| Abstract
| - Ammonia easily reacts on cyanoacetylene in the gas phase or in a solvent to form the Z- and E-isomers ofaminoacrylonitrile (3-amino-2-propenenitrile, 2). This kinetically stable enamine presents interest for its possiblepresence 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 imineisomer is significantly less stable than the enamine 2. DFT and G2 calculations indicate that the Z-isomer ofcompound 2 lies ca. 8.0 kJ mol-1 lower in energy than the E-isomer. The infrared spectra of theaminoacrylonitrile, in both the gas and condensed phases were recorded in the range 500−4000 cm-1. Consistentwith the theoretical calculations, the imine and the E-isomer of the enamine have never been detected in theinfrared spectrum of a gaseous sample and only the Z-isomer has been observed. With a neat sample in thecondensed phase, IR spectra of a 1:1 and 20:1/Z:E mixtures were recorded. The comparison of these datawith 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 CC bond. A possible mechanism involvinga previous enamine−imine tautomerism must be discarded because it implies a much larger barrier than thedirect isomerization process. Consistently, the presence of a deuterium atom has not been observed on thesp2 carbon of the products of distillation of a 1:1/E:Z mixture of the NCCHCHND2.
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