The absorbance spectrum of 1,3-butadiene displays an absorption in the UV region (max= 217nm ), while the absorption spectrum of 1,2-butadiene does not display a similar absorption. Explain. The UV absorption for 1,2-butadiene is missing from the spectrum because the bonds in 1,2butadiene are and max is therefore :han 217nm and beyond the range used by most UV-Vis spectrometers