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Journal articles on the topic 'Distonic ion'

Author: Grafiati

Published: 4 June 2021

Last updated: 18 February 2022

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1

Karapanayiotis, Thanasis, and Richard D. Bowen. "Differentiation of Ionised Benzimidazole from its Isomeric α-Distonic Ion by Collision-Induced Dissociation and Neutralisation—Reionisation Mass Spectrometry." European Journal of Mass Spectrometry 11, no. 4 (August 2005): 381–87. http://dx.doi.org/10.1255/ejms.775.

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Ionised benzimidazole and its isomeric α-distonic ion (or ionised ylid) have been examined by recording their metastable ion, collision-induced dissociation and neutralisation–reionisation mass spectra. These tautomers may be distinguished by careful consideration of key features of the collision-induced dissociation spectra, with or without prior neutralisation and reionisation. Formation of doubly-charged ions by charge stripping occurs preferentially when the α-distonic ion is subjected to collision. This α-distonic ion survives neutralisation and reionisation, thus establishing that the corresponding ylid is stable on the microsecond time frame. The effects of benzannulation on the ease of differentiation of classical and distonic radical cations derived from biologically important heterocycles are considered.

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2

Gozzo, Fabio C., Luiz Alberto B. Moraes, Marcos N. Eberlin, and Kenneth K. Laali. "The First Nonclassical Distonic Ion." Journal of the American Chemical Society 122, no. 32 (August 2000): 7776–80. http://dx.doi.org/10.1021/ja993749m.

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3

Milliet, Arielle, Eric Lecarpentier, and Henri-Edouard Audier. "Unimolecular reactions of βdistonic ion." Organic Mass Spectrometry 29, no. 2 (February 1994): 90–95. http://dx.doi.org/10.1002/oms.1210290205.

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4

Stirk, Krista M., L. K. Marjatta Kiminkinen, and Hilkka I. Kenttamaa. "Ion-molecule reactions of distonic radical cations." Chemical Reviews 92, no. 7 (November 1992): 1649–65. http://dx.doi.org/10.1021/cr00015a008.

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5

Chou, Phillip K., Rebecca L. Smith, Leonard J. Chyall, and Hilkka I. Kenttamaa. "Reactivity of the Prototype Organosulfur Distonic Ion: .bul.CH2SH2+." Journal of the American Chemical Society 117, no. 15 (April 1995): 4374–78. http://dx.doi.org/10.1021/ja00120a020.

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6

STIRK, K. M., L. K. M. KIMINKINEN, and H. I. KENTTAEMAA. "ChemInform Abstract: Ion-Molecule Reactions of Distonic Radical Cations." ChemInform 24, no. 22 (August 20, 2010): no. http://dx.doi.org/10.1002/chin.199322312.

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7

Traeger, John C., Charles E. Hudson, and David J. McAdoo. "The distonic ion˙CH2CH2CO+ and its formation from ionized cyclopentanone." Organic Mass Spectrometry 24, no. 4 (April 1989): 230–34. http://dx.doi.org/10.1002/oms.1210240406.

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8

van Amsterdam, Margot W., Paul O. Staneke, Steen Ingemann, and Nico M. M. Nibbering. "Gas-phase reactions of the sulphur distonic ion with alkenes." Organic Mass Spectrometry 28, no. 8 (August 1993): 919–20. http://dx.doi.org/10.1002/oms.1210280816.

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9

Chyall, Leonard J., and Hilkka I. Kenttamaa. "The 4-Dehydroanilinium Ion: a Stable Distonic Isomer of Ionized Aniline." Journal of the American Chemical Society 116, no. 7 (April 1994): 3135–36. http://dx.doi.org/10.1021/ja00086a058.

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10

Kirchhoff, Dirk, Hans-Friedrich Grützmacher, and Hansjörg Grützmacher. "Trends in the Periodic System: The Mass Spectrum of Dimethylphenyl Phosphane and a Comparison of the Gas Phase Reactivity of Dimethylphenyl Pnictogene Radical Cations C6H5E(CH3)2•+, (E = N, P, As)." European Journal of Mass Spectrometry 15, no. 2 (April 2009): 131–44. http://dx.doi.org/10.1255/ejms.940.

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The mass spectrometric reactions of dimethylphenyl phosphane, 1, under electron impact have been studied by methods of tandem mass spectrometry and by using labeling with deuterium. The results are compared to those for the previously investigated dimethylaniline, 2, and dimethylphenyl arsane, 3, to examine the effects of heavy main group heteroatoms on the reactions of radical cations of the pnictogen derivatives C6H5E(CH3)2. Decomposition of the radical cation 1•+ gives rise to large peaks in the 70 eV electron impact (EI) mass spectrum for loss of a radical, •CH3, which is followed by abundant loss of a molecule, H2, and formation of ion C7H7+, and the 70 eV EI mass spectrum of the deuterated derivative 1d3 shows that excessive positional hydrogen/deuterium (H/D) exchange accompanies all fragmentation reactions. This is confirmed by the mass analyzed kinetic energy (MIKE) spectrum of the molecular ion 1d6•+ which displays a group of signals for the loss of all isotopomers, •C(H/D)3, and three signals for formation of ions C7H5D2+, C7H4D3+ and C7H3D4+. The intensity distribution within this latter group of ions corresponds to a statistical positional exchange (“scrambling”) of all six D atoms of the methyl substituents with only two H atoms of the phenyl group. In contrast, the intensity distribution of the signals for loss of •C(H/D)3 uncovers a bimodal reaction. About 39% of metastable molecular ions 1•+ eliminate •CH3 after scrambling of the six H atoms of the methyl substituents with two H atoms of the phenyl group, while the remaining 61% of metastable 1•+ lose specifically a CH3 substituent without positional H exchange. Further, the metastable ion [M – CH3]+ eliminates, almost exclusively, a molecule H2, which is preceded by excessive positional H/D exchange in the case of metastable ion [M – CD3]+. The formation of ion C7H7+ from metastable ion [M – CH3]+ is not observed and this is a minor process, even under the high energy condition of collision-induced dissociation (CID). The mechanisms of these fragmentation and exchange reactions have been modeled by theoretical calculations using the DFT functionals at the level UHBLY/6-311+G(2d,p)//UHBLYP/6-31+G(d). The key feature is a rearrangement of molecular ion 1•+ to an α-distonic isomer 1dist1•+ by a 1,2-H shift from the CH3 substituent to the P atom in competition with a direct loss of a CH3 substituent. The distonic ion 1dist1•+ performs positional H exchange between H atoms of both CH3 substituents and H atoms at the ortho-positions of the phenyl group and rearranges readily to the (conventional) isomer benzylmethyl phosphane radical cation 1bzl•+. The ion 1bzl•+ undergoes further positional H exchange before decomposition to ion C7H7+ and a radical CH3P•H or by loss of a radical •CH3. Finally, ions [M – CH3]+ of methylphenyl phosphenium structure 1a+ and benzyl phosphenium structure 1b+ interconvert easily parallel to positional H exchange involving all H atoms of the ions. Eventually, a molecule H2 is lost by a 1,1-elimination from the PH2 group of the protomer 1b–H+ of 1b+. The trends observed in the gas phase chemistry of the pnictogen radical cations dimethylaniline 2•+, dimethylphenyl phosphane 1•+ and dimethylphenyl arsane 3•+ can be comprehended by considering the variation of the energetic requirements of three competing reaction: (i) α-cleavage by loss of •H from a methyl substituent, (ii) rearrangement of the molecular ion to an α-distonic isomer by a 1,2-H shift and (iii) loss of •CH3 by cleavage of the C-heteroatom bond. 2•+ exhibits a strong N–C bond and a high activation barrier for 1,2-H shift and fragments far more predominantly by α-cleavage. Both 1•+ and 3•+ eliminate •CH3 by cleavage of the weak C-heteroatom bond. The barrier for a 1,2-H shift is also distinctly smaller than for 2•+ and, for the P-derivative 1•+, the generation of the α-distonic ion is able to compete with loss of •CH3.

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11

Wright, Andrew D., and Richard D. Bowen. "Investigation of the mechanism of alkyl radical elimination from ionised pentenyl methyl and hexenyl methyl ethers by analysis of the collision-induced dissociation mass spectra of C4H7O+ and C5H9O+ ions." Canadian Journal of Chemistry 71, no. 7 (July 1, 1993): 1073–85. http://dx.doi.org/10.1139/v93-143.

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Collision-induced dissociation (CID) mass spectra are reported for C4H7O+ and C5H9O+ ions generated by loss of an alkyl radical from 11 isomers of C5H9OCH3+• and 8 isomers of C6H11OCH3+• produced by ionisation of alkenyl methyl ethers derived from stable alkenols. The oxonium product ions have acyclic structures (CH=CHCH=O+CH3 for C4H7O+; CH2=CH(CH3)C=O+CH3, CH3CH=CHCH=O+CH3, or CH2=(CH3)CCH=O+CH3 in the case of C5H9O+). Elimination of a methyl radical does not always occur by simple α-cleavage. Expulsion of an alkyl substituent attached to a carbon atom at either end of the C=C double bond also takes place readily; this process sometimes competes with or pre-empts α-cleavage, as is shown by 2H-labelling experiments. Plausible mechanisms for this σ′-cleavage are considered. A route involving a 1,2-H shift to the radical centre of a distonic ion, followed by γ-cleavage of the resultant ionised enol ether, is shown to provide the most accurate unifying description of this unusual fragmentation. The mechanistic significance of this interpretation of the σ′-cleavage is discussed by analysing the reverse reaction (addition of an alkyl radical to a methyl cationated enal) in frontier molecular orbital terms. A comparison is made between the mechanisms by which an alkyl radical is lost from ionised alkenyl methyl ethers by σ′-cleavage and the parallel process starting from ionised carboxylic acids or isomeric distonic ions derived from these CnH2n+1CO2H+• species. Both classes of fragmentation are best understood to occur via γ-cleavage of a distonic ion of general structure R1CH2CH•C+(X)OR2 (R1 = alkyl; X = OH, R2 = H; or X = H, R2 = CH3), thus yielding (R′)• and CH2 = CHC+(X)OR2.

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12

Stirk, Krista M., Rebecca L. Smith, Joe C. Orlowski, and Hilkka I. Kenttämaa. "Bimolecular reactions involving the radical site of the distonic ion ·CH2CH2CH2CO+." Rapid Communications in Mass Spectrometry 7, no. 5 (May 1993): 392–99. http://dx.doi.org/10.1002/rcm.1290070516.

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13

Moraes, Luiz Alberto B., and Marcos N. Eberlin. "Dehydrobenzoyl Cations: Distonic Ions with Dual Free Radical and Acylium Ion Reactivity." Journal of the American Chemical Society 120, no. 43 (November 1998): 11136–43. http://dx.doi.org/10.1021/ja981152l.

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14

Yates, Brian F. "Structural and electronic characterisation of the organometallic distonic ion (C6H6)Fe+(p-C6H4)·." International Journal of Mass Spectrometry 201, no. 1-3 (July 2000): 297–305. http://dx.doi.org/10.1016/s1387-3806(00)00227-x.

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15

CHYALL, L. J., and H. I. KENTTAEMAA. "ChemInform Abstract: The 4-Dehydroanilinium Ion: A Stable Distonic Isomer of Ionized Aniline." ChemInform 25, no. 33 (August 19, 2010): no. http://dx.doi.org/10.1002/chin.199433076.

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16

Troude, V., D. Leblanc, P. Mourgues, and H. E. Audier. "Regiospecific addition of CH2O at the radical site of the˙CH2CH2OHCH3+ distonic ion." Journal of Mass Spectrometry 30, no. 12 (December 1995): 1747–51. http://dx.doi.org/10.1002/jms.1190301216.

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17

Moraes, Luiz Alberto B., and Marcos N. Eberlin. "ChemInform Abstract: Dehydrobenzoyl Cations: Distonic Ions with Dual Free Radical and Acylium Ion Reactivity." ChemInform 30, no. 14 (June 16, 2010): no. http://dx.doi.org/10.1002/chin.199914020.

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18

Tichy, Shane E., Brian T. Hill, J. Larry Campbell, and Hilkka I. Kenttämaa. "Synthesis and Characterization of a Distonic Nitrene Ion: Gas-Phase Reactivity of Singlet and TripletN-Phenyl-3-Nitrenopyridinium Ion." Journal of the American Chemical Society 123, no. 32 (August 2001): 7923–24. http://dx.doi.org/10.1021/ja0157088.

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19

Moraes, Luiz Alberto B., and Marcos N. Eberlin. "Acyclic distonic acylium ions: Dual free radical and acylium ion reactivity in a single molecule." Journal of the American Society for Mass Spectrometry 11, no. 8 (August 2000): 697–704. http://dx.doi.org/10.1016/s1044-0305(00)00141-0.

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20

BOUCHOUX, G. "ChemInform Abstract: Gas-Phase Chemistry of Carbonyl Radical Cations: Distonic Ions and Ion- Neutral Complexes." ChemInform 27, no. 41 (August 4, 2010): no. http://dx.doi.org/10.1002/chin.199641278.

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21

Wittneben, Doris, and Hans-Friedrich Grützmacher. "Reactions of the β-distonic ion+CH2OCH2CH2˙ with butyronitrile: Evidence for an intermediate three-body ion-neutral complex during deprotonation." Organic Mass Spectrometry 27, no. 4 (April 1992): 533–34. http://dx.doi.org/10.1002/oms.1210270431.

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22

Wang, Xian, and John L. Holmes. "A study of the isomerization and dissociation of formal [acetonemethanol]+· ionmolecule complexes." Canadian Journal of Chemistry 83, no. 11 (November 1, 2005): 1903–12. http://dx.doi.org/10.1139/v05-200.

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The energy barrier for the ketoenol isomerization of the isolated acetone ion to its distonic (enol) isomer lies above its lowest dissociation limit and so the spontaneous isomerization can never be observed. Ketoenol isomerizations can be catalyzed within appropriate ionmolecule complexes. The present study involved two systems, [(CH3)2C=O···H+···O(H)CH2·] (ion 1) and [(CH3)2C=O···H+····OCH3] (ion 2), in both stable and metastable adducts. When acetone is bound to ·CH2OH though a proton bridge, shown as ion 1, an enol acetone ion is produced. This reaction results from a proton attaching to the acetone, which then gives an H· atom back to the radical site by a 1,6-H transfer, involving a transition state of low energy requirement. In contrast, when the acetone is protonated and bound to the radical CH3O· (ion 2), the above rearrangement does not take place. The metastable complex ion 2 loses a methyl radical, producing a new [C3H7O2]+ isomer of structure [CH3C+(O)···(H)OCH3]. Tandem mass spectrometry combined with ab initio calculations were used to investigate the two systems. Potential energy surface diagrams were obtained by calculations at the MP2/6-31+G(d) level of theory to aid further elucidation of the reaction mechanisms. Key words: ionmolecule complexes, ketoenol mechanisms, ion rearrangements and structures.

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23

Wenthold, Paul G., Jun Hu, Brian T. Hill, and Robert R. Squires. "Gas-phase negative ion chemistry of molecular fluorine. Synthesis of distonic radical anions and related species." International Journal of Mass Spectrometry 179-180 (November 1998): 173–83. http://dx.doi.org/10.1016/s1387-3806(98)14077-0.

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24

Jobst, Karl J., Julien De Winter, Robert Flammang, Johan K. Terlouw, and Pascal Gerbaux. "Differentiation of the pyridine radical cation from its distonic isomers by ion–molecule reactions with dioxygen." International Journal of Mass Spectrometry 286, no. 2-3 (September 2009): 83–88. http://dx.doi.org/10.1016/j.ijms.2009.06.012.

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25

Brenner, Valerie, Arielle Milliet, Philippe Mourgues, Gilles Ohanessian, and Henri-Edouard Audier. "Unimolecular and Bimolecular Reactions of the .beta.-Distonic Ion CH3CH2OH+CH2CH2.bul.: An Experimental and Theoretical Study." Journal of Physical Chemistry 99, no. 27 (July 1995): 10837–46. http://dx.doi.org/10.1021/j100027a026.

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26

Xu, Young C., Quan Chen, Sara K. Poehlein, and Ben S. Freiser. "A gas-phase study of ligand effects on the reactivity of organometallic distonic ion Fe(p-benzyne)+˙." Rapid Communications in Mass Spectrometry 13, no. 8 (April 30, 1999): 645–49. http://dx.doi.org/10.1002/(sici)1097-0231(19990430)13:8<645::aid-rcm533>3.0.co;2-s.

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27

Colburn, AW, Peter J. Derrick, and Richard D. Bowen. "Peter J Derrick and the Grand Scale ‘Magnificent Mass Machine’ mass spectrometer at Warwick." European Journal of Mass Spectrometry 23, no. 6 (November 29, 2017): 319–26. http://dx.doi.org/10.1177/1469066717737643.

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The value of the Grand Scale ‘Magnificent Mass Machine’ mass spectrometer in investigating the reactivity of ions in the gas phase is illustrated by a brief analysis of previously unpublished work on metastable ionised n-pentyl methyl ether, which loses predominantly methanol and an ethyl radical, with very minor contributions for elimination of ethane and water. Expulsion of an ethyl radical is interpreted in terms of isomerisation to ionised 3-pentyl methyl ether, via distonic ions and, possibly, an ion-neutral complex comprising ionised ethylcyclopropane and methanol. This explanation is consistent with the closely similar behaviour of the labelled analogues, C3H7CH2CD2OCH3+. and C3H7CD2CH2OCH3+., and is supported by the greater kinetic energy release associated with loss of ethane from ionised n-propyl methyl ether compared to that starting from directly generated ionised 3-pentyl methyl ether.

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28

Postma, R., S. P. Van Helden, J. H. Van Lenthe, P. J. A. Ruttink, J. K. Terlouw, and J. L. Holmes. "The [CH2 = CHOH/H2O]+˙ system: A theoretical study of distonic ions, hydrogen-bridged ions and ion-dipole complexes." Organic Mass Spectrometry 23, no. 7 (July 1988): 503–10. http://dx.doi.org/10.1002/oms.1210230702.

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29

Dechamps, Noémie, Robert Flammang, Pascal Gerbaux, Pham-Cam Nam, and Minh Tho Nguyen. "Characterization of a distonic isomer C6H5C+(OH)OCH2 of methyl benzoate radical cation by associative ion–molecule reactions." International Journal of Mass Spectrometry 249-250 (March 2006): 484–92. http://dx.doi.org/10.1016/j.ijms.2005.10.014.

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30

Wittneben, Doris, and Hans-Friedrich Grützmacher. "Unimolecular and bimolecular reactions of the β-distonic ion CH2CH2OCH+2 and its deuterated derivatives." International Journal of Mass Spectrometry and Ion Processes 100 (October 1990): 545–63. http://dx.doi.org/10.1016/0168-1176(90)85094-i.

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31

Polce, Michael J., and Chrys Wesdemiotis. "The distonic ion ·CH2CH2CH+OH, keto ion CH3CH2CH=O +·, enol ion CH3CH=CHOH+·, and related C3H6O+· radical cations. Stabilities and isomerization proclivities studied by dissociation and neutralization-reionization." Journal of the American Society for Mass Spectrometry 7, no. 6 (June 1996): 573–89. http://dx.doi.org/10.1016/1044-0305(96)00053-0.

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32

Taggert, Bethany I., Richard A. J. O’Hair, and Uta Wille. "Environmental Polymer Degradation: Using the Distonic Radical Ion Approach to Study the Gas-Phase Reactions of Model Polyester Radicals." Journal of Physical Chemistry A 121, no. 28 (July 6, 2017): 5290–300. http://dx.doi.org/10.1021/acs.jpca.7b04217.

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33

Gerbaux, Pascal, Yves Van Haverbeke, and Robert Flammang. "Ion-molecule reaction of pyridine with CS3 radical cations: experimental evidence for the production of pyridineN-thioxide distonic ions." Journal of Mass Spectrometry 32, no. 11 (November 1997): 1170–78. http://dx.doi.org/10.1002/(sici)1096-9888(199711)32:11<1170::aid-jms573>3.0.co;2-4.

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34

Li, Cong H., George N. Khairallah, Adrian K. Y. Lam, Richard A. J. O'Hair, Benjamin B. Kirk, Stephen J. Blanksby, Gabriel da Silva, and Uta Wille. "Reaction of Aromatic Peroxyl Radicals with Alkynes: A Mass Spectrometric and Computational Study Using the Distonic Radical Ion Approach." Chemistry - An Asian Journal 8, no. 2 (December 6, 2012): 450–64. http://dx.doi.org/10.1002/asia.201200933.

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35

Kirk, Benjamin B., David G. Harman, and Stephen J. Blanksby. "Direct Observation of the Gas Phase Reaction of the Cyclohexyl Radical with Dioxygen Using a Distonic Radical Ion Approach." Journal of Physical Chemistry A 114, no. 3 (January 28, 2010): 1446–56. http://dx.doi.org/10.1021/jp9073398.

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36

Khairallah, George N., Richard A. J. O’Hair, and Uta Wille. "Mass Spectrometric and Computational Studies on the Reaction of Aromatic Peroxyl Radicals with Phenylacetylene Using the Distonic Radical Ion Approach." Journal of Physical Chemistry A 118, no. 18 (April 23, 2014): 3295–306. http://dx.doi.org/10.1021/jp411477e.

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37

Fell, Lorne M., Peter C. Burgers, Paul JA Ruttink, and Johan K. Terlouw. "The decarbonylation of ionized β-hydroxypyruvic acid: the hydrogen-bridged radical cation [CH2=O . . .H . . .==C-OH].+ studied by experiment and theory." Canadian Journal of Chemistry 76, no. 3 (March 1, 1998): 335–49. http://dx.doi.org/10.1139/v98-022.

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The intriguing gas-phase ion chemistry of β-hydroxypyruvic acid (HPA), HOCH2C(==O)COOH, has been investigated using tandem mass spectrometry (metastable ion (MI) and (multiple) collision-induced dissociation (CID) experiments, neutralization-reionization mass spectrometry (NRMS), 18O and D isotopic labelling on both the acid and its methyl ester) in conjunction with computational chemistry (ab initio MO and density functional theories). HPA does not enolize upon evaporation, but it retains its keto structure. When ionized, decarbonylation occurs and, depending on the internal-energy content, this dissociation reaction proceeds via two distinct routes. The source-generated, high-energy ions lose the keto C==O, not via a least-motion extrusion into ionized glycolic acid, HOCH2COOH.+ , but via a rearrangement that yields the title H-bridged radical cation CH2==O ... H ... O==C-OH.+ for which Δ Hf0 = 99 ± 3 kcal/mol. The long-lived low-energy ions enolize prior to decarbonylation and lose the carboxyl C==O. Again, this is not a least-motion extrusion (which would produce the most stable isomer, HOC(H)==C(OH)2.+ Δ Hf0 = 73 kcal/mol) but a rearrangement yielding the ion-dipole complex HOC(H)C==C==O.+/H2O. The methyl ester of HPA behaves analogously, yielding CH2==O... H ...O==C-OCH3.+ and HOC(H)C==C==O.+ / CH3OH upon decarbonylation of the high- and low-energy ions, respectively. Decarboxylation into the ylidion CH2OH2.+ characterizes the dissociation chemistry of both the title H-bridged ion and its glycolic acid isomer HOCH2COOH.+ . A computational analysis of this reaction (which satisfies the experimental observations) leads to the proposal that the decarboxylation of the acid occurs via CH2-O(H) ... H ... ==C==O.+ as the key intermediate, whereas the title H-bridged ion follows a higher energy route that involves ion-dipole rotations leading to the ionized carbene HO(H2)CO-C-OH.+ and the distonic ion H2O-C(H2)-O-C==O.+ as key intermediates.Key words: tandem mass spectrometry, hydrogen-bridged radical cation, hydroxypyruvic acid, ab initio calculations, keto-enol tautomerization, 18O labelling.

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38

Gervasoni, B. D., G. N. Khairallah, R. A. J. O'Hair, and U. Wille. "The role of peroxyl radicals in polyester degradation – a mass spectrometric product and kinetic study using the distonic radical ion approach." Physical Chemistry Chemical Physics 17, no. 14 (2015): 9212–21. http://dx.doi.org/10.1039/c4cp06056c.

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39

Jariwala, Freneil B., John A. Hibbs, Carl S. Weisbecker, John Ressler, Rahul L. Khade, Yong Zhang, and Athula B. Attygalle. "A Distonic Radical-Ion for Detection of Traces of Adventitious Molecular Oxygen (O2) in Collision Gases Used in Tandem Mass Spectrometers." Journal of The American Society for Mass Spectrometry 25, no. 9 (July 8, 2014): 1670–73. http://dx.doi.org/10.1007/s13361-014-0945-5.

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40

Osburn, Sandra, Bun Chan, Victor Ryzhov, Leo Radom, and Richard A. J. O’Hair. "Role of Hydrogen Bonding on the Reactivity of Thiyl Radicals: A Mass Spectrometric and Computational Study Using the Distonic Radical Ion Approach." Journal of Physical Chemistry A 120, no. 41 (October 11, 2016): 8184–89. http://dx.doi.org/10.1021/acs.jpca.6b08544.

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41

Drewello, Thomas, Nikolaus Heinrich, Wilfried P. M. Maas, Nico M. M. Nibbering, Thomas Weiske, and Helmut Schwarz. "Generation of the distonic ion CH2NH3.bul.+: nucleophilic substitution of the ketene cation radical by ammonia and unimolecular decarbonylation of ionized acetamide." Journal of the American Chemical Society 109, no. 16 (August 1987): 4810–18. http://dx.doi.org/10.1021/ja00250a010.

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42

Audier, Henri Edouard, Arielle Milliet, Danielle Leblanc, and Thomas Hellman Morton. "Unimolecular decompositions of the radical cations of ethylene glycol and its monomethyl ether in the gas phase. Distonic ions versus ion-neutral complexes." Journal of the American Chemical Society 114, no. 6 (March 1992): 2020–27. http://dx.doi.org/10.1021/ja00032a014.

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43

Yu, Sophia J., Christopher L. Holliman, Don L. Rempel, and Michael L. Gross. "The .beta.-distonic ion from the reaction of pyridine radical cation and ethene: a demonstration of high-pressure trapping in Fourier transform mass spectrometry." Journal of the American Chemical Society 115, no. 21 (October 1993): 9676–82. http://dx.doi.org/10.1021/ja00074a037.

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Schaftenaar, Gijs, Ron Postma, Pual J. A. Ruttink, Peter C. Burgers, Graham A. McGibbon, and Johan K. Terlouw. "The gas phase chemistry of the methyl carbamate radical cation H2NCOOCH+3: isomerization into distonic ions, hydrogen-bridged radical cations and ion—dipole complexes." International Journal of Mass Spectrometry and Ion Processes 100 (October 1990): 521–44. http://dx.doi.org/10.1016/0168-1176(90)85093-h.

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45

AUDIER, H. E., A. MILLIET, D. LEBLANC, and T. H. MORTON. "ChemInform Abstract: Unimolecular Decompositions of the Radical Cations of Ethylene Glycol and Its Monomethyl Ether in the Gas Phase. Distonic Ions versus Ion- Neutral Complexes." ChemInform 23, no. 27 (August 21, 2010): no. http://dx.doi.org/10.1002/chin.199227039.

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46

Molenaar-Langeveld, T. A., A. M. van der Burg, and S. Ingemann. "Multiple Hydrogen Shifts Leading to Ammonia Loss from the Molecular Ions of Cyanocyclohexanes." European Journal of Mass Spectrometry 8, no. 6 (December 2002): 435–45. http://dx.doi.org/10.1255/ejms.521.

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Abstract:

The loss of ammonia from the metastable molecular ions of cyclic cyano compounds has been examined with the use of deuterium labeling and tandem mass spectrometry. Loss of ammonia is significant for ionized cyanocyclohexane, 1-methyl-, 4-methyl-, 4-cyano-and 4-phenyl-cyanocyclohexanes, 4-cyanopiperidine, cyanocycloheptane and 2-cyanonorbornane. By contrast, loss of ammonia is of minor importance (or absent) for the molecular ions of cyanocyclopentane, 2-methyl-cyanocyclohexane, 1-phenyl-cyanocyclohexane, 1-cyanocyclohexene, 4-cyanotetrahydrothiopyran, 2-cyano-5-norbornene and isocyanocyclohexane. Deuterium labeling of cyanocyclohexane reveals the occurrence of an H-shift from the 4-position to the cyano function, followed by a 1,2-H shift from the 1-position to the C-atom of the newly-formed–CNH group. Subsequently, a series of H-shifts leads to a distonic ion that is formulated as an N-protonated methylamine attached to a cyclohexadienyl radical. Loss of ammonia ensues and leads to ionized toluene as indicated by collision-induced dissociation experiments. For 4-phenyl-cyanocyclohexane, the metastable ions of the cis- and trans-isomers display, essentially, the same unimolecular chemistry. Briefly, the labeling of 4-phenyl-cyanocyclohexane indicates the following: (i) the H atom at the 4-position of the cyclohexane ring is incorporated, to a minor extent, in the ammonia molecule, (ii) loss of NHD2 predominates in the reactions of the molecular ions of 2,2,6,6-d4-4-phenyl-cyanocyclohexane and (iii) the ionized 3,3,5-d3-labeled species expels mainly NH2D. In addition, the metastable molecular ions of the 4-[d5-phenyl]-cyanocyclohexane expel NH3 and NH2D in a ratio of 35:65. A mechanistic scheme is proposed that is consistent with the labeling results for 4-phenyl-cyanocyclohexane as well as the indicated formation of ionized 4-methylbiphenyl as the product ion of ammonia loss.

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Rubino, Federico Maria, Luigi Zecca, Paolo Mascaro, and Walter Hunkeler. "A study of some imidazo[l,5-a]benzodiazepin-6-ones by electron impact mass spectrometry. characterization by tandem mass spectrometry of a distonic fragment ion." Organic Mass Spectrometry 26, no. 7 (July 1991): 636–44. http://dx.doi.org/10.1002/oms.1210260705.

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48

Opitz, Joachim, A. Stephen K. Hashmi, Burkhard Miehlich, and Michael Wölfle. "Electron-induced ionization of undeuterated and deuterated benzoic acid isopropyl esters and nicotinic acid isopropyl esters: Some implications for the mechanism of the McLafferty rearrangement." European Journal of Mass Spectrometry 26, no. 1 (July 18, 2019): 3–24. http://dx.doi.org/10.1177/1469066719857994.

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Electron ionization mass spectra, ionization, and appearance energies and bond energies (as dissociation energies) are reported for benzoic acid-1-methyl-ethyl ester (BAIPE), benzoic acid-1-deutero-1-methyl-ethyl ester (BAIPED1), benzoic acid-2,2,2-trideutero-1-trideuteromethyl-ethyl ester (BAIPED6) as well as nicotinic acid-1-methyl-ethyl ester (NAIPE), nicotinic acid-1-deutero-1-methyl-ethyl ester (NAIPED1), and nicotinic acid-2,2,2-trideutero-1-trideuteromethyl-ethyl ester (NAIPED6). Ionization energies of 9.39 eV for BAIPE, 9.40 eV for BAIPED1, 9.26 eV for BAIPED6 as well as 9.70 eV for NAIPE, 9.79 eV for NAIPED1, and 9.65 eV for NAIPED6 were determined. A gas-phase formation enthalpy of [Formula: see text] = (−4.10 ± 0.1) eV for BAIPE is calculated as well as [Formula: see text] = (−3.35 ± 0.1) eV for NAIPE. Molecular ions show two main fragmentation pathways. The first is a classical McLafferty rearrangement, characterized by the transfer of one γ-hydrogen atom from the isopropyl ester chain leading to the ions of the corresponding acid and neutral propene. The second is the double hydrogen transfer from the ester chain leading to the formation of the protonated acid and a C3H5√ allyl radical. For BAIPE, both hydrogen atoms originate from the methyl groups of the aliphatic chain with a probability of ≥98%, whereas the C-1-hydrogen is transferred with a probability of ≤2%. For NAIPE, both hydrogen atoms originate from the methyl groups of the aliphatic chain with a probability of 90%. Experimental proton affinities of PA = (8.75 ± 0.2) eV for benzoic acid and PA = (8.43 ± 0.2) eV for nicotinic acid are derived. For the protonation of the carbonyl group, B3LYP DFT calculations yielded PA = 8.66 eV for benzoic acid and PA = 8.41 eV for nicotinic acid. The overall fragmentation mechanism is explained with the initial formation of a 1,5-distonic ion by transfer of the first hydrogen. For the transfer of the second hydrogen, an intermediate ion/neutral complex is formulated.

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Bowen, Richard D., and Andrew D. Wright. "The mechanism of alkyl radical loss from ionised pentenyl methyl and hexenyl methyl ethers: the importance of a 1,2-hydrogen shift to the radical site of a distonic ion." Journal of the Chemical Society, Chemical Communications, no. 2 (1992): 96. http://dx.doi.org/10.1039/c39920000096.

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Rusli, Ridwan D., and Helmut Schwarz. "Mechanism of CH2+ Transfer from Distonic Ions X - CH2+ (X = CH2O, CH2CH2) to π- and n-Electron Bases in the Gas Phase. A Fourier Transform Ion Cyclotron Resonance (FTICR) Study Supplemented by ab initio MO Calculations." Chemische Berichte 123, no. 3 (March 1990): 535–40. http://dx.doi.org/10.1002/cber.19901230320.

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