ChemInform Abstract: HINDERED ROTATION OF THE CARBONAMIDE BOND IN CROWN ETHERS, CRYPTANDS, AND SIMILAR SYSTEMS - ELECTRONIC AND STERIC SUBSTITUENT EFFECTS

1979 ◽  
Vol 10 (16) ◽  
Author(s):  
E. BUHLEIER ◽  
W. WEHNER ◽  
F. VOEGTLE
Keyword(s):  
Crown Ethers ◽  
Substituent Effects ◽  
Hindered Rotation

Substituent effects on complexation and extraction of alkali metals with chromogenic crown ethers

1982 ◽  
Vol 139 ◽  
pp. 307-313 ◽  
Author(s):  
B.P. Bubnis ◽  
J.L. Steger ◽  
Y.P. Wu ◽  
L.A. Meyers ◽  
G.E. Pacey
Keyword(s):  
Crown Ethers ◽  
Alkali Metals ◽  
Substituent Effects

1H and 13C dynamic nuclear magnetic resonance study of hindered rotation in thiobenzoylpiperidines and thiobenzoylmorpholines. Correlation between barrier heights of amides and thioamides

1977 ◽  
Vol 55 (14) ◽  
pp. 2649-2655 ◽  
Author(s):  
Carla Piccinni-Leopardi ◽  
Omer Fabre ◽  
Daniel Zimmermann ◽  
Jacques Reisse ◽  
F. Cornea ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Linear Correlation ◽  
Substituent Effects ◽  
Nuclear Magnetic Resonance Study ◽  
Free Energies ◽  
Magnetic Resonance Study ◽  
Hindered Rotation ◽  
Barrier Heights ◽  
Dynamic Nuclear Magnetic Resonance

The free energies of activation for hindered rotation around the C—N bond have been determined for a series of N,N-disubstituted thioamides by means of 13C and 1H dynamic nmr.A comparison between barriers for 20 amides and the corresponding thioamides, studied under similar conditions, has been drawn up using both our results and data obtained from the literature. An excellent linear correlation has been obtained. The same correlation also holds for primary (thio)amides and seems to be of general significance. Substituent effects on the barrier heights of thioamides and amides are discussed in connection with some particular cases.

Hindered rotation around the amide bond in a series of derivatives of 2-acetamidothiophenes

1991 ◽  
Vol 88 ◽  
pp. 689-707 ◽  
Author(s):  
P Andriamadio ◽  
D Nicole ◽  
A Cartier ◽  
M Wierzbicki ◽  
G Kirsch
Keyword(s):  
Amide Bond ◽  
Hindered Rotation ◽  
Derivatives Of

Substituent effects and solvents

1992 ◽  
Vol 89 ◽  
pp. 1567-1571
Author(s):  
O Pytela ◽  
M Ludwig
Keyword(s):  
Substituent Effects

Substituent Effects on the Thermal Decomposition of Phosphate Esters on Ferrous Surfaces

2019 ◽  
Author(s):  
James Ewen ◽  
Carlos Ayestaran Latorre ◽  
Arash Khajeh ◽  
Joshua Moore ◽  
Joseph Remias ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Film Formation ◽  
Substituent Effects ◽  
Vapour Phase ◽  
Industrial Applications ◽  
Phosphate Esters ◽  
Antiwear Additives ◽  
Formation Mechanisms ◽  
Phosphate Ester ◽  
Wide Range

<p>Phosphate esters have a wide range of industrial applications, for example in tribology where they are used as vapour phase lubricants and antiwear additives. To rationally design phosphate esters with improved tribological performance, an atomic-level understanding of their film formation mechanisms is required. One important aspect is the thermal decomposition of phosphate esters on steel surfaces, since this initiates film formation. In this study, ReaxFF molecular dynamics simulations are used to study the thermal decomposition of phosphate esters with different substituents on several ferrous surfaces. On Fe<sub>3</sub>O<sub>4</sub>(001) and α-Fe(110), chemisorption interactions between the phosphate esters and the surfaces occur even at room temperature, and the number of molecule-surface bonds increases as the temperature is increased from 300 to 1000 K. Conversely, on hydroxylated, amorphous Fe<sub>3</sub>O<sub>4</sub>, most of the molecules are physisorbed, even at high temperature. Thermal decomposition rates were much higher on Fe<sub>3</sub>O<sub>4</sub>(001) and particularly α-Fe(110) compared to hydroxylated, amorphous Fe<sub>3</sub>O<sub>4</sub>. This suggests that water passivates ferrous surfaces and inhibits phosphate ester chemisorption, decomposition, and ultimately film formation. On Fe<sub>3</sub>O<sub>4</sub>(001), thermal decomposition proceeds mainly through C-O cleavage (to form surface alkyl and aryl groups) and C-H cleavage (to form surface hydroxyls). The onset temperature for C-O cleavage on Fe<sub>3</sub>O<sub>4</sub>(001) increases in the order: tertiary alkyl < secondary alkyl < primary linear alkyl ≈ primary branched alkyl < aryl. This order is in agreement with experimental observations for the thermal stability of antiwear additives with similar substituents. The results highlight surface and substituent effects on the thermal decomposition of phosphate esters which should be helpful for the design of new molecules with improved performance.</p>

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