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A superbase is a compound that has a particularly high affinity for protons. Superbases are of theoretical interest and potentially valuable in organic synthesis . [ 1 ] [ 2 ] Superbases have been described and used since the 1850s.
According to calculations, ortho-diethynylbenzene dianion is the strongest superbase and has a proton affinity of 1,843.987 kJ/mol (440.723 kcal/mol). [1] The meta isomer is the second-strongest, and the para isomer is the third. All three are readily able to accept any proton to its ethynyl tails, from almost any compound.
In chemistry, the Verkade base (or Verkade superbase) is a powerful superbase with the formula P(MeNCH 2 CH 2) 3 N. A colorless oil, it is an aminophosphine although its inventor John Verkade called it proazaphosphatrane. The trimethyl derivative or 2,5,8,9-tetraaza-1-phosphabicyclo[3.3.3]undecane is the simplest. [1]
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. [2] LiO − has a proton ...
Strongest superbases are synthesised in only gas phase: Ortho-diethynylbenzene dianion (C 6 H 4 (C 2) 2) 2− (the strongest superbase ever synthesized) Meta-diethynylbenzene dianion (C 6 H 4 (C 2) 2) 2− (second strongest superbase) Para-diethynylbenzene dianion (C 6 H 4 (C 2) 2) 2− (third strongest superbase)
With a pK a of 12.34 [4] for its conjugate acid in aqueous solution, 1,8-bis(dimethylamino)naphthalene is one of the strongest organic bases. However, it only absorbs protons slowly—hence the trade name. The high basicity is attributed to the relief of strain upon protonation and/or the strong interaction between the nitrogen lone pairs. [3]
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The higher the proton affinity, the stronger the base and the weaker the conjugate acid in the gas phase.The (reportedly) strongest known base is the ortho-diethynylbenzene dianion (E pa = 1843 kJ/mol), [3] followed by the methanide anion (E pa = 1743 kJ/mol) and the hydride ion (E pa = 1675 kJ/mol), [4] making methane the weakest proton acid [5] in the gas phase, followed by dihydrogen.