Rotational spectrum and ab initio calculations of N-methylformamide

Fantoni, A.C.; Camináti, Walther

doi:10.1039/ft9969200343

Cited by 73 publications

(55 citation statements)

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“…We started our analysis of the trans N-methylformamide spectrum from refitting the data available from the literature (Fantoni & Caminati 1996;Fantoni et al 2002;Kawashima et al 2010) using the RAM36 code. Application of the RAM36 code allowed us to fit almost within experimental error the data available in the literature including those lines which were previously excluded from the fits due to rather high observed-minus-calculated values ).…”

Section: Methodsmentioning

confidence: 99%

“…According to this convention applied for N-methylformamide, one should use the D * (Y − N − C − X) dihedral angle, where X is the carbonyl hydrogen and Y is the methyl group. Cis and trans conformers named using this convention are thus the opposite of the cis and trans conformers in Fantoni & Caminati (1996) and Fantoni et al (2002). Here we use the naming adopted by Kawashima et al (2010), i.e.…”

Section: Introductionmentioning

confidence: 99%

“…For this reason, N-methylformamide has been the subject of extensive spectroscopic investigations, but the analysis of its microwave rotational spectrum for a long time did not yield satisfactory results. Fantoni & Caminati (1996) were the first to succeed in assigning rotational spectral lines belonging to the trans conformer in the CH 3 internal rotation ground state of A symmetry. They performed measurements between 18 and 40 GHz, however they could not identify any spectral lines of the E species.…”

Section: Introductionmentioning

confidence: 99%

“…Fantoni & Caminati (1996) and Fantoni et al (2002) • was named trans. Kawashima et al (2010) used another convention widely accepted for molecules with a peptide bond.…”

Section: Introductionmentioning

confidence: 99%

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Rotational spectroscopy, tentative interstellar detection, and chemical modeling of N-methylformamide

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Meshcheryakov

Garrod

et al. 2017

A&A

156

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Context. N-methylformamide, CH 3 NHCHO, may be an important molecule for interstellar pre-biotic chemistry because it contains a peptide bond, which in terrestrial chemistry is responsible for linking amino acids in proteins. The rotational spectrum of the most stable trans conformer of N-methylformamide is complicated by strong torsion-rotation interaction due to the low barrier of the methyl torsion. For this reason, the theoretical description of the rotational spectrum of the trans conformer has up to now not been accurate enough to provide a firm basis for its interstellar detection. Aims. In this context, as a prerequisite for a successful interstellar detection, our goal is to improve the characterization of the rotational spectrum of N-methylformamide. Methods. We use two absorption spectrometers in Kharkiv and Lille to measure the rotational spectra over the frequency range 45-630 GHz. The analysis is carried out using the Rho-axis method and the RAM36 code. We search for N-methylformamide toward the hot molecular core Sagittarius (Sgr) B2(N2) using a spectral line survey carried out with the Atacama Large Millimeter/submillimeter Array (ALMA). The astronomical spectra are analyzed under the assumption of local thermodynamic equilibrium. The astronomical results are put into a broader astrochemical context with the help of a gas-grain chemical kinetics model. Results. The new laboratory data set for the trans conformer of N-methylformamide consists of 9469 distinct line frequencies with J ≤ 62, including the first assignment of the rotational spectra of the first and second excited torsional states. All these lines are fitted within experimental accuracy for the first time. Based on the reliable frequency predictions obtained in this study, we report the tentative detection of N-methylformamide towards Sgr B2(N2). We find N-methylformamide to be more than one order of magnitude less abundant than formamide (NH 2 CHO), a factor of two less abundant than the unsaturated molecule methyl isocyanate (CH 3 NCO), but only slightly less abundant than acetamide (CH 3 CONH 2 ). We also report the tentative detection of the 15 N isotopologue of formamide ( 15 NH 2 CHO) toward Sgr B2(N2). The chemical models indicate that the efficient formation of HNCO via NH + CO on grains is a necessary step in the achievement of the observed gas-phase abundance of CH 3 NCO. Production of CH 3 NHCHO may plausibly occur on grains either through the direct addition of functional-group radicals or through the hydrogenation of CH 3 NCO. Conclusions. Provided the detection of N-methylformamide is confirmed, the only slight underabundance of this molecule compared to its more stable structural isomer acetamide and the sensitivity of the model abundances to the chemical kinetics parameters suggest that the formation of these two molecules is controlled by kinetics rather than thermal equilibrium.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Fantoni & Caminati (1996) and Fantoni et al (2002) • was named trans. Kawashima et al (2010) used another convention widely accepted for molecules with a peptide bond.…”

Section: Introductionmentioning

confidence: 99%

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Rotational spectroscopy, tentative interstellar detection, and chemical modeling of N-methylformamide

Беллоче

Meshcheryakov

Garrod

et al. 2017

A&A

156

261

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“…Eventually, I bequeathed my data to colleagues, to no avail. Recently, the spectrum has finally been solved (16). I mention this episode as representative of other failures (omitted, as in most memoirs!…”

Section: At Harvard: Microwave Spectroscopy With Bright Wilson (1955-mentioning

confidence: 99%

Fifty Years in Physical Chemistry: Homage to Mentors, Methods, and Molecules

Herschbach

2000

Annu. Rev. Phys. Chem.

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A nostalgic account is given of my scientific odyssey, recalling early encounters, some fateful, some just fun, with mentors, methods, and molecules. These include stories of my student years at Stanford, pursuing chemical kinetics with Harold Johnston; graduate study at Harvard, doing molecular spectroscopy with Bright Wilson; and fledgling faculty years at Berkeley, launching molecular beam studies of reaction dynamics. A few vignettes from my "ever after " era on the Harvard faculty emphasize thematic motivations or methods inviting further exploration. An Appendix provides a concise listing of colleagues in research and the topics we have pursued. INTRODUCTIONIn his book Imagined Worlds, Freeman Dyson asserts that new directions in science are launched by new tools much more often than by new concepts (1). He says, "The effect of a concept-driven revolution is to explain old things in new ways. The effect of a tool-driven revolution is to discover new things that have to be explained." I would add that new tools or methods often emerge from a symbiotic interaction of old tools and concepts in fresh combinations. That is a good reason for young scientists to learn something about the historical development of their field. For physical chemistry, this can readily be traced over the past 50 years in the volumes of Annual Reviews. These record a saga of new methods-experimental, theoretical, and computational-that have greatly enhanced our ability to probe the wondrous processes of chemistry at the molecular level.Witnessing this saga unfold, and contributing to it here and there, has been a joyful odyssey. Most of all, I have cherished the fellowship of striving with students and colleagues, mutual mentors. Here I relate some experiences of the kind I liked to hear about as a student. Such stories helped me understand that good science and scientists often grow from rude or maverick beginnings, and that the process usually owes much to human catalysis. Elsewhere I've reminisced about 0066 2 HERSCHBACH the main path of my scientific life, the happy pursuit of molecular beam studies of reaction dynamics (2-5). The present article is designed to complement those memoirs, with much interleaving but little overlap. Chiefly I'll tell more about my formative years, interactions with remarkable scientists I've tried to emulate, and adventures outside the main path, especially recent and ongoing work. AT STANFORD: Chemical Kinetics with Hal Johnston (1950-1955)My romance with chemical dynamics began on a sparkling Sunday afternoon in September 1950, the day before classes were to begin at Stanford University. I'd arrived to start my freshman year two weeks before and, by dint of vigorous collision dynamics, had won a spot as right end on the football team. Until that afternoon, I'd never met a professor or, as far as I knew, even anybody who had graduated from a college. My parents had warned me, the first of their six children to leave home, to be wary. They'd heard that many professors had weird, farfetched i...

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C(SINGLE BOND)H(DOTTED BOND)O and N(SINGLE BOND)H(DOTTED BOND)O hydrogen bonds in liquid amides investigated by Monte Carlo simulation

Cordeiro

1997

Int. J. Quant. Chem.

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Monte Carlo simulations of liquid formamide, N-methylformamide Ž .Ž . MF , and N, N-dimethylformamide DMF have been performed in the isothermal and isobaric ensemble at 298 K and 1 atm, aiming to investigate the C-H иии O and N-H иии O hydrogen bonds. The interaction energy was calculated using the classical 6-12 Lennard-Jones pairwise potential plus a Coulomb term on a rigid six-site molecular model with the potential parameters being optimized in this work. Theoretical values obtained for heat of vaporization and liquid densities are in good agreement with the w Ž .x experimental data. The radial distribution function RDF, g r obtained compare well Ž . with R-X diffraction data available. The RDF and molecular mechanics MM2 minimization show that the C-H иии O interaction has a significant role in the structure of the three liquids. These results are supported by ab initio calculations. This interaction is particularly important in the structure of MF. The intensity of the N-H иии O hydrogen bond is greater in the MF than formamide. This could explain some anomalous properties verified in MF.

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Rotational spectrum and ab initio calculations of N-methylformamide

Cited by 73 publications

References 16 publications

Rotational spectroscopy, tentative interstellar detection, and chemical modeling of N-methylformamide

Rotational spectroscopy, tentative interstellar detection, and chemical modeling of N-methylformamide

Fifty Years in Physical Chemistry: Homage to Mentors, Methods, and Molecules

C(SINGLE BOND)H(DOTTED BOND)O and N(SINGLE BOND)H(DOTTED BOND)O hydrogen bonds in liquid amides investigated by Monte Carlo simulation

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