Pirimidina: Perbedaan antara revisi

Menurut klasifikasi Albert<ref name="Albert1968p56">{{cite book|author=Albert, Adrien|title=Heterocyclic Chemistry, an Introduction|publisher=Athlone Press|location=London|year=1968|pages=56–62[https://archive.org/details/heterocyclicchem0000albe/page/56 56]–62|isbn=|url=https://archive.org/details/heterocyclicchem0000albe|accessdate=}}</ref> heterosiklik enam karbon dapat dikatakan "π-deficient" ("kekurangan π"). Substitusi oleh gugus elektronegatif atau atom nitrogen tambahan dalam cincin secara signifikan meningkatkan "kekurangan π" itu. Efek ini juga menurunkan kadar basa.<ref name="Albert1968p437">{{cite book|author=Albert, Adrien|title=Heterocyclic Chemistry, an Introduction|publisher=Athlone Press|location=London|year=1968|pages=437–439[https://archive.org/details/heterocyclicchem0000albe/page/437 437]–439|isbn=|url=https://archive.org/details/heterocyclicchem0000albe|accessdate=}}</ref>