Photoisomerization of .beta.-diketones and .beta.-keto esters

Monitoring ultrafast intramolecular proton transfer processes in an unsymmetric β-diketone

“…1) and are attributed to pp* transitions (S 2 ' S 0 ) of CE species as is common for most b-diketones. 17 The minor band in the deep UV (in case of BZA and DBM) is believed to have a partial contribution from the np* transition of the diketone conformer (Scheme 1a) [17][18][19] which constitutes a small fraction of molecules in equilibrium. BZA has a large molar extinction coefficient (on the order of 10 À4 M À1 cm À1 ) 18 as well as a large oscillator strength, 22 but fluorescence is not observed at room temperature, suggesting very efficient non-radiative deactivation processes.…”

“…6 In contrast, when b-diketones in solution are subjected to UV irradiation, short-lived species and further products are formed, 17 which fully reverse to the reactant in the dark over a period of hours. 4,[17][18][19][20][21] However, questions remain on the time scale of the primary processes (including the PT) leading to the formation of photoproducts in solution.…”

Enolization rates control mono- versus di-fluorination of 1,3-dicarbonyl derivatives

“…The photochemistry and photophysics of 1,3-diaryl-1,3-dicarbonyl derivatives have been extensively studied. 40,41 In the 1970s, the groups of Markov 42,43 and Mazur [44][45][46] reported photoisomerization of 1,3-dicarbonyl compounds, whereby the keto-enol equilibrium was perturbed towards the keto tautomer upon irradiation. This process reverses to attain the tautomeric equilibrium by a nonphotochemical reaction in darkness.…”

Fate and implication of acetylacetone in photochemical processes for water treatment

“…The population of keto and enol depends on many factors, such as the solvent polarity , temperature (Burdett and Rogers, 1966), and the presence of UV irradiation (Coussan et al, 2003;Veierov et al, 1973Veierov et al, , 1977. For example, in aliphatic hydrocarbon solvents, including n-hexane, n-heptane, cyclohexane, and benzene, AA exists predominantly in the chelated enol (Veierov et al, 1977), while the keto form predominates in aqueous solutions due to the strong intermolecular hydrogen bonding with water .…”