Pyrolysis Studies. VIII.1Polar Substituent Effects in the Vapor Phase Thermal Decomposition of Isopropyl Benzoates

1963 ◽  
Vol 28 (12) ◽  
pp. 3496-3499 ◽  
Author(s):  
Grant Gill Smith ◽  
D. A. K. Jones
Keyword(s):  
Thermal Decomposition ◽  
Vapor Phase ◽  
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>

PYRAZOLINES: PART III. THE PREPARATION AND PYROLYSIS OF 4,5-DIMETHYL-3-CARBOMETHOXY-Δ2-PYRAZOLINE AND 3,5-DIMETHYL-3-CARBOMETHOXY-Δ1-PYRAZOLINE

1963 ◽  
Vol 41 (3) ◽  
pp. 726-731 ◽  
Author(s):  
Donald E. McGreer ◽  
Peter Morris ◽  
George Carmichael
Keyword(s):  
Vapor Phase ◽  
Substituent Effects ◽  
Product Analysis

4,5-Dimethyl-3-carbomethoxy-Δ2-pyrazoline and 3,5-dimethyl-3-carbomethoxy-Δ1-pyrazoline have been synthesized and pyrolized neat and in the vapor phase. The product analysis from these and a related dimethyl-3-carbomethoxypyrazoline indicate that substituent effects of methyls in the ring are cumulative.

The Kinetics of the Palladium-Catalyzed Vapor-Phase Thermal Decomposition of Ethanol

2001 ◽  
Vol 40 (1) ◽  
pp. 101-107 ◽  
Author(s):  
J. Michael Davidson ◽  
Caroline M. McGregor (née Shirrida ◽  
L. K. Doraiswamy
Keyword(s):  
Thermal Decomposition ◽  
Vapor Phase ◽  
Palladium Catalyzed ◽  
Kinetics Of

Substituent effects of rate constants for thermal [4π + 2π] cycloreversion of spiro-fused β-lactam oxadiazolines

1993 ◽  
Vol 71 (6) ◽  
pp. 907-911 ◽  
Author(s):  
Michel Zoghbi ◽  
John Warkentin
Keyword(s):  
Thermal Decomposition ◽  
Rate Constant ◽  
Rate Constants ◽  
Transition States ◽  
Substituent Effects ◽  
Ground States ◽  
Phenyl Substituent ◽  
First Order ◽  
Average Value ◽  
Carbonyl Ylide

Twelve Δ3-1,3,4-oxadiazolines in which C-2 is also C-4 of a β-lactam moiety (spiro-fused β-lactam oxadiazoline system) were thermolyzed as solutions in benzene. Substituents in the β-lactam portion affect the rate constant for thermal decomposition of the oxadiazolines to N2, acetone, and a β-lactam-4-ylidene. The total spread of first-order rate constants at 100 °C was 47-fold and the average value was 6.7 × 10−4 s−1. A phenyl substituent at N-1 or at C-3 was found to be rate enhancing, relative to methyl. At C-3, H and Cl were also rate enhancing, relative to methyl. The data are interpreted in terms of the differential effects of substituents on the stabilities of the ground states, and on the stabilities of corresponding transition states for concerted, suprafacial, [4π + 2π] cycloreversion. The first products, presumably formed irreversibly, are N2 and a carbonyl ylide. The latter subsequently fragments to form acetone (quantitative) and a β-lactam-4-ylidene.

THE THERMAL DECOMPOSITION OF PERACETIC ACID IN THE VAPOR PHASE

1963 ◽  
Vol 41 (7) ◽  
pp. 1819-1825 ◽  
Author(s):  
C. Schmidt ◽  
A. H. Sehon
Keyword(s):  
Thermal Decomposition ◽  
Vapor Phase ◽  
Dissociation Energy ◽  
Peracetic Acid ◽  
Kcal Mole ◽  
Temperature Range ◽  
Primary Reactions

The thermal decomposition of peracetic acid in a stream of toluene was studied over the temperature range 127–360 °C. The main products of the reaction were CO2, CH3COOH, C2H6, CH4, HCHO, O2, and traces of CO. Dibenzyl was also formed.The overall decomposition of peracetic acid was partly heterogeneous and was represented by the two parallel primary reactions[Formula: see text] [Formula: see text]The dissociation energy of the O—O bond in peracetic acid was estimated to be 30–34 kcal/mole.

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