Fragmentation of 1- and 3-methoxypropene ions another part of the C₄H₈O^+•potential energy surface

Abstract

The fragmentation mechanisms of metastable ionized 1- and 3-methoxypropene have been examined in detail by using ionization and appearance energy measurements, metastable ion and collisional activation mass spectra, and a variety of isotopically labeled molecules. These metastable C4H8O(+•) ions fragment by loss of H; CH3, and H2CO, and the experimental observations allowed the construction of the potential energy diagram which describes their interconversion and the participation of four other distonic and carbene C4H8O(+•) ions. It was found that these two methyl alkenyl ether ions had no common reaction channel with either the 2-methoxy isomer or with any of the alcohol, keto, or enol C4H8O(n+•) isomers which previously have been extensively studied.

Dissociation Reactions of Low-Energy Pentenyl Methyl Ether Radical Cations C5H9OCH3•+

“…Studies of metastable ionised allyl methyl ether 34,35 and the four isomeric butenyl methyl ethers 36 shed further light on the chemistry of these radical cations. From experiments with 2 H-labelled analogues of C 3 H 5 OCH 3…”

Photodissociation kinetics of the isobutanal radical cation: a combined experimental and theoretical study

“…In fact, to reveal the reaction mechanisms for the unimolecular dissociation of 1, it is necessary to thoroughly explore the potential energy surface for all possible fragmentation channels. [13][14][15] In this study, therefore, we theoretically examine the photodissociation process of 1 with the competitive reaction product channels aer onephoton excitation from the cationic ground state prepared by a (2 + 1) REMPI scheme. The quantum chemical calculation alongside experimental observations will further provide insights to the photodissociation dynamics of 1 in the gas phase.…”

The mechanism of alkyl radical elimination from ionised γγ-disubstituted alkenyl methyl ethers

“…Reference spectra of ions of known structure are also given in these Tables. The structures of these ions (13)(14)(15)(16)(17)(18), which were generated by ionisation and alkyl radical loss from secondary and tertiary alkenyl methyl ethers (8)(9)(10)(11)(12) , as shown by their similar CID spectra, which are distinct from that of the isomeric ion, 18, Table 3.…”

“…16,17 Further investigation of higher homologues showed that loss of a methyl radical from ionised allylic alkenyl methyl ethers containing β-and γ-methyl substituents was consistent with a general mechanism involving formation and γ-cleavage of an ionised enol ether. Thus, 14 These results were inconsistent with expulsion of a β-alkyl group by β-cleavage of the relevant DI.…”

“…14 Later CID studies refuted the suggestion that allylic rearrangement precedes C 16 In view of these developments, a fuller investigation of the mechanism of alkyl radical elimination from ionised allylic alkenyl methyl ethers with two different γ-alkyl substituents is timely. It is particularly important to consider the possibility that methyl and larger alkyl groups may be lost via different mechanisms because earlier work in these and related systems has revealed that a methyl radical is lost much less readily than an ethyl or higher homologous radical.…”