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Search for "mechanical" in Full Text gives 251 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Diazocine-functionalized TATA platforms

  • Roland Löw,
  • Talina Rusch,
  • Fynn Röhricht,
  • Olaf Magnussen and
  • Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1485–1490, doi:10.3762/bjoc.15.150

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  • ][2][3][4]. However, there are very few reactions which do not follow the classical Eyring theory [5][6]. The rate of these reactions is not dependent on an activation barrier but controlled by quantum mechanical transition probabilities between two quantum states [7][8][9][10]. The majority of these
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Published 05 Jul 2019

Understanding the unexpected effect of frequency on the kinetics of a covalent reaction under ball-milling conditions

  • Ana M. Belenguer,
  • Adam A. L. Michalchuk,
  • Giulio I. Lampronti and
  • Jeremy K. M. Sanders

Beilstein J. Org. Chem. 2019, 15, 1226–1235, doi:10.3762/bjoc.15.120

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  • ), including a significant induction time before the nucleation and growth process starts. This indicates that to start the reaction an initial energy accumulation is necessary. Other than mixing, the energy supplied by the mechanical treatment has two effects: (i) reducing the crystal size and (ii) creating
  • less expensive than traditional solution-based methods, because they require little or no solvent. Moreover, mechanochemical syntheses often give quantitative yields of products [2][3][4]. Manual or mechanical grinding can be performed “neat”, i.e., in the absence of solvent (neat grinding, NG
  • ) activation of these contacts by mechanical impact. This is analogous to traditional chemical kinetics, limited by collision and activation. Macroscopically, a general irreversible mechanochemical reaction reaching equilibrium can be thus considered according to Scheme 2. A notable assumption is that all
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Published 05 Jun 2019

Mechanochemical amorphization of chitin: impact of apparatus material on performance and contamination

  • Thomas Di Nardo and
  • Audrey Moores

Beilstein J. Org. Chem. 2019, 15, 1217–1225, doi:10.3762/bjoc.15.119

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  • is reduced by mechanical forces [17][24][50][51] or otherwise [52] by deforming particles and breaking lattice imperfections [50]. For biomass processing, amorphization has been used in several studies [24][53][54], either as a pretreatment [21] prior to deacetylation [18][55], enzymatic [22][56][57
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Published 05 Jun 2019

Extending mechanochemical porphyrin synthesis to bulkier aromatics: tetramesitylporphyrin

  • Qiwen Su and
  • Tamara D. Hamilton

Beilstein J. Org. Chem. 2019, 15, 1149–1153, doi:10.3762/bjoc.15.111

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  • Information File 1). Although we are not certain of the identity of intermediates or side products from the mechanochemical reaction, it may be possible that via milling they are activated enough so that mechanical stirring during the oxidation with DDQ in solution continues to promote the formation of
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Published 22 May 2019

Unexpected polymorphism during a catalyzed mechanochemical Knoevenagel condensation

  • Sebastian Haferkamp,
  • Andrea Paul,
  • Adam A. L. Michalchuk and
  • Franziska Emmerling

Beilstein J. Org. Chem. 2019, 15, 1141–1148, doi:10.3762/bjoc.15.110

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  • ] in understanding reaction kinetics of these processes. Early insight into formation pathways was provided ex situ, in which the mechanical treatment was stopped, and powder removed for analysis [10][11]. More recently, further detail has been gained by monitoring mechanochemical transformations in
  • ). Shortly after the melting of 2, Bragg reflections were observed and remained visible for a period of approximately two minutes (Figure 4, gray box). These reflections, however, were found to correspond to the monoclinic phase of the product (m3a) [22][23]. Phase m3a remained stable under mechanical
  • effects. First, the lifetime of the initial molten/liquid phase was nearly doubled, suggesting that mechanical treatment has an important effect on this largely solution-phase reaction. This may be a result of heating, mechanical activation of the fluid-phase molecules or differences in energy for
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Published 21 May 2019

Fabrication, characterization and adsorption properties of cucurbit[7]uril-functionalized polycaprolactone electrospun nanofibrous membranes

  • Changzhong Chen,
  • Fengbo Liu,
  • Xiongzhi Zhang,
  • Zhiyong Zhao and
  • Simin Liu

Beilstein J. Org. Chem. 2019, 15, 992–999, doi:10.3762/bjoc.15.97

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  • that all nanofibers kept their fibrous shape after the absorption experiment, which indicates that the nanofibrous membranes have good mechanical properties and can be easily removed from the adsorption tail liquid. Conclusion CB[7]-based nanofibers with varying CB[7] contents were prepared by
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Letter
Published 29 Apr 2019

Mechanochemical synthesis of poly(trimethylene carbonate)s: an example of rate acceleration

  • Sora Park and
  • Jeung Gon Kim

Beilstein J. Org. Chem. 2019, 15, 963–970, doi:10.3762/bjoc.15.93

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  • important for chain-length control. Liquid-assisted grinding was applied for the synthesis of high molecular weight polymers, but it failed to protect the polymer chain from mechanical degradation. Keywords: aliphatic polycarbonate; green polymerization; mechanochemistry; organocatalyst; poly(trimethylene
  • carbonate); Introduction Nowadays mechanochemical syntheses are widespread in many areas of chemistry [1][2][3][4]. The efficient mixing and energy input induced by mechanical motions have promoted many chemical reactions with superior efficiencies [5]. Sometimes, unexpected outcomes that cannot be
  • achieved by solution synthesis occur, which makes mechanochemistry a topic of rigorous research [6]. In the area of polymer chemistry, the use of mechanical forces has a long history. Strong mechanical forces can break covalent bonds, including strong C–C bonds, thus their utilization has generally focused
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Published 23 Apr 2019

Mechanochemistry of supramolecules

  • Anima Bose and
  • Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

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  • differences in the crystal packing in the solid state. The products 32 were obtained via thermodynamic control (Figure 18) from a dynamic combinatorial library [53][88]. In 2010, Otto and co-workers observed unprecedented product selectivity for the formation of disulfide macromolecules based on mechanical
  • shaking and stirring [89]. Peptide-chain containing distal thiol groups underwent an aerial oxidation process to give different disulfide-containing macromolecules. They observed that under mechanical shaking conditions preferentially the cyclic hexamer 33 is formed, whereas stirring resulted in formation
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Published 12 Apr 2019

Synthesis of acylglycerol derivatives by mechanochemistry

  • Karen J. Ardila-Fierro,
  • Andrij Pich,
  • Marc Spehr,
  • José G. Hernández and
  • Carsten Bolm

Beilstein J. Org. Chem. 2019, 15, 811–817, doi:10.3762/bjoc.15.78

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  • ; diacylglycerols; lipids; mechanochemistry; Introduction In addition to being guided by chemical signals, cells respond to mechanical cues by sensing and transducing external mechanical inputs into biochemical and electrical signals [1]. Consequently, every time a cell is subjected to mechanical loads, the
  • biomolecules that constitute the cell do also experience the effects of the mechanical forces. For example, from the moment a nascent peptide begins growing in the ribosome, such peptide experiences mechanical signals that regulate the speed of protein synthesis [2]. Not surprisingly, the natural ability of
  • peptides to endure mechanical stress in nature has allured scientists to evaluate the mechanical stability of proteins by using single-molecule nanomechanical techniques (e.g., magnetic and optical tweezers or atomic force microscopy) [3][4]. Additionally, the resilience of the peptide bond to mechanical
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Published 29 Mar 2019

Influence of per-O-sulfation upon the conformational behaviour of common furanosides

  • Alexey G. Gerbst,
  • Vadim B. Krylov,
  • Dmitry A. Argunov,
  • Maksim I. Petruk,
  • Arsenii S. Solovev,
  • Andrey S. Dmitrenok and
  • Nikolay E. Nifantiev

Beilstein J. Org. Chem. 2019, 15, 685–694, doi:10.3762/bjoc.15.63

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  • gauche-orientation upon sulfation. The effect is less pronounced in the galactosides. For all the studied structures changes in the conformational distribution were revealed by quantum mechanical calculations, that explained the observed changes in intraring coupling constants occurring upon introduction
  • mechanical calculations. All the mentioned changes certainly affect the values of the intraring 1H–1H coupling constants. To study this influence in detail, DFT/B3LYP/pcJ-1 calculation of the constants for low-energy conformers (A–M) denoted in Table 4 was performed (Table 6). The first thing to note is that
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Published 15 Mar 2019

Low-budget 3D-printed equipment for continuous flow reactions

  • Jochen M. Neumaier,
  • Amiera Madani,
  • Thomas Klein and
  • Thomas Ziegler

Beilstein J. Org. Chem. 2019, 15, 558–566, doi:10.3762/bjoc.15.50

Graphical Abstract
  • reliable connection from the reactor to the tubing. For that purpose, we used a 1/16 inch ethylene tetrafluoroethylene (ETFE) tubing (0.75 mm ID) with standard PEEK HPLC fittings (10–32 thread). Due to the soft mechanical properties of PP, it is very difficult to cut a thread into the reactor after
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Published 26 Feb 2019

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

  • Patrycja Żak and
  • Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

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  • can significantly improve such properties of the polymer as thermal and oxidative resistance, surface properties, improvement of mechanical properties as well as reduced flammability, heat release and viscosity during processing [29]. Synthesis, properties and applications of POSS-containing materials
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Published 04 Feb 2019

Olefin metathesis in multiblock copolymer synthesis

  • Maria L. Gringolts,
  • Yulia I. Denisova,
  • Eugene Sh. Finkelshtein and
  • Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

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  • nanomaterials that combine various functional properties with durability and enhanced mechanical characteristics. Our mini-review addresses synthetic approaches to the design of multiblock copolymers from unsaturated monomers and polymers using olefin metathesis reactions and other ways of chemical modification
  • electronics, fuel cells, gene and drug delivery [8][9][15][38][39][40]. Compared with diblock and triblock copolymers, not to speak about polymer blends, multiblock copolymers often demonstrate superior mechanical properties, biocompatibility, biodegradability, compatibilizing ability, and tendency to form
  • , IBI, and SIBIS multiblock copolymers, which include glassy, rubbery, and semicrystalline polymer segments and demonstrate peculiar mechanical behavior [57][58]. References [59] and [60] report on the preparation of fluorescent polymer nanoparticles for bioimaging and in vivo targeting of tumors and
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Published 24 Jan 2019

Ammonium-tagged ruthenium-based catalysts for olefin metathesis in aqueous media under ultrasound and microwave irradiation

  • Łukasz Gułajski,
  • Andrzej Tracz,
  • Katarzyna Urbaniak,
  • Stefan J. Czarnocki,
  • Michał Bieniek and
  • Tomasz K. Olszewski

Beilstein J. Org. Chem. 2019, 15, 160–166, doi:10.3762/bjoc.15.16

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  • interesting transformation. Furthermore, in the continuous search for new sustainable protocols for chemical reactions to induce new reactivates or reduce the energetic cost of the processes, the replacement of mechanical mixing and/or heating of the reacting species with microwave (μW) [46][47][48] and
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Published 17 Jan 2019

Adhesion, forces and the stability of interfaces

  • Robin Guttmann,
  • Johannes Hoja,
  • Christoph Lechner,
  • Reinhard J. Maurer and
  • Alexander F. Sax

Beilstein J. Org. Chem. 2019, 15, 106–129, doi:10.3762/bjoc.15.12

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  • adsorbates of different sizes. We discuss the different roles of adhesion energies and adhesive forces and friction forces for the description of the stability of condensed matter systems, and we show that use of the vector quantity force is essential for the understanding of mechanical stability of solids
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Published 11 Jan 2019

Synthesis, biophysical properties, and RNase H activity of 6’-difluoro[4.3.0]bicyclo-DNA

  • Sibylle Frei,
  • Adam K. Katolik and
  • Christian J. Leumann

Beilstein J. Org. Chem. 2019, 15, 79–88, doi:10.3762/bjoc.15.9

Graphical Abstract
  • calculated using quantum mechanical methods. For the calculations we used the Gaussian 09 software package [47] at the second order Møller–Plesset (MP2) level of theory, the 6-311G* basis set, and the same methodology as for the 6’F-bc4,3- T [37]. The obtained energy profile of nucleoside 7 (Figure 3a
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Published 08 Jan 2019

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

  • Anne Schnell,
  • J. Alexander Willms,
  • S. Nozinovic and
  • Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

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  • -proline and the carbonyl substrate acetone [40]. Houk and co-worker [41] verified the mechanism with quantum mechanical calculations, thus giving rise to the “List–Houk” mechanism. A discussion about the role of oxazolidinones as isomeric species to enamines has been raised in the scientific community [42
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Published 03 Jan 2019

6’-Fluoro[4.3.0]bicyclo nucleic acid: synthesis, biophysical properties and molecular dynamics simulations

  • Sibylle Frei,
  • Andrei Istrate and
  • Christian J. Leumann

Beilstein J. Org. Chem. 2018, 14, 3088–3097, doi:10.3762/bjoc.14.288

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  • of nucleoside 8 using quantum mechanical methods. The calculations were performed in vacuum with the Gaussian 09 software package [65] utilizing the second order Møller–Plesset perturbation theory (MP2) and the 6-311G* basis set. The energy profile of nucleoside 8 was obtained through a stepwise
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Published 20 Dec 2018

Dispersion interactions

  • Peter R. Schreiner

Beilstein J. Org. Chem. 2018, 14, 3076–3077, doi:10.3762/bjoc.14.286

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  • : they sum up to zero. The neglect of the attractive part of the vdW potential probably derives from the fact that there is no classic analogue as in the case of repulsion for which the hard sphere atom model works well. LD is a purely quantum mechanical effect due to electron correlation. It is present
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Editorial
Published 18 Dec 2018

Repurposing the anticancer drug cisplatin with the aim of developing novel Pseudomonas aeruginosa infection control agents

  • Mingjun Yuan,
  • Song Lin Chua,
  • Yang Liu,
  • Daniela I. Drautz-Moses,
  • Joey Kuok Hoong Yam,
  • Thet Tun Aung,
  • Roger W. Beuerman,
  • May Margarette Santillan Salido,
  • Stephan C. Schuster,
  • Choon-Hong Tan,
  • Michael Givskov,
  • Liang Yang and
  • Thomas E. Nielsen

Beilstein J. Org. Chem. 2018, 14, 3059–3069, doi:10.3762/bjoc.14.284

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  • anesthetized by topical administration of xylocaine 1%. A corneal wound was made by using a 5 mm trephine and mechanical removal of epithelial cells was carried out by sterile mini blade (BD-Beaver) leaving the basal lamina intact [22][23]. All the groups were treated by topical administration of the
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Published 14 Dec 2018

Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

  • Nicholas G. Jentsch,
  • Jared D. Hume,
  • Emily B. Crull,
  • Samer M. Beauti,
  • Amy H. Pham,
  • Julie A. Pigza,
  • Jacques J. Kessl and
  • Matthew G. Donahue

Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

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  • precipitated out after about 30 minutes at 70 °C. The heterogeneous reaction mixture was aged for 12 hours then cooled to room temperature (25 °C). The slurry was poured into a 600 mL beaker equipped with overhead mechanical stirrer (PTFE 75 mm paddle) containing 250 mL of deionized water. With vigorous
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Published 28 Sep 2018

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

  • Hendrik V. Schröder and
  • Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

Graphical Abstract
  • gradients control repetitive motions of these biological nanomachines, researchers have been seeking for synthetic analogues, i.e., artificial molecular machines (AMMs), with the ultimate goal to convert energy into directional mechanical motion on the nanoscale [4][5][6]. The field of AMMs beautifully
  • molecules, the mechanical bond provides cohesive supramolecular assemblies with unique properties and a high flexibility and mobility of the subcomponents in a small molecular space. To control molecular motion, one of the most important construction principles to transform a simple MIM into an AMM is to
  • -electron-poor molecule. The electrochemical switching of a TTF unit and the change of electronic or conformational properties not necessarily results in a mechanical motion of a MIM. A prerequisite is that at least one of the above-mentioned properties of TTF is interacting with other parts of the MIM. If
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Published 20 Aug 2018

A switchable [2]rotaxane with two active alkenyl groups

  • Xiu-Li Zheng,
  • Rong-Rong Tao,
  • Rui-Rui Gu,
  • Wen-Zhi Wang and
  • Da-Hui Qu

Beilstein J. Org. Chem. 2018, 14, 2074–2081, doi:10.3762/bjoc.14.181

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  • polymers. Keywords: alkenyl bond; functional crown ether; stimuli-responsiveness; switchable rotaxane; Introduction Along with the development of supramolecular chemistry, much attention has been paid to the design and synthesis of novel and complicated mechanical interlocked molecules (MIMs) [1][2][3][4
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Published 08 Aug 2018

A hemicryptophane with a triple-stranded helical structure

  • Augustin Long,
  • Olivier Perraud,
  • Erwann Jeanneau,
  • Christophe Aronica,
  • Jean-Pierre Dutasta and
  • Alexandre Martinez

Beilstein J. Org. Chem. 2018, 14, 1885–1889, doi:10.3762/bjoc.14.162

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  • parallel peptide chains coil about each other in a triple stranded left-handed helical structure. Its high thermal and mechanical stability results mainly from the numerous hydrogen bonds found in the triple helix framework [2]. Bioinspired structures, based on peptide backbones, have been built, allowing
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Published 24 Jul 2018

Efficient catenane synthesis by cucurbit[6]uril-mediated azide–alkyne cycloaddition

  • Antony Wing Hung Ng,
  • Chi-Chung Yee,
  • Kai Wang and
  • Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2018, 14, 1846–1853, doi:10.3762/bjoc.14.158

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  • simultaneously mediate the mechanical and covalent bond formations. By coupling the mechanical interlocking with covalent macrocyclization, formation of topological isomers is eliminated and the [3]catenanes are formed exclusively in good yields. The efficient access to these [3]catenanes and the presence of
  • other recognition units render them promising building blocks for the construction of other high-order interlocked structures. Keywords: azide–alkyne cycloaddition; catenane; click chemistry; cucurbit[6]uril; mechanical bond; Introduction Catenanes are topologically non-trivial molecules possessing
  • mechanically interlocked macrocycles. The flexible but strong mechanical bond between the interlocked macrocycles offers a unique opportunity for exploiting catenanes as molecular machines or new materials with unusual mechanical properties [1][2][3][4][5][6][7][8][9]. Over the years, different templates and
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Published 20 Jul 2018
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