View source for Chemistry:Ortho-Diethynylbenzene dianion

{{mergefrom|meta-Diethynylbenzene dianion|discuss=Talk:ortho-Diethynylbenzene dianion#Proposed merger of two related articles|date=May 2018}}
{{mergefrom|para-Diethynylbenzene dianion|discuss=Talk:ortho-Diethynylbenzene dianion#Proposed merger of two related articles|date=May 2018}}

{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 459445215
| Name = 
| ImageFile = Ortho-Diethynylbenzene-dianion.svg
| ImageFile2 = 
| ImageSize = 240
| OtherNames = 
| IUPACName = ''Ortho''-diethynylbenzene dianion
| SystematicName = 
| Section1 = {{Chembox Properties
| Formula = {{Chem|C|6|H|4|C|4|2-}}
}}
| Section2 = 
| Section3 = {{Chembox Related
| OtherFunction_label = [[Chemistry:Base|base]]s
| OtherFunction = Meta-diethynylbenzene dianion<br />
Para-diethynylbenzene dianion<br />
[[Chemistry:Lithium monoxide anion|Lithium monoxide anion]]
}}
| Section4 = 
| Section5 = 
| Section6 = 
}}
{{DISPLAYTITLE:''ortho''-Diethynylbenzene dianion}}
'''''Ortho''-diethynylbenzene dianion''' is a [[Chemistry:Superbase|superbase]] with the chemical formula of [C<sub>6</sub>H<sub>4</sub>(C<sub>2</sub>)<sub>2</sub>]<sup>2−</sup>.<ref name="article">{{cite journal|last1=Poad|first1=Berwyck L. J.|last2=Reed|first2=Nicholas D.|last3=Hansen|first3=Christopher S.|last4=Trevitt|first4=Adam J.|last5=Blanksby|first5=Stephen J.|last6=Mackay|first6=Emily G.|last7=Sherburn|first7=Michael S.|last8=Chan|first8=Bun|last9=Radom|first9=Leo|title=Preparation of an ion with the highest calculated proton affinity: ortho-diethynylbenzene dianion|journal=Chem. Sci.|date=2016|volume=7|issue=9|pages=6245–6250|doi=10.1039/C6SC01726F}}{{open access}}</ref><ref>{{cite web|title=Basically record breaking|url=https://www.chemistryworld.com/news/basically-record-breaking/1010062.article|website=Chemistry World|first1= Will|last1=Bergius|date=19 July 2016}}</ref>  The base was created in mass spectroscopy experiments by researchers in Australia.<ref name="article" />

== Background ==

The largest possible [[Chemistry:Proton affinity|proton affinity]] value for a base in a solution of water is that of hydroxide, 1,633.14 kJ/mol.  Bases with higher proton affinities irreversibly abstract protons from water, and as a result the anions cannot be observed.  Therefore, stronger bases must be used in an aprotic solvent such as [[Chemistry:Tetrahydrofuran|tetrahydrofuran]] (oxolane). According to calculations, ortho-diethynylbenzene dianion is the strongest possible organic base, with a proton affinity of 1843 kJ [[Mole (unit)|mol]]<sup>−1</sup>.

Ortho-diethynylbenzene dianion has two isomers: ''Meta-''diethynylbenzene dianion and ''Para-''diethynylbenzene dianion.  Because these ions would abstract protons from any organic solvent, they are known only in the gas phase.<ref name="article" />

== Synthesis and Observation ==

Since ortho-diethynylbenzene dianion cannot be made in solution, investigation of the dianion is difficult. In the gas phase, however, the absence of any solvent interaction provides an ideal environment for investigating the basicity of the compound, and the gas phase value of the proton affinity can be calculated with greater precision.

The synthesis of ortho-diethynlbenzene dianion was performed in a linear quadrupole mass spectometer. Electrospray Ionisation (ESI) of the diacid precursor results in the dicarboxylate dianion ([C<sub>6</sub>H<sub>4</sub>(C<sub>3</sub>HO<sub>2</sub>)<sub>2</sub>]) losing two Hydrogen ions to become ([C<sub>6</sub>H<sub>4</sub>(C<sub>3</sub>O<sub>2</sub>)<sub>2</sub>]<sup>2−</sup>). The dianion was mass-selected and then subjected to Collision Induced Dissociation (CID), resulting in the loss of two dioxide molecules and generation of the ortho-diethynylbenzene dianion:
[[File:O-diethynylbenzene dianion preparation.png|thumb|center|upright=3.0|Preparation of o-diethynylbezene dianion from the dicarboxylate precursor]]

The meta and para isomers were prepared analogously. 

Reactions of the gas-phase dianions were studied by passing them, in a helium carrier gas, over a small amount of the reagent of interest. Reaction with [[Chemistry:Heavy water|heavy water]] produced a singly-deuterated monanion with m/z 126. Reaction with benzene produced the phenyl anion, with m/z of 77, highlighting the extreme basicity of the dianion. Attempted reaction with [[Physics:Deuterium|deuterium]] gas and deuterated [[Chemistry:Methane|methane]] was not successful despite the favourable thermodynamics; the authors attribute this to the high [[Chemistry:Activation energy|activation barrier]] for proton abstraction from those substrates.<ref name="article" />


==See also==
*[[Chemistry:Lithium monoxide anion|Lithium monoxide anion]].
*[[Chemistry:Tetrahydrofuran|Tetrahydrofuran]]. (Recently in 2013, the preferred IUPAC name has been changed to Oxolane)
*[[Chemistry:Lithium diisopropylamide|Lithium diisopropylamide]].
*[[Chemistry:Sodium hydride|Sodium Hydride]].

== References ==
{{reflist}}

[[Category:Superbases]]
[[Category:Anions]]

{{Sourceattribution|Ortho-Diethynylbenzene dianion|1}}