Ion cyclotron resonance study of ion-molecule reactions in methanol

Abstract

A branching chain mechanism is observed in the methanol ion-molecule system which involves complex formation and collisional stabilization of complex ions. A protonated methanol ion CH3OH2+ is the main product of the reactions of primary ions present. Collisions of this ion with methanol lead to complex ions (CH3OH)"H + at high pressure. At lower pressure, in the absence of collisional stabilization, a protonated dimethyl ether ion (CH3)2OH+ is produced. The structure of the (CH3)2OH+ ion was verified, and the effects of mode of formation and internal excitation on ionic reactivity were observed. The lifetime of the (CH3OH)2H+ and (CH3)2OH+ ions were estimated to be 2 X KM and 1 X KM sec, respectively. A comparison of ion cyclotron resonance with sector mass spectrometry is made, and the unusual and useful features of cyclotron resonance are discussed. Among the important advantages of ion cyclotron resonance spectrometry are long ion path length and ion lifetimes, and the ease with which path lengths and residence times can be varied. Also important is the ability to study reaction sequences of high-order ions using double-resonance techniques.A program has been developed in this laboratory using ion cyclotron resonance techniques to study gasphase ion-molecule reactions. This paper is concerned with the properties of ion cyclotron resonance (icr) as they pertain to such reactions in methanol. Previous reports of ion-molecule reactions in methanol have appeared in the literature and provide an excellent basis for comparing icr with other techniques used in the study of ion-molecule chemistry. Since this is the first report of our work in this field, a discussion of equipment and experimental techniques is included.

APPI-MS: Effects of mobile phases and VUV lamps on the detection of PAH compounds

“…The reaction of methanol to [CH 3 ] 2 OH ϩ has been previously observed as the dominant fragmentation product generated in a potential field of 70 V and a 50 m path at 10 Ϫ5 torr [43]. In this earlier study, the identity of this species has been confirmed as the protonated dimethyl ether ion, hypothesized to be a product of the protonated methanol dimer.…”

Ion-neutral reactions in the ion source of a mixture of CO2/CH3OH, CO2/C2H5OH, and CO2/2-C3H7OH by packed capillary supercritical fluid chromatography-mass spectrometry (SFC-MS)

“…We therefore conclude that the structure of the ion at m/z 47 in the mass spectra of methanol is protonated dimethyl ether. This agrees with the results reported by Henis in 1968 [21].…”

An Approach to Stereochemical Analysis by Ion Cyclotron Resonance. Distinguishing exo- and endo-Norborneol

“…techniques employed here, except for ion ejection double resonance (9), were those described by Henis (19). Our ionizing current was 0.05 PA; total ion current, < 10 PA; typical cell voltages were: trap, 0.48 V; analyzer, split (20) From the optical absorption spectrum observed by a sub-nanosecond pulse radiolysis method it is concluded that irradiated pure liquid formamide (dielectric constant = 109) does not yield solvated electrons with lifetimes > lo-'' s. In formamide-water mixtures the hydrated electron is formed in low yield and the position of the absorption band of e,,-is not altered by changing the composition.…”