Photoelectron spectroscopy of cyclic .beta.-diketones and their enolone tautomers

Houk, K. N.; Davis, Larry P.; Newkome, George R.; DUKE, R. E. JUN.; Nauman, R. V.

doi:10.1021/ja00806a026

Cited by 36 publications

(11 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Equilibrium Constant for Diketone-Enolone Tautomerization of Acetylacetone. Acetylacetone, like other β-diketones, 58 preferentially adopts either the diketone or the enolone form, depending on its environment. At room temperature in the gas phase 59,60 or in nonpolar solvents 10 AcAc exists primarily as the enolone.…”

Section: Resultsmentioning

confidence: 99%

To Boldly Look Where No One Has Looked Before: Identifying the Primary Photoproducts of Acetylacetone

et al. 2019

View full text Add to dashboard Cite

We investigate the gas-phase photochemistry of the enolone tautomer of acetylacetone (pentane-2,4-dione) following S2(ππ*) ← S0 excitation at λ = 266 and 248 nm, using three complementary time-resolved spectroscopic methods. Contrary to earlier reports, which claimed to study one-photon excitation of acetylacetone and found OH and CH3 as the only important gas-phase products, we detect 15 unique primary photoproducts and demonstrate that five of them, including OH and CH3, arise solely by multiphoton excitation. We assign the one-photon products to six photochemical channels and show that the most significant pathway is phototautomerization to the diketone form, which is likely an intermediate in several of the other product channels. Furthermore, we measure the equilibrium constant of the tautomerization of the enolone to diketone on S0 from 320 to 600 K and extract ΔH = 4.1 ± 0.3 kcal·mol–1 and ΔS = 6.8 ± 0.5 cal·mol–1·K–1 using a van’t Hoff analysis. We correct the C–OH bond dissociation energy in acetylacetone, previously determined as 90 kcal·mol–1 by theory and experiment, to a new value of 121.7 kcal·mol–1. Our experiments and electronic structure calculations provide evidence that some of the product channels, including phototautomerization, occur on S0, while others likely occur on excited triplet surfaces. Although the large oscillator strength of the S2 ← S0 transition results from the (ππ*) excitation of the CCCO backbone, similar to conjugated polyenes, the participation of triplets in the dissociation pathways of acetylacetone appears to have more in common with ketone photochemistry.

show abstract

Section: Resultsmentioning

confidence: 99%

To Boldly Look Where No One Has Looked Before: Identifying the Primary Photoproducts of Acetylacetone

et al. 2019

View full text Add to dashboard Cite

show abstract

“…The enolic forms of MC are both predicted to be less stable than the diketo form, in agreement with the photoelectron study. 25 In these calculations…”

Section: Methodsmentioning

confidence: 99%

Thermochemical and theoretical studies on cyclohexanediones

Pilcher¹,

Parchment²,

Hillier³

et al. 1993

J. Phys. Chem.

View full text Add to dashboard Cite

“…The same applies for diethers us. diketones (15,26). Then we see that the carbonyl 0 is stabilized slightly while the ether 0 is stabilized quite appreciably by the interaction.…”

Section: Resultsmentioning

confidence: 71%

“…The second photoelectron band of (3) (9.90 eV or 79 800 cm-l) can only relate to ionization from the carbonyl oxygen lone pair orbital (cf. [24][25][26][27][28] which in the ketone (2) is related to the IP at 9.45 eV.…”

Section: Resultsmentioning

confidence: 99%

On the photoelectron and ultraviolet spectra of molecules containing a divalent sulfur atom and a carbonyl group separated by a methylene group

Olivato¹,

Viertler²,

Wladislaw³

et al. 1976

Can. J. Chem.

View full text Add to dashboard Cite

Can. J. Chem. 54, 3026 (1976).Photoelectron spectra show that in CH3SCH2COCH3 the sulfur and carbonyl lone pair orbitals (S,O) are both stabilized with respect to the compounds containing S or CO only. This is in keeping with the observed values of the basicity constants. The ultraviolet absorption spectra contain the expected T * c 0 and a* t S bands and give evidence for a significant amount of mixing between the excited orbitals. P. R. OLIVATO, H. VIERTLER, B. WLADISLAW, K. C. COLE et C. SANDORFY. Can. J. Chern. 54, 3026 (1976).Nous avons mis en evidence par la mesure de spectres photoelectroniques que dans la molecule CH3SCH2COCH3 les orbitales des doublets libres du soufre et du carbonyle sont toutes deux stabilisies par rapport B leur valeur dans les molecules respectives qui ne contiennent que S ou CQ. Cela esten accord avec les valeurs observies des constantes de basiciti. Les frequences des bandes T * + 0 et U * t S dans le spectre d'absorption ultraviolet indiquent qu'il se produit un melange apprkiable entre les orbitales excities.

show abstract

Photoelectron spectroscopy of cyclic .beta.-diketones and their enolone tautomers

Cited by 36 publications

References 5 publications

To Boldly Look Where No One Has Looked Before: Identifying the Primary Photoproducts of Acetylacetone

To Boldly Look Where No One Has Looked Before: Identifying the Primary Photoproducts of Acetylacetone

Thermochemical and theoretical studies on cyclohexanediones

On the photoelectron and ultraviolet spectra of molecules containing a divalent sulfur atom and a carbonyl group separated by a methylene group

Contact Info

Product

Resources

About