Lithium monoxide anion (LiO
−) is a
superbase
A superbase is a compound that has a particularly high affinity for protons. Superbases are of theoretical interest and potentially valuable in organic synthesis. Superbases have been described and used since the 1850s.''Superbases for Organic ...
existing in the gas phase. It was the strongest known base until 2008, when the isomeric
diethynylbenzene dianions were determined to have a higher proton affinity. The
methanide ion CH
3− was the strongest known base before lithium monoxide anion was discovered.
LiO
− has a
proton affinity
The proton affinity (PA, ''E''pa) of an anion or of a neutral atom or molecule is the negative of the enthalpy change in the reaction between the chemical species concerned and a proton in the gas phase:
::: A- + H+ -> HA
::: B + H+ -> BH+
...
of ~1782 kJ
mol−1.
Synthesis of the lithium monoxide anion
The anion is prepared in a mass spectrometer by successive decarboxylation and decarbonylation of lithium oxalate anion under collision induced dissociation (CID) conditions: LiO(C=O)(CO) → LiOCO
− + CO
2, LiOCO
− → LiO
− + CO.
The above method to synthesize the lithium monoxide anion is inefficient and difficult to carry out. The required ion rapidly reacts with traces of moisture and molecular oxygen present in the air. The reaction is further intensified by the high pressure argon that is introduced into the instrument to carry out the CID step.
References
See also
*
Lithium oxide
Lithium oxide ( O) or lithia is an inorganic chemical compound. It is a white solid. Although not specifically important, many materials are assessed on the basis of their Li2O content. For example, the Li2O content of the principal lithium miner ...
{{Lithium compounds
Superbases
Lithium compounds