Mass neutralization-reionization

Sulfurous acid has never been isolated as a pure compound, although it has recently been detected in the gas phase by neutralization reionization mass spectrometry (NRMS) following the facile dissociative ionization (70 eV) of either diethyl sulfite or ethanesulfonic acid " ... 

The oxide S3O has been identified only in the gas-phase by means of neutralization reionization mass spectrometry [58]. The precursor ion SsO was generated by the following sequence of reactions ... 

Turecek F (2003) Transient Intermediates of Chemical Reactions by Neutralization-Reionization Mass Spectrometry. 225 75-127... 

Turecek F (2003) Transient Intermediates of Chemical Reactions by Neutralization-Reionization Mass Spectrometry. 225 75-127 Ublacker GA.see Maul JJ (1999) 206 79-105 Uemura S,see Nishibayashi Y (2000) 208 201-233 Uemura S, see Nishibayashi Y (2000) 208 235-255... 

Neutralization-reionization mass spectrometry (NRMS) is used to generate neutral species in the gas phase that are difficult to prepare or identify by other methods. During NRMS, both cations and anions may be neutralized, generally by collision, and then reionized to confirm the stability of the neutral species. Two reviews, with particular examples in coordination chemistry, provide good information on this method and offer many examples (76,77). A good example is AuF, which has been predicted to be stable. The [AuF]+ and AuF complexes were both neutralized and reionized and the AuF species was obtained in each recovery signal. It was postulated that the elusiveness of this molecule in the condensed phases was not due to instability but rather to inter-molecular reactions (78). 

Although no En cluster molecules with n > 4 are known in the condensed phase, it has been shown [27] that neutral P6 can be generated in the gas phase by neutralization-reionization mass spectrometry with cp 2 6 as a precursor [cp = C5(CH3)5] [28]. Since the cp 2P6 precursor molecule already has a hetero-benzvalene P6 skeleton, it was inferred that the neutral P6 molecule should have the benzvalene structure as shown in Figure 2.6-5. This is in agreement with a multitude of quantum chemical calculations [8, 11, 27, 29-32]. Note that the handle of the basket of P6 includes two dicoordinate P atoms linked by a P=P double bond (cf. R-P=P-R 203 pm [33]). 

The technique of neutralization/reionization mass spectrometry (NRMS), originally introduced by McLafferty, invokes the formation of fast neutrals from a preselected ion beam, any residual ions being deflected, followed by collision-induced reionization of the neutrals and a subsequent mass spectrometric analysis16-21. 

FIGURE 4. Neutralization/reionization mass spectrum of [M — C2H4]+ ion of 1-nitropropane15... 

The sites of protonation of aromatic compounds, including the possible three mono fluoronitrobenzenes, have been studied by neutralization-reionization mass spectrometry (NRMS)22. The NRMS experiments on the MD+ species generated by D2 chemical ionization clearly indicated that the D+ attachment takes place to the nitro group rather than to the aromatic ring, as evidenced by the abundant losses of OD and DNO2 (NO + OD )22. 

Schwarz and coworkers115 used 1,2,3-butatriene, along with 1,3-butadiyne, as a precursor for the generation of neutral 1,2,3-butatrienylidene in a neutralization/reionization mass spectrometric sequence (C4H4 - C4H2- - C4H2 - C4H2+ ). 

CH4/O2 and CF4 as the reactant gases and observed the formation of [M — 4 H] ions in the Cl plasma (Scheme 13)166. Thus, repeated deprotonation and electron transfer processes appear to offer an efficient access to more highly unsaturated and/or ring condensed trimethylenemethane radical anions. The [M — 4 H]- ion is considered identical to the molecular radical anion (42) of acepentalene (43), which was generated as a short-lived species from the former by neutralization-reionization mass spectrometry167. Efforts to apply Squires methodology to triquinacene 41 and the tribenzotriquinacenes 44 have been made168. 

Yates, B.F. Bouma, W.J. Radom, L. Detection of the Prototype Phosphonium (CH2PH3), Sulfonium (CH2SH2), and Chloronium (CH2CIH) Ylides by Neutralization-Reionization Mass Spectrometry a Theoretical Prediction. J. Am. Chem. Soc. 1984,106, 5805-5808. 

The dithiazolidine (44) <77CCC2672> and dioxazolidine (45) <69JOC2269> are ring systems in which the fragmentation pattern, has been used to affirm the structures. In the latter case the absence of CO2 primary loss allows differentiation from the isomeric oxadiazolidone (46) co-product. A new technique, e.g. the neutralization-reionization mass spectrometry (NRMS) in combination with... 

The adduct free radical formed in reaction (4) [which has been detected directly using neutralization/reionization mass spectrometry (Egsgaard et al., 1988)] subsequently reacts with 02 ... 

The prototypical ylide H3P=CH2 has been detected by neutralization-reionization mass spectrometry17 as predicted by calculation18, but no data are yet available for it. 

The reactivities of phosphonium ylides and ylidones have been predicted by ab initio molecular orbital calculations22 and these results have been correlated with neutralization-reionization mass spectrometry. 

Azacyclohexatriene-2-ylidene (3), the 2-isomer of pyridine, has been generated by one-electron oxidation of the corresponding radical cation in neutralization-reionization mass spectrometry.17 It was determined by ab initio H-F calculations that the charge polarization of the radical fonned by H-abstraction from pyrazine can be... 

Schwarz and coworkers have used the technique of neutralization-reionization mass spectrometry (NRMS) to structurally characterize numerous elusive silicon-containing molecules of interstellar interest342. The identification of HNSi was supported by ab initio calculations. The radical ion [HNSi] + was produced from N2 and SiH3I in the chemical ionization source of the mass spectrometer. 

TABLE 2. Oxygen- and nitrogen-containing neutral molecules with silicon as studied by neutralization-reionization mass spectrometry... 

Evidence for the formation of 34 (R = Ph) was provided by neutralization reionization mass spectrometry and more directly by the matrix isolation and spectroscopic investigations on 34 (R = Ph) in an argon matrix at 12 K. The UV spectrum of 34 (R = Ph) exhibits characteristic bands at X = 364, 386, 404, 420, 440, 470 and 502 nm, resembling those of the electronic spectrum of anthracene, but with the expected bathochromic shifts. If one irradiates into the maximum at X = 502 nm, all bands shown in the spectrum disappear completely within 5 minutes. The vanishing of these characteristic bands can again be explained by the photoisomerization of silaanthracene 34 (R = Ph) to the corresponding Dewar valence isomer. 

A particle whose connectivities are indicative of structure 104 has earlier been detected by neutralization-reionization mass spectrometry134. Furthermore, 1-silacyclopropenylidene (104) was recently identified by microwave spectroscopy135. 1-Silacyclopropenylidene (104) (kmax = 286 nm136 a delocalized three-center jr-bond orbital128) generated from 102 and matrix-isolated is transformed into ethynylsilylene... 

In neutralization-reionization mass spectrometric experiments on CH2Si+ formed by electron-impact dissociative ionization of ClCH2SiH3, Srinivas, Stilzle and Schwarz found evidence for the formation of a viable neutral molecule whose fragmentation pattern and collisional activation mass spectrum were in accord with a H2C=Si structure422. These authors suggested that their experiments supported electron-capture by CH2Si+" as a mechanism for the formation of H2C=Si in interstellar space. Various models have predicted that H2C=Si is one of the most abundant forms of silicon in dense interstellar clouds423. 

The last seven years have also witnessed important developments in the field of thiocarbonyl chemistry. Synthetic and reactivity studies have maintained their steady growth. New or improved experimental methods have been applied to the study of the physicochemical properties of these compounds as well as to the generation and observation of important fleeting species. In particular, flash vacuum thermolysis (FVT or FVP)20 and neutralization-reionization mass spectrometry21-22. 

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