Temperature Dependence of the Conformational Equilibria of Cyclic Sulfites

1965 ◽  
Vol 30 (12) ◽  
pp. 4363-4364 ◽  
Author(s):  
C. G. Overberger ◽  
T. Kurtz ◽  
S. Yaroslavsky
Keyword(s):  
Temperature Dependence ◽  
Conformational Equilibria ◽  
Cyclic Sulfites

Conformational Equilibria in Cyclic Sulfites and Sulfates. The Configurations and Conformations of the Two Isomeric Thiodans1

1965 ◽  
Vol 30 (1) ◽  
pp. 169-175 ◽  
Author(s):  
Sylvan E. Forman ◽  
Antony J. Durbetaki ◽  
Michael V. Cohen ◽  
R. A. Olofson
Keyword(s):  
Conformational Equilibria ◽  
Cyclic Sulfites

ALICYCLIC KETYLS: II. TEMPERATURE DEPENDENCE OF THE CONFORMATIONAL MOBILITY OF MEDIUM-SIZED RINGS

1965 ◽  
Vol 43 (12) ◽  
pp. 3294-3303 ◽  
Author(s):  
J. W. Lown
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Close Agreement ◽  
Conformational Equilibrium ◽  
Dihedral Angles ◽  
Paramagnetic Resonance ◽  
Conformational Equilibria ◽  
Electron Paramagnetic ◽  
Hyperfine Couplings

The electron paramagnetic resonance spectra of ketyls derived from alicyclic ketones containing from 6 to 12 carbons have been recorded in 1,2-dimethoxyethane or dimethoxymethane at temperatures from −96 to +87 °C. At −96° individual conformers of the cyclohexyl ketyl are observed with hyperfine couplings in close agreement with that of the conformationally 'frozen' 4-tert-butyl analogue at room temperature. The cycloheptyl ketyl conformational equilibrium between forms which have a plane of symmetry through the C—O bond axis is 'frozen' with respect to the spectrometer frequency at temperatures from −40 to +88 °C. Cyclooctyl ketyl equilibrates at ordinary temperatures between two conformers lacking a plane of symmetry through the C—O bond axis. The electron paramagnetic resonance spectra of the ketyls derived from 10- and 12-membered rings show dramatic temperature dependence, which is interpreted in terms of two or more simultaneous conformational equilibria. Values for the dihedral angles of the alpha protons and for the spin density on the sp2 carbon are derived.

SPECTROSCOPIC STUDIES OF ALCOHOLS: VI. INTRAMOLECULAR HYDROGEN BONDS IN ETHANOLAMINE AND ITS O- AND N-METHYL DERIVATIVES

1965 ◽  
Vol 43 (11) ◽  
pp. 2970-2977 ◽  
Author(s):  
P. J. Krueger ◽  
H. D. Mettee
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Temperature Dependence ◽  
Spectroscopic Studies ◽  
Intramolecular Hydrogen Bonds ◽  
Distinct Band ◽  
Conformational Equilibria ◽  
Methyl Derivatives ◽  
Intramolecular Hydrogen

The competitive intramolecular [Formula: see text] hydrogen bonding in ethanolamine and N-methylethanolamine has been studied in dilute C2Cl4 solution by means of the temperature dependence of the fundamental OH and NH stretching bands. Of the three conformers identified for each of these compounds, the least stable shows a distinct band which is assigned to a "terminal" OH group involved in an intramolecular [Formula: see text] hydrogen bond. Enthalpy differences between conformers are reported and discussed, and compared with those found for the conformational equilibria in 2-methoxyethylamine and N,N-dimethyl-ethanolamine.

Nuclear magnetic resonance study of conformational equilibria in some fluorinated alkenes

1964 ◽  
Vol 282 (1391) ◽  
pp. 559-568 ◽  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Temperature Dependence ◽  
Opposite Sign ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Magnetic Resonance Study ◽  
Close Proximity ◽  
Conformational Equilibria ◽  
Enthalpy Difference

From a temperature study of coupling constants in cis and trans i -C 3 F 7 CH═CHF several coupling constants characteristic of the fixed rotamers have been calculated. The observed temperature dependence is consistent with there being only two rotamers of significant population for each isomer. The enthalpy difference between rotamers is – 1700 and – 900 cal/mole for the cis and trans isomers respectively. Long-range F–F coupling constants appear to be large where the interacting nuclei are in close proximity. Some of the coupling constants are found to be of opposite sign when the isomers change their conformations.

Temperature Dependence of the Critical Electron Dose for Fatty Acid Monolayers

1982 ◽  
Vol 40 ◽  
pp. 78-79
Author(s):  
Kenneth H. Downing ◽  
Robert M. Glaeser
Keyword(s):  
Electron Beam ◽  
Fatty Acid ◽  
Inelastic Scattering ◽  
Temperature Dependence ◽  
Structural Damage ◽  
Direct Result ◽  
Second Step ◽  
Strong Temperature Dependence ◽  
Electron Dose ◽  
Covalent Bonds

The structural damage of molecules irradiated by electrons is generally considered to occur in two steps. The direct result of inelastic scattering events is the disruption of covalent bonds. Following changes in bond structure, movement of the constituent atoms produces permanent distortions of the molecules. Since at least the second step should show a strong temperature dependence, it was to be expected that cooling a specimen should extend its lifetime in the electron beam. This result has been found in a large number of experiments, but the degree to which cooling the specimen enhances its resistance to radiation damage has been found to vary widely with specimen types.

Temperature Dependence of Magnetic Domains and Wall Structures

1972 ◽  
Vol 30 ◽  
pp. 496-497
Author(s):  
Sonoko Tsukahara ◽  
Tadami Taoka ◽  
Hisao Nishizawa
Keyword(s):  
Temperature Dependence ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Iron Film ◽  
Objective Lens ◽  
Lorentz Microscopy ◽  
Domain Structures ◽  
Wall Structures ◽  
Crystal Films ◽  
Metallurgical Structure

The high voltage Lorentz microscopy was successfully used to observe changes with temperature; of domain structures and metallurgical structures in an iron film set on the hot stage combined with a goniometer. The microscope used was the JEM-1000 EM which was operated with the objective lens current cut off to eliminate the magnetic field in the specimen position. Single crystal films with an (001) plane were prepared by the epitaxial growth of evaporated iron on a cleaved (001) plane of a rocksalt substrate. They had a uniform thickness from 1000 to 7000 Å.The figure shows the temperature dependence of magnetic domain structure with its corresponding deflection pattern and metallurgical structure observed in a 4500 Å iron film. In general, with increase of temperature, the straight domain walls decrease in their width (at 400°C), curve in an iregular shape (600°C) and then vanish (790°C). The ripple structures with cross-tie walls are observed below the Curie temperature.

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