The Spectrum of Allene in the Photographic Infra-Red

The spectrum of allene between 7000 and 12,000A has been photographed under high dispersion, the observed bands being assigned as harmonics and combinations of fundamental frequencies of the molecule. Rotational analysis of the parallel band at 11,444A has given 97.0×10^—40 g cm² as the large moment of inertia. The perpendicular band at 11,017A has been found to be unexpectedly complicated, but was too weak for detailed analysis. It has been concluded that the dimensions in ethylene and allene are: $$\mathrm{C}-\mathrm{H}\text{=1.087}\mathrm{A}\mathrm{,\hspace{0.17em}\hspace{0.17em}}\mathrm{C}=\mathrm{C}\text{=1.330}\mathrm{A}\mathrm{,\hspace{0.17em}\hspace{0.17em}}\mathrm{H}–\mathrm{C}–\mathrm{H}{\text{=116}}^{\circ }.$$