A distonic ion, showing that the molecule's radical site and charge are in different locations.

Distonic ions are chemical species that contain two ionic charges on the same molecule, separated by two or more carbon or heteroatoms.[1] A feature of distonic radical ions is that their charges and radical sites are in different locations (on separate atoms), unlike regular radicals where the formal charge and unpaired electron are in the same location. These molecular species are created by ionization of either zwitterions or diradicals; ultimately, a neutral molecule loses an electron.[2] Through experimental research distonic radicals have been found to be extremely stable gas phase ions[3] and can be separated into different classes depending on the inherent features of the charged portion of the ion.[4]

History

In 1984 scientists Bouma, Radom and Yates originated the term through extensive experimental research but they were not the first to deal with distonic ions. Experiments date back to the 1970s with Gross and McLafferty who were the first to propose the idea of such a species.[5]

[6] Example of distonic ion in the class -ate

Ion structure

Several efficient techniques are available to detect the presence of distonic ions; the most appropriate method will depend on the ion's internal energy and lifespan.[3] Collisions between ions and uncharged molecules allow one to detect the location of the radical and charge site in order to confirm that the ion is not just a regular radical ion.[7] When a molecule is ionized and can structurally be classified as a distonic ion, the molecule's kinetics and thermodynamic properties have been greatly altered. However, additional chemical properties are based on the reactions of the central excited ions. Mass spectrometry techniques are used to study their chemistry.[8]

Experimental data

Distonic ions have been extensively examined due to their unique behavior and how commonly they can occur.[2] It has been shown that in most cases distonic ions have a bonding arrangement corresponding to that of the original molecule before ionization occurred; but that distonic ions are less stable than before ionization occurred; even so, distonic ions are considered stable ions and have caught many scientists' attention because they possess more stability than its traditional isomer.[3] It may be difficult to decipher the functions of the charge and radical site because distonic ions are limited to elementary reactions such as unimolecular reactions involving highly excited and short-lived species.[9]

References

  1. ↑ Muller, P. (1994). "Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)". Pure and Applied Chemistry. 66 (5): 1077–1184. doi:10.1351/pac199466051077. ISSN 1365-3075. S2CID 195819485.
  2. 1 2 Tomazela, Daniela Maria; Sabino, Adão A.; Sparrapan, Regina; Gozzo, Fabio C.; Eberlin, Marcos N. (July 2006). "Distonoid ions". Journal of the American Society for Mass Spectrometry. 17 (7): 1014–1022. doi:10.1016/j.jasms.2006.03.008. PMID 16713292.
  3. 1 2 3 Stirk, Krista M.; Kiminkinen, L. K. Marjatta; Kenttamaa, Hilkka I. (November 1992). "Ion-molecule reactions of distonic radical cations". Chemical Reviews. 92 (7): 1649–1665. doi:10.1021/cr00015a008.
  4. ↑ Hill, Brian T.; Poutsma, John C.; Chyall, Leonard J.; Hu, Jun; Squires, Robert R. (September 1999). "Distonic ions of the 'ate' class". Journal of the American Society for Mass Spectrometry. 10 (9): 896–906. doi:10.1016/S1044-0305(99)00053-7. S2CID 97267758.
  5. ↑ Williams, Peggy E.; Jankiewicz, Bartlomiej J.; Yang, Linan; Kenttamaa, Hilkka I. (12 November 2013). "ChemInform Abstract: Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites". ChemInform. 44 (46): no. doi:10.1002/chin.201346233.
  6. ↑ Hill, Brian T.; Poutsma, John C.; Chyall, Leonard J.; Hu, Jun; Squires, Robert R. (September 1999). "Distonic ions of the "Ate" class". Journal of the American Society for Mass Spectrometry. 10 (9): 896–906. doi:10.1016/S1044-0305(99)00053-7. S2CID 97267758.
  7. ↑ Yu, Sophia J.; Holliman, Christopher L.; Rempel, Don L.; Gross, Michael L. (1993-10-01). "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 (21): 9676–9682. doi:10.1021/ja00074a037. ISSN 0002-7863.
  8. ↑ Holman, R.W.; Rozeboom, M.D.; Gross, M.L.; Warner, C.D. (January 1986). "Mass spectrometry for investigations of gas-phase radical cation chemistry". Tetrahedron. 42 (22): 6235–6244. doi:10.1016/S0040-4020(01)88085-6.
  9. ↑ Stirk, Krista G.; Kenttamaa, Hilkka I. (1991-07-01). "Radical type reactivity in a .gamma.-distonic radical cation: a gas-phase experimental study". Journal of the American Chemical Society. 113 (15): 5880–5881. doi:10.1021/ja00015a062. ISSN 0002-7863.
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