Membranes for separation of CO2/CH4 at harsh conditions

Carbon-Fluorine (C-F) bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that often required harsh conditions. The alloying of Pt with Pd is crucial to activate C-F bond. The reaction profile kinetics revealed that the major source of hydrogen in the defluorinated product is the alcoholic proton of 2-propanol, and the rate-determining step is the reduction of the metal upon transfer of the beta-H from 2-propanol. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction

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A Mild and Simple Method for Making MIDA Boronates

10.26434/chemrxiv.12054036.v1 ◽

2020 ◽

Author(s):

Aidan Kelly ◽

Peng-Jui (Ruby) Chen ◽

Jenna Klubnick ◽

Daniel J. Blair ◽

Martin D. Burke

Keyword(s):

Organic Synthesis ◽

Boronic Acids ◽

Simple Method ◽

Direct Preparation ◽

Synthesis Procedure ◽

Harsh Conditions

<div> <div> <div> Existing methods for making MIDA boronates require harsh conditions and complex procedures to achieve dehydration. Here we disclose that a pre-dried form of MIDA, MIDA anhydride, acts as both a source of the MIDA ligand and an in situ desiccant to enable a mild and simple MIDA boronate synthesis procedure. This method expands the range of sensitive boronic acids that can be converted into their MIDA boronate counterparts. Further utilizing unique properties of MIDA boronates, we have developed a MIDA Boronate Maker Kit which enables the direct preparation and purification of MIDA boronates from boronic acids using only heating and centrifuge equipment that is widely available in labs that do not specialize in organic synthesis. </div> </div> </div>

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Visible Light-Mediated Oxidative Debenzylation

10.26434/chemrxiv.13135814 ◽

2020 ◽

Author(s):

Cristian Cavedon ◽

Eric T. Sletten ◽

Amiera Madani ◽

Olaf Niemeyer ◽

Peter H. Seeberger ◽

...

Keyword(s):

Reaction Time ◽

Visible Light ◽

Functional Groups ◽

Continuous Flow ◽

Protecting Groups ◽

Benzyl Ether ◽

Complex Molecules ◽

Protective Groups ◽

Benzyl Ethers ◽

Harsh Conditions

Protecting groups are key in the synthesis of complex molecules such as carbohydrates to distinguish functional groups of similar reactivity. The harsh conditions required to cleave stable benzyl ether protective groups are not compatible with many other protective and functional groups. The mild, visible light-mediated debenzylation disclosed here renders benzyl ethers orthogonal protective groups. Key to success is the use of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as stoichiometric or catalytic photooxidant such that benzyl ethers can be cleaved in the presence of azides, alkenes, and alkynes. The reaction time for this transformation can be reduced from hours to minutes in continuous flow.

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Porous Aluminophosphates as Adsorbents for the Separation of CO2/CH4 and CH4/N2 Mixtures – a Monte Carlo Simulation Study

10.26434/chemrxiv.6133346.v2 ◽

2018 ◽

Author(s):

Michael Fischer

Keyword(s):

Monte Carlo ◽

Landfill Gas ◽

Experimental Studies ◽

Chem Phys ◽

Monte Carlo Simulation Study ◽

Mixture Adsorption ◽

Vacuum Swing Adsorption ◽

Separation Of Co2 ◽

Pressure Swing ◽

Gcmc Simulations

<div>Aluminophosphates with zeolite-like topologies (AlPOs) have received considerable attention as potential adsorbents for use in the separation of methane-containing gas mixtures. Such separations, especially the removal of carbon dioxide and nitrogen from methane, are of great technological relevance in the context of the “upgrade” of natural gas, landfill gas, and biogas. While more than 50 zeolite frameworks have been synthesised in aluminophosphate composition or as heteroatom substituted AlPO derivatives, only a few of them have been characterised experimentally with regard to their adsorption and separation behaviour. In order to predict the potential of a variety of AlPO frameworks for applications in CO2/CH4 and CH4/N2 separations, atomistic grand-canonical Monte Carlo (GCMC) simulations were performed for 53 different structures. Building on previous work, which studied CO2/N2 mixture adsorption in AlPOs (M. Fischer, Phys. Chem. Chem. Phys., 2017, 19, 22801–22812), force field parameters for methane adsorption in AlPOs were validated through a comparison to available experimental adsorption data. Afterwards, CO2/CH4 and CH4/N2 mixture isotherms were computed for all 53 frameworks for room temperature and total pressures up to 1000 kPa (10 bar), allowing the prediction of selectivities and working capacities for conditions that are relevant for pressure swing adsorption (PSA) and vacuum swing adsorption (VSA). For CO2/CH4 mixtures, the GIS, SIV, and ATT frameworks were found to have the highest selectivities and CO2 working capacities under VSA conditions, whereas several frameworks, among them AFY, KFI, AEI, and LTA, show higher working capacities under PSA conditions. For CH4/N2 mixtures, all frameworks are moderately selective for methane over nitrogen, with ATV exhibiting a significantly higher selectivity than all other frameworks. While some of the most promising topologies are either not available in pure-AlPO4 composition or collapse upon calcination, others can be synthesised and activated, rendering them interesting candidates for future experimental studies. In addition to predictions of mixture adsorption isotherms, further simulations were performed for four selected systems in order to investigate the microscopic origins of the macroscopic adsorption behaviour, e.g. with regard to the very high CH4/N2 selectivity of ATV and the loading-dependent evolution of the heat of CO2 adsorption and CO2/CH4 selectivity of AEI and GME.</div>

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Cooperative Self-Assembly of Pyridine-2,6-Diimine-Linked Macrocycles into Mechanically Robust Nanotubes

10.26434/chemrxiv.8080043 ◽

2019 ◽

Author(s):

Michael J. Strauss ◽

Darya Asheghali ◽

Austin Evans ◽

Rebecca Li ◽

Anton Chavez ◽

...

Keyword(s):

Aspect Ratio ◽

High Aspect Ratio ◽

Self Assembly ◽

Gel Permeation Chromatography ◽

Synthetic Polymers ◽

Young’S Moduli ◽

Structural Rigidity ◽

Assembly Mechanism ◽

Low Dimensionality ◽

Harsh Conditions

Nanotubes assembled from macrocyclic precursors offer a unique combination of low dimensionality, structural rigidity, and distinct interior and exterior microenvironments. Usually the weak stacking energies of macrocycles limit the length or strength of the resultant nanotubes. Imine-linked macrocycles were recently found to assemble into high-aspect ratio (>103), lyotropic nanotubes in the presence of excess acid. Yet these harsh conditions are incompatible with many functional groups and processing methods, and lower acid loadings instead catalyze macrocycle degradation. Here we report pyridine-2,6-diimine-linked macrocycles that assemble into high-aspect ratio nanotubes in the presence of less than 1 equiv of CF3CO2H per macrocycle. Analysis by gel permeation chromatography and fluorescence spectroscopy revealed a cooperative self-assembly mechanism. Nanofibers obtained by touch-spinning the pyridinium-based nanotubes exhibit Young’s moduli of 1.48 GPa, which exceeds that of many synthetic polymers and biological filaments. These findings will enable the design of structurally diverse nanotubes from synthetically accessible macrocycles.

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Efficient Route for Synthesis of Enamines from 1,3-Alkyl-2-Thioxodihydropyrimidine-4,6(1H,5H)-dione Enols

Letters in Organic Chemistry ◽

10.2174/1570178616666190409145118 ◽

2019 ◽

Vol 16 (7) ◽

pp. 538-540

Author(s):

Anamika Sharma ◽

Zainab M. Almarhoon ◽

Ayman El-Faham ◽

Beatriz G. de la Torre ◽

Fernando Albericio

Keyword(s):

Ammonium Chloride ◽

Thiobarbituric Acid ◽

Acid Acid ◽

Efficient Route ◽

Harsh Conditions

Here we report a greener approach for the synthesis of enamines from enols of 1,3-alkyl-2- thioxodihydropyrimidine-4,6(1H,5H)-dione (thiobarbituric acid) acid using ammonium chloride and ethanol as solvents. This protocol removes the need for catalysts or harsh conditions.

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Metal and Non-Metal Catalysts in the Synthesis of Five-Membered S-Heterocycles

Current Organic Synthesis ◽

10.2174/1570179416666181207144430 ◽

2019 ◽

Vol 16 (2) ◽

pp. 258-275 ◽

Cited By ~ 2

Author(s):

Navjeet Kaur

Keyword(s):

Organic Synthesis ◽

Biological Activities ◽

Reaction Times ◽

Research Field ◽

Environmentally Benign ◽

Metal Catalyst ◽

Efficient Synthesis ◽

Heterocyclic Molecules ◽

The Past ◽

Harsh Conditions

Background:A wide variety of biological activities are exhibited by N, O and S containing heterocycles and recently, many reports appeared for the synthesis of these heterocycles. The synthesis of heterocycles with the help of metal and non-metal catalyst has become a highly rewarding and important method in organic synthesis. This review article concentrated on the synthesis of S-heterocylces in the presence of metal and non-metal catalyst. The synthesis of five-membered S-heterocycles is described here.Objective:There is a need for the development of rapid, efficient and versatile strategy for the synthesis of heterocyclic rings. Metal, non-metal and organocatalysis involving methods have gained prominence because traditional conditions have disadvantages such as long reaction times, harsh conditions and limited substrate scope.Conclusion:The metal-, non-metal-, and organocatalyst assisted organic synthesis is a highly dynamic research field. For ßthe chemoselective and efficient synthesis of heterocyclic molecules, this protocol has emerged as a powerful route. Various methodologies in the past few years have been pointed out to pursue more sustainable, efficient and environmentally benign procedures and products. Among these processes, the development of new protocols (catalysis), which avoided the use of toxic reagents, are the focus of intense research.

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Naturalizing Moral Regression

10.1093/oso/9780190868413.003.0008 ◽

2018 ◽

Author(s):

Allen Buchanan

Keyword(s):

Cognitive Biases ◽

Social Conditions ◽

Moral Progress ◽

Detailed Knowledge ◽

Social Environments ◽

Human Beings ◽

Group Threat ◽

Epistemic Practices ◽

Harsh Conditions ◽

Development And Evolution

This chapter proposes a theory of moral regression, arguing that inclusivist gains can be eroded not only if certain harsh biological and social conditions indicative of out-group threat actually reappear but also if significant numbers of people come to believe that such harsh conditions exist even when they do not. It argues that normal cognitive biases in conjunction with defective social-epistemic practices can cause people wrongly to believe that such harsh conditions exist, thus triggering the development and evolution of exclusivist moralities and the dismantling of inclusivist ones. Armed with detailed knowledge of the biological and social environments in which progressive moralities emerge and are sustained, as well as the conditions under which they are likely to be dismantled, human beings can take significant steps toward transforming the classic liberal faith in moral progress into a practical, empirically grounded hope.

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