Infrared fluorescence from nascent CO2 and COF2 photoproducts in IR multiphoton dissociation of trifluoroacetic acid

Kumar, Awadhesh; Vatsa, R.K.; Naik, Prakash D.; Rao, K. V. S. Rama; Mittal, Jai P.

doi:10.1016/0009-2614(93)87160-5

Cited by 10 publications

(7 citation statements)

References 24 publications

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“…Many experimental studies have been made of the dissociation of trifluoroacetic acid. In particular, the dissociation has been effected by UV light, ,− multiple IR photons, heat, − intermolecular energy transfer from SF 6 , and gamma radiation. , Products that have been identified include CO 2 , C 2 F 2 , CO, CF 3 H, H 2 , CF 2 , COF 2 , CF 3 COF, C 2 F 4 , SiF 4 , CF 3 CO 2 CF 2 H, and HF. In addition, some products have been inferred but not observed directly: CF 3 , COOH, and F 2 CCO 2 .…”

Section: Resultsmentioning

confidence: 99%

Overtone-Induced Chemistry of Trifluoroacetic Acid: An Experimental and Theoretical Study

Reynard

Donaldson

2002

J. Phys. Chem. A

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The effect of overtone-induced chemistry on the atmospheric fate of trifluoroacetic acid has been investigated. We report the absolute absorption intensities for the v OH = 3, 4, and 5 overtone transitions as well as an ab initio calculation of the energetics of the dissociation pathways. Calculations at the MP2 level give the lowest dissociation barrier as 50.3 kcal mol-1 for the elimination of HF. Integrated cross sections for v OH = 3, 4, and 5 are 2.70 × 10-20, 1.68 × 10-21, and 1.5 × 10-22 cm2 molecule-1 cm-1, respectively. Dissociation may proceed after absorption into v = 5 or 6, giving an upper limit to the photodissociation rate constants of 3.7 × 10-9 s-1 or 2.5 × 10-10 s-1, respectively. These correspond to a tropospheric lifetime of between 8 and 127 years. The overtone-driven photodissociation is more important than the ultraviolet photodissociation in the troposphere but is insignificant in comparison to wet deposition and the reaction with OH radicals.

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Section: Resultsmentioning

confidence: 99%

Overtone-Induced Chemistry of Trifluoroacetic Acid: An Experimental and Theoretical Study

Reynard

Donaldson

2002

J. Phys. Chem. A

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“…The decomposition of simple carboxylic acids may proceed via either dehydration or decarboxylation. 1 Dehydration is, however, not possible for trifluoroacetic acid and other perfluorinated acids but loss of HF is a reasonable alternative. The thermal decomposition of trifluoroacetic acid in a static system has been previously studied by Blake and Prichard 2 in which both silica and steel cells were used.…”

Section: Introductionmentioning

confidence: 99%

An in situ IR study of the thermal decomposition of trifluoroacetic acid

Jollie¹,

Harrison²

1997

J. Chem. Soc., Perkin Trans. 2

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The pyrolysis of trifluoroacetic acid has been carried out in the temperature range 513-593 K both as the neat gas and also in the presence of nitrogen as diluent. Reactions were carried out in a sealed sodium borosilicate glass cell, and the progress of the reaction was monitored by in situ Fourier transform IR spectroscopy. The principal products are CHF 3 , CF 3 COF and CO 2 , but significant amounts of other species including C 2 F 4 , CO and SiF 4 are also produced. The formation of HF is observed directly for the first time for this reaction as is the formation of a number of other minor species (formaldehyde, formyl fluoride and hexafluoropropylene oxide).

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“…In earlier experimental works, − the 1,3-HF elimination is assumed to take place in dissociation of FAA to explain the stable products observed. Our ab initio theoretical calculations support this assumption, and suggest that the 1,3-HF elimination is the lowest energy dissociation pathway from the ground electronic pathway of DFA.…”

Section: Results and Analysismentioning

confidence: 99%

“…There exists a long-standing interest in the dissociation dynamics of FAA. − The replacement of nonacidic H atoms in acetic acid by F atoms radically alters the mode of thermal decomposition of FAA, particularly with respect to decarboxylation and dehydration channels. For example, direct decarboxylation and dehydration channels, observed in the thermal decomposition of acetic acid, are stated to be absent or unimportant in all three FAAs, i.e., TFA, − difluoroacetic acid (DFA), and MFA . The primary dissociation channel of FAA is assumed to be HF elimination in all these studies.…”

Section: Introductionmentioning

confidence: 99%

Dissociation Dynamics of Difluoroacetic Acid from the Ground and Excited Electronic States

2004

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The photodissociation dynamics of difluoroacetic acid (DFA) is investigated in both its ground and the first excited electronic states employing, respectively, pulsed CO 2 and ArF (193 nm) lasers. DFA undergoes facile infrared multiphoton dissociation (IRMPD) on irradiation with a pulsed CO 2 laser to open up various dissociation channels from the ground electronic state. Energetically the most preferred primary dissociation channel of DFA is 1,3-HF elimination, as demonstrated by ab initio molecular orbital (MO) calculations and the unimolecular rates for all molecular channels using Rice-Ramsperger-Kassel-Marcus theory. Contrary to an assumed dissociation mechanism for fluorinated carboxylic acids, the decarboxylation reaction is observed as a primary dissociation channel in the IRMPD of DFA. The vibrationally excited photoproducts CO, CO 2 , COFH, and HF have been detected by measurement of time-resolved infrared fluorescence. Photoexcitation of DFA to the electronically excited S 1 state at 193 nm leads to the cleavage of the C-OH bondsa higher energy channel absent in IRMPDsproducing OH(V,J), which was detected state-selectively employing the laser-induced fluorescence technique. We measured partitioning of the available energy, and observed that the nascent OH(V,J) is generated vibrationally cold (i.e., in V ) 0) with moderate rotational excitation (T R ) 630 ( 80 K). But, a high fraction of energy goes to the relative translation (f T value of 0.37) of the photofragments. This observation is explained on the basis of the presence of an exit barrier for the C-OH bond cleavage reaction, and supported by modeling of the measured partitioning of energy and ab initio MO calculations. The transition-state structure for the C-OH bond cleavage producing OH could be calculated in the electronically excited state, T 1 .

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Infrared fluorescence from nascent CO2 and COF2 photoproducts in IR multiphoton dissociation of trifluoroacetic acid

Cited by 10 publications

References 24 publications

Overtone-Induced Chemistry of Trifluoroacetic Acid: An Experimental and Theoretical Study

Overtone-Induced Chemistry of Trifluoroacetic Acid: An Experimental and Theoretical Study

An in situ IR study of the thermal decomposition of trifluoroacetic acid

Dissociation Dynamics of Difluoroacetic Acid from the Ground and Excited Electronic States

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