Phenyl propyl ether ions, decomposition

The rates of losses of C3(H, D)6 from the molecular ions of phenyl-1-propyl-1, l-d2, phenyl-l-propyl-2, 2-dj and phenyl-1-propyl-3, 3, 3-d3 ether showed that hydrogen randomisation did not precede decomposition in the time range from 10ps to 10 ps [86], The losses were initiated by hydrogen transfers from C-l, C-2 or C-3 of the propyl chain to the oxygen atom and, on the basis of the kinetics, it was suggested that the densities of states of the 4-, 5- and 6-membered cyclic transition states were similar. 

Another mass spectrometric experiment from this laboratory (P.S. Mayer and T.H. Morton, unpublished results) confirms the pathway for decomposition of the covalent oxonium ion shown in Scheme 13 for R=C2H5. Chemical ionization of -propyl phenyl ether with methane reagent gas at... 

Various forms of radiation have been used to produce ions in sufficient quantitites to yield neutral products for subsequent analysis. In principle, it should be possible to use intense beams of UV below ionization threshold for this purpose. To date, however, efforts to collect neutrals from resonant multiphoton ionization (REMPI) have not succeeded. In one experiment, 1 mbar of gaseous -propyl phenyl ether was irradiated at room temperature with a 0.1 W beam of 266 nm ultraviolet (from an 800 Hz laser that gives 8 n pulses) concurrent with a 0.5 W beam at 532 nm. The beams were intense enough not only to ionize the ether in the mass spectrometer, but also to excite it so that it expels propene. After several hours of irradiation < 10% of the starting material remained. Production of carbon monoxide and acetylene (decomposition products of the phenoxy group) could be detected by infrared absorption spectroscopy, but the yield of neutral propene (as measured by NMR spectroscopy) was infinitesimal. 

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