Photodecomposition of acrolein in oxygen-nitrogen mixtures

We investigated the dynamics of isomerization and multi-channel dissociation of propenal (CH(2)CHCHO), methyl ketene (CH(3)CHCO), hydroxyl propadiene (CH(2)CH(2)CHOH), and hydroxyl cyclopropene (cyclic-C(3)H(3)-OH) in the ground potential-energy surface using quantum-chemical calculations. Optimized structures and vibrational frequencies of molecular species were computed with method B3LYP∕6-311G(d,p). Total energies of molecules at optimized structures were computed at the CCSD(T)∕6-311+G(3df,2p) level of theory. We established the potential-energy surface for decomposition to CH(2)CHCO + H, CH(2)CH + HCO, CH(2)CH(2)∕CH(3)CH + CO, CHCH∕CH(2)C + H(2)CO, CHCCHO∕CH(2)CCO + H(2), CHCH + CO + H(2), CH(3) + HCCO, CH(2)CCH + OH, and CH(2)CC∕cyclic-C(3)H(2) + H(2)O. Microcanonical rate coefficients of various reactions of trans-propenal with internal energies 148 and 182 kcal mol(-1) were calculated using Rice-Ramsperger-Kassel-Marcus and Variational transition state theories. Product branching ratios were derivable using numerical integration of kinetic master equations and the steady-state approximation. The concerted three-body dissociation of trans-propenal to fragments C(2)H(2) + CO + H(2) is the prevailing channel in present calculations. In contrast, C(3)H(3)O + H, C(2)H(3) + HCO and C(2)H(4) + CO were identified as major channels in the photolysis of trans-propenal. The discrepancy between calculations and experiments in product branching ratios indicates that the three major photodissociation channels occur mainly on an excited potential-energy surface whereas the other channels occur mainly on the ground potential-energy surface. This work provides profound insight in the mechanisms of isomerization and multichannel dissociation of the system C(3)H(4)O.

Section: Introductionmentioning

confidence: 99%

“…Fang 14 computed the S 0 , S 1 and T 1 (π -π *) potential-energy surfaces (PES) of propenal for reactions (1)- (3). Asymptotes CH 2 CHCO + H and CH 2 CH + HCO correlate adiabatically with the S 0 and T 1 PES.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of isomerization and decomposition of propenal

Chin

Lee

2011

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Three primary dissociation pathways (1)-(3) were observed upon optical excitation to the S 1 (n-π *) state of propenal with wavelengths 300, 313, and 334 nm, 3,7,11 CH 2 CHCHO → CH 2 CHCO + H H 0K = 87.5 (86.9) kcal mol −1 , …”

Section: Introductionmentioning

confidence: 99%

Molecular-beam experiments for photodissociation of propenal at 157 nm and quantum-chemical calculations for migration and elimination of hydrogen atoms in systems C3H4O and C3H3O

Chin¹,

Chaudhuri²,

Lee³

2011

We investigated the dynamics of photodissociation of propenal (acrolein, CH(2)CHCHO) at 157 nm in a molecular beam and of migration and elimination of hydrogen atoms in systems C(3)H(4)O and C(3)H(3)O using quantum-chemical calculations. Compared with the previous results of photodissociation of propenal at 193 nm, the major difference is that the C(3)H(3)O fragment present at the 193-nm photolysis disappears at the 157-nm photolysis whereas the C(3)H(2)O fragment absent at 193 nm appears at 157 nm. Optimized structures and harmonic vibrational frequencies of molecular species with gross formula C(3)H(2-4)O were computed at the level of B3LYP/6-311G(d,p) and total energies of those molecules at optimized structures were computed at the level of CCSD(T)/6-311+G(3df,2p). Based on the calculated potential-energy surfaces, we deduce that the C(3)H(3)O fragment observed in the photolysis of propenal at 193 nm is probably CHCCHOH ((2)A") and/or CH(2)CCOH ((2)A") produced from an intermediate hydroxyl propadiene (CH(2)CCHOH) following isomerization. Adiabatic and vertical ionization potentials of eight isomers of C(3)H(3)O and two isomers of C(3)H(2)O were calculated; CHCCHOH ((2)A") and CH(2)CCOH ((2)A") have ionization potentials in good agreement with the experimental value of ∼7.4 eV. We also deduce that all the nascent C(3)H(3)O fragments from the photolysis of propenal at 157 nm spontaneously decompose mainly to C(2)H(3) + CO and C(3)H(2)O + H because of the large excitation energy. This work provides profound insight into the dynamics of migration and elimination of hydrogen atoms of propenal optically excited in the vacuum-ultraviolet region.

“…Photodissociation studies at 313 nm by Gardner et al in air mixtures found five different primary dissociation channels among which CO was one of the products in three different channels. 27 The other products formed in these CO-producing pathways were ethylene and singlet and triplet states of ethylidene. The formation of ethylene in this case was attributed to molecular rearrangement in the S 1 state.…”

Section: Introductionmentioning

confidence: 99%

State-resolved imaging of CO from propenal photodissociation: Signatures of concerted three-body dissociation

Dey

Fernando

Suits

2014

Articles you may be interested inDissociation of internal energy-selected methyl bromide ion revealed from threshold photoelectron-photoion coincidence velocity imaging Monte Carlo simulation of nitrogen dissociation based on state-resolved cross sections Phys. Fluids 26, 012006 (2014); 10.1063/1.4862541Raman spectroscopy and crystal-field split rotational states of photoproducts CO and H2 after dissociation of formaldehyde in solid argon H and D release in 243.1 nm photolysis of vibrationally excited 3ν 1 , 4ν 1 , and 4ν CD overtones of propyne-d 3State-selected DC sliced images of propenal photodissociation show clear signatures of a novel synchronous concerted three-body dissociation of propenal recently proposed by Lee and co-workers to give C 2 H 2 + H 2 + CO [S. H. Lee, C. H. Chin, C. Chaudhuri, ChemPhysChem 12, 753 (2011)]. Unlike any prior example of a concerted 3-body dissociation event, this mechanism involves breaking three distinct bonds and yields 3 distinct molecules. DC sliced images of CO fragments were recorded for a range of rotational levels for both v = 0 and v = 1. The results show formation of two distinct CO product channels having dissimilar translational energy distributions with characteristic rovibrational state distributions. The images for CO (v = 0) show a large contribution of slower CO fragments at lower rotational levels (J = 5-25). This slow component is completely absent from the v = 1 CO images. The images for the higher rotational levels of the v = 0 and v = 1 CO are nearly identical, and this provides a basis for decomposing the two channels for v = 0. The quantum state and translational energy distributions for the slow channel are readily assigned to the 3-body dissociation based on the properties of the transition state. The faster CO fragments dominating the higher rotational levels in both v = 0 and v = 1 are attributed to formation of CH 3 CH + CO, also in agreement with the inferences based on previous non-state-resolved measurements with supporting theoretical calculations.