23614-50-8Relevant academic research and scientific papers
Heats of Formation of the Annulene Dianion and Neutral Molecule
Stevenson, Gerald R.,Forch, Brad E.
, p. 5985 - 5988 (1980)
The enthalpy of reaction of the disodium salt of annulene with water and the heat of combustion of neutral annulene were both measured calorimetrically.These measurements were utilized in a thermochemical cycle to yield the heat of reaction of sodium metal with annulene to give the solid dianion salt.The enthalpy of reaction of the dianion with water (-10.9 kcal/mol) is much less exothermic than that for the dianion of annulene.The results indicate that the annulene dianion is greatly stabilized via aromatization.Further, its relative thermodynamic stability over that of the annulene dianion has been attributed to a reduced electron-electron repulsion force in the larger annulene dianion.The combustion measurements indicate that the neutral annulene does not possess any conjugative stability.The heat of combustion of annulene (-2182.2 kcal/mol) is more exothermic by 9 kcal/mol than that for two annulenes.
Isotopic Exchange Involving the Annulene Anion Radical and Its Dimerization to the Annulene Anion Radical
Stevenson, Cheryl D.,Burton, Richard D.,Peters, Steve J.,Reiter, Richard C.
, p. 5838 - 5842 (2007/10/02)
The addition of D2O to hexamethylphosphoramide solutions of the potassium salt of the annulene anion radical results in the slow (days) formation of the monodeuteriated anion radical (C8H7D1.1-).However, several days after a similar addition to the sodium salt solution, no C8H7D1.1- is present.Instead, the anion radical of annulene is found.These observations led to EPR and NMR studies, which have revealed the mechanism of each process.The mechanisms are based upon the facts that ion association is necessary for the isotope exchange reaction and the absence of ion association is required for the dimerization.Solutions of deuteriated annulene anion radical, annulene dianion, annulene anion radical, and annulene dianion can be readily generated from reduced solutions of annulene for EPR, NMR, etc. studies by making use of the isotopic exchange and dimerization mentioned above.
