Ethanimine (CH₃CHNH) was identified toward Sagittarius B2 North, Sgr B2(N), by Loomis et al. in 2013. The detection of both the E- and Z- isomers of ethanimine was made possible by new experimental measurements of the spectra of the species. The lines were then identified in the PRIMOS Project data from the Green Bank Telescope. Twelve rotational transitions of E-ethaninine and eight transitions of Z-ethanimine were identified.

Z-ethanimine	E-ethanimine

The first imine in the series, methanimine, has also been detected. Ethanimine is evidently not used in any commercial chemical process. The isomer labels Z- and E- are from the German words zusammen (together) and entgegen (opposite).