The Electronic Spectra of Unsubstituted Mono‐ to Pentaacetylene in the Gas Phase and in Solution in the Range 1100 to 4000 Å

The electronic spectra of the title compounds I (n), n = 1 to 5, were recorded under standard conditions for quantitative comparison. Spectra of I(1) to I(4) in the gas phase and of I(2) to I(5) in nonpolar solutions are presented in a computer plotted form, and wave length maxima and intensities are listed. Tentative assignments of the medium‐intensity, first transition ( A band) and the ultrahigh‐intensity, second transition ( B band) are given. Finally, spectra of I(2) to I(5) recorded at − 150° are presented and discussed ( A band). The syntheses of I(3) to I(5) are given in detail.