Knowledge Bank

The microwave spectrum of $1-CH3B5H5$ has been studied primarily to obtain the height of the twelvefold barrier internal rotation. The observed transitions of the normal $B11$ species and two monosubstituted $B10$ species may be fitted to free internal rotation Hamiltonians with vibration-internal rotation interactions. From the lack of splitting of lines sensitive to the barrier height, an absolute upper limit of 6 cal/mole may be placed on the barrier. Structural results are $d[B(1)-B(2)]=1.684\backslash AA,d[B(2)-B(3)]=1.796\backslash AA$. A preliminary value of the dipole moment is $1.86D$.