The 3hyphen;fluoropropene molecule has been confirmed by microwave spectroscopy to exist in two rotational isomers,cisandgauche.Rotational constants in the ground vibrational state areA= 17236.638,B= 6002.915,C= 4579.827Mc/sec for thecisandA= 27720.349,B= 4263.628,C= 4131.984Mc/sec for thegaucheform. Rotational transitions are also assigned for isotopic species, eight of thecisand nine of thegaucheform. By using Costain's method the molecular structure is determined separately for the two isomers. The dipole moment and its components along the principal axes of inertia are mgr;a=0.742plusmn;0.008, mgr;b=1.601plusmn;0.011, mgr;total=1.765plusmn;0.014 D for thecisand mgr;a=1.595plusmn;0.006, mgr;b=0.908plusmn;0.012, mgr;c=0.623plusmn;0.014, mgr;total=1.939plusmn;0.015 D for thegaucheform. Through the temperature dependence of the intensity ratio thecisform is found more stable than thegaucheform by 166plusmn;67 cal/mole.The energies of the first and the second excited states of the Csngbnd;C torsion are determined by the relative intensity measurement to be 169.6plusmn;4.2 cmminus;1and 322.2plusmn;9.9 cmminus;1for thecisand 84.6plusmn;2.8 cmminus;1and 185plusmn;25 cmminus;1for thegaucheform. Some of the spectra in the excited states of thegaucheform are doublets due to the tunnel effect through thetransbarrier. Using these data a potential function for the rotation around the Csngbnd;C single bond is discussed. A correlation is pointed out between the potential function and the binding states of carbon atoms forming the rotation axis.
展开▼
