STUDY OF TRANSITION STATE IN ISOMERIZATION OF TRANS-N2F2 TO CIS-N2F2 BY EXTENDED HUCKEL THEORY

The quantitative agreement with experimental barrier height and the extra stabilization energy of cis-N2F2 over trans-N2F2 may not be considered to be very good, but this is only to be expected as small differences between large quantities are being calculated. It appears from our present calculations that the use of Cusachs relation for evaluating the off-diagonal matrix elements in this system is open to question since the experimentally observed planarity of N2F2 is not correctly predicted by the use of this relation. We therefore prefer the use of the Wolfsberg-Helmholz relation in this system. A value of K= 1.75 appears to be preferable. The results of all the E.H.T. calculations made here for difluorodiazine clearly show that a twisted transition state is more probable than a linear one (LT or LC) in the isomerization of trans-N2F2 to cis-N2F2. This conclusion also receives further support from a consideration of the high preexponential factor in the rate equation [1] and the multiplicity of the transition state. © 1968 Springer-Verlag.