Initial mechanisms for the unimolecular decomposition of electronically excited nitrogen-rich energetic materials with tetrazole rings: 1-DTE, 5-DTE, BTA, and BTH

Reactions have been observed between excited ions of carbon disulfide and carbon disulfide, water, iodine and ethylene. The ions CS3+, C2S2+, C2S3+, H2OS⁺, CSI⁺, SI⁺, C2H3S⁺ and C2H4S+ are formed in these reactions. An additional contribution to the C2S2+ ion results from reaction of CS+ with CS2. The reaction of Ι2+ with CS2 leads to the ion CS2I⁺. Reactions of excited molecular ions have also been found in benzonitrile, chlorobenzene, bromobenzene and iodobenzene. Ions of the C12 series such as C12H9CN⁺, C12H10+ and C12H⁺9 are formed in these processes. In all cases, the appearance potential of the secondary ion is lower than the first dissociation limit of the molecular ion. It is therefore concluded that the excited ions are stable towards unimolecular decomposition. Repeller field studies show that they must be metastable towards decay by photon emission. In the case of aromatic ions this is explained by fast internal conversion of electronically excited ions into high vibrational levels of their electronic ground states. The form of the ionization efficiency curves of the secondary ions at high electron energies corresponds to what is expected if the excited precursors are formed in optically allowed transitions.

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Synthesis of methanediol [CH2(OH)2]: The simplest geminal diol

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2111938119 ◽

2021 ◽

Vol 119 (1) ◽

pp. e2111938119

Author(s):

Cheng Zhu ◽

N. Fabian Kleimeier ◽

Andrew M. Turner ◽

Santosh K. Singh ◽

Ryan C. Fortenberry ◽

...

Keyword(s):

Gas Phase ◽

Atmospheric Chemistry ◽

Reactive Intermediates ◽

Hydroxyl Groups ◽

Unimolecular Decomposition ◽

Flight Mass Spectrometry ◽

Criegee Intermediates ◽

Aldehydes And Ketones ◽

Electronically Excited ◽

Geminal Diol

Geminal diols—organic molecules carrying two hydroxyl groups at the same carbon atom—have been recognized as key reactive intermediates by the physical (organic) chemistry and atmospheric science communities as fundamental transients in the aerosol cycle and in the atmospheric ozonolysis reaction sequence. Anticipating short lifetimes and their tendency to fragment to water plus the aldehyde or ketone, free geminal diols represent one of the most elusive classes of organic reactive intermediates. Here, we afford an exceptional glance into the preparation of the previously elusive methanediol [CH2(OH)2] transient—the simplest geminal diol—via energetic processing of low-temperature methanol–oxygen ices. Methanediol was identified in the gas phase upon sublimation via isomer-selective photoionization reflectron time-of-flight mass spectrometry combined with isotopic substitution studies. Electronic structure calculations reveal that methanediol is formed via excited state dynamics through insertion of electronically excited atomic oxygen into a carbon–hydrogen bond of the methyl group of methanol followed by stabilization in the icy matrix. The first preparation and detection of methanediol demonstrates its gas-phase stability as supported by a significant barrier hindering unimolecular decomposition to formaldehyde and water. These findings advance our perception of the fundamental chemistry and chemical bonding of geminal diols and signify their role as an efficient sink of aldehydes and ketones in atmospheric environments eventually coupling the atmospheric chemistry of geminal diols and Criegee intermediates.

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Reactive scattering of an electronically-excited nitrogen atom with H 2 and its isotopic variants:N(2D)+H2/D2/T2

Computational and Theoretical Chemistry ◽

10.1016/j.comptc.2016.02.010 ◽

2016 ◽

Vol 1081 ◽

pp. 38-43

Author(s):

Emine Tanis

Keyword(s):

Nitrogen Atom ◽

Reactive Scattering ◽

Electronically Excited ◽

Excited Nitrogen

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