Radical Stabilization and Ground State Polar Substituent Effects in the Thermal Decomposition of Azoalkanes

1994 ◽  
Vol 116 (24) ◽  
pp. 10972-10982 ◽  
Author(s):  
Werner M. Nau ◽  
Heinrich M. Harrer ◽  
Waldemar Adam
Keyword(s):  
Thermal Decomposition ◽  
Ground State ◽  
Substituent Effects ◽  
Polar Substituent

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>

Polar substituent effects on13C NMR spectra in ethylcis-2-substituted cyclopropane carboxylates

1982 ◽  
Vol 20 (3) ◽  
pp. 159-161 ◽  
Author(s):  
Yoshiaki Kusuyama ◽  
Satoru Inoshita ◽  
Ginjiro Okada ◽  
Minoru Yanagi ◽  
Kenjiro Tokami ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Substituent Effects ◽  
Polar Substituent

4-Substituted quinuclidinium perchlorates in the determination of polar substituent effects

1973 ◽  
Vol 14 (37) ◽  
pp. 3627-3630 ◽  
Author(s):  
E. Ceppi ◽  
W. Eckhardt ◽  
C.A. Grob
Keyword(s):  
Substituent Effects ◽  
Polar Substituent
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