A Theoretical Investigation of the Reaction Between Glycolaldehyde and H+ and Implications for the Organic Chemistry of Star Forming Regions (original) (raw)
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Glycolaldehyde + OH Gas Phase Reaction: A Quantum Chemistry + CVT/SCT Approach
The Journal of Physical Chemistry A, 2005
We present a theoretical study of the mechanism and kinetics of the OH hydrogen abstraction from glycolaldehyde. Optimum geometries, frequencies, and gradients have been computed at the BHandHLYP/ 6-311++G(d,p) level of theory for all stationary points, as well as for additional points along the minimum energy path (MEP). Energies are obtained by single-point calculations at the above geometries using CCSD-(T)/6-311++G(d,p) to produce the potential energy surface. The rate coefficients are calculated for the temperature range 200-500 K by using canonical variational theory (CVT) with small-curvature tunneling (SCT) corrections. Our analysis suggests a stepwise mechanism involving the formation of a reactant complex in the entrance channel and a product complex in the exit channel, for all the modeled paths. The overall agreement between the calculated and experimental kinetic data that are available at 298 K is very good. This agreement supports the reliability of the parameters obtained for the temperature dependence of the glycolaldehyde + OH reaction. The expressions that best describe the studied reaction are k overall ) 7.76 × 10 -13 e 1328/RT cm 3 ‚molecule -1 ‚s -1 and k overall ) 1.09 × 10 -21 T 3.03 e 3187/RT cm 3 molecule -1 s -1 , for the Arrhenius and Kooij approaches, respectively. The predicted activation energy is (-1.36 ( 0.03) kcal/mol, at about 298 K. The agreement between the calculated and experimental branching ratios is better than 10%. The intramolecular hydrogen bond in OO-s-cis glycolaldehyde is found to be responsible for the discrepancies between SAR and experimental rate coefficients. * Corresponding authors. E-mail: A.G., agalano@imp.mx; J.R.A.-I., jidaboy@imp.mx † Instituto Mexicano del Petróleo. ‡ Universidad Autónoma Metropolitana.
Monthly Notices of the Royal Astronomical Society
Glycolaldehyde (CH2OHCHO) is the simplest monosaccharide sugar in the interstellar medium, and it is directly involved in the origin of life via the ‘RNA world’ hypothesis. We present the first detection of glycolaldehyde (CH2OHCHO) towards the hot molecular core G358.93–0.03 MM1 using the Atacama Large Millimeter/Submillimeter Array (ALMA). The calculated column density of CH2OHCHO towards G358.93–0.03 MM1 is (1.52 ± 0.9) × 1016 cm−2 with an excitation temperature of 300 ± 68.5 K. The derived fractional abundance of CH2OHCHO with respect to H2 is (4.90 ± 2.92) × 10−9, which is consistent with that estimated by existing two-phase warm-up chemical models. We discuss the possible formation pathways of CH2OHCHO within the context of hot molecular cores and hot corinos and find that CH2OHCHO is likely formed via the reactions of radical HCO and radical CH2OH on the grain surface of G358.93–0.03 MM1.
Quantum chemical analysis for the formation of glycine in the interstellar medium
Research in Astronomy and Astrophysics, 2013
Glycine (C 2 H 5 NO 2) was the first amino acid to be detected in space by the stardust space probe in Comet Wild2, and is used by living organisms to make proteins. We discuss three different reaction paths for the formation of glycine in interstellar space from some simpler molecules detected in the interstellar medium. The possibility of the formation of glycine in interstellar space is considered by radicalradical and radical-molecule interaction schemes using quantum chemical calculations with density functional theory at the B3LYP/6-31G (d,p) level. In the chemical pathways we discuss, a few reactions are found to be totally exothermic and barrierless while others are endothermic with a very small reaction barrier, thus giving rise to a high probability of forming glycine in interstellar space.
Astronomy and Astrophysics, 2010
Context. The formation of glycine is strongly relevant to our understanding of the interstellar medium and is most accuretely studied computationally. Aims. We carry out a theoretical study of the reactions between the radical cation of ammonia and CH 3 COOH/CH 2 COOH as possible processes leading to glycine derivatives. Methods. The gas-phase reactions were theoretically studied using ab initio methods. We employed the second-order Moller-Plesset level in conjunction with the cc-pVTZ basis set. In addition, the electronic energies were refined by means of single-point calculations at the CCSD(T) level on the MP2/cc-pVTZ geometries with the aug-cc-pVTZ basis set. Results. We report accurate potential energy surfaces for the reactions considered in this work. The different intermediate species as well as the most relevant transition states for these reactions are characterized. Conclusions. Formation of protonated glycine from the reaction of NH + 3 with acetic acid is an exothermic (−9.15 kcal/mol at CCSD(T) level) barrier free process. However, the results obtained indicate that the hydrogen-transfer process forming NH + 4 and CH 2 COOH is clearly the dominating path, in agreement with the experimental evidence. The formation of ionized glycine from the reaction of product CH 2 COOH with NH + 3 is a quasi-isoenergetic (2.03 kcal/mol at CCSD(T) level) barrier free process that leads to a highly stable intermediate: protonated glycine.
Glycolaldehyde Formation via the Dimerization of the Formyl Radical
The Astrophysical Journal, 2013
Glycolaldehyde, the simplest monosaccharide sugar, has recently been detected in low-and high-mass star-forming cores. Following our previous investigation into glycolaldehyde formation, we now consider a further mechanism for the formation of glycolaldehyde that involves the dimerization of the formyl radical, HCO. Quantum mechanical investigation of the HCO dimerization process upon an ice surface is predicted to be barrierless and therefore fast. In an astrophysical context, we show that this mechanism can be very efficient in star-forming cores. It is limited by the availability of the formyl radical, but models suggest that only very small amounts of CO are required to be converted to HCO to meet the observational constraints.
Astrophysical Journal, 2007
Binary mixtures of methanol (CH 3 OH ) and carbon monoxide (CO) ices were irradiated at 10 K with energetic electrons to mimic the energy transfer processes that occur in the track of the trajectories of MeV cosmic-ray particles. The formation of glycolaldehyde (HCOCH 2 OH) was established through the appearance of new bands in the infrared spectrum at 1757, 1700, 1690, 1367, 1267, and 1067 cm À1 . A second C 2 H 4 O 2 isomer, methyl formate (HCOOCH 3 ), was also identified by absorptions appearing at 1718, 1159, and 914 cm À1 . Mass spectrometer signals during the warm-up of the ice sample showed sublimation of both the glycolaldehyde and methyl formate; these species were monitored via the C 2 H 4 O 2 + molecular ion at mass-to-charge ratio, m/e, of 60 originating from both glycolaldehyde and the methyl formate isomer. The latter was distinguishable by the presence of a second signal at m/e = 45, i.e., the HCO 2 + ion. Kinetic fits of the column densities of the reactants and products suggest the initial step of the formation process is the cleavage of a CÀH bond in the methanol molecule to generate either the hydroxymethyl (CH 2 OH) or methoxy (CH 3 O) radical plus atomic hydrogen. The hydrogen atom holds excess kinetic energy, allowing it to overcome entrance barriers required; therefore, a hydrogen could add to a CO molecule, generating the formyl radical (HCO). This can recombine with the hydroxymethyl radical to form glycolaldehyde or with the methoxy radical to yield methyl formate. Similar processes are expected to form glycolaldehyde and methyl formate in the interstellar medium on grains and possibly on cometary ices, thus providing alternatives to gas-phase processes for the generation of complex species whose fractional abundances compared with H 2 of typically a few times 10 À9 cannot be accounted for solely by gas-phase chemistry.
Monthly Notices of the Royal Astronomical Society, 2015
Among all existing complex organic molecules, glycolaldehyde HOCH 2 CHO and ethylene glycol HOCH 2 CH 2 OH are two of the largest detected molecules in the interstellar medium. We investigate both experimentally and theoretically the low-temperature reaction pathways leading to glycolaldehyde and ethylene glycol in interstellar grains. Using infrared spectroscopy, mass spectroscopy and quantum calculations, we investigate formation pathways of glycolaldehyde and ethylene glycol based on HCO • and • CH 2 OH radical-radical recombinations. We also show that • CH 2 OH is the main intermediate radical species in the H 2 CO to CH 3 OH hydrogenation processes. We then discuss astrophysical implications of the chemical pathway we propose on the observed gas-phase ethylene glycol and glycolaldehyde.
Hemiaminal route for the formation of interstellar glycine: a computational study
Journal of Molecular Modeling, 2019
Calculations related to two simple two-step paths (path-I: H 2 C ¼ O þ NH 3 →α−hydroxy amine → þCO glycine; path-II: H 2 C ¼ NH þ H 2 O→α−hydroxy amine → þCO glycine) for the formation of glycine have been discussed. Calculations show that at interstellar conditions these two paths are feasible only in hot cores, not in the cold interstellar clouds (cold core formation is possible only if CH 2 = NH, H 2 O (excess) and CO of path-II, react in a concerted manner). For the laboratory synthesis of glycine, the possibility suggested is via path-I and the reaction being carried out as controlled temperature one-pot synthesis. This study can also be extended to other α-amino acids and possibly enantiomeric excess can be expected. We think this work will not only be able to enrich our future understanding about the formation of amino acids in interstellar medium but also be able to suggest alternative paths for laboratory synthesis of amino acids using either Strecker's or Miller's ingredients.
First Detection of Glycolaldehyde Outside the Galactic Center
The Astrophysical Journal, 2009
Glycolaldehyde is the simplest of the monosaccharide sugars and is directly linked to the origin of life. We report on the detection of glycolaldehyde (CH 2 OHCHO) towards the hot molecular core G31.41+0.31 through IRAM PdBI observations at 1.4, 2.1, and 2.9 mm. The CH 2 OHCHO emission comes from the hottest (≥ 300 K) and densest (≥2×10 8 cm −3) region closest (≤ 10 4 AU) to the (proto)stars. The comparison of data with gas-grain chemical models of hot cores suggests for G31.41+0.31 an age of a few 10 5 yr. We also show that only small amounts of CO need to be processed on grains in order for existing hot core gas-grain chemical models to reproduce the observed column densities of glycolaldehyde, making surface reactions the most feasible route to its formation.
Astrophysical Journal, 2005
The synthetic routes to form acetaldehyde [CH 3 CHO(X 1 A 0 )] in extraterrestrial ices were investigated experimentally in a contamination-free ultrahigh vacuum scattering machine. Binary ice mixtures of carbon monoxide [CO(X 1 AE + )] and methane [CH 4 (X 1 A 1 )] were condensed at 10 K onto a silver monocrystal and irradiated with 5 keV electrons to mimic the electronic energy transfer processes initiated by MeV cosmic-ray particle-induced -electrons in the ''ultratrack'' of MeV ion trajectories; the carbon monoxide-methane ices served as model compounds to simulate neighboring COÀCH 4 molecules in astrophysical ices, as present in cold molecular clouds and in cometary matter. Upon completion of the high-energy processing, the ice samples sublimed during the heating phase to 293 K, thus releasing the remaining reactants as well as the newly formed molecules into the gas phase. The experiment was monitored on line and in situ via a Fourier transform infrared (FTIR) spectrometer in absorption-reflection-absorption mode (solid state) and a quadrupole mass spectrometer (gas phase). Our investigations were combined with electronic structure calculations. At 10 K, the primary reaction step involved the cleavage of the carbon-hydrogen bond of the methane molecule via an electronic energy transfer process from the impinging electron to the methane molecule to form a methyl radical [CH 3 (X 2 A 00