Lithium monoxide anion
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. Ortho-diethynylbenzene dianion is the strongest base, followed by meta-diethynylbenzene dianion and para-diethynylbenzene dianion. The methyl anion CH3− was the strongest known base before lithium monoxide anion was discovered.[2]
| Names | |
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| IUPAC name
Lithium monoxide anion | |
| Identifiers | |
3D model (JSmol) |
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| Properties | |
| LiO− | |
| Conjugate acid | Lithium hydroxide |
| Hazards | |
| Main hazards | Extremely corrosive |
| Related compounds | |
Related bases |
Meta-diethynylbenzene dianion Para-diethynylbenzene dianion |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
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| Infobox references | |
LiO− has a proton affinity of ~1782 kJ mol−1.[3]
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)(CO2−) → LiOCO− + CO2, 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.[4]
References
- "Lithium oxide anion". webbook.nist.gov.
- 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.
- "OLi3O− anion: Designing the strongest base to date using OLi3 superalkali". 6 February 2016.
- 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. doi:10.1073/pnas.0801393105. ISSN 0027-8424. PMC 2409378. PMID 18511563.