Millimeterwave Spectrum and Dipole Moment in the ν5, ν6, and ν9Excited States of Ketene: Comparison toab InitioResults for Ketene and Ketene-d2

Hinze, R.; Zerbe-Foese, H.; Doose, J.; Guarnieri, A.

doi:10.1006/jmsp.1996.0069

Cited by 12 publications

(6 citation statements)

References 6 publications

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“…After removal of CH 2 CO (ref ) lines, a second spectrum becomes apparent, and is shown in the bottom panel of Figure . The carrier is identified as acetaldehyde (CH 3 CHO) with a rotational temperature T rot = 5 ± 2 K. Using the PGOPHER software with the known dipole moments of both species, , and accounting for the splitting of acetaldehyde lines due to the CH 3 internal rotor levels interactions, the CH 3 CHO:CH 2 CO relative abundance is determined to be 0.03 –0.02 +0.07 . The determination of the relative abundance is sensitive to rotational temperature, and the wide range of the derived branching ratio values between 1% and 10% is largely driven by the relatively poor determination of the rotational temperature of ketene.…”

Section: Resultsmentioning

confidence: 99%

Substitution Reactions in the Pyrolysis of Acetone Revealed through a Modeling, Experiment, Theory Paradigm

et al. 2021

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The development of high-fidelity mechanisms for chemically reactive systems is a challenging process that requires the compilation of rate descriptions for a large and somewhat ill-defined set of reactions. The present unified combination of modeling, experiment, and theory provides a paradigm for improving such mechanism development efforts. Here we combine broadband rotational spectroscopy with detailed chemical modeling based on rate constants obtained from automated ab initio transition state theory-based master equation calculations and high-level thermochemical parametrizations. Broadband rotational spectroscopy offers quantitative and isomer-specific detection by which branching ratios of polar reaction products may be obtained. Using this technique, we observe and characterize products arising from H atom substitution reactions in the flash pyrolysis of acetone (CH 3 C(O)CH 3 ) at a nominal temperature of 1800 K. The major product observed is ketene (CH 2 CO). Minor products identified include acetaldehyde (CH 3 CHO), propyne (CH 3 CCH), propene (CH 2 CHCH 3 ), and water (HDO). Literature mechanisms for the pyrolysis of acetone do not adequately describe the minor products. The inclusion of a variety of substitution reactions, with rate constants and thermochemistry obtained from automated ab initio kinetics predictions and Active Thermochemical Tables analyses, demonstrates an important role for such processes. The pathway to acetaldehyde is shown to be a direct result of substitution of acetone's methyl group by a free H atom, while propene formation arises from OH substitution in the enol form of acetone by a free H atom.

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Section: Resultsmentioning

confidence: 99%

Substitution Reactions in the Pyrolysis of Acetone Revealed through a Modeling, Experiment, Theory Paradigm

et al. 2021

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“…The 13 C isotopologue entries are based on Guarnieri & Huckauf (2003). Predictions for excited states were generated by one of us (HSPM) from an unpublished fit based on the infrared analysis from Nemes et al (2000) with rotational transitions in the range of our survey from Hinze et al (1996). The carbonyl C of ethenone is very close to the center of mass of the molecule.…”

Section: Ethenone Ch 2 Comentioning

confidence: 99%

Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)

Беллоче

Müller

Menten

et al. 2013

A&A

390

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Context. The discovery of amino acids in meteorites fallen to Earth and the detection of glycine, the simplest of them, in samples returned from a comet to Earth strongly suggest that the chemistry of the interstellar medium is capable of producing such complex organic molecules and that they may be widespread in our Galaxy. Aims. Our goal is to investigate the degree of chemical complexity that can be reached in the interstellar medium, in particular in dense star-forming regions. Methods. We performed an unbiased, spectral line survey toward Sgr B2(N) and (M), two regions where high-mass stars are formed, with the IRAM 30 m telescope in the 3 mm atmospheric transmission window. Partial surveys at 2 and 1.3 mm were performed in parallel. The spectra were analyzed with a simple radiative transfer model that assumes local thermodynamic equilibrium but takes optical depth effects into account. Results. About 3675 and 945 spectral lines with a peak signal-to-noise ratio higher than 4 are detected at 3 mm toward Sgr B2(N) and (M), i.e. about 102 and 26 lines per GHz, respectively. This represents an increase by about a factor of two over previous surveys of Sgr B2. About 70% and 47% of the lines detected toward Sgr B2(N) and (M) are identified and assigned to 56 and 46 distinct molecules as well as to 66 and 54 less abundant isotopologues of these molecules, respectively. In addition, we report the detection of transitions from 59 and 24 catalog entries corresponding to vibrationally or torsionally excited states of some of these molecules, respectively, up to a vibration energy of 1400 cm −1 (2000 K). Excitation temperatures and column densities were derived for each species but should be used with caution. The rotation temperatures of the detected complex molecules typically range from ∼50 to 200 K. Among the detected molecules, aminoacetonitrile, n-propyl cyanide, and ethyl formate were reported for the first time in space based on this survey, as were five rare isotopologues of vinyl cyanide, cyanoacetylene, and hydrogen cyanide. We also report the detection of transitions from within twelve new vibrationally or torsionally excited states of known molecules. Absorption features produced by diffuse clouds along the line of sight are detected in transitions with low rotation quantum numbers of many simple molecules and are modeled with ∼30-40 velocity components with typical linewidths of ∼3-5 km s −1 . Conclusions. Although the large number of unidentified lines may still allow future identification of new molecules, we expect most of these lines to belong to vibrationally or torsionally excited states or to rare isotopologues of known molecules for which spectroscopic predictions are currently missing. Significant progress in extending the inventory of complex organic molecules in Sgr B2(N) and deriving tighter constraints on their location, origin, and abundance is expected in the near future thanks to an ongoing spectral line survey at 3 mm with ALMA in its cycles 0 and 1. The present single-dish surve...

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“…In order to improve our understanding of the measured spectra and validate the experimental assignments proposed for ketene, we analyzed simultaneously all the experimental line information available to us, 9,12,13,15,19,24,25,40 indicated in Table II. The MARVEL protocol employed for this purpose proved to be successful for a similar analysis of the rovibrational states of several water isotopologues.…”

Section: Marvel Energy Levelsmentioning

confidence: 99%

Variational quantum mechanical and active database approaches to the rotational-vibrational spectroscopy of ketene, H2CCO

Fábri

Mátyus

Furtenbacher

et al. 2011

The Journal of Chemical Physics

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A variational quantum mechanical protocol is presented for the computation of rovibrational energy levels of semirigid molecules using discrete variable representation of the Eckart-Watson Hamiltonian, a complete, "exact" inclusion of the potential energy surface, and selection of a vibrational subspace. Molecular symmetry is exploited via a symmetry-adapted Lanczos algorithm. Besides symmetry labels, zeroth-order rigid-rotor and harmonic-oscillator quantum numbers are employed to characterize the computed rovibrational states. Using the computational molecular spectroscopy algorithm presented, a large number of rovibrational states, up to J = 50, of the ground electronic state of the parent isotopologue of ketene, H(2) (12)C=(12)C=(16)O, were computed and characterized. Based on 12 references, altogether 3982 measured and assigned rovibrational transitions of H(2) (12)C=(12)C=(16)O have been collected, from which 3194 were validated. These transitions form two spectroscopic networks (SN). The ortho and the para SNs contain 2489 and 705 validated transitions and 1251 and 471 validated energy levels, respectively. The computed energy levels are compared with energy levels obtained, up to J = 41, via an inversion protocol based on this collection of validated measured rovibrational transitions. The accurate inverted energy levels allow new assignments to be proposed. Some regularities and irregularities in the rovibrational spectrum of ketene are elucidated.

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Millimeterwave Spectrum and Dipole Moment in the ν5, ν6, and ν9Excited States of Ketene: Comparison toab InitioResults for Ketene and Ketene-d2

Cited by 12 publications

References 6 publications

Substitution Reactions in the Pyrolysis of Acetone Revealed through a Modeling, Experiment, Theory Paradigm

Substitution Reactions in the Pyrolysis of Acetone Revealed through a Modeling, Experiment, Theory Paradigm

Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)

Variational quantum mechanical and active database approaches to the rotational-vibrational spectroscopy of ketene, H2CCO

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