scholarly journals Diastereoselective Formation of Trans-HC(O)SH through Hydrogenation of OCS on Interstellar Dust Grains

2021 ◽  
Vol 923 (2) ◽  
pp. 159
Author(s):  
Germán Molpeceres ◽  
Juan García de la Concepción ◽  
Izaskun Jiménez-Serra
Keyword(s):  
Interstellar Dust ◽  
Organic Molecules ◽  
Amorphous Solid ◽  
Radical Intermediate ◽  
Apparent Absence ◽  
Interstellar Dust Grains ◽  
Reaction Proceeds ◽  
Prebiotic Molecule ◽  
Dust Grain ◽  
Complex Organic

Abstract With the presence of evermore complex S-bearing molecules being detected lately, studies of their chemical formation routes need to keep up the pace to rationalize observations, suggest new candidates for detection, and provide input for chemical evolution models. In this paper, we theoretically characterize the hydrogenation channels of OCS on top of amorphous solid water (ASW) as an interstellar dust grain analog in molecular clouds. Our results show that the significant reaction outcome is trans-HC(O)SH, a recently detected prebiotic molecule toward G+0.693. The reaction is diastereoselective, explaining the apparent absence of the cis isomer in astronomical observations. We found that the reaction proceeds through a highly localized radical intermediate (cis-OCSH), which could be essential in the formation of other sulfur-bearing complex organic molecules due to its slow isomerization dynamics on top of ASW.

scholarly journals 6. From Dust to Comets

1977 ◽  
Vol 39 ◽  
pp. 491-497 ◽  
Author(s):  
J. M. Greenberg
Keyword(s):  
Chemical Evolution ◽  
Interstellar Dust ◽  
Organic Molecules ◽  
Bulk Material ◽  
The Other ◽  
Contraction Phase ◽  
Dense Cloud ◽  
Small Grains ◽  
Dust Grain ◽  
Complex Organic

The growth and chemical evolution of a typical interstellar dust grain are followed starting from average interstellar conditions to the dense cloud and contraction phase. Based on the theory of cometary accretion directly from cold interstellar dust it is shown that the bulk material of a primordial comet would consist mostly of an icy conglomerate of complex organic molecules and frozen radicals in which are imbedded approximately equal volumes (10% each) of small grains in two different sizes - one variety being the order of 0.05 μ and the other ~0.005 μ in size - consisting mostly of silicates

scholarly journals Formation of complex organic molecules in ice mantles: An ab initio molecular dynamics study

2019 ◽  
Vol 629 ◽  
pp. A28 ◽  
Author(s):  
Natalia Inostroza ◽  
Diego Mardones ◽  
Jose Cernicharo ◽  
Hans Zinnecker ◽  
Jixing Ge ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Organic Molecules ◽  
Closed Shell ◽  
Ab Initio Molecular Dynamics ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Detailed Simulation ◽  
Dust Grain ◽  
Complex Organic

We present a detailed simulation of a dust grain covered by a decamer of (CH3OH)10-ice-mantle, bombarded by an OH− closed-shell molecule with kinetic energies from 10–22 eV. The chemical pathways are studied through Born-Oppenheimer (ab initio) molecular dynamics. The simulations show that methanol ice-mantles can be a key generator of complex organic molecules (COMs). We report the formation of COMs such as methylene glycol (CH2(OH)2) and the OCH2OH radical, which have not been detected yet in the interstellar medium (ISM). We discuss the chemical formation of new species through the reaction of CH3OH with the hydroxyl projectile. The dependence of the outcome on the kinetic energy of the projectile and the implications for the observation and detection of these molecules might explain why the methoxy radical (CH3  ⋅ ) has been observed in a wider range of astrophysical environments than the hydroxymethyl (CH2OH ⋅) isomer. Because of the projectile kinetic energies required for these reactions to occur, we suggest that these processes are likely relevant in the production of COMs in photodissociation and shock regions produced by high-velocity jets and outflows from young stellar objects.

On the formation and survival of complex prebiotic molecules in interstellar grain aggregates

2004 ◽  
Vol 3 (4) ◽  
pp. 287-293 ◽  
Author(s):  
Cesare Cecchi-Pestellini ◽  
Flavio Scappini ◽  
Rosalba Saija ◽  
Maria Antonia Iatì ◽  
Arianna Giusto ◽  
...  
Keyword(s):  
Interstellar Dust ◽  
Organic Molecules ◽  
Star Forming ◽  
Cometary Dust ◽  
Star Forming Regions ◽  
The Earth ◽  
Reducing Conditions ◽  
Prebiotic Molecules ◽  
Internal Volume ◽  
Dust Grain

The aggregation of interstellar grains as a result of ballistic collisions produces loosely packed structures with much of their internal volume composed by vacuum (cavities). The molecular material present on the surfaces of the cavities gives rise to a series of reactions induced by cosmic rays, UV radiation, thermal shocks, etc., in high reducing conditions. Thus, a terrestrial type chemistry is given the possibility to evolve inside these cavities. The resulting products are different and of a wider range than those from gas-phase or surface chemistry in molecular clouds. Under conditions similar to those in the aggregate cavities, laboratory experiments have produced amino acids, sugars and other organic compounds from simple precursors. In dense star-forming regions, the molecular species inside aggregates are efficiently shielded against the local UV field. The same molecules were incorporated in the material which formed the Earth, as well as other planets, during the process of its formation and afterwards fell on the surface via comets, meteorites, interstellar dust, etc. This was the source material that can produce, under favorable circumstances, the biopolymers needed for life. The astronomical observations of organic molecules in star-forming regions and the results of analyses of meteorites and cometary dust seem to support the present hypothesis that complex prebiotic molecules form inside dust aggregates and therein survive the journey to planetary systems. The Miller experiment is revisited through innumerable repetitions inside dust grain aggregates.

scholarly journals Interstellar Dust and the Organic Inventories of Early Solar Systems

2004 ◽  
Vol 213 ◽  
pp. 163-168
Author(s):  
D. C. B. Whittet
Keyword(s):  
Solar System ◽  
Interstellar Dust ◽  
Organic Molecules ◽  
Solar Nebula ◽  
Chemical Elements ◽  
Interstellar Space ◽  
Complex Molecules ◽  
Solar Systems ◽  
Physical Conditions ◽  
Interstellar Dust Grains

Interstellar dust grains are vectors for cosmic carbon and other biogenic chemical elements. They deliver carbon to protoplanetary disks in various refractory phases (amorphous, graphitic, etc.), and they are coated with icy mantles that contain organic molecules and water. The nature of the organics present in and on the dust appears to be closely related to physical conditions. Complex molecules may be synthesized when simple ices are irradiated. Astronomical observations show that this occurs in the vicinity of certain massive protostars, but it is not known whether our Solar System formed in such a region. Organic matter does not survive cycling though diffuse regions of interstellar space; any organics delivered to the early Earth must have originated in the parent molecular cloud, or in the solar nebula itself. A key question is thus identified: What was the star-formation environment of the Solar System? Possible constraints are briefly discussed.

scholarly journals Modeling of Interstellar Dust Grains

2008 ◽  
Vol 7 (2) ◽  
pp. 78-87
Author(s):  
Nagalakshmi A. Rao
Keyword(s):  
Interstellar Medium ◽  
Interstellar Dust ◽  
Interstellar Extinction ◽  
Dipole Approximation ◽  
Dust Grains ◽  
Scattering Parameters ◽  
Light Passing ◽  
Interstellar Dust Grains ◽  
Blue Wavelength ◽  
Dust Grain

Dust has two major effects on light passing through the Interstellar Medium - Interstellar Extinction and Reddening. Interstellar dust grains are typically a fraction of a micron, approximately the wavelength of blue light and hence light passing through dust is depleted in blue wavelength, causing Interstellar Reddening. Dust Grain Models are mainly based on the analysis of interstellar extinction and polarization curves. Discrete Dipole Approximation (DDA) is the best studied model to compute scattering parameters of the grain.

scholarly journals Solid-state production of complex organic molecules: H-atom addition versus UV irradiation

2017 ◽  
Vol 13 (S332) ◽  
pp. 429-434
Author(s):  
K.-J. Chuang
Keyword(s):  
Organic Molecules ◽  
Methyl Formate ◽  
Cumulative Effect ◽  
Quantitative Comparison ◽  
Recombination Reaction ◽  
Laboratory Studies ◽  
State Production ◽  
Dust Grain ◽  
First Time ◽  
Complex Organic

AbstractComplex organic molecules (COMs) have been observed in comets, hot cores and cold dense regions of the interstellar medium. It is generally accepted that these COMs form on icy dust grain through the recombination reaction of radicals triggered by either energetic UV-photon or non-energetic H-atom addition processing. In this work, we present for the first time laboratory studies that allow for quantitative comparison of hydrogenation and UV-induced reactions as well as their cumulative effect in astronomically relevant CO:CH3OH=4:1 ice analogues. The formation of glycolaldehyde (GA) and ethylene glycol (EG) is confirmed in pure hydrogenation experiments at 14 K, except methyl formate (MF), which is only clearly observed in photolysis. The fractions for MF:GA:EG are 0 : (0.2-0.4) : (0.8-0.6) for pure hydrogenation, and 0.2 : 0.3 : 0.5 for UV involving experiments and can offer a diagnostic tool to derive the chemical origin of these species. The GA/EG ratios in the laboratory (0.3-1.5) compare well with observations toward different objects.

Imine as a Linchpin Approach for Distal C(sp2)–H Functionalization

2020 ◽  
Author(s):  
Sukdev Bag ◽  
Sadhan Jana ◽  
Sukumar Pradhan ◽  
Suman Bhowmick ◽  
Nupur Goswami ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Bond Activation ◽  
Bond Formation ◽  
Ancillary Ligand ◽  
Significant Challenge ◽  
Site Selectivity ◽  
Directing Group ◽  
Covalently Linked ◽  
Complex Organic ◽  
Post Functionalization

<p>Despite the widespread applications of C–H functionalization, controlling site selectivity remains a significant challenge. Covalently attached directing group (DG) served as an ancillary ligand to ensure proximal <i>ortho</i>-, distal <i>meta</i>- and <i>para</i>-C-H functionalization over the last two decades. These covalently linked DGs necessitate two extra steps for a single C–H functionalization: introduction of DG prior to C–H activation and removal of DG post-functionalization. We introduce here a transient directing group for distal C(<i>sp<sup>2</sup></i>)-H functionalization <i>via</i> reversible imine formation. By overruling facile proximal C-H bond activation by imine-<i>N</i> atom, a suitably designed pyrimidine-based transient directing group (TDG) successfully delivered selective distal C-C bond formation. Application of this transient directing group strategy for streamlining the synthesis of complex organic molecules without any necessary pre-functionalization at the distal position has been explored.</p>

scholarly journals A Sustainable Improvement of ω-Bromoalkylphosphonates Synthesis to Access Novel KuQuinones

Organics ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 107-117
Author(s):  
Mattia Forchetta ◽  
Valeria Conte ◽  
Giulia Fiorani ◽  
Pierluca Galloni ◽  
Federica Sabuzi
Keyword(s):  
Metal Oxides ◽  
Phosphonic Acid ◽  
Organic Molecules ◽  
Building Blocks ◽  
Reaction Conditions ◽  
Phosphonic Acids ◽  
Sustainable Improvement ◽  
Phosphonate Esters ◽  
First Time ◽  
Complex Organic

Owing to the attractiveness of organic phosphonic acids and esters in the pharmacological field and in the functionalization of conductive metal-oxides, the research of effective synthetic protocols is pivotal. Among the others, ω-bromoalkylphosphonates are gaining particular attention because they are useful building blocks for the tailored functionalization of complex organic molecules. Hence, in this work, the optimization of Michaelis–Arbuzov reaction conditions for ω-bromoalkylphosphonates has been performed, to improve process sustainability while maintaining good yields. Synthesized ω-bromoalkylphosphonates have been successfully adopted for the synthesis of new KuQuinone phosphonate esters and, by hydrolysis, phosphonic acid KuQuinone derivatives have been obtained for the first time. Considering the high affinity with metal-oxides, KuQuinones bearing phosphonic acid terminal groups are promising candidates for biomedical and photo(electro)chemical applications.

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