Orbital Valency Force Field Constants and Ionicity of M—X Bond of Tetrahalides of IV Group Elements

Orbital valency force field constants are evaluated utilising the recent vapour phase vibrational spectral data for some IV group tetrahalides. The results are discussed in the light of ionicity of M-X bond and bond stretching force constants for fluoro species of Si and Fe have been predicted

The electronic absorption and vibrational spectra of 2,6-and 3,5-dichlorobenzonitriles

The electronic absorption spectra of 2.6- and 3,5-dichlorobenzonitriles have been photographed in vapour phase on medium quartz spectrograph. The observed spectra correspond to A1g → B2u transition of benzene. The 0,0 band of the observed absorption systems for 2,6- and 3,5-dichlorobenzo- nitriles have been identified at 34 015 and 34 262 cm-1 respectively. Best of the bands were assigned as ground and excited state fundamentals, their combinations and overtones. In the case of 2,6-dichlorobenzonitrile the shorter wavelength band system corresponding to A1g → B1u transition of benzene has also appeared. The infrared absorption spectra of these mole- cules have also been studied in the region (200-4 000 cm-1). The assigned ground and excited state fundamentals from ultraviolet absorption spectra have been correlated with infrared data