Photochemistry of Organic Molecules Within Zeolites: Role of Cations

1995 ◽  
pp. 239-282 ◽  
Author(s):  
V. Ramamurthy ◽  
Nicholas J. Turro
Keyword(s):  
Organic Molecules

scholarly journals Did Cyclic Metaphosphates Have a Role in the Origin of Life?

2021 ◽  
Author(s):  
Thomas Glonek
Keyword(s):  
Organic Molecules ◽  
Water Soluble ◽  
Holliday Junction ◽  
Additional Energy ◽  
Condensed Phosphate ◽  
Geological Processes ◽  
The Origin Of Life ◽  
Complex Forms ◽  
Self Replication

AbstractHow life began still eludes science life, the initial progenote in the context presented herein, being a chemical aggregate of primordial inorganic and organic molecules capable of self-replication and evolution into ever increasingly complex forms and functions.Presented is a hypothesis that a mineral scaffold generated by geological processes and containing polymerized phosphate units was present in primordial seas that provided the initiating factor responsible for the sequestration and organization of primordial life’s constituents. Unlike previous hypotheses proposing phosphates as the essential initiating factor, the key phosphate described here is not a polynucleotide or just any condensed phosphate but a large (in the range of at least 1 kilo-phosphate subunits), water soluble, cyclic metaphosphate, which is a closed loop chain of polymerized inorganic phosphate residues containing only phosphate middle groups. The chain forms an intrinsic 4-phosphate helix analogous to its structure in Na Kurrol’s salt, and as with DNA, very large metaphosphates may fold into hairpin structures. Using a Holliday-junction-like scrambling mechanism, also analogous to DNA, rings may be manipulated (increased, decreased, exchanged) easily with little to no need for additional energy, the reaction being essentially an isomerization.A literature review is presented describing findings that support the above hypothesis. Reviewed is condensed phosphate inorganic chemistry including its geological origins, biological occurrence, enzymes and their genetics through eukaryotes, polyphosphate functions, circular polynucleotides and the role of the Holliday junction, previous biogenesis hypotheses, and an Eoarchean Era timeline.

scholarly journals Polar molecules catalyze CO insertion into metal-alkyl bonds through the displacement of an agostic C-H bond

2019 ◽  
Vol 116 (9) ◽  
pp. 3419-3424
Author(s):  
Tian Zhou ◽  
Santanu Malakar ◽  
Steven L. Webb ◽  
Karsten Krogh-Jespersen ◽  
Alan S. Goldman
Keyword(s):  
Transition Metal Complexes ◽  
Density Functional ◽  
Organic Molecules ◽  
Polar Molecules ◽  
Functional Theory ◽  
Bond Forming ◽  
Co Insertion ◽  
The Subject ◽  
Kinetics Of

The insertion of CO into metal-alkyl bonds is the key C-C bond-forming step in many of the most important organic reactions catalyzed by transition metal complexes. Polar organic molecules (e.g., tetrahydrofuran) have long been known to promote CO insertion reactions, but the mechanism of their action has been the subject of unresolved speculation for over five decades. Comprehensive computational studies [density functional theory (DFT)] on the prototypical system Mn(CO)5(arylmethyl) reveal that the polar molecules do not promote the actual alkyl migration step. Instead, CO insertion (i.e. alkyl migration) occurs rapidly and reversibly to give an acyl complex with a sigma-bound (agostic) C-H bond that is not easily displaced by typical ligands (e.g. phosphines or CO). The agostic C-H bond is displaced much more readily, however, by the polar promoter molecules, even though such species bind only weakly to the metal center and are themselves then easily displaced; the facile kinetics of this process are attributable to a hydrogen bonding-like interaction between the agostic C-H bond and the polar promoter. The role of the promoter is to thereby catalyze isomerization of the agostic product of CO insertion to give an η2-C,O-bound acyl product that is more easily trapped than the agostic species. This ability of such promoters to displace a strongly sigma-bound C-H bond and to subsequently undergo facile displacement themselves is without reported precedent, and could have implications for catalytic reactions beyond carbonylation.

scholarly journals The role of H<sub>2</sub>SO<sub>4</sub>-NH<sub>3</sub> anion clusters in ion-induced aerosol nucleation mechanisms in the boreal forest

2018 ◽  
Vol 18 (17) ◽  
pp. 13231-13243 ◽  
Author(s):  
Chao Yan ◽  
Lubna Dada ◽  
Clémence Rose ◽  
Tuija Jokinen ◽  
Wei Nie ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Atmospheric Aerosols ◽  
Organic Molecules ◽  
Special Focus ◽  
Anion Clusters ◽  
Nucleation Mechanisms ◽  
Important Pathway ◽  
Chamber Studies ◽  
Good Agreement

Abstract. New particle formation (NPF) provides a large source of atmospheric aerosols, which affect the climate and human health. In recent chamber studies, ion-induced nucleation (IIN) has been discovered as an important pathway of forming particles; however, atmospheric investigation remains incomplete. For this study, we investigated the air anion compositions in the boreal forest in southern Finland for three consecutive springs, with a special focus on H2SO4-NH3 anion clusters. We found that the ratio between the concentrations of highly oxygenated organic molecules (HOMs) and H2SO4 controlled the appearance of H2SO4-NH3 clusters (3<no.S<13): all such clusters were observed when [HOM] ∕ [H2SO4] was smaller than 30. The number of H2SO4 molecules in the largest observable cluster correlated with the probability of ion-induced nucleation (IIN) occurrence, which reached almost 100 % when the largest observable cluster contained six or more H2SO4 molecules. During selected cases when the time evolution of H2SO4-NH3 clusters could be tracked, the calculated ion growth rates exhibited good agreement across measurement methods and cluster (particle) sizes. In these cases, H2SO4-NH3 clusters alone could explain ion growth up to 3 nm (mobility diameter). IIN events also occurred in the absence of H2SO4-NH3, implying that other NPF mechanisms also prevail at this site, most likely involving HOMs. It seems that H2SO4 and HOMs both affect the occurrence of an IIN event, but their ratio ([HOMs] ∕ [H2SO4]) defines the primary mechanism of the event. Since that ratio is strongly influenced by solar radiation and temperature, the IIN mechanism ought to vary depending on conditions and seasons.

Carbohydrate-controlled precipitation of apatite with coprecipitation of organic molecules in human saliva: Stabilizing role of polyols

1989 ◽  
Vol 44 (4) ◽  
pp. 258-268 ◽  
Author(s):  
Kauko K. Mäkinen ◽  
Eva Söderling ◽  
Donald R. Peacor ◽  
Pirkko-Liisa Mäkinen ◽  
Linda M. Park
Keyword(s):  
Organic Molecules ◽  
Human Saliva ◽  
Controlled Precipitation

An introduction to biominerals and the role of organic molecules in their formation

1984 ◽  
Vol 304 (1121) ◽  
pp. 411-424 ◽  
Keyword(s):  
Organic Molecules ◽  
Organic Materials ◽  
Solubility Limit ◽  
Nucleation And Growth ◽  
The Other ◽  
Medical Problems ◽  
Calcium Compounds ◽  
Inorganic Components ◽  
Iron And Calcium

The minerals of biology have two components, one of which is inorganic and the other organic. Understanding rests initially in the description of the factors that control the nucleation and growth of the inorganic components in the absence of organic materials, and in the study of the organic materials in the absence of the inorganic phase. Brief summaries of these studies are given and then an attempt is made to examine some of the interactive features of the whole mineral. There are very few generalizations that can be formulated yet since each mineral appears to be associated with the metabolic processes of a special cell. Partly, this is due to the diverse function that biominerals perform: supports, protection, sensors, storage and even homeostasis. We must also be aware of the vulnerable nature of precipitation control above the solubility limit. Many widespread medical problems involve the incorrect precipitation of iron and calcium compounds especially.

Adsorption of nucleic acid bases on magnesium oxide (MgO)

2012 ◽  
Vol 12 (1) ◽  
pp. 78-86 ◽  
Author(s):  
Teresa Fornaro ◽  
John Robert Brucato ◽  
Sergio Branciamore ◽  
Amaranta Pucci
Keyword(s):  
Nucleic Acid ◽  
Metal Oxides ◽  
Magnesium Oxide ◽  
Organic Molecules ◽  
Adsorption Properties ◽  
Equilibrium Adsorption ◽  
Nucleic Acid Bases ◽  
Adsorption Of Organic Molecules ◽  
Emergence Of Life

AbstractThe adsorption of organic molecules on mineral matrices might have played a fundamental role in processes that led to the emergence of life. We investigated the adsorption properties of the nucleobases adenine, cytosine, uracil and hypoxanthine on magnesium oxide (MgO), determining the single solute batch equilibrium adsorption isotherms. Langmuir-type isotherms were fitted to data, assuming a rapid reversible equilibration of adsorption, demonstrated effectively through desorption experiments. The Langmuir equilibrium adsorption constantKand the amount of the solute per unit of adsorbent mass necessary to complete the monolayerbwere calculated. The results indicate that MgO is a good adsorbent for nucleobases (adenine > uracil > hypoxantine > cytosine), suggesting a role of metal oxides in concentrating biomolecules in prebiotic conditions that might have favoured the passage from geochemistry to biochemistry.

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