Ortho-Diethynylbenzene dianion

Ortho-Diethynylbenzene dianion
	File:Orthodiethynylbenzene dianion.png
Names
	IUPAC name Ortho-diethynylbenzene dianion
Properties
Chemical formula	C; 6H; 4C2−; 4
Related compounds
Related bases	Meta-diethynylbenzene dianion; Para-diethynylbenzene dianion; Lithium monoxide anion
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Ortho-diethynylbenzene dianion is a superbase with the chemical formula of [C₆H₄(C₂)₂]²⁻.^[1]^[2] The base was created in mass spectroscopy experiments by researchers in Australia.^[1]

This base is reportedly the strongest superbase, with a proton affinity of 1843 kJ mol⁻¹.

The hydroxide anion has the largest proton affinity possible in an aqueous solution because any base with a larger Proton Abstraction value will abstract a proton from a water molecule. Therefore 1,633.14 kJ/mol, which is the Proton Abstraction value for the Hydroxide anion, is the largest possible value for a base in a solution of water. Therefore, stronger bases must be used in an aprotic solvent such as tetrahydrofuran (Oxolane). Such stronger bases are known as Superbases, and according to calculations, Ortho-diethynylbenzene dianion is the strongest base.

It has two isomers: Meta-diethynylbenzene dianion and Para-diethynylbenzene dianion. All of these isomers, including ortho-diethynylbenzene dianion, exist in the gas phase,^[1] contrary to the normal bases (such as the hydroxide anion) which exists in the solution state.

Up until 2008, the lithium monoxide anion (LiO⁻) was the strongest superbase. But it existed in the solution state, in an aprotic (not aqueous) solvent. Most of the bases are found in the solution state. The hydroxide anion is made in an aqueous solvent, water. The lithium monoxide anion is made in an aprotic solvent solution. Even though as of now, ortho-diethynylbenzene dianion has no known use, in the future, it could have various applications in industry, including the battery industry, as a component in alkaline batteries.^[1]

Nomenclature

The IUPAC chemical name - ortho-diethynylbenzene dianion is derived from the functional groups which make up the compound. Benzene is mentioned in ortho-diethynylbenzene dianion because the compound has a benzene ring. diethynyl is mentioned in the name of the compound because the compound has two ethynyl functional groups as constituents. dianion is mentioned in the name of the compound because the compound has a charge of -2 (di- is two and anion refers to compounds having negative charge). There are two functional groups in the compound which is the '-ethynyl ' group. Counting the number of carbon atoms in a clockwise manner, one of the '-ethynyl ' groups forms a bond with the first carbon atom while the other '-ethynyl ' group forms a bond with the second carbon atom in the benzene ring. When aromatic compounds have two functional groups bonded to the carbon atom, the carbon atom to which one of the functional group bonds with is known as the first carbon atom. That carbon atom is used as a starting point to number the other carbon atoms. But when the other functional group bonds with a second or third or fourth carbon atom, the IUPAC name of the compound takes the following prefix: ortho- ; meta- ; para-. In this compound, the second functional group (i.e., the '-ethynyl ' group) bonds with the second carbon atom. Hence, the IUPAC name of the compund takes the suffix -ortho. Hence, the IUPAC name of the compound is ortho-diethynylbenzene dianion.

Conditions of Synthesis and Observation

Since the bases as strong as Ortho-diethynylbenzene dianion cannot be made in a solution of water; and other solutions have the respective problems investigation and comparison of the basicity of Ortho-diethynylbenzene dianion is difficult. Probing the reactivity of the base in the gaseous phase, an environment free from any solvent interaction, provides an ideal way to investigate the basicity of the compound as the true nature of basicity of the compound can be studied more effectively, and the value of the Proton Affinity can be calculated with greater precision, in the gaseous phase rather than in a solution phase.

The synthesis of Ortho-diethynlbenzene dianion was performed, at a mass to charge ratio of 62, using TMS, Tandem Mass Spectroscopy, in a linear quadrupole. The Electrospray Ionisation (ESI) of the diacid precursor results in the diacid precursor ([C₆H₄(C₃HO₂)₂]) losing two Hydrogen ions to become ([C₆H₄(C₃O₂)₂]²⁻), which is, the dicarboxylate dianion. This anion is mass-selected and then subjected to Collision Induced Dissociation repeatedly for two times. Each time, the dicarboxylate dianion loses a Carbon dioxide molecule while retaining the negative charge. After both the Collision Induced Dissociation processes, the Ortho-diethynylbenzene dianion is created. In a similar way, taking the suitable structural isomers of the parent compound i.e., the diacid precursor, and applying the same method, meta-diethynylbenzene dianion and para-diethnynylbenzene dianion can be created.

Decarboxylation of the Carboxylate anions by Collision Induced Dissociation (CID) has been shown as an effective way to prepare such anions in the gas phase.

Summary of Synthesis

Step 1: The compound [C₆H₄(C₃HO₂)₂], used for synthesizing ortho-diethynylbenzene dianion, is taken.

Step 2: In this step, the parent compound is ionized by the process of Electrospray Ionization (ESI). The ionized compound has lost, in total, 2 (positively charged) hydrogen ions, because of which, the compound acquires a charge of -2.

Step 3: The ionized parent compound [C₆H₄(C₃O₂)₂]²⁻ is subjected to collisional activation, because of which, one of the carboxylate anion loses a carbon dioxide molecule.

Step 4: The ionized parent compound is again subjected to collisional activation, because of which, the other carboxylate anion loses the other carbon dioxide molecule. Therefore, the ortho-diethynylbenzene dianion [C₆H₄(C₂)₂]²⁻ is formed, having lost, in total, 2 hydrogen atoms and 2 molecules of carbon dioxide.

This is the reaction through which the researchers in Australia created the super base.

Summary of the reaction

{\ce {\overset {}{C6H4(C3HO2)2->[{\ce {ESI}}][][C6H4(C3O2)2]^{2-}->[{\ce {CID}}][][C6H4(C5O2)]^{2-}->[{\ce {CID}}][][C6H4(C2)2]^{2-}}}}

Step 1 - The compound ${\ce {ortho-[C6H4(C3HO2)2]}}$ , used for the synthesis of ortho-diethynylbenzene dianion, is taken.
Step 2 - The compound ${\ce {ortho-[C6H4(C3HO2)2]}}$ is ionized. The ionized compound ${\ce {ortho-[C6H4(C3O2)2]^{2-}}}$ , having lost two positively charged hydrogen ions, acquires a charge of -2.
Step 3 - The ionized precursor compound ${\ce {ortho-[C6H4(C3O2)2]^{2-}}}$ is subjected through Collision Induced Dissociation. This results in the precursor compound ${\ce {ortho-[C6H4(C3O2)2]^{2-}}}$ to lose a carbon dioxide molecule to become ${\ce {ortho-[C6H4(C5O2)]^{2-}}}$ .
Step 4 - The final step in the process of synthesizing ortho-diethynylbenzene dianion. The ionized parent compound once again, through collisional activation, loses another carbon dioxide molecule. But the charge is still present. The ionized precursor compound ${\ce {ortho-[C6H4(C5O2)]^{2-}}}$ is subjected through Collision Induced Dissociation for the second time. Thus, the compound ${\ce {ortho-[C6H4(C5O2)]^{2-}}}$ loses another carbon dioxide molecule to become ${\ce {ortho-[C6H4(C2)2]^{2-}}}$ . Thus, the compound ortho-diethynylbenzene dianion has been synthesized.

Step 4 - The final step in the process of synthesizing ortho-diethynylbenzene dianion. The ionized parent compound once again, through collisional activation, loses another carbon dioxide molecule. But the charge is still present. The ionized precursor compound ${\ce {ortho-[C6H4(C5O2)]^{2-}}}$ is subjected through Collision Induced Dissociation for the second time. Thus, the compound ${\ce {ortho-[C6H4(C5O2)]^{2-}}}$ loses another carbon dioxide molecule to become ${\ce {ortho-[C6H4(C2)2]^{2-}}}$ . Thus, the compound ortho-diethynylbenzene dianion has been synthesized.

Note: CID means Collision Induced Dissociation and ESI means Electrospray Ionization.

Properties

Each of the ethynyl groups in ortho-diethynylbenzene dianion has a negative charge.

References

^ ^a ^b ^c ^d 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". Chem. Sci. 7 (9): 6245–6250. doi:10.1039/C6SC01726F.
^ Bergiusdate=19 July 2016, Will. "Basically record breaking". Chemistry World.{{cite web}}: CS1 maint: numeric names: authors list (link)

[article-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". Chem. Sci. 7 (9): 6245–6250. doi:10.1039/C6SC01726F.

[2] Bergiusdate=19 July 2016, Will. "Basically record breaking". Chemistry World.{{cite web}}: CS1 maint: numeric names: authors list (link)

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