2 ELECTRONIC-TRANSITIONS IN THE NEAR-UV REGION OF 6 ISOMERIC DIFLUOROBENZONITRILES .1.

A new technique-photoacoustic spectroscopy (PAS)-is applied to the study of the electronic transitions in the six isomers 3,5-; 2,4-; 2,5-; 3,4-; 2,3-; and 2,6-difluorobenzonitriles. The PAS spectra are compared with solution spectra recorded. The two pi-pi* transitions analogous to the benzene strong 200 nm, and weak and forbidden 260 nm transitions could be identified in these molecules. An interesting observation is that the origins of the electronic transitions in these molecules are in fairly good agreement with the additive rule which is routed through different starting points and also a prediction of the origin of meta fluorobenzonitrile at 37,536.1 cm-1 from the data of 3,4- and 2,5-difluorobenzonitriles. The fluorescence spectrum for all six isomers is reported here for the first time.