Homolytic Bond Cleavage

Question

Calculate the wavelength of the photons that will homolytically cleave a typical C-I bond.

Answer 1

We need to know the bond dissociation energy for the bond of interest. It looks like you've written a carbon - iodine bond (C-I). Looking up the bond dissociation energy for this, I find it to be 234 kJ/mole (you may find a different value).

234 kJ / mol C-I x 1 mol C-I / 6.022x10²³ C-I bonds = 3.89x10^-22 kJ of energy needed

E = hc / λ

E = energy = 3.89x10^-22 kJ x 1x10³ J / kJ = 3.89x10^-19 J

h = Planks constant = 6.626x10^-34 J-sec

c = speed of light = 3x10⁸ m / sec

λ = wavelength in meters

Solving for λ, we have ...

λ = hc / E

λ = (6.626x10^-34 J-sec)(3x10⁸ m / sec) / 3.89x10^-19 J)

λ = 5.11x10^-7 m = 511 nm = wavelength of the photon to cleave a typical C-I bond