UV spectrum

Question

I have a problem with UV Spectrum chemistry. I dont know how to calculate lambda max for molecules with a single C-c double bond. Please help :) for exmple for Cholesterol

Answer 1

Not sure there's a way to calculate lambda max for double bonds that aren't conjugated.  If conjugated, and other variants, one can use Woodward-Fieser Rules.  However, I've not seen calculations for a single double bond. It may be possible if one knew the change in energy required to promote the electron from the π orbital to the π* anti-bonding orbital, and then to use ∆E = hc/λ to calculate λ, because λ will depend on the change in energy between the 2 energy levels.  The greater the ∆E, the lower the λ.  Sorry I can't provide any actual calculations.  Maybe someone else will contribute.