Microwave spectra, centrifugal distortion constants, and rz structure of acetonitrile and its isotopic species

Demaison, J.; Dubrulle, A.; Boucher, D.; Burie, J.; Typke, V.

doi:10.1016/0022-2852(79)90214-5

Cited by 74 publications

(19 citation statements)

References 18 publications

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“…The calculated structures of 3-5 as well as 2H-azirine 10, the cyanomethyl radical 11, and aziridin-2-ylidene 14 at the MP2/6-31G* level are presented in Figure 1. The calculated structures of ketenimine 4 and acetonitrile 5 are in excellent agreement with the available experimental 24,25 parameters as well as previous calculations. 26 Overall, the computed energies given in Table 1 are in broad agreement with recent calculations at MP4(SDTQ) 27 and CCSD(T) levels 28,29 as far as comparisons are possible.…”

Section: Direct 13-h Shiftssupporting

confidence: 87%

Ethynamine - Ketenimine - Acetonitrile - Rearrangements: A computational Study of Flash Vacuum Pyrolysis Processes

Wentrup

Bégué²,

Leung-Toung³

2017

Preprint

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The rearrangements of ethynamine 3 (H-CºC-NH2) to ketenimine 4 (CH2=C=NH) and acetonitrile 5 (CH3CN) were investigated computationally up to the MP4(SDTQ)/6-31G*//MP2(FU)/6-31G* level. The calculated barrier for a concerted reaction 3 -> 4 is very high, 74 kcal/mol, the structure of the transition state very unusual, and this path is discredited. A lower barrier of about 60 kcal/mol via aminovinylidene 2 and imidoylcarbene 15 has been found. The calculated barrier for a concerted second step 4 -> 5 is 61 kcal/mol, and the transition state structure is again very unusual with a virtually linear CCN backbone, but this does not appear to correspond to physical reality. Instead, CASPT2 calculations predict reaction via vinylnitrene 9 and/or homolysis of 4 to the radical pair ·CH2CN + H· (11) with a barrier of 67-70 kcal/mol in agreement with experimental shock-tube data. Recombination (maybe via roaming) affords acetonitrile 5. There is strong experimental evidence for homolytic paths in pas-phase pyrolyses of ketenimines.

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Section: Direct 13-h Shiftssupporting

confidence: 87%

Ethynamine - Ketenimine - Acetonitrile - Rearrangements: A computational Study of Flash Vacuum Pyrolysis Processes

Wentrup

Bégué²,

Leung-Toung³

2017

Preprint

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“…The excited states of the 13 C isotopologues are based on unpublished work. Groundstate data in the range of our survey were taken from , Demaison et al (1979), and Bauer et al (1975) for the main, the 13 C, and the 15 N isotopologues, respectively. Bauer & Maes (1969), Bauer (1971), and Cosleou et al (1991) provided corresponding data for the 8 = 1, 8 = 2, and 4 = 1 states, respectively, of the main isotopic species.…”

Section: Methyl Cyanide Ch 3 Cnmentioning

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

385

523

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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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“…Predictions for isotopic species with 15 N or one or two 13 C in their ground vibrational states are from the CDMS. They are based on Müller et al (2009) with transition frequencies in the range of our survey from Demaison et al (1979). Predictions for 13 C isotopologues in their 8 = 1 states are based on preliminary data from Müller et al (2016a).…”

Section: Spectroscopic Predictionsmentioning

confidence: 99%

Exploring molecular complexity with ALMA (EMoCA): Deuterated complex organic molecules in Sagittarius B2(N2)

Беллоче

Müller

Garrod

et al. 2016

A&A

198

345

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Context. Deuteration is a powerful tracer of the history of the cold prestellar phase in star-forming regions. Apart from methanol, little is known about deuterium fractionation of complex organic molecules in the interstellar medium, especially in regions forming high-mass stars. Aims. Our goal is to detect deuterated complex organic molecules toward the high mass star-forming region Sagittarius B2 (Sgr B2) and derive the level of deuteration for these molecules. Methods. We use a complete 3-mm spectral line survey performed with the Atacama Large Millimeter/submillimeter Array (ALMA) to search for deuterated complex organic molecules toward the hot molecular core Sgr B2(N2). We constructed population diagrams and integrated intensity maps to fit rotational temperatures and emission sizes for each molecule. Column densities are derived by modeling the full spectrum under the assumption of local thermodynamic equilibrium. We compare the results to predictions of two astrochemical models that treat the deuteration process. Results. We report the detection of CH 2 DCN toward Sgr B2(N2) with a deuteration level of 0.4%, and tentative detections of CH 2 DOH, CH 2 DCH 2 CN, the chiral molecule CH 3 CHDCN, and DC 3 N with levels in the range 0.05%-0.12%. A stringent deuteration upper limit is obtained for CH 3 OD (<0.07%). Upper limits in the range 0.5-1.8% are derived for the three deuterated isotopologues of vinyl cyanide, the four deuterated species of ethanol, and CH 2 DOCHO. Ethyl cyanide is less deuterated than methyl cyanide by at least a factor five. The [CH 2 DOH]/[CH 3 OD] abundance ratio is higher than 1.8. It may still be consistent with the value obtained in Orion KL. Except for methyl cyanide, the measured deuteration levels lie at least a factor four below the predictions of current astrochemical models. The deuteration levels in Sgr B2(N2) are also lower than in Orion KL by a factor of a few up to a factor ten. Conclusions. The discrepancy between the deuteration levels of Sgr B2(N2) and the predictions of chemical models, and the difference between Sgr B2(N2) and Orion KL may both be due to the higher kinetic temperatures that characterize the Galactic center region compared to nearby clouds. Alternatively, they may result from a lower overall abundance of deuterium itself in the Galactic center region by up to a factor ten.

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Microwave spectra, centrifugal distortion constants, and rz structure of acetonitrile and its isotopic species

Cited by 74 publications

References 18 publications

Ethynamine - Ketenimine - Acetonitrile - Rearrangements: A computational Study of Flash Vacuum Pyrolysis Processes

Ethynamine - Ketenimine - Acetonitrile - Rearrangements: A computational Study of Flash Vacuum Pyrolysis Processes

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

Exploring molecular complexity with ALMA (EMoCA): Deuterated complex organic molecules in Sagittarius B2(N2)

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