A Monte Carlo-Quantum Mechanics Study of the Solvent-Induced Spectral Shift and the Specific Role of Hydrogen Bonds in the Conformational Equilibrium of Furfural in Water

2002 ◽  
Vol 106 (47) ◽  
pp. 12317-12322 ◽  
Author(s):  
Roberto Rivelino ◽  
Kaline Coutinho ◽  
Sylvio Canuto
Keyword(s):  
Monte Carlo ◽  
Quantum Mechanics ◽  
Hydrogen Bonds ◽  
Conformational Equilibrium ◽  
Spectral Shift ◽  
Specific Role

Role of the gauche effect and local 1,3-dipole–dipole interactions in stabilizing an unusual conformation of tartarodinitriles

2008 ◽  
Vol 64 (4) ◽  
pp. 497-503 ◽  
Author(s):  
Urszula Rychlewska ◽  
Natalia Waścinska ◽  
Beata Warżajtis ◽  
Jacek Gawroński
Keyword(s):  
Hydrogen Bonds ◽  
Tartaric Acid ◽  
Conformational Equilibrium ◽  
Carbon Chain ◽  
Dipolar Interactions ◽  
Nmr Studies ◽  
X Ray ◽  
Gauche Effect ◽  
Dipole Interactions

This paper reports the synthesis, X-ray and NMR investigations of chiral and meso dinitriles of tartaric acid (tartarodinitriles) and their O,O′-diacetyl and O,O′-dibenzoyl derivatives. While in chiral tartaric acid its esters and NH amides the four-atom carbon chain is overwhelmingly trans, it is gauche in chiral tartarodinitriles. Conversely, meso-tartaric acid, its esters and amides display a tendency for the gauche conformation, but meso-tartarodinitriles usually have the trans conformation. The NMR studies of tartarodinitriles reveal the presence of a conformational equilibrium in solution with a preference for those conformers found in crystals. The gauche conformation of meso-tartarodinitriles seems to be stabilized by local dipolar interactions, intramolecular C—H...O hydrogen bonds and by a tendency for maximization of the gauche effect, the latter effect also operating in chiral tartarodinitriles. Stabilization of the trans conformers of tartarodinitriles in the crystals seems to originate from specific intermolecular interactions.

Interpassivity and Misdemeanours: The Art of Thinking in Examples and the Žižekian Toolbox

2018 ◽  
Author(s):  
Robert Pfaller
Keyword(s):  
Specific Role ◽  
Slavoj Zizek ◽  
Slavoj Žižek ◽  
The Sublime

Starting from a passage from Slavoj Žižek`s brilliant book The Sublime Object of Ideology, the very passage on canned laughter that gave such precious support for the development of the theory of interpassivity, this chapter examines a question that has proved indispensable for the study of interpassivity: namely, what does it mean for a theory to proceed by examples? What is the specific role of the example in certain example-friendly theories, for example in Žižek’s philosophy?

Randomness and Complexity

2018 ◽  
Author(s):  
Steven E. Vigdor
Keyword(s):  
Quantum Mechanics ◽  
Natural Selection ◽  
Rna World ◽  
Biological Evolution ◽  
Variable Theory ◽  
Cosmological Natural Selection ◽  
Einstein Podolsky Rosen ◽  
World Hypothesis ◽  
Rna World Hypothesis

Chapter 7 describes the fundamental role of randomness in quantum mechanics, in generating the first biomolecules, and in biological evolution. Experiments testing the Einstein–Podolsky–Rosen paradox have demonstrated, via Bell’s inequalities, that no local hidden variable theory can provide a viable alternative to quantum mechanics, with its fundamental randomness built in. Randomness presumably plays an equally important role in the chemical assembly of a wide array of polymer molecules to be sampled for their ability to store genetic information and self-replicate, fueling the sort of abiogenesis assumed in the RNA world hypothesis of life’s beginnings. Evidence for random mutations in biological evolution, microevolution of both bacteria and antibodies and macroevolution of the species, is briefly reviewed. The importance of natural selection in guiding the adaptation of species to changing environments is emphasized. A speculative role of cosmological natural selection for black-hole fecundity in the evolution of universes is discussed.

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