The Mass Spectra of Pyridyl Aryl Ethers

Abstract

The mass spectra of pyridyl phenyl ether(I)and three isomeric pyridyl tolyl ethers(II, III, and IV)are recorded and their fragmentations are discussed. In the spectrum of pyridyl phenyl ether(I)(Fig. 1), the formation of the M-1 peak at m/e 170 is accounted for by the fragmentation shown in Scheme 1. On the other hand, the accurate mass measurement indicated that the ion at m/e 143 corresponds to M-CO, and therefore, the ion would be formed by a mechanism depicted in Scheme 2. While the spectral features of p-and m-tolyl ethers(II and III)(Fig. 2 and 3)are essentially the same as those of I, the spectrum of o-tolyl ether(IV)(Fig. 4)exhibited a different fragmentation pattern. Thus, a very intense M-17 peak appeared but the M-CO peak was absent. A meta-stable ion peak at m/e 152.6 suggests a one step formation of the M-17(M-OH)ion from the molecular ion, and a probable pathway is shown in Scheme 3. The formation of both M-1 and M-15 ions from IV justifies the mechanism in Scheme 1.