The suffix en for alkenes

can someone help me understand when to use the suffix en for alkenes please

if there's something in the hydrocarbon that has an alkene group (double bond between C=C) and something else? an example that comes to mind is 3-buten-1-ol (CH2=CH-CH2-CH2OH) where the alcohol group (OH) takes priority before the double bond..?

Reply 2

bl0bf1sh

Original post by bobbbobb

can someone help me understand when to use the suffix en for alkenes please

If you've got some spare time, there's a decent wikipedia page on IUPAC nomenclature (https://en.wikipedia.org/wiki/IUPAC_nomenclature_of_organic_chemistry), also https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_I_(Liu)/02%3A_Fundamental_of_Organic_Structures/2.04%3A_IUPAC_Naming_of_Organic_Compounds_with_Functional_Groups explains it nicely.
(There's also a good one on stereoisomers (including E/Z isomerism): https://en.wikipedia.org/wiki/Cahn–Ingold–Prelog_priority_rules)

If there's something (i.e. most functional groups) in the molecule that is higher up in priority than alkenes (e.g. alcohol), then the name of the molecule will end "-ol" (for the alcohol) and there will be an "en" somewhere in the rest of the name.
So HO–CH2–CH=CH–CH3 would be but-2-en-1-ol because the OH group is on carbon-1 and the alkene double bond starts on carbon-2 (between 2 and 3) – OH takes priority so "ol" is at the end of the name, and "en" goes somewhere else, and then you stick the relevant numbers in so you know what's where. :smile: