Mesoionic

Mesoionic chemical compounds or mesoionic compounds are dipolar five membered heterocyclic compounds in which both the negative and the positive charges are delocalized.[1][2] A completely uncharged structure cannot be written and mesoionic compounds cannot be represented satisfactorily by any one mesomeric structure.[2] Mesoionic compounds are a subclass of betaines.[2] Examples are sydnones and sydnone imines (e.g. the stimulant mesocarb), and münchnones.[1][2][3]

The formal positive charge is associated with the ring atoms and the formal negative charge is associated either with ring atoms or an exocyclic nitrogen atom.[4] These compounds are stable zwitterionic compounds[5] and belong to nonbenzenoid aromatics.[6]

References

  1. 1.0 1.1 Bhosale, Sachin K.; Deshpande, Shreenivas R.; Wagh, Rajendra D. (2012). "Mesoionic sydnone derivatives: An overview". Journal of Chemical and Pharmaceutical Research 4 (2): 1185–99.
  2. 2.0 2.1 2.2 2.3 IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006) "mesoionic compounds".
  3. Ollis, W.David; Stanforth, Stepher P.; Ramsden, Christopher A. (1985). "Heterocyclic mesomeric betaines". Tetrahedron 41 (12): 2239. doi:10.1016/S0040-4020(01)96625-6.
  4. "SYDNONES".
  5. "Seeking Mesoionic Compounds".
  6. Badami, Bharati V (2006). "Mesoionic compounds". Resonance 11 (10): 40. doi:10.1007/BF02835674.

Further reading