Isomerization of cyanopropyne in solid argon

Thomas Custer (1) , Urszula Szczepaniak (1, 2) , Marcin Gronowski (1) , Nathalie Piétri (3) , Isabelle Couturier-Tamburelli (3) , Jean-Claude Guillemin (4) , Michal Turowski (1) , Robert Kolos (1)

1 PAN - Polska Akademia Nauk = Polish Academy of Sciences = Académie polonaise des sciences
2 ISMO - Institut des Sciences Moléculaires d'Orsay
3 PIIM - Physique des interactions ioniques et moléculaires
4 ISCR - Institut des Sciences Chimiques de Rennes

Cyanopropyne, CH3-C[triple bond, length as m-dash]C-CN, is a simple molecule whose photochemistry is still unexplored. Here we investigate the UV photolysis of this astrophysically significant nitrile trapped in solid argon. The FTIR study was assisted with 15N-isotopic substitution data and with DFT-level computations including the analyses of ground- and excited-state potential energy surfaces. Cyanopropyne was found to decay mainly via a two-step isomerization process. Infrared absorption spectra evolved to show signals from allenyl cyanide, CH2[double bond, length as m-dash]C[double bond, length as m-dash]CH-CN, which then further convert into propargyl cyanide, H-C[triple bond, length as m-dash]C-CH2-CN. Some evidence for the presence of allenyl isocyanide, propargyl isocyanide, 3-cyanocyclopropene, and 1,2,3-butatrien-1-imine under particular experimental conditions was also observed. Although cyano/isocyano interconversion has been observed during photolysis of other closely related species in solid argon matrices, including H-C[triple bond, length as m-dash]C-CN, no evidence could be found for production of 1-isocyano-1-propyne, CH3-C[triple bond, length as m-dash]C-NC for these experiments.

Domaines: Chimie

Thomas Custer, Urszula Szczepaniak, Marcin Gronowski, Nathalie Piétri, Isabelle Couturier-Tamburelli, et al.. Isomerization of cyanopropyne in solid argon. Physical Chemistry Chemical Physics, 2019, 21 (25), pp.13668-13678. ⟨10.1039/c8cp06739b⟩. ⟨hal-02278409⟩