scholarly journals Why base-catalyzed isomerization of N-propargyl amides yields mostly allenamides rather than ynamides

2015 ◽  
Vol 11 ◽  
pp. 1441-1446 ◽  
Author(s):  
Armando Navarro-Vázquez
Keyword(s):  
Ab Initio ◽  
Equilibrium Position ◽  
Structural Changes ◽  
Energy Gap ◽  
Equilibrium Mixture ◽  
Experimental Results ◽  
Exchange Equilibrium ◽  
Small Energy ◽  
Dft Computations ◽  
Ab Initio And Dft

The base-catalyzed isomerization of N-propargylamides or carbamates may furnish N-allenyl compounds (allenamides/allencarbamates) or further evolve to N-alkynyl compounds (ynamides or yncarbamates). The particular fate of this reaction varies from experiment to experiment and there is no clear rule for predicting the reaction outcome for a particular structure. With the support of ab initio and DFT computations, this work shows that observed results can be explained by assuming an exchange equilibrium between energetically close N-propargyl, allenyl and N-alkynyl forms and that the reaction outcome correlates to a particular equilibrium mixture. Due to the very small energy gap between the N-allenyl and N-alkynyl forms, small structural changes may easily alter the equilibrium position, explaining the variety of observed experimental results. Based on CBS-QB3 computations, the ωB97 functional provided reasonably accurate isomerization energies and could successfully predict the experimentally observed behavior for several examples from the literature.

ESR and ENDOR Investigations on Various Wurster?s Radical Cations in Solution. Experimental Results, Theoretical Ab Initio, and DFT Calculations

2005 ◽  
Vol 136 (4) ◽  
pp. 519-536 ◽  
Author(s):  
G�nter Grampp ◽  
Anne-Marie Kelterer ◽  
Stephan Landgraf ◽  
Michael Sacher ◽  
Dominique Niethammer ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Ab Initio ◽  
Radical Cations ◽  
Experimental Results ◽  
Ab Initio And Dft

Effect of the structural changes on the mechanical properties of the sintered films

2016 ◽  
Vol 12 (1) ◽  
pp. 4141-4144
Author(s):  
Garima Jain
Keyword(s):  
Crystallite Size ◽  
Lattice Constant ◽  
Structural Changes ◽  
Structural Investigation ◽  
Energy Gap ◽  
Lattice Parameter ◽  
Metal Chalcogenides ◽  
Optical Energy Gap ◽  
Tin Telluride ◽  
Physical Quantities

Polycrystalline films of tin telluride were prepared by sintering technique. The structural investigation of the films with different thicknesses enables to determine lattice parameter, crystallite size and strain existing in the films. The XRD traces showed that strain was tensile in nature. The crystallite size increases with thickness while strain decreases. Higher the value of tensile strain, larger is the lattice constant. The optical energy gap shows a descending nature with increasing strain and so with the lattice constant. Such an attempt made to delve into interdependence of basic physical quantities helps to explore the properties of SnTe and utilize it as an alternative to heavy metal chalcogenides in various technological applications.  

scholarly journals Ion-Induced Volume Transition in Gels and Its Role in Biology

Gels ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 20
Author(s):  
Matan Mussel ◽  
Peter J. Basser ◽  
Ferenc Horkay
Keyword(s):  
Nonlinear Response ◽  
Structural Changes ◽  
Ionic Composition ◽  
Biological Systems ◽  
Experimental Results ◽  
Resting Potential ◽  
Cell Secretion ◽  
Solvent Quality ◽  
Volume Transition ◽  
Biological Milieu

Incremental changes in ionic composition, solvent quality, and temperature can lead to reversible and abrupt structural changes in many synthetic and biopolymer systems. In the biological milieu, this nonlinear response is believed to play an important functional role in various biological systems, including DNA condensation, cell secretion, water flow in xylem of plants, cell resting potential, and formation of membraneless organelles. While these systems are markedly different from one another, a physicochemical framework that treats them as polyelectrolytes, provides a means to interpret experimental results and make in silico predictions. This article summarizes experimental results made on ion-induced volume phase transition in a polyelectrolyte model gel (sodium polyacrylate) and observations on the above-mentioned biological systems indicating the existence of a steep response.

Ab initio and DFT investigations on the stereochemistry of ring opening of episulfides

2006 ◽  
Vol 763 (1-3) ◽  
pp. 1-5 ◽  
Author(s):  
Anbarasan Kalaiselvan ◽  
Ponnambalam Venuvanalingam
Keyword(s):  
Ab Initio ◽  
Ring Opening ◽  
Ab Initio And Dft
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