Methylenecyanamide (CH₂═NCN) and (Z)- and (E)-Iminoacetonitriles (NC–CH═NH), Dimers of Hydrogen Cyanide

Abstract

(Z)- and (E)-iminoacetonitriles (NCCHNH), two hydrogen cyanide dimers, are described as key compounds in prebiotic chemistry. Among the many possible dimers of HCN with covalent bonds, even the second on the scale of thermodynamic stability, methylenecyanamide (CH2NCN), has been investigated little. We show that this compound can be isolated, is stable enough to give an adduct with a nucleophile or a diene, and can be easily generated under prebiotic conditions, highlighting a possible role in this medium. Comparison between isomers shows significant differences in formation and chemical reactivity.

Vacuum Ultraviolet Single Photon Ionization and Decomposition of 2-Aminopropionitrile in Astrophysical Objects

“…Thus, for the two molecules, loss of H from AAN + and CH 3 from 2-APN + will lead to the same stable ion N≡CC(H)NH 2 + , which is formally a protonated HCN dimer. HCN dimers are currently discussed as important intermediates on the road to prebiotic building blocks (Melosso et al 2018;Shingledecker et al 2020;Sandström & Rahm 2021;Ayachi et al 2023). This will be further discussed in Section 4.…”

Synthesis and Characterization of N-Unsubstituted 2- and 3-Furanimines

“…7−11 Thus, the recording of their microwave or millimetric spectra led to the discovery of five simple N−H aldimines in the interstellar medium. 12,13 Methanimine, or derivatives substituted by an alkyl, vinyl, ethynyl, or nitrile group, has been isolated after synthesis using a reaction like dehydrochlorination, 7,9 dehydrocyanation, 8,9,11 retro-ene, 10,14 or retro-Diels−Alder reactions, 9 thermolysis of tetrazole derivatives, 15 and photolysis or thermolysis of azides. 15,16 These approaches were particularly efficient for small molecules with a low boiling point.…”

“…N–H aldimines are kinetically unstable compounds of great interest in the free state, or as intermediates in Strecker, Mannich, Kabachnik–Fields, and Ugi reactions, and A3 coupling reactions, or as iminium in Diels–Alder reactions . Many reactive N–H aldimines have been synthesized and characterized by spectroscopy. − Thus, the recording of their microwave or millimetric spectra led to the discovery of five simple N–H aldimines in the interstellar medium. , Methanimine, or derivatives substituted by an alkyl, vinyl, ethynyl, or nitrile group, has been isolated after synthesis using a reaction like dehydrochlorination, , dehydrocyanation, ,, retro-ene, , or retro-Diels–Alder reactions, thermolysis of tetrazole derivatives, and photolysis or thermolysis of azides. , These approaches were particularly efficient for small molecules with a low boiling point. The synthesis of arylaldimines, more difficult compounds to vaporize, was achieved by other approaches such as the reaction of azides with a ruthenium complex but without isolation of the product .…”