Intermolecular dehydration reactions of protonated alkenol adducts

Abstract

Collisionally activated intermolecular dehydration reactions of proton-bound alkenol dimers and proton-boundalkenol-dimethyl ether adducts were examined in both a triple quadrupole mass spectrometer and a quadrupole ion trap mass spectrometer. Ion-molecule reactions of protonated dimethyl ether (DME) with allyl alcohol, Ibuten-l-01 and 4-penten-1-01 (M) produced the ions [ M + HI +, I2M + HI +, [ M + H + DMEI' and [ M + H + DME -H,O] +. Collisionally activated dissociation was used to characterize the structures of the product ions, and energy-minimized structures and heats of formation of ions were calculated by molecular mechanics and semiempirical computational methods. The loosely bound [ M + H + DMEl' ions rearrange and dissociate by an intermolecular dehydration reaction to form [ M + H + DME -H,OI + ions, with methylated ether stuctures. These [ M + H + DME -H,O] + ions dissociate predominantly via direct cleavage of the ether linkage. Comparisons of the bimolecular and dissociation reactions of the alkenols were made with those of simple alcohols, diols and alkenes to demonstrate that the presence of the carbon-carbon double bond specifically assists in many of the observed processes.

Comparing differentiation of xylene isomers by electronic ionization, chemical ionization and self‐ion/molecule reactions and the first observation of methyne addition ions for xylene isomers in self‐ion/molecule reactions for non‐nitrogenated compounds

“…The base peaks in the DME CI mass spectra from the external source ITMS for these three isomers are all at m/z 119 ([M+13] + ). These [M+13] + ions can also be assigned as [M+CH] + since they are produced from the dissociations of [M+45] + complexes via elimination of one molecule of formaldehyde, according to Brodbelt's studies 12–31. In addition, the DME CI spectra obtained in the internal source ITMS (refer to Fig.…”

“…Brodbelt et al . have examined methyne addition reactions by dimethyl ether (DME) CI in a number of systems using an ITMS and have characterized the reaction product ions using collisionally activated dissociation (CAD) and isotopic labeling 12–31. Isomer discrimination for o ‐, m ‐ and p ‐xylene using metal ions has been described by Bjarnason et al 32,33.…”

Substituent Effect on Fragmentations and Ion-Molecule Reactions of Ionized Alkyn Alcohols

“…Molecules with specific functional groups undergo typical fragmentation patterns, which can be used to obtain structural information. [6][7][8][9][10][11][12][13][14][15] The typical example is the formation of prominent ions of general formula, C n H 2n O +• , observed in the mass spectra of alcohols and ethers. 9,10 The relative abundances of fragment ions and their fragmentation patterns depend on the functional groups of ionized molecule.…”

Probing reactive sites for ion‐molecule reactions of anthraquinones with dimethyl ether using an external source ion trap tandem mass spectrometer and computational chemistry

“…Therefore, CIMS of DME was examined herein with several anthraquinones in an external source ion trap mass spectrometer. Two kinds of reagent ions with chemical reactivity can be produced in the ion trap: the CH 3 O=CH 2 + ( m/z 45) and CH 3 OHCH 3 + ( m/z 47) ions 1–21. These ions can form various ion‐molecular products, including [M + H] + , [M + 13] + , [M + 15] + , [M + 45] + and [M + 47] + ions, after reacting with various organic compounds, depending on the structures of those compounds 1–21.…”

“…Two kinds of reagent ions with chemical reactivity can be produced in the ion trap: the CH 3 O=CH 2 + ( m/z 45) and CH 3 OHCH 3 + ( m/z 47) ions 1–21. These ions can form various ion‐molecular products, including [M + H] + , [M + 13] + , [M + 15] + , [M + 45] + and [M + 47] + ions, after reacting with various organic compounds, depending on the structures of those compounds 1–21. When DME reacts with electron‐releasing substituents of the compounds it produces [M + 13] + adducts via methylene addition, and with electron‐withdrawing substituents it forms [M + 15] + adducts via methyl addition reactions 3.…”