead to the same locant set of (1,4).

However, according to the italicised portion of the quoted text, the double bond is considered to have the higher priority, and the name would correctly be pent-1-en-4-yne.

Note that the final "-e" from "-ene" is dropped if the following suffix begins with a vowel or "y," and is retained if the suffix begins with a consonant. Additionally, spaces are only used in very specific cases, like in the carboxylic acid ending "-oic acid." Otherwise, dashes are used to separate different functional groups and numbers in the name.