نتایج جستجو برای: hindered rotation
تعداد نتایج: 83881 فیلتر نتایج به سال:
In the 40 years since the inception of dynamic NMR methods, much effort has been invested to quantify and understand the barrier to rotation about the C-N bond in amides.1 Carbamates, which also exhibit the approximately planar N-CdO framework responsible for hindered rotation in amides, have received considerably less attention, although they are important biologically as anticonvulsants, loca...
Poly(N-acetyl)iminoethylene. poly(N-propionyl)iminoethylene and poly(N-acetyl)-2,2-dimethyliminoethylene were prepared by cationic polymerization in solution of 2-methyl2-oxazoline, 2-ethyl-2-oxazoline, and 2,4,4-trimethyl-2-oxazoline respectively. The 13C NMR spectra of the polymers obtained showed different sets of shifts for the carbon atoms of the backbone as well as for the N-acylimino sid...
Infrared spectra of the mass selected ionic complexes H2–HCO 1 and D2–DCO 1 have been recorded in the vicinity of their n1 vibrations ~H2 /D2 stretch! by means of photofragmentation spectroscopy. The anomalous rotational constants obtained by fitting the observed line positions to a semirigid Watson A-type Hamiltonian reflect the appreciable zero-point excursions of the H2 /D2 molecule. Barrier...
in chapter one we will describe definitions and preliminary results to provide the global context of our own results to be presented in detail in the subsequent chapters in chapter two we consider degree-one maps of the circle and we study their rotation set. our main result in this chapter says that if the map is topologically mixing then its rotation interval is nontrivial (that is, not reduc...
The synthesis and structural characterization of zwitterionic [(η(6)-C6H5-BPh3)M(coe)2] (M = Rh, Ir) cyclooctene complexes is described. Both complexes exhibit an unusual exo-endo conformation of both cyclooctene ligands in the solid state. However, an equilibrium between the endo-endo and exo-endo rotational isomers arising from the hindered rotation about the metal-cyclooctene bond is observe...
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