Low resolution microwave spectra and indo calculations of phenylisothiocyanate and phenylisocyanate

The low resolution spectra of φNCS and φNCO have been studied in the microwave R-band region. The spectroscopic constant (B + C) has been evaluated for both molecules. These data have been used to obtain information on the orientation of the linear NCS and NCO group relative to the bond from the phenyl ring. The results indicate an opening of the φ-N-C angle over that found in the hydrogen counterparts HNCS and HNCO. A modified INDO calculation yields structural parameters which are consistent with the trends observed, and indicate that the opening of the angle in going from HNCS (HNCO) to φNCS (φNCO) can be attributed to delocalization with the phenyl ring.