Origin of the stability of carbon tetrafluoride: negative hyperconjugation reexamined

The energetic preference for multiple fluorine substitution at carbonhas been examined theoretically. Both the stabilization and bond shortening with increasing fluorine substitution may be attributed to Coulombic interactions between the negatively charged fluorines and the increasingly more positively charged carbon. This conclusion leads to the prediction that multiple silyl substitution should also lead to stabilization, and it was confirmed by calculations. Conversely, FCH 2 SiH 3 , in which the carbon will be close to neutral because of the opposing electron demand of the substituents, has negligible stabilization