Effect of reaction exothermicity on the proton transfer chemical ionization mass spectra of isomeric C<sub>5</sub> and C<sub>6</sub> alkanols

Herman, Jan A.; Harrison, Alex G.

doi:10.1139/v81-307

Cited by 23 publications

(12 citation statements)

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“…These values are in particular higher than the PA/GB of N 2 , 118.0/111.0 kcal mol −1 , and comparable, within combined uncertainties, with the PA/GB of CO 2 , 129.2/123.3 kcal mol −1 . Ionized mixtures of H 2 and N 2 produce HN 2 + according to well‐established ion/molecule reactions 44. We therefore ionized a ternary mixture of H 2 , N 2 and GeF 4 (approximate ratio: 10:1:1) and could actually detect, at delay times of ca 10 m s , an intense GeF 4 H + signal arising from the proton transfer from N 2 H + to GeF 4 (experiments performed with D 2 /N 2 /GeF 4 mixtures confirmed the occurrence of D + transfer from N 2 D + to GeF 4 ): …”

Section: Resultsmentioning

confidence: 99%

Gas‐phase chemistry of ionized and protonated GeF₄: a joint experimental and theoretical study

et al. 2011

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The gas-phase ion chemistry of GeF(4) and of its mixtures with water, ammonia and hydrocarbons was investigated by ion trap mass spectrometry (ITMS) and ab initio calculations. Under ITMS conditions, the only fragment detected from ionized GeF(4) is GeF(3)(+). This cation is a strong Lewis acid, able to react with H(2)O, NH(3) and the unsaturated C(2)H(2), C(2)H(4) and C(6)H(6) by addition-HF elimination reactions to form F(2)Ge(XH)(+), FGe(XH)(2)(+), Ge(XH)(3)(+) (X = OH or NH(2)), F(2)GeC(2)H(+), F(2)GeC(2)H(3)(+) and F(2)GeC(6)H(5)(+). The structure, stability and thermochemistry of these products and the mechanistic aspects of the exemplary reactions of GeF(3)(+) with H(2)O, NH(3) and C(6)H(6) were investigated by MP2 and coupled cluster calculations. The experimental proton affinity (PA) and gas basicity (GB) of GeF(4) were estimated as 121.5 ± 6.0 and 117.1 ± 6.0 kcal mol(-1), respectively, and GeF(4)H(+) was theoretically characterized as an ion-dipole complex between GeF(3)(+) and HF. Consistently, it reacts with simple inorganic and organic molecules to form GeF(3)(+)-L complexes (L = H(2)O, NH(3), C(2)H(2), C(2)H(4), C(6)H(6), CO(2), SO(2) and GeF(4)). The theoretical investigation of the stability of these ions with respect to GeF(3)(+) and L disclosed nearly linear correlations between their dissociation enthalpies and free energies and the PA and GB of L. Comparing the behavior of GeF(3)(+) with the previously investigated CF(3)(+) and SiF(3)(+) revealed a periodically reversed order of reactivity CF(3)(+) < GeF(3)(+) < SiF(3)(+). This parallels the order of the Lewis acidities of the three cations.

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Section: Resultsmentioning

confidence: 99%

Gas‐phase chemistry of ionized and protonated GeF₄: a joint experimental and theoretical study

et al. 2011

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“…Reagent gas pressures were not measured directly but were estimated to be 0.2 to 0.3 Torr (I Torr = 133.3 Pa). The H3+ and D3+ reactant ions were produced by electron impact ionization of H, and Dz, respectively, at high pressure, while the N2H' and HCO+ reagent ions were prepared by electron impact ionization of the appropriate gas X (10%) in Hz as described previously (7,14). Unimoledular (metastable) fragmentation reactions of the CsH, ,O' ions and de~terated analogues (formed by CH, or CD4 chemical ionization) were recorded for fragmentation reactions occurring in the second drift region (between the magnetic and electric sectors) of a ZAB-2F mass spectrometer (University of Ottawa) using the MIKES (mass analyzed ion kinetic energy spectroscopy) technique.…”

Section: Methodsmentioning

confidence: 99%

Structure and fragmentation of C₅H₁₁O⁺ ions formed by chemical ionization

Headley¹,

Harrison²

1985

Can. J. Chem.

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. J . Chem. 63, 609 (1985). The proton transfer chemical ionization mass spectra of eleven C5HI,,0 isomers have been obtained using H3+, NZH+, HCO', and D3' as reagent ions. The chemical ionization mass spectra in combination with isotopic labelling and metastable ion studies have made it possible to elucidate the major fragmentation reaction channels of the C5H,,0' ions formed and their dependence on precursor structure. From collision induced dissociation studies nine stable distinct C5H Introduction The C,,H2,, i. ,O' ions are abundant fragment ions in the electron impact mass spectra of aliphatic alcohols and ethers (1) and, because of their widespread occurrence, have received extensive study with respect to their thermochemistry, structures, and unimolecular fragmentation reactions. The thermochemistry of the lower members of the series (up to C,) is well established as a result of the elegant work of Lossing (2). The structures and low energy (metastable) unimolecular fragmentation reactions of the C2H50t, C3H70i, and C4H,0t ions formed by electron impact have been studied exhaustiv~ly by many groups and are now well understood (for a review and summary of these studies see ref.3). Indeed, the study of these systems played a large role in the development of the potential energy profile approach (4-6) to the interpretation of the low energy unimolecular chemistry of isolated gaseous organic ions. The C,,H2,,, '0' ions also can be prepared by proton transfer chemical ionization of carbonyl compounds and cyclic ethers and, recently, the chemistry of the C3H70t ions (7,8) and C4H90t ions (9) formed by proton transfer chemical ionization have been studied in detail and interpreted in terms of the potential energy profiles established from the earlier EI studies. In this chemical ionization approach a number of structures, such as protonated cyclic ethers inaccessible by electron impact methods, become available for study.In contrast to the extensive studies of the lower members of the series, the higher members of the C,,H,,,, '0' series have received much less attention. McLafferty and Sakai (10) have reported the collision-induced dissociation (CID) mass spectra of a few C 5 H l 1 0 t ions, while Zahorszky (1 1) has surveyed briefly the unimolecular ion chemistry of higher members of the series. The most extensive study has been that of Audier et al. (12) of the C5HIIOt ions of nominal structures 1 to 7 (Scheme I ) prepared by electron impact methods. They studied not only the unimolecular metastable ion chemistry but also the CID mass spectra, and were able to show that all the ions

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“…Reaction [4], loss of NH3, was found to proceed without a barrier additional to the endothermicity with the C3H7+ and NH3 products merely drifting apart with no maximum in the potential energy curve. The calculated reaction endothermicity is in good agreement with the experimental endothermicity.…”

Section: ~~~S~~~~~u S Smentioning

confidence: 96%

“…By analogy with the behaviour of protonated aliphatic alcohols, which have been studied extensively (2)(3)(4), the major fragmentation reactions of the protonated amines, RNH3+, might be expected to be elimination of NH3 forming the corresponding alkyl ion. In agreement with this prediction two early limited studies (5,6) reported significant yields of R + ions, although, because of the high proton affinity of ammonia, fragmentation was not particularly facile (7).…”

Section: Introductionmentioning

confidence: 99%

Unimolecular fragmentation of some gaseous protonated amines

et al. 1986

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. Can. J. Chem. 64, 1652Chem. 64, (1986.The proton-transfer chemical ionization mass spectra of the C3 to C5 monoalkyl amines as well as a number of di-and tri-alkyl amines have been determined using H3+ and (in some cases) HCO' as protonating agent. The RNH3+ ions fragment to form alkyl ions R+ and eliminate alkenes to form NH4+. In addition, abundant immonium ions are observed in the CI mass spectra corresponding to elimination of alkane from RNH3+ or to direct alkide ion abstraction from RNH2; these ions serve to characterize the alkyl groups attached to the a-carbon atom of the amine. Although alkane elimination from RNH3+ is the thermochemically favoured reaction, only R+ and NH4+ are formed in decomposition of metastable R N H~+ ions. The potential energy profile for fragmentation of i-C3H7NH3+ has been calculated by ab initio molecular orbital methods. These calculations show that CH4 elimination has a large energy barrier additional to the reaction endothermicity while formation of NH4+ has only a small additional barrier and formation of C3H7+ has no barrier additional to the endothermicity. It is concluded that the immonium ions probably arise primarily by direct alkide ion abstraction reactions.ERIC J. REINER, RAYMOND A. POIRIER, MICHAEL R. PETERSON, IMRE G. CSIZMADIA et ALEX G. HARRISON. Can. J. Chem. 64, 1652Chem. 64, (1986.Utilisant le H3+ et (dans quelques cas) le HCO+ c o m e agents protonants, on a determink les spectres de masse par ionisation chimique par transfert de proton des amines primaires en C3 5L C5 ainsi que d'un certain nombre d'amines secondaires et tertiaires. Les ions RNH3+ se fragmentent pour former des ions alkyles R+ ou pour Climiner des alctnes avec formation de NH4+. De plus, on observe la formation abondante d'ions immonium dans les spectres de masse par ionisation chimique et ceux-ci correspondent A une tlmination d'alcane de l'ion RNH3+ ou gun enlkvement direct d'ion alkide i partir du RNH2; ces ions servent 2t caracteriser les groupements alkyles attaches k l'atome de carbone en a de l'amine. M&me si 1'Climination d'alcane A partir de l'ion RNH3+ est la reaction qui est thermodynamiquement favorisbe, il ne se forme que les ions R+ et NH4+ lors de la dCcomposition des ions mktastables RNH3+. Utilisant des mCthodes d'orbitales moltculaires ab initio, on a calculC les profiles d'Cnergie potentielle pour la fragmentation de l'ion i-C3H7NH3+. Ces calculs dCmontrent que l'klimination de CH4 est soumise A une forte barritre Cnergktique qui s'additionne a l'endothermicitk de la reaction alors que la formation de l'ion NH4+ n'est soumise qu'h une faible barritre additionnelle et que la formation de l'ion C3H7+ n'est soumise i aucune barritre additionnelle par rapport i l'endothermicitk de la rkaction. On en conclut que les ions immonium proviennent probablement de rkactions primaires d'abstractions directes de l'ion alkide.[Traduit par la revue]

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Effect of reaction exothermicity on the proton transfer chemical ionization mass spectra of isomeric C₅ and C₆ alkanols

Cited by 23 publications

References 7 publications

Gas‐phase chemistry of ionized and protonated GeF₄: a joint experimental and theoretical study

Gas‐phase chemistry of ionized and protonated GeF₄: a joint experimental and theoretical study

Structure and fragmentation of C₅H₁₁O⁺ ions formed by chemical ionization

Unimolecular fragmentation of some gaseous protonated amines

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Effect of reaction exothermicity on the proton transfer chemical ionization mass spectra of isomeric C5 and C6 alkanols

Cited by 23 publications

References 7 publications

Gas‐phase chemistry of ionized and protonated GeF4: a joint experimental and theoretical study

Gas‐phase chemistry of ionized and protonated GeF4: a joint experimental and theoretical study

Structure and fragmentation of C5H11O+ ions formed by chemical ionization

Unimolecular fragmentation of some gaseous protonated amines

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Effect of reaction exothermicity on the proton transfer chemical ionization mass spectra of isomeric C₅ and C₆ alkanols

Gas‐phase chemistry of ionized and protonated GeF₄: a joint experimental and theoretical study

Gas‐phase chemistry of ionized and protonated GeF₄: a joint experimental and theoretical study

Structure and fragmentation of C₅H₁₁O⁺ ions formed by chemical ionization