N-Fluoro substituents

The C=C and C—N bond lengths are in each case and each basis set shorter than in unsubstituted 115 of Table 4. The N—F distances depend strongly on the type of hybridization at nitrogen They are shorter in the planar N sp2 case (type 116) than for pyramidal N sp3 of type 117 and of type 121. 6-31G N—F distances are significantly shorter, by more than 0.04 A, than the 3-21G and 6-31G values. 

The NCXC2 angle is significantly shorter than that of unsubstituted 115 in the Af,Af-difluoro-substituted 135 and shows a strong narrowing to 118° on rotation to type 121. 

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