Question

Why Hydrogen of CHCl3 is more acidic than hydrogen of CHF3 ?

Answer 1

Dear Student, While comparing two compounds for acidic strength, we can check for the stability of their conjugate bases. The one having the most stable (weak) conjugate base is the strong acid. The conjugate bases of Chloroform and Fluoroform are -CCl3 and -CF3 respectively. The negative charge in -CF3 is stabilized by the inductive effect of the electronegative fluorine atoms while the negative charge in -CCl3 is more stabilized due the fact that the negative charge is delocalized in the vacant d-orbitals of Cl atoms by back donation. F can’t stabilize the negative charge by delocalization as it does not have d-orbitals. Delocalization stabilizes charges more than inductive effect. So, -CCl3 is more stable than -CF3 . Hence, Chloroform is a stronger acid than Fluoroform. Regards