O-Nucleophilicity of Hydroxamate Ions for Cleavage of Carboxylate and Phosphate Esters in Cationic Micelles

2014 ◽  
Vol 46 (8) ◽  
pp. 419-432 ◽  
Author(s):  
MANMOHAN L. SATNAMI ◽  
INDRAPAL KARBHAL ◽  
HITESH K. DEWANGAN
Keyword(s):  
Phosphate Esters ◽  
Cationic Micelles ◽  
Hydroxamate Ions

Effect of cationic gemini surfactants on the hydrolysis of carboxylate and phosphate esters using hydroxamate ions

2007 ◽  
Vol 286 (3) ◽  
pp. 293-303 ◽  
Author(s):  
Kallol K. Ghosh ◽  
Sancheeta Kolay ◽  
Sunita Bal ◽  
Manmohan L. Satnami ◽  
Pierluigi Quagliotto ◽  
...  
Keyword(s):  
Gemini Surfactants ◽  
Phosphate Esters ◽  
Cationic Gemini Surfactants ◽  
Hydroxamate Ions ◽  
Hydrolysis Of

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>

An Indication that Chloride Affects the Phosphate Esters in Tubers of the White Potato 1

1959 ◽  
Vol 51 (12) ◽  
pp. 750-751 ◽  
Author(s):  
H. W. Gausman ◽  
G. R. Cooper ◽  
R. A. Struchtemeyer
Keyword(s):  
Phosphate Esters ◽  
White Potato

Paper Chromatography of Phosphate Esters

Nature ◽  
1953 ◽  
Vol 171 (4358) ◽  
pp. 838-839 ◽  
Author(s):  
E. FLETCHER ◽  
F. H. MALPRESS
Keyword(s):  
Paper Chromatography ◽  
Phosphate Esters

Hydrophobic interactions in human casein micelle formation: β-casein aggregation

1989 ◽  
Vol 56 (3) ◽  
pp. 427-433 ◽  
Author(s):  
Charles W. Slattery ◽  
Satish M. Sood ◽  
Pat Chang
Keyword(s):  
Light Scattering ◽  
Conformational Transition ◽  
Hydrophobic Interactions ◽  
Micelle Formation ◽  
Tryptophan Fluorescence ◽  
Phosphate Esters ◽  
Casein Micelle ◽  
Protein Association ◽  
P Protein ◽  
Micelle Size

SummaryThe association of non-phosphorylated (0-P) and fully phosphorylated (5-P) human β-caseins was studied by fluorescence spectroscopy and laser light scattering. The tryptophan fluorescence intensity (FI) level increased between 20 and 35 °C, indicating a change in the environment of that residue. A similar transition occurred when ANS was used as a probe. Transition temperatures were slightly lower in 10 mM-CaCl2 but were not affected by an equivalent increase in ionic strength caused by NaCl. The magnitude of the FI change was less for the 5-P than the 0-P protein but was increased for both by CaCl2 addition. These FI data were characteristic of a conformational change and this was supported by fluorescence polarization which indicated that with CaCl2, tryptophan and ANS mobility increased at the transition temperature even though the extent of protein association also increased. Light scattering suggested that protein association proeeeded with the primary formation of submicellar aggregates containing 20–30 monomers which then associated further to form particles of minimum micelle size (12–15 submicelles), and eventually larger. The temperature of precipitation of the 5-P form in the presence of CaCl2 was lower than the conformational transition and suggested that both hydrophobic interactions and Ca bridges between phosphate esters on adjacent molecules are important in micelle formation.

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