Vapour pressure of 2,4-pentanedione

Raviprasad, A.; Rao, K. Venkateswara

doi:10.1016/0021-9614(85)90063-1

Cited by 6 publications

(3 citation statements)

References 5 publications

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“…The enthalpy of vaporization of acetylacetone has also been measured several times. − The resulting values, in chronological order, are summarized in Table . Good agreement is found for most of the recent measurements if the experimental data are adjusted to T = 298.15 K. Equation 1 was used for this purpose.…”

Section: Introductionmentioning

confidence: 99%

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The Thermochemistry of 2,4-Pentanedione Revisited: Observance of a Nonzero Enthalpy of Mixing between Tautomers and Its Effects on Enthalpies of Formation

et al. 2005

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The enthalpies of formation of pure liquid and gas-phase (Z)-4-hydroxy-3-penten-2-one and 2,4-pentanedione are examined in the light of some more recent NMR studies on the enthalpy differences between gas-phase enthalpies of the two tautomers. Correlation gas chromatography experiments are used to evaluate the vaporization enthalpies of the pure tautomers. Values of (51.2 ( 2.2) and (50.8 ( 0.6) kJ‚mol -1 are measured for pure 2,4-pentanedione and (Z)-4-hydroxy-3-penten-2-one, respectively. The value of (50.8 ( 0.6) kJ‚mol -1 can be contrasted to a value of (43.2 ( 0.2) kJ‚mol -1 calculated for pure (Z)-4-hydroxy-3-penten-2-one when the vaporization enthalpy is measured in a mixture of tautomers. The difference is attributed to an endothermic enthalpy of mixing that destabilizes the mixture relative to the pure components. Calculation of new enthalpies of formation for (Z)-3-hydroxy-3-penten-2-one and 2,4-pentanedione in both the gas, ∆ f H°m(g) ) (-378.2 ( 1.2) and (-358.9 ( 2.5) kJ‚mol -1 , respectively, and liquid phases, ∆ f H°m(l) ) (-429.0 ( 1.0) and (-410.1 ( 1.2) kJ‚mol -1 , respectively, results in enthalpy differences between the two tautomers both in the liquid and gas phases that are identical within experimental error, and in excellent agreement with recent gas-phase NMR studies.

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Section: Introductionmentioning

confidence: 99%

“…The enthalpy of vaporization of acetylacetone has also been measured several times. [5][6][7][8][9][10][11] The resulting values, in chronologi-cal order, are summarized in Table 1. Good agreement is found for most of the recent measurements if the experimental data are adjusted to T ) 298.15 K. Equation 1 was used for this purpose.…”

Section: Introductionmentioning

confidence: 99%

The Thermochemistry of 2,4-Pentanedione Revisited: Observance of a Nonzero Enthalpy of Mixing between Tautomers and Its Effects on Enthalpies of Formation

et al. 2005

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“…The expansion was skimmed to produce a molecular beam, which was intersected by counter-propagating and spatially overlapped UV and VUV laser beams. Based on the vapor pressure of AcAc at 273 K, , the expansion is estimated to contain 0.2% AcAc.…”

Section: Experimental Methodsmentioning

confidence: 99%

Acetylacetone Photolysis at 280 nm Studied by Velocity-Map Ion Imaging

Rinaman

Murray

2023

J. Phys. Chem. A

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The photolysis of acetylacetone (AcAc) has been studied using velocity-map ion imaging with pulsed nanosecond lasers. The enolone tautomer of AcAc (CH3C(O)CHC(OH)CH3) was excited in the strong UV absorption band by UV pulses at 280 nm, preparing the S2(ππ*) state, and products were probed after a short time delay by single-photon VUV ionization at 118.2 nm. Two-color UV + VUV time-of-flight mass spectra show enhancement of fragments at m/z = 15, 42, 43, 58, and 85 at the lowest UV pulse energies and depletion of the parent ion at m/z = 100. Ion images of the five major fragments are all isotropic, indicating dissociation lifetimes that are long on the timescale of molecular rotation but shorter than the laser pulse duration (<6 ns). The m/z = 15 and 85 fragments have identical momentum distributions with moderate translational energy release, suggesting that they are formed as a neutral product pair and likely via a Norrish type I dissociation of the enolone to form CH3 + C(O)CHC(OH)CH3 over a barrier on a triplet surface. The m/z = 43 fragment may be tentatively assigned to the alternative Norrish type I pathway that produces CH3CO + CH2C(O)CH3 on S0 following phototautomerization to the diketone, although alternative mechanisms involving dissociative ionization of a larger primary photoproduct cannot be conclusively ruled out. The m/z = 42 and 58 fragments are not momentum-matched and consequently are not formed as a neutral pair via a unimolecular dissociation pathway on S0. They also likely originate from the dissociative ionization of primary photofragments. RRKM calculations suggest that unimolecular dissociation pathways that lead to molecular products on S0 are generally slow, implying an upper-limit lifetime of <46 ns after excitation at 280 nm. Time-dependent measurements suggest that the observed photofragments likely do not arise from dissociative ionization of energized AcAc S0*.

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