Heterocyclic studies—XXIV: Mass spectra of some pteridin‐4(3H)‐ones and 3‐methoxypteridin‐4(3H)‐ones

Abstract

AbstractMass spectra of pteridin‐4(3H)‐one and all its mono‐, di‐ and tri‐C‐methyl derivatives are recorded. Spectra of 3‐methoxypteridin‐4(3H)‐one and four of its mono‐ and dimethyl derivatives are also recorded.Pteridin‐4(3H)‐one fragments mainly by loss of CO and HCN in either order. Methyl substitution in the pyrazine ring leads to that ring fragmenting in preference to the oxygen bearing pyrimidine ring. Elucidation of fragmentation pathways was facilitated by changes in peak positions with changing methyl substitution patterns.3‐Methoxypteridin‐4(3H)‐ones fragment mainly through initial loss of CH2O, but the ions so produced break down differently from isomeric molecular ions of pteridin‐4(3H)‐ones. Several fragmentation pathways are discussed.