Lithium monoxide anion (LiO−) is a superbase 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 of ~1782 kJ/mol.
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−2 → LiO−C(=O)− + CO2 LiO−C(=O)− → LiO− + COThe 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.3
See also
References
Poad, Berwyck L. J.; Reed, Nicholas D.; Hansen, Christopher S.; Trevitt, Adam J.; Blanksby, Stephen J.; Mackay, Emily G.; Sherburn, Michael S.; Chan, Bun; Radom, Leo (2016). "Preparation of an ion with the highest calculated proton affinity: ortho-diethynylbenzene dianion". Chemical Science. 7 (9): 6245–6250. doi:10.1039/C6SC01726F. PMC 6024202. PMID 30034765. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6024202 ↩
Srivastava, Ambrish Kumar; Misra, Neeraj (6 February 2016). "OLi3O– anion: Designing the strongest base to date using OLi3 superalkali". Chemical Physics Letters. 648: 152–155. Bibcode:2016CPL...648..152S. doi:10.1016/j.cplett.2016.02.010. /wiki/Bibcode_(identifier) ↩
Tian, Zhixin; Chan, Bun; Sullivan, Michael B.; Radom, Leo; Kass, Steven R. (2008-06-03). "Lithium monoxide anion: A ground-state triplet with the strongest base to date". Proceedings of the National Academy of Sciences of the United States of America. 105 (22): 7647–7651. Bibcode:2008PNAS..105.7647T. doi:10.1073/pnas.0801393105. ISSN 0027-8424. PMC 2409378. PMID 18511563. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2409378 ↩