When a heterocycle acts as a substituent, it is named following the rules that we already know, and then the final vowel of the name is deleted, and it is replaced by “n-il”, where n is the locator of the atom of the heterocycle that is attached to the rest of the molecule. If there is a choice, the lowest possible value is given.

[1] 1,3-dioxan-4-yl

[2] 4-hydroxy-1H-pyrrol-2-yl

[3] 3-methanoylphosphet-2-yl

[4] pyridin-2-yl (2-pyridyl)

[5] 2-furyl

[6] 2-thienyl