Fluorocarbon Rubber-Based Inert Dry Adhesive for Applications under Harsh Conditions

2021 ◽  
Author(s):  
Sung Ho Lee ◽  
Hyo Sung Kim ◽  
Hyun Woo Song ◽  
Moon Kyu Kwak
Keyword(s):  
Dry Adhesive ◽  
Harsh Conditions

Pt-Pd Nanoalloy for the Unprecedented Activation of Carbon-Fluorine Bond at Low Temperature

2019 ◽  
Author(s):  
Raghu Nath Dhital ◽  
keigo nomura ◽  
Yoshinori Sato ◽  
Setsiri Haesuwannakij ◽  
Masahiro Ehara ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Dft Calculations ◽  
Bond Activation ◽  
Mild Conditions ◽  
Selective Transformation ◽  
Rate Determining Step ◽  
Highly Active ◽  
Harsh Conditions ◽  
Reaction Profile

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 <i>beta</i>-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

A Mild and Simple Method for Making MIDA Boronates

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> <p>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. </p> </div> </div> </div>

Visible Light-Mediated Oxidative Debenzylation

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. <br>

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

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

<p>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 (>10<sup>3</sup>), 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 CF<sub>3</sub>CO<sub>2</sub>H 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. </p>

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

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.

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

2019 ◽  
Vol 16 (2) ◽  
pp. 258-275 ◽  
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.

Naturalizing Moral Regression

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.

Preparation of a novel poly (ether ether ketone) self-reinforced paper appropriate for harsh conditions

2021 ◽  
Vol 56 (18) ◽  
pp. 11174-11185
Author(s):  
Xin Cong ◽  
Jiannan Ren ◽  
Chunhui Xiang ◽  
Xuzhao Gai ◽  
Guibin Wang ◽  
...  
Keyword(s):  
Ether Ether Ketone ◽  
Poly Ether Ether Ketone ◽  
Ether Ketone ◽  
Harsh Conditions

scholarly journals Tin Complexes of 4-(Benzylideneamino)benzenesulfonamide: Synthesis, Structure Elucidation and Their Efficiency as PVC Photostabilizers

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2434
Author(s):  
Hassan Ghani ◽  
Emad Yousif ◽  
Dina S. Ahmed ◽  
Benson M. Kariuki ◽  
Gamal A. El-Hiti
Keyword(s):  
Vinyl Chloride ◽  
Structure Elucidation ◽  
Poly Vinyl Chloride ◽  
Polymeric Chains ◽  
Process Decomposition ◽  
Stabilizing Effect ◽  
Surface Alteration ◽  
Tin Complexes ◽  
High Yields ◽  
Harsh Conditions

Poly(vinyl chloride) (PVC) suffers from photo-xidation and photodegradation when exposed to harsh conditions. Application of PVC thus relies on the development of ever more efficient photostabilizers. The current research reports the synthesis of new complexes of tin and their assessment as poly(vinyl chloride) photostabilizers. The three new complexes were obtained in high yields from reaction of 4-(benzylideneamino)benzenesulfonamide and tin chlorides. Their structures were elucidated using different tools. The complexes were mixed with poly(vinyl chloride) at a very low concentration and thin films were made from the blends. The effectiveness of the tin complexes as photostabilizers has been established using a variety of methods. The new tin complexes led to a decrease in weight loss, formation of small residues, molecular weight depression, and surface alteration of poly(vinyl chloride) after irradiation. The additives act by absorption of ultraviolet light, removal the active chlorine produced through a dehydrochlorination process, decomposition of peroxides, and coordination with the polymeric chains. The triphenyltin complex showed the greatest stabilizing effect against PVC photodegradation as a result of its high aromaticity.

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