Bond lengths carbon-fluorine

Since the size of halogen atom Increases as we go down the group in the periodic table, fluorine atom is the smallest and iodine atom, the largest. Consequently the carbon-halogen bond length also Increases from C—to C— I. Some typical bond lengths, bond enthalpies and dipole moments are given in Table 10.2. 

Further insight into gas-phase SN2 reactions can be gained from recent calculations by Wolfe et al. (1981a,b). For the series of reactions (46), optimization of the transition-state geometry using a split Gaussian representation for the atomic orbitals reveals that the carbon—fluorine bond lengths vary... 

Figure 8.10 Representation of the crystal structure of [Cs((if-PhMe)3(p-Fln N(SiMe3)2 3)]. ° Indium, caesium, nitrogen and silicon atoms are shown as black spheres, fluorine atoms are grey and carbon atoms are white. Selected bond lengths Inl-NI 2.121(3), lnl-N2 2.128(3), In1-N3 2.127(3), Inl-FI 2.065(2), Cs1-F1 2.777(2)A...

Optimized Geometries. As the elements of the NMR shielding tensor for a nucleus represent local properties, the most important geometrical parameter influencing the value of the 19F shielding constant can be expected to be the length of the bond which attaches the fluorine to the benzene ring. The optimized values of the carbon-fluorine... 

Predict the bond length between carbon and fluorine in 1-chloro-l-fluoroetheylene (refer to Table 9-2) and predict if there is likely to be variation from your calculations. 

Ans. The predicted bond length is 141 pm however, the presence of the C=C and the chlorine will tend to affect this prediction. Fluorine and chlorine are quite electronegative (compared with carbon), forming negative centers that tend to repel. 

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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