Mass spectra of important heterocyclic compounds: Cycloalkane fused pyrimidines

The electron impact mass spectra of several new cycloalkane-substituted pyr imidines are reported. The cleavage of the cycloalkanepyrimidines depends s trongly on the alkyl ring size and on the substituents attached to this rin g. The pyrimidines with fused small rings (cyclobutapyrimidines) undergo co nsecutive elimination of two nitrile molecules affording cyclobutadiene. Ho wever, for the pyrimidines with rings larger than cyclobutane, the main fra gmentation observed involves ring opening with loss of alkyl radicals, The substituents with strong electronic effects attached to the alkyl ring prom ote a different cleavage mechanism with elimination of these groups. Copyri ght (C) 1999 John Wiley & Sons, Ltd.