Structure and spectra of 1,3,2-dioxaphospholenes 1.microwave spectra of 2-chloro-4,5-dimethyl-1,3,2-dioxaphospholene and its isotopomers in the ground and excited vibrational states

摘要

The microwave spectrum of 2-chloro-4,5-dimethyl-1,3,2-dioxaphospholene(1) was studiedint he frequency range from 7 to 53 GHz.Rotational transitions of the parent moelcule in the ground and elecen excited vibrational states and those of its mono-substituted ~(37)Cl,~(13)C_(Me),and ~(13)C_(Cycle) isotopomers in the ground vibrational state were identified.Rotational constants and partial r_s-structure were obtained.The quartic centrifugal distortion constants,dipole moment components #mu#_a=3.8D and #mu#_c=0.24 D,and the ~(35)Cl quadrupole coupling constants were determined for the parent molecule.The fine structure of the microwave transitions in the parent moelcule was analyzed under the assumption of noninteracting methyl groups.The height of the barrier to internal rotation and the frequency of torsional vibrations were found.The frequencies of two lowest vibrational modes corresponding to deformation vibrations of the five-membered ring were estimated from the relative intensities of rotational transitions for different vibrational states.