The 355 nm laser photolysis of jet-cooled methyl nitrite (CH3ONO). Internal energy distributions of the NO fragment

McCoustra, Martin R. S.; Hippler, Michael; Pfab, Josef

doi:10.1016/0009-2614(92)80074-l

Cited by 33 publications

(23 citation statements)

References 23 publications

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“…11,[13][14][15][16][17][18][19][20][21][22][23][24] In a few cases, this foundation of conformation-specific spectroscopy has served as the basis for population transfer studies that directly measure the energy thresholds to isomerization between pairs of conformers. From the standpoint of theory, one of the most useful and direct points of comparison with experiment would be the a͒ Present address: Eastman Chemical Company, Kingsport, TN 37662. b͒ relative energies of the minima.…”

Section: Introductionmentioning

confidence: 99%

Entropy-driven population distributions in a prototypical molecule with two flexible side chains: O-(2-acetamidoethyl)-N-acetyltyramine

Shubert

Baquero

Clarkson

et al. 2007

The Journal of Chemical Physics

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Resonant two-photon ionization (R2PI), resonant ion-dip infrared (RIDIR), and UV-UV hole-burning spectroscopies have been employed to obtain conformation-specific infrared and ultraviolet spectra under supersonic expansion conditions for O-(2-acetamidoethyl)-N-acetyltyramine (OANAT), a doubly substituted aromatic in which amide-containing alkyl and alkoxy side chains are located in para positions on a phenyl ring. For comparison, three single-chain analogs were also studied: (i) N-phenethyl-acetamide (NPEA), (ii) N-(p-methoxyphenethyl-acetamide) (NMPEA), and (iii) N-(2-phenoxyethyl)-acetamide (NPOEA). Six conformations of OANAT have been resolved, with S(0)-S(1) origins ranging from 34,536 to 35,711 cm(-1), denoted A-F, respectively. RIDIR spectra show that conformers A-C each possess an intense, broadened amide NH stretch fundamental shifted below 3400 cm(-1), indicative of the presence of an interchain H bond, while conformers D-F have both amide NH stretch fundamentals in the 3480-3495 cm(-1) region, consistent with independent-chain structures with two free NH groups. NPEA has a single conformer with S(0)-S(1) origin at 37,618 cm(-1). NMPEA has three conformers, two that dominate the R2P1 spectrum, with origin transitions between 35,580 and 35,632 cm(-1). Four conformations, one dominate and three minor, of NPOEA have been resolved with origins between 35,654 and 36,423 cm(-1). To aid the making of conformational assignments, the geometries of low-lying structures of all four molecules have been optimized and the associated harmonic vibrational frequencies calculated using density functional theory (DFT) and RIMP2 methods. The S(0)-S(1) adiabatic excitation energies have been calculated using the RICC2 method and vertical excitation energies using single-point time-dependent DFT. The sensitivity of the S(0)-S(1) energy separation in OANAT and NPOEA primarily arises from different orientations of the chain attached to the phenoxy group. Using the results of the single-chain analogs, tentative assignments have been made for the observed conformers of OANAT. The RIMP2 calculations predict that interchain H-bonded conformers of OANAT are 25-30 kJ/mol more stable than the extended-chain structures. However, the free energies of the interchain H-bonded and extended structures calculated at the preexpansion temperature (450 K) differ by less than 10 kJ/mol, and the number of extended structures far outweighs the number of H-bonded conformers. This entropy-driven effect explains the presence of the independent-chain conformers in the expansion, and cautions future studies that rely solely on relative energies of conformers in considering possible assignments.

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Section: Introductionmentioning

confidence: 99%

Entropy-driven population distributions in a prototypical molecule with two flexible side chains: O-(2-acetamidoethyl)-N-acetyltyramine

Shubert

Baquero

Clarkson

et al. 2007

The Journal of Chemical Physics

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“…In the range from 177 to 235 GHz, the Istok backward wave oscillator (BWO) is used as a source of radiation. It is phase locked to a harmonic of Agilent E8257D synthesizer (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). In the frequency ranges: 75-93, 150-186 and 400-465 GHz the solid state sources are used.…”

Section: Methodsmentioning

confidence: 99%

“…[3][4][5][6]), but only scarce information is available in the high resolution infrared and microwave regions.…”

Section: Introductionmentioning

confidence: 99%

Reinvestigation of the microwave and new high resolution far-infrared spectra of cis-methyl nitrite, CH3ONO: Rotational study of the two first torsional states

Sironneau

Chelin

Tchana

et al. 2011

Journal of Molecular Spectroscopy

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“…The UV photolysis of methyl nitrite (MeONO) provides one such opportunity to explore solvent effects because there is an extensive body of prior experimental and theoretical work on its gasphase photolysis, albeit with some controversy about the precise dissociation mechanism(s) [3][4][5][6][7][8][9][10][11][12][13]. Here, we present observations of the ultrafast dissociation and geminate recombination dynamics of MeONO dissolved in a liquid perfluorocarbon (PFC).…”

Section: Introductionmentioning

confidence: 99%

Conformer-specific geminate recombination following methyl nitrite photolysis in solution

Coulter

Grubb

Orr-Ewing

2017

Chemical Physics Letters

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms UV excitation in the structured S1  S0 absorption band induces dissociation, with geminate recombination and vibrational cooling of syn and anti-conformers of methyl nitrate on a timescale of ~56 ps. Solvent-induced vibrational cooling favours relaxation to the higher-energy anti-conformer on entropic grounds, and subsequent inter-conversion to the lower-energy synconformer is prevented by a 3500 cm -1 barrier. UV excitation to the 2 state produces a transient electronic absorption band resembling the absorption spectrum of NO2.

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The 355 nm laser photolysis of jet-cooled methyl nitrite (CH3ONO). Internal energy distributions of the NO fragment

Cited by 33 publications

References 23 publications

Entropy-driven population distributions in a prototypical molecule with two flexible side chains: O-(2-acetamidoethyl)-N-acetyltyramine

Entropy-driven population distributions in a prototypical molecule with two flexible side chains: O-(2-acetamidoethyl)-N-acetyltyramine

Reinvestigation of the microwave and new high resolution far-infrared spectra of cis-methyl nitrite, CH3ONO: Rotational study of the two first torsional states

Conformer-specific geminate recombination following methyl nitrite photolysis in solution

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