Infrared spectra of a species of astrochemical interest: aminoacrylonitrile (3-amino-2-propenenitrile).
Ammonia easily reacts on cyanoacetylene in the gas phase or in a solvent to form the Z- and E-isomers of aminoacrylonitrile (3-amino-2-propenenitrile, 2). This kinetically stable enamine presents interest for its possible presence in the interstellar medium, the comets, the atmospheres of Planets including the Primitive Earth, and from a theoretical point of view. B3LYP/6-311+G(3df,2p) and G2 calculations indicate that the imine isomer is significantly less stable than the enamine 2. DFT and G2 calculations indicate that the Z-isomer of compound 2 lies ca. 8.0 kJ mol(-1) lower in energy than the E-isomer. The infrared spectra of the aminoacrylonitrile, in both the gas and condensed phases were recorded in the range 500-4000 cm(-1). Consistent with the theoretical calculations, the imine and the E-isomer of the enamine have never been detected in the infrared spectrum of a gaseous sample and only the Z-isomer has been observed. With a neat sample in the condensed phase, IR spectra of a 1:1 and 20:1/Z:E mixtures were recorded. The comparison of these data with the spectrum of the Z-isomer in the gas phase allowed us to deduce the IR spectrum of the E-isomer. The E-Z isomerization takes place through a torsion around the C=C bond. A possible mechanism involving a previous enamine-imine tautomerism must be discarded because it implies a much larger barrier than the direct isomerization process. Consistently, the presence of a deuterium atom has not been observed on the sp2 carbon of the products of distillation of a 1:1/E:Z mixture of the NCCH=CHND2.
Benidar
Abdessamad
A
PALMS, UMR CNRS 6627, Université de Rennes 1, 35042 Rennes, France, Laboratoire de Synthèse et Activation de Biomolécules, UMR CNRS 6052, ENSCR, Institut de Chimie de Rennes, 35700 Rennes, France.
Guillemin
Jean-Claude
JC
Mó
Otilia
O
Yañez
Manuel
M
D005118:Extraterrestrial Environment / Q000737:chemistry*; D007536:Isomerism; D008958:Models, Molecular; D015394:Molecular Structure; D009570:Nitriles / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D014732:Vibration
C516496:3-amino-2-propenenitrile; D009570:Nitriles; C520231:aminoacrylonitrile(3-amino-2-propenenitrile)