Decompositions of ionized isopropyl methyl ether: complex-mediated and direct processes in unimolecular dissociations

Evidence for ion‐neutral complex‐mediated reactions well above the threshold for dissociation of the complex

“…6) and a critical energy for CH,OCH-CHt'-C,H,O+ of 10.56 eV." This value is higher than would be predicted by values in Table 2, as the fragmentation has a reverse critical energy.…”

H-transfer rates in ion-neutral complexes versus those in intact aliphatic ions

“…Simple dissociation typically quickly suppresses alkane eliminations with increasing internal energy. 10,11,14,33 It also implies that complex-mediated H-transfer becomes much faster than intramolecular rearrangement at energies further above threshold than those accessed in the alkane eliminations. This suggests that at those energies there is relatively little relative movement of the partners prior to H-transfer.…”

“…The adiabatic ionization energy could be lower by 0.05 eV owing to low ion count and structure in the curve near threshold. A range of predicted values is given for m/z 70 because, as from ionized n-butanol, 30 water elimination from 2-pentanol probably gives a mixture of C 5 H 10 Cž products. AE C 5 H 10 Cž , 9.90 eV, is lower than expected for formation of cyclopentane (10.45 eV) or methylcyclobutane (10.31 eV) ions, indicating some formation of a more stable C 5 H 10…”

“…Substantial experimental 10,31,32 and theoretical 17 information demonstrates that alkane eliminations from ionized ethers, including 2-methoxypentane, 32 are complexmediated. Differential PIE curves were obtained (Fig.…”

Unimolecular metastable decompositions of 1,1,1‐trifluoroisopropyl methyl ether [CF3(CH3)CHOCH3] upon electron ionization

“…Unimolecular decompositions of ionized isopropyl methyl ether [(CH 3 ) 2 CH‐OCH 3 , MW 74] have been studied extensively 1–10. Many of these studies were addressed to the losses of CH 3 and CH 4 from the molecular ion 3–10. The kinetic energy release (KER) accompanying the loss of CH 4 from the molecular ion was also measured4, 10 to clarify the fragmentation mechanism.…”