scholarly journals A new multi-beam apparatus for the study of surface chemistry routes to formation of complex organic molecules in space

2020 ◽  
Vol 91 (12) ◽  
pp. 124504
Author(s):  
E. Congiu ◽  
A. Sow ◽  
T. Nguyen ◽  
S. Baouche ◽  
F. Dulieu
Keyword(s):  
Surface Chemistry ◽  
Organic Molecules ◽  
Complex Organic

scholarly journals Complex organic molecules along the accretion flow in isolated and externally irradiated protoplanetary disks

2014 ◽  
Vol 168 ◽  
pp. 389-421 ◽  
Author(s):  
Catherine Walsh ◽  
Eric Herbst ◽  
Hideko Nomura ◽  
T. J. Millar ◽  
Susanna Widicus Weaver
Keyword(s):  
Surface Chemistry ◽  
Gas Phase ◽  
Organic Molecules ◽  
Molecular Layer ◽  
Accretion Flow ◽  
Chemical Complexity ◽  
Outer Disk ◽  
Molecular Abundances ◽  
Grain Surface ◽  
Complex Organic

The birth environment of the Sun will have influenced the physical and chemical structure of the pre-solar nebula, including the attainable chemical complexity reached in the disk, important for prebiotic chemistry. The formation and distribution of complex organic molecules (COMs) in a disk around a T Tauri star is investigated for two scenarios: (i) an isolated disk, and (ii) a disk irradiated externally by a nearby massive star. The chemistry is calculated along the accretion flow from the outer disk inwards using a comprehensive network which includes gas-phase reactions, gas-grain interactions, and thermal grain-surface chemistry. Two simulations are performed, one beginning with complex ices and one with simple ices only. For the isolated disk, COMs are transported without major chemical alteration into the inner disk where they thermally desorb into the gas reaching an abundance representative of the initial assumed ice abundance. For simple ices, COMs can efficiently form on grain surfaces under the conditions in the outer disk. Gas-phase COMs are released into the molecular layer via photodesorption. For the irradiated disk, complex ices are also transported inwards; however, they undergo thermal processing caused by the warmer conditions in the irradiated disk which tends to reduce their abundance along the accretion flow. For simple ices, grain-surface chemistry cannot efficiently synthesise COMs in the outer disk because the necessary grain-surface radicals, which tend to be particularly volatile, are not sufficiently abundant on the grain surfaces. Gas-phase COMs are formed in the inner region of the irradiated disk via gas-phase chemistry induced by the desorption of strongly bound molecules such as methanol; hence, the abundances are not representative of the initial molecular abundances injected into the outer disk. These results suggest that the composition of comets formed in isolated disks may differ from those formed in externally irradiated disks with the latter composed of more simple ices.

Chemical modelling of N-bearing COMs in star-forming regions

2017 ◽  
Vol 13 (S332) ◽  
pp. 415-417
Author(s):  
David Quénard ◽  
Izaskun Jiménez-Serra ◽  
Serena Viti ◽  
Jonathan Holdship
Keyword(s):  
Surface Chemistry ◽  
Gas Phase ◽  
Organic Molecules ◽  
Methyl Isocyanate ◽  
Star Forming ◽  
Star Forming Regions ◽  
Chemical Modelling ◽  
Grain Surface ◽  
Complex Organic

AbstractThe study of complex organic molecules, and more specifically those of prebiotic interest, is important to understand the chemical richness of star-forming regions. The chemistry of nitrogen bearing molecules such as formamide or methyl isocyanate is poorly constrained. We study different chemical pathways to form and destroy these molecules from both the gas phase and grain surface chemistry. From comparison with observations of four different relevant astrophysical regions, we show that both the gas phase and grain surface chemistry are required to explain the observed abundances of these species.

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.

scholarly journals Not Just Transporters: Alternative Functions of ABC Transporters in Bacillus subtilis and Listeria monocytogenes

2021 ◽  
Vol 9 (1) ◽  
pp. 163
Author(s):  
Jeanine Rismondo ◽  
Lisa Maria Schulz
Keyword(s):  
Bacillus Subtilis ◽  
Listeria Monocytogenes ◽  
Abc Transporters ◽  
Organic Molecules ◽  
Atp Hydrolysis ◽  
The Past ◽  
Wide Range ◽  
Regulatory Functions ◽  
Complex Organic ◽  
Detoxification Mechanisms

ATP-binding cassette (ABC) transporters are usually involved in the translocation of their cognate substrates, which is driven by ATP hydrolysis. Typically, these transporters are required for the import or export of a wide range of substrates such as sugars, ions and complex organic molecules. ABC exporters can also be involved in the export of toxic compounds such as antibiotics. However, recent studies revealed alternative detoxification mechanisms of ABC transporters. For instance, the ABC transporter BceAB of Bacillus subtilis seems to confer resistance to bacitracin via target protection. In addition, several transporters with functions other than substrate export or import have been identified in the past. Here, we provide an overview of recent findings on ABC transporters of the Gram-positive organisms B. subtilis and Listeria monocytogenes with transport or regulatory functions affecting antibiotic resistance, cell wall biosynthesis, cell division and sporulation.

Electrochemical Radical C(sp3)-H Arylation of Xanthenes with Electron-Rich Arenes

2022 ◽  
Author(s):  
Bin Wei ◽  
Jing-Hao Qin ◽  
Yong-Zheng Yang ◽  
Ye-Xiang Xie ◽  
Xuan-Hui Ouyang ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Bond Formation ◽  
Carbon Bond ◽  
Carbon Carbon Bond ◽  
Complex Organic

C(sp3)-H arylation has recently emerged as a powerful straegy for complex organic molecules synthesis through a new carbon-carbon bond formation. We herein describe an efficient electrochemical C(sp3)-H arylation of xanthenes...

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