Microwave Spectrum of Allyl Isothiocyanate: gauche Conformer

Centrifugal distortion analysis of the microwave spectrum of allyl isothiocyanate (C-gauche conformer)

“…The results of dipole moment calculation from the model geometry in [1] give ¾ ¼ Although a reasonably good fit was obtained, the rotational constant and the centrifugal distortion constant à could not be determined independently. The resultant correlation matrix of the fit indicated a strong correlation between and à (matrix element between and à ½ ¼¼¼).…”

“…In [1] 36 -type Ê-branch transitions were and some CD ( parameters) constants where remained undetermined. Using these constants, -type spectrum was predicted up to 37 GHz which covers  ½ ½¿ and  ½ ½ series.…”

“…The resultant least-squares fit of all the new and previously reported [1] microwave data gives more accurate values of all the rotational and CD constants.…”

“…In an earlier paper [1] we have reported an analysis of the microwave spectrum of allyl isothiocyanate (H ¾ C CHCH ¾ NCS) in the frequency range 12.4-26.0 GHz. From this analysis of -type Ê-branch transitions, it was concluded that in the vapour phase, allyl isothiocyanate predominantly exists in the C-gauche conformation having NCS group cis with respect to the C-C bond.…”

“…Since allyl isothiocyanate is a relatively lighter open chain molecule the effect of centrifugal distortion on the rotational energy levels should be substantial. Although a partial CD analysis was done in [1], all the CD parameters could not be determined accurately because of the lack of sufficient data. However, this can be achieved by extending the microwave measurements to more higher rotational states and by incorporating -type transitions (¡Ã ½ ¼ ) in the leastsquares analysis.…”