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Lithium monoxide anion

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Lithium monoxide anion (LiO−) is a superbase existing in the solution state in an aprotic solvent. It was the world's strongest known base until 2008, when Orthodiethynylbenzene dianion, Meta-diethynylbenzene dianion and Para-diethynylbenzene dianion became the world's strongest known bases. Orthodiethynylbenzene dianion is the strongest base, followed by Meta-diethynylbenzene dianion and Para-diethynylbenzene dianion. Strong bases like lithium monoxide anion (LiO−) is made in an aprotic solvent such as tetrahydrofuran. The deprotonation agent used in the creation of Lithium monoxide anion is lithium diisopropylamide. The methyl anion CH3− was the strongest known base before lithium monoxide anion was discovered.[1]

This base is reportedly the fourth strongest superbase, with a proton affinity of ~1782 kJ mol−1[2]

Synthesis of the Lithium Monoxide anion

Step 1: A small amount Lithium oxalate (LiC2O4) is taken as the precursor compound.


Step 2: The Lithium oxalate is subjected to a process known as Electrospray Ionization (ESI). This results in the formation of the Lithium oxalate anion (LiC2O4-).[3]


Step 3: The Lithium oxalate anion is isolated.


Step 4: The Lithium oxalate anion is subjected to a process known as Collision Induced Dissociation (CID).


Step 5: After being subjected to Collision Induced Dissociation, the Lithium oxalate anion loses a Carbon dioxide molecule. The products of the reaction are: Lithium salt of doubly deprotonated formic acid (LiCO2-) and Carbon dioxide molecule.[4]

Step 6: The Lithium salt of the doubly deprotonated formic acid is isolated.


Step 7: The Lithium salt of the doubly deprotonated formic acid is subjected to Collision Induced Dissociation. This results in the formation of the Lithium monoxide anion (LiO-) and a Carbon dioxide molecule.[5]

The above method to synthesize 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 of Argon that is introduced into the instrument to carry out the CID step.[6]

References

  1. ^ 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.
  2. ^ "OLi3O− anion: Designing the strongest base to date using OLi3 superalkali" (PDF). 6 February 2016.
  3. ^ 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.{{cite journal}}: CS1 maint: PMC format (link)
  4. ^ 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.{{cite journal}}: CS1 maint: PMC format (link)
  5. ^ 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.{{cite journal}}: CS1 maint: PMC format (link)
  6. ^ 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.{{cite journal}}: CS1 maint: PMC format (link)

See also

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