A Thermodynamic assessment of the reported room-temperature chemical synthesis of C2

10.26434/chemrxiv.12237980 ◽

2020 ◽

Author(s):

Henry S. Rzepa

Keyword(s):

Chemical Synthesis ◽

Room Temperature ◽

Thermodynamic Assessment ◽

Iodonium Salt

Chemical formation of C2 from an alkynyl iodonium salt precursor is calculated to be strongly endo-energetic, in contrast to the reported chemical synthesis and trapping which is facile at room temperatures. If C2 is to be formed at such temperatures, a mechanism to counter the unfavourable thermodynamic energies must be identified.

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A Thermodynamic assessment of the reported room-temperature chemical synthesis of C2

10.26434/chemrxiv.12237980.v1 ◽

2020 ◽

Author(s):

Henry S. Rzepa

Keyword(s):

Chemical Synthesis ◽

Room Temperature ◽

Thermodynamic Assessment ◽

Iodonium Salt

Chemical formation of C2 from an alkynyl iodonium salt precursor is calculated to be strongly endo-energetic, in contrast to the reported chemical synthesis which is facile at room temperatures. If C2 is to be formed at such temperatures, a mechanism to counter the unfavourable thermodynamic energies is yet to be identified.

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A thermodynamic assessment of the reported room-temperature chemical synthesis of C2

Nature Communications ◽

10.1038/s41467-021-21433-8 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Henry S. Rzepa

Keyword(s):

Chemical Synthesis ◽

Room Temperature ◽

Thermodynamic Assessment

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Reply to “A Thermodynamic assessment of the reported room-temperature chemical synthesis of C2”

Nature Communications ◽

10.1038/s41467-021-21439-2 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Kazunori Miyamoto ◽

Shodai Narita ◽

Yui Masumoto ◽

Takahiro Hashishin ◽

Taisei Osawa ◽

...

Keyword(s):

Chemical Synthesis ◽

Room Temperature ◽

Thermodynamic Assessment

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No Free C2 Is Involved in the DFT-Computed Mechanistic Model for the Reported Room-Temperature Chemical Synthesis of C2.

10.26434/chemrxiv.13560260 ◽

2021 ◽

Author(s):

Henry Rzepa

Keyword(s):

Free Energy ◽

Chemical Synthesis ◽

Room Temperature ◽

Mechanistic Model ◽

Reaction Times ◽

Carbon Chain ◽

Isotopic Substitution ◽

Displacement Reactions ◽

Iodonium Salt ◽

Zwitterionic Intermediate

Trapping experiments were claimed to demonstrate the first chemical synthesis of the free diatomic species C2 at room temperatures, as generated by unimolecular fragmentation of an alkynyl iodonium salt precursor. Alternative mechanisms based on DFT energy calculations are reported here involving no free C2, but which are instead bimolecular 1,1- or 1,2-iodobenzene displacement reactions from the zwitterionic intermediate 11 by galvinoxyl radical, or by hydride transfer from 9,10-dihydroanthracene. These result in the same trapped products as observed experimentally, but unlike the mechanism involving unimolecular generation of free C2, exhibit calculated free energy barriers commensurate with the reaction times observed at room temperatures. The relative energies of the transition states for 1,1 vs 1,2 substitution provide a rationalisation for the observed isotopic substitution patterns and the same mechanism also provides an energetically facile path to polymerisation by extending the carbon chain attached to the iodonium group, eventually resulting in formation of species such as amorphous carbon and C60.<div> <div> </div></div>

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No Free C2 Is Involved in the DFT-Computed Mechanistic Model for the Reported Room-Temperature Chemical Synthesis of C2.

10.26434/chemrxiv.13560260.v1 ◽

2021 ◽

Author(s):

Henry Rzepa

Keyword(s):

Free Energy ◽

Chemical Synthesis ◽

Room Temperature ◽

Mechanistic Model ◽

Reaction Times ◽

Carbon Chain ◽

Isotopic Substitution ◽

Displacement Reactions ◽

Iodonium Salt ◽

Zwitterionic Intermediate

Trapping experiments were claimed to demonstrate the first chemical synthesis of the free diatomic species C2 at room temperatures, as generated by unimolecular fragmentation of an alkynyl iodonium salt precursor. Alternative mechanisms based on DFT energy calculations are reported here involving no free C2, but which are instead bimolecular 1,1- or 1,2-iodobenzene displacement reactions from the zwitterionic intermediate 11 by galvinoxyl radical, or by hydride transfer from 9,10-dihydroanthracene. These result in the same trapped products as observed experimentally, but unlike the mechanism involving unimolecular generation of free C2, exhibit calculated free energy barriers commensurate with the reaction times observed at room temperatures. The relative energies of the transition states for 1,1 vs 1,2 substitution provide a rationalisation for the observed isotopic substitution patterns and the same mechanism also provides an energetically facile path to polymerisation by extending the carbon chain attached to the iodonium group, eventually resulting in formation of species such as amorphous carbon and C60.<div> <div> </div></div>

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Room-Temperature Chemical Synthesis of C2

10.26434/chemrxiv.8009633 ◽

2019 ◽

Author(s):

Kazunori Miyamoto ◽

Shodai Narita ◽

Yui Masumoto ◽

Takahiro Hashishin ◽

Mutsumi Kimura ◽

...

Keyword(s):

Chemical Synthesis ◽

Ground State ◽

Room Temperature ◽

Chemical Species ◽

Quadruple Bond ◽

Photon Excitation ◽

Physical Energy ◽

Theoretical Predictions ◽

Carbon Arc ◽

Inherent Nature

Diatomic carbon (C2) is historically an elusive chemical species. It has long been believed that the generation of C2 requires extremely high “physical” energy, such as an electric carbon arc or multiple photon excitation, and so it has been the general consensus that the inherent nature of C2 in the ground state is experimentally inaccessible. Here, we present the first “chemical” synthesis of C2 in a flask at room temperature or below, providing the first experimental evidence to support theoretical predictions that (1) C2 has a singlet biradical character with a quadruple bond, thus settling a long-standing controversy between experimental and theoretical chemists, and that (2) C2 serves as a molecular element in the formation of sp2-carbon allotropes such as graphite, carbon nanotubes and C60.

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