Fluoromethane, bond length

Table 5 lists C—F bond lengths for fluoromethanes where hydrogen atoms are replaced by various atoms or groups. If the substituents have electron-donating properties, such as methyl or phenyl groups, the C—F bonds are even longer than that in fluoromethane. 

Unfortunately, structures of monosubstituted cyclic hydrocarbons which would allow a systematic correlation between C—F bond distances and ring size have not been reported in the literature. Some polyfluorinated and the perfluorinated cyclopropanes were studied by MW and ED and the C—F bond lengths are listed in Table 14. If only one fluorine is bonded to a ring carbon atom, the C—F bonds are long ca 137 to 139 pm), very similar to that in fluoromethane [139.1(1) pm]. An unexpected result is that the cis standing bonds... 

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