The vibrational spectra, molecular structure and conformation of organic azides Part II. 2-Azido-1,3-butadiene

A sample of 2-azido-1,3-butadiene was synthesized from 4-bromo-1,2-butadiene and tetramethylguanidinium azide. Although the sample is highly explosive, we succeeded in making a structure determination by gaseous electron diffraction. IR spectra of the vapour, of the matrix isolated species in argon at 15 K, and of an amorphous and crystalline solid at 90 K were recorded. A Raman spectrum of the liquid, including semiquantitative polarization data, was obtained at 240 K.

The title compound was found to be planar with the CNN angle 117° oriented syn to the adjacent C=C double bond, the NNN angle was ca. 177° oriented anti to the C---N bond. The following bond distances (r_a) were obtained: N---N(N), 114.3; N---N(C), 125.3; C---N, 143.4; C=C, 135.0; and C---C, 146.7 pm.

No additional conformers were observed in the vapour, liquid, amorphous or crystalline states.