Photodissociation dynamics of acetylacetone: The OH product state distribution

Abstract

Acetylacetone in the supersonic jet, which exists predominantly as an enolic form, is found to give rise to the OH fragment after the -* transition induced by the UV absorption. The nascent OH product state distributions are determined using a laser-induced fluorescence technique at the excitation wavelengths of 291 and 266 nm. The OH fragment is vibrationally cold, and its rotational state distribution is peaked at Nϭ3 or 4 at the pump wavelength of 291 or 266 nm, respectively. No fluorescence from the excited acetylacetone has been observed even in the energy region near the origin, suggesting the ultrafast nonradiative processes of the excited state. From the measured OH product state distributions, the upper bound for the dissociation energy of the acetylacetone is estimated to be 90.3 kcal/mol. The ratios of ⌳-doublets and spin-orbit states of the OH fragment are also measured. A slight preference of the OH fragment in the 2 ⌸ 3/2 state over the 2 ⌸ 1/2 state is observed. The ⌸ Ϫ /⌸ ϩ ratios, determined by the relative intensity ratios of Q and P ͑or R͒ lines, are found to be less than unity, suggesting the preferential cleavage of the C-OH bond on the molecular plane probably due to a relatively strong intramolecular hydrogen bonding of the enolic acetylacetone. The prior calculation reproduces the experiment quite well for the OH rotational state distribution at 291 nm, while it does not for that at 266 nm. This suggests that the transition state in the acetylacetone dissociation, at the low energy near threshold, may be completely loosely defined on the potential energy surface which does not have a barrier to recombination, and it becomes tightened as the energy increases above the reaction threshold.

Ultrafast Intersystem Crossing in Acetylacetone via Femtosecond X-ray Transient Absorption at the Carbon K-Edge

“…3,8 Experimentally, the lowest triplet state has been invoked to explain the rotational energy distribution of the product OH radical in the photodissociation of AcAc, which is probed by laser-induced fluorescence. [8][9] The T 1 state is proposed to be a common intermediate in both the 266-and 248-nm photolysis of AcAc. 10 The theoretical reaction pathway proposed (depicted in Figure 1) for this reaction indeed reinforces the picture of non-adiabatic population transfer from the excited singlet to the triplet state following internal conversion, and calculations even reveal the possibility of a triple S 1 /T 1 /T 2 curve-crossing region.…”

UV–visible spectra and gas-phase rate coefficients for the reaction of 2,3-pentanedione and 2,4-pentanedione with OH radicals

“…For example -dicarbonyls compounds are used as solvents [1] and starting materials for the organic compounds synthesis. Due to their Keto -diketones are widely used in several industrial sectors, mainly in the preparation of chelate compounds [2]. In addition to these emission sources, these compounds can be formed in situ in the atmosphere through the oxidation of anthropogenically emitted VOCs [3].…”

Equilibrium and Kinetic Studies for Extracting Cu, Mn, and Fe From Pulp Wastewater onto a C-18 Column with Acetylacetone Complexing Ligand

“…In solid phase extraction studies of heavy metal ions based on chelation, the pH of aqueous solutions is one of the main factors influencing the quantitative recoveries of the analytes (Korn et al 2006;de Castro, de Alâcantara, and dos Santos Roldan 2004;Gilli et al 1989;Yoon, Choi, and Kim 1999;Tateki, Fumio, and Shigeki 1999;Xu et al 2004;Pearson and Anderson 1970). Environmental samples are comprised of complex matrixes depending on the sample type and sediment biogeochemistry.…”