Chemical Shift. VII. The Long-range Shielding Effects of the Cyano Group

1972 ◽  
Vol 50 (14) ◽  
pp. 2351-2356 ◽  
Author(s):  
J. W. ApSimon ◽  
H. Beierbeck ◽  
D. K. Todd
Keyword(s):  
Chemical Shift ◽  
Long Range ◽  
Field Effect ◽  
Cyano Group ◽  
Electric Field Effect ◽  
Minor Contribution ◽  
Anisotropy Effect ◽  
A Minor ◽  
Good Agreement ◽  
Shielding Effects

Using the methods described in parts I–VI of this series, we have examined the long-range shielding effects of the cyano group upon the C-18 and -19 methyl protons in several cyano-steroids and the ring protons in 2-endo- and 2-exo-cyanonorbornenes.It was found that the most important shielding mechanism of the cyano group is its electric field effect, with the magnetic anisotropy effect making at most a minor contribution to the screening. However, only in the cases of the cyano-steroids was good agreement obtained between the calculated and the experimental shifts.

Chemical Shift. VI. The Long-range Shielding Effects of Ethylene–Ketal and −Thioketal Groups

1971 ◽  
Vol 49 (9) ◽  
pp. 1335-1338 ◽  
Author(s):  
J. W. ApSimon ◽  
H. Beierbeck ◽  
D. K. Todd ◽  
P. V. Demarco ◽  
W. G. Craig
Keyword(s):  
Chemical Shift ◽  
Electric Field ◽  
Long Range ◽  
Field Effect ◽  
Chemical Shifts ◽  
Electric Field Effect ◽  
Electric Dipoles ◽  
Derivatives Of ◽  
Shielding Effects

The calculation of chemical shift values by the method used in parts I–V (1–5) has been extended to a derivation of the shielding effects of the ethylene–ketal and −thioketal groups. For these studies ketal and thioketal derivatives of monoketoandrostanes were prepared. The chemical shifts of the C-18 and -19 methyl protons in these compounds are reported for the solvents CDCl3, CCl4 and benzene.Representing both groups by point dipoles, values for the anisotropies and for K, a parameter descriptive of the electric field effect, were derived for various, coincidental, locations of the magnetic and electric dipoles along the symmetry axes of the two groups.

SUBSTITUTIONAL AND CONFIGURATIONAL EFFECTS ON CHEMICAL SHIFT IN PYRANOID CARBOHYDRATE DERIVATIVES

1965 ◽  
Vol 43 (7) ◽  
pp. 2059-2070 ◽  
Author(s):  
R. U. Lemieux ◽  
J. D. Stevens
Keyword(s):  
Chemical Shift ◽  
Long Range ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Equatorial Orientation ◽  
Free Energies ◽  
Bonding Interaction ◽  
Conformational Properties ◽  
Good Agreement ◽  
Shielding Effects

The effects of long-range and virtual long-range coupling on the observed spectra of acetylated hexopyranoses and pentopyranoses are examined. Use is made of both spin decoupling and specific deuteration for the assignment of signals. It is seen that specific solvent effects on chemical shift can be superior to increasing the applied magnetic field for the resolution of the signals of closely related protons. The alteration of virtual long-range coupling effects in these ways can be useful in the diagnosis of spectra. Empirical rules are derived for estimating the long-range shielding effects which occur on changing configurations. It is seen that the inversion of a center can lead to deshielding of axial protons and to shielding of equatorial protons at other centers relative to the chemical shifts observed in reference compounds wherein all the acetoxy groups are in equatorial orientation. The effects in several cases result in equatorial protons giving their signal to higher field than chemically similar but axial protons. The conformational properties of pentopyranose tetraacetates as estimated from chemical shifts and coupling constants are seen to be in good agreement with expectations based on non-bonding interaction free energies. As expected, 2-deoxy-β-D-ribopyranose triacetate has the 1C-conformation when dissolved in chloroform.

Evidence for the existence of an electric field effect from the vinyl proton magnetic resonance spectra of 4-substituted styrenes

1968 ◽  
Vol 46 (24) ◽  
pp. 3813-3820 ◽  
Author(s):  
G. K. Hamer ◽  
W. F. Reynolds
Keyword(s):  
Chemical Shift ◽  
Electric Field ◽  
Field Effect ◽  
Chemical Shifts ◽  
Electric Field Effect ◽  
Vinyl Proton ◽  
Concentration Effects ◽  
Electric Field Effects ◽  
Field Effects ◽  
Proton Chemical Shifts

Vinyl proton chemical shifts of styrene and six 4-substituted styrenes have been determined at infinite dilution in cyclohexane. It is shown that changes in the chemical shift difference of the β protons, Δ(δC − δB) can be accounted for by electric field effects. Reasonable values of the constant in the Buckingham equation of(−3.11 ± 0.50) × 10−12 and (−4.77 ± 0.83) × 10−12 are obtained from two different types of field effect calculations. Residual chemical shift changes for β protons after correction for electric field effects can be explained in terms of mesomeric and possibly inductive mechanisms. α-Proton chemical shift values cannot be satisfactorily rationalized. Small concentration effects are noted, usually resulting in high field shifts with increasing concentration. Previous results are reexamined in order to resolve a conflict in the literature.

Long-Range Nonvolatile Electric Field Effect in Epitaxial Fe/Pb(Mg1/3 Nb2/3 )0.7 Ti0.3 O3 Heterostructures

2018 ◽  
Vol 28 (20) ◽  
pp. 1707027 ◽  
Author(s):  
Cai Zhou ◽  
Lvkang Shen ◽  
Ming Liu ◽  
Cunxu Gao ◽  
Chenglong Jia ◽  
...  
Keyword(s):  
Electric Field ◽  
Long Range ◽  
Field Effect ◽  
Electric Field Effect

Chemical Shift. V. Further Studies on the Long-range Shielding Effects of the C—H and C=O Bonds

1971 ◽  
Vol 49 (9) ◽  
pp. 1328-1334 ◽  
Author(s):  
J. W. ApSimon ◽  
H. Beierberck
Keyword(s):  
Chemical Shift ◽  
Magnetic Anisotropy ◽  
Long Range ◽  
Methyl Groups ◽  
X Ray ◽  
X Ray Crystallography ◽  
Geometric Factors ◽  
Atomic Coordinates ◽  
Shielding Effects

The long-range shielding effects of the C=O and C—H bonds were reexamined by the method described in part IV of this series, with the objective of resolving the discrepancies between some of the conclusions presented and earlier findings by Zürcher. The C—H bond magnetic anisotropy was treated as a variable and found to be small enough to be negligible. Upon omission of this term, both electrostatic and magnetic anisotropy effects had to be invoked to account for the shielding effects of the carbonyl group.The necessary geometric quantities were calculated from atomic coordinates for androsterone, as determined by X-ray crystallography, and freely rotating methyl groups were approximated by superpositions of 24 conformations of the group. The results were in essential agreement with those obtained with the use of geometric factors computed as described in part IV.

Electric Field Effect on Friction Coefficient of Diamond-Like Carbon Film Heated by Laser Irradiation

2021 ◽  
Vol 69 (3) ◽  
Author(s):  
Hiroshi Tani ◽  
Yuki Izutani ◽  
Renguo Lu ◽  
Shinji Koganezawa ◽  
Norio Tagawa
Keyword(s):  
Friction Coefficient ◽  
Electric Field ◽  
Laser Irradiation ◽  
Field Effect ◽  
Carbon Film ◽  
Diamond Like Carbon ◽  
Electric Field Effect ◽  
Diamond Like Carbon Film

scholarly journals Electric field effect on the thermal conductivity of wurtzite GaN

2021 ◽  
Vol 118 (16) ◽  
pp. 162110
Author(s):  
Yujie Quan ◽  
Sheng-Ying Yue ◽  
Bolin Liao
Keyword(s):  
Thermal Conductivity ◽  
Electric Field ◽  
Field Effect ◽  
Electric Field Effect

scholarly journals The Influence of La and Ce on Microstructure and Mechanical Properties of an Al-Si-Cu-Mg-Fe Alloy at High Temperature

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 384
Author(s):  
Andong Du ◽  
Anders E. W. Jarfors ◽  
Jinchuan Zheng ◽  
Kaikun Wang ◽  
Gegang Yu
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
High Temperature ◽  
Intermetallic Phases ◽  
High Temperature Strength ◽  
Thermal Expansion Mismatch ◽  
Strengthening Mechanisms ◽  
High Temperature Mechanical Properties ◽  
Minor Contribution ◽  
A Minor

The effect of lanthanum (La)+cerium (Ce) addition on the high-temperature strength of an aluminum (Al)–silicon (Si)–copper (Cu)–magnesium (Mg)–iron (Fe)–manganese (Mn) alloy was investigated. A great number of plate-like intermetallics, Al11(Ce, La)3- and blocky α-Al15(Fe, Mn)3Si2-precipitates, were observed. The results showed that the high-temperature mechanical properties depended strongly on the amount and morphology of the intermetallic phases formed. The precipitated tiny Al11(Ce, La)3 and α-Al15(Fe, Mn)3Si2 both contributed to the high-temperature mechanical properties, especially at 300 °C and 400 °C. The formation of coarse plate-like Al11(Ce, La)3, at the highest (Ce-La) additions, reduced the mechanical properties at (≤300) ℃ and improved the properties at 400 ℃. Analysis of the strengthening mechanisms revealed that the load-bearing mechanism was the main contributing mechanism with no contribution from thermal-expansion mismatch effects. Strain hardening had a minor contribution to the tensile strength at high-temperature.

scholarly journals Electric field effect on electrospun fiber alignment using a parallel electrode plate

2021 ◽  
Vol 1719 (1) ◽  
pp. 012064
Author(s):  
Karnjana Oncheurn ◽  
Yingyot Infahsaeng
Keyword(s):  
Electric Field ◽  
Field Effect ◽  
Electrospun Fiber ◽  
Electric Field Effect ◽  
Fiber Alignment ◽  
Parallel Electrode ◽  
Electrode Plate
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