Characterization of New Cumulenes C<sub>2</sub>NX<sub>2</sub> (X = O or S):  Tandem Mass Spectrometry and ab Initio Studies

Wong, Ming Wah; Wentrup, Curt; Mørkved, Eva H.; Flammang, Robert

doi:10.1021/jp960391x

Cited by 15 publications

(10 citation statements)

References 32 publications

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“…The cumulenic ion OCN + CS has recently been formed and characterized in the gas phase 12a. With 2‐methyl‐1,3‐dioxolane, this interesting acylium‐thioacylium ion reacts uniquely (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The instrument, denoted Q 1 q 2 Q 3 q 4 Q 5 , is composed of a sequential arrangement of three mass‐analyzing (Q1, Q3, Q5) and two ‘r.f.‐only’ ion‐focusing reaction quadrupoles (q2, q4). By 70 eV electron ionization (EI), appropriate precursors form the reactant acylium ions: ethoxycarbonyl isocyanate forms OCN + CO,11 benzoylacetone8 forms OCCH + CO and ethoxycarbonyl thyoisocyanate12 forms OCN + CS. When performing MS 2 ion–molecule reactions, Q1 was used to mass select the ion of interest for further reactions in q2 with a selected neutral reagent.…”

Section: Methodsmentioning

confidence: 99%

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Double transacetalization of diacylium ions

2000

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A novel gas‐phase reaction of diacylium ions of the OCX+CO type (X = N, CH) is reported: double transacetalization with cyclic acetals or ketals. The reaction is exothermic and highly efficient, and forms members of a new class of highly charged‐delocalized ions: cyclic ionic diketals. Pentaquadrupole double‐ and triple‐stage mass spectrometric (MS2 and MS3) experiments reveal the high double transacetalization reactivity of OCN+CO and OCCH+CO, whereas the synthesis of differently substituted cyclic ionic diketals is performed in MS3 experiments via sequential mono‐ and double transacetalization of OCN+CO and OCCH+CO with different acetals. With cyclic acetals, the acylium‐thioacylium ion OCN+CS reacts promptly and selectively by mono‐transacetalization at its acylium site, but the free thiacylium site of its cyclic ionic ketal is nearly unreactive by double transacetalization. Therefore, only the acylium site of OCN+CS can be efficiently protected by transacetalization. Low‐energy MS3 collision‐induced dissociation of the cyclic ionic diketals of OCN+CO and OCCH+CO sequentially frees each of the protected acylium site to form the mono‐derivatized ion, and then the fully deprotected diacylium ion. Copyright © 2000 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Double transacetalization of diacylium ions

2000

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“…For example, the development of new experimental techniques such as the neutralization-reionization (NR) procedures [1][2][3][4] made possible the identification of elusive chemical compounds, characterized by short lifetimes, as well as non-conventional compounds. In this respect the contributions of R. Flammang have been remarkable 5,6 and his work on cumulenes [7][8][9][10][11][12][13][14][15] is a paradigmatic example of his achievements in this field.…”

Section: Introductionmentioning

confidence: 99%

Is Allylphosphine a Carbon or a Phosphorus Base in the Gas Phase?

Sicilia

Mó

Yáñez

et al. 2003

Eur J Mass Spectrom (Chichester)

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The gas-phase basicity of allylphosphine (2-propenylphosphine) was measured by means of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry techniques. A complete survey of the allylphosphine-H + potential energy surface, carried out through the use of high-level G2(MP2) and B3LYP/6-311+G(3df,2p) calculations, allows us to conclude that, under low-pressure, low-energy ICR conditions, the interaction between the protonated reference base, B ref H + , and allylphosphine leads to a complex in which B ref H + attaches to the phosphorus atom of allylphosphine, where the electrostatic potential is strongly attractive. Hence, in the first step only the phosphorus protonated species should be formed. Its isomerization to yield the C β -protonated form, which is the global minimum of the potential energy surface, implies a very high activation barrier that cannot be overtaken under normal experimental ICR conditions. Therefore, the main conclusion of our study is that allylphosphine behaves as a phosphorus base in the gas phase, even though the C β -protonated structure is the most stable protonated species. We have also shown that both C β -and C γ -protonation triggers a cyclization of the system. An analysis of the bonding of the different protonated species as compared with that of the neutral system is presented.

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“…(Wong et al reported that the MS/MS/MS experiments on (C 2 ,N,S) ions in case of SNCCS and SCNCS isomers were inconclusive. 28 Another report by McGibbon et al indicates that the (C 2 ,N,S) ions derived from various precursor molecules give rise to virtually identical CA spectra. 33 ) We also found that (C 2 ,N,S) ions generated from various precursors including methylenedithiocyanate gave rise to identical CA spectra.…”

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confidence: 98%

“…14 Of the three [C 2 ,N,S 2 ] heterocumulene isomers, two of them, [S=C=C-N=S] /0 and [S=C-N=C=S] /0 , have been very well characterized by collisional activation and neutralization-reionization mass spectrometric (NRMS) [15][16][17][18][19][20][21][22][23][24][25][26] experiments. 27,28 Here we report the generation and characterization of the third isomeric species, thiocarbonylthiocyanate [S=C=S-C ---N] /0 , by the NRMS technique.…”

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confidence: 99%