The Spectra of the Diethynylbenzenes

Abstract

<p>The vibrational spectra of the three isomeric diethynylbenzenes (ortho, meta and para) are analyzed and the fundamental frequencies are assigned.</p> <p>Three electronic absorption systems are observed for each diethynylbenzene. The observed positions and intensities of these three transitions agree closely with the results of CNDO calculations. The transitions show large red shift with respect to the analogous absorptions in benzene.</p> <p>Rotational band contour analysis confirms the occurrence of two types of bands, single and double headed, in the lowest-energy transition of the diethynylbenzenes.</p> <p>It is argued that, at present, nothing definitive can be said about the geometry of the aromatic ring in the ground and first excited electronic state of derivatives of benzene.</p>