# What is the hybridisation of trifluoromethyl free radical? Tags: inorganic-chemistry, hybridization, radicals - Score: 14 - Views: 15200 - Answers: 1 - Answered: yes - Asked by: James Hunt (503 rep) - Asked: 2016-04-19 - Edited: 2020-03-02 - Site: chemistry ## Question Having three σ bonds in a similar manner to $\ce{CH3^·}$ free radical, $\ce{CF3^·}$ should also have $\mathrm{sp^2}$ hybridisation. However, if we look at its shape, it is pyramidal and not planar like $\ce{CH3^·}$ free radical (which is $\mathrm{sp^2}$-hybridised), which signifies that $\ce{CF3^·}$ should have $\mathrm{sp^3}$ hybridisation. But how is this possible because the three σ-bonds will bond with three hybrid orbitals? Where does the third p-orbital come? If its hybridisation is $\mathrm{sp^3},$ then why is it? ## Answers ### Answer by EJC (score: 13) Hyperconjugation between the orbital that contains the lone pair and the $\ce{C-F}$ antibonding orbital contributes to the pyramidalization of $\ce{CF3^·}$ radical: In the planar geometry the orbitals are perpendicular and no overlap occurs. References Carey, F. A.; Sundberg, R. J. Advanced Organic Chemistry, Part A: Structure and Mechanisms, 5th