(a) Explain why 2,4-pentanedione (Eq. 22.15) contains much less enol form in water (15%) than it does in hexane (92%).

(b) Explain why the same compound has a strong UV absorption in hexane solvent (λ_max = 272 nm, ϵ = 12,000), but a weaker absorption in water (λ_max = 274 nm, ϵ = 2050).

Transcribed Image Text:

H₂C :O: || C. :O: H CH3 H 2,4-pentanedione (acetylacetone) (a ß-dicarbonyl compound) H3C -H Ö: CH3 H enol form 92% in hexane solution (22.15)