Tribochemical Reaction Dynamics of Phosphoric Ester Lubricant Additive by Using a Hybrid Tight-Binding Quantum Chemical Molecular Dynamics Method

Koyama, Michihisa; Hayakawa, Jun; Onodera, Tomohiro; Ito, Kosuke; Tsuboi, Hideyuki; Endou, Akira; Kubo, Momoji; Carpio, Carlos A. Del; Miyamoto, Akira

doi:10.1021/jp061210m

Cited by 63 publications

(78 citation statements)

References 43 publications

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“…In the absence of mechanical stress, the phosphorothionate molecules adsorbed on the substrate at low temperature (303-353 K), as described by Koyama et al [27]. The activation temperature for the thermal decomposition of TPPT molecules was found to be around 423 K. The thermal films produced at this temperature consisted of short-chain polyphosphates and oxidized sulfur species, as indicated by the XPS results.…”

Section: Introductionmentioning

confidence: 64%

Reactivity of Triphenyl Phosphorothionate in Lubricant Oil Solution

2009

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Investigating the thermo-oxidative reactivity of anti-wear additives in lubricant oil solution at high temperature can significantly contribute to an understanding of the mechanism of thermal film and tribofilm formation on metal surfaces. In this study, the reactivity of triphenyl phosphorothionate (TPPT) in lubricant oil solution at high temperature (423 and 473 K) has been studied by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The results show that the TPPT molecule was highly thermally stable and did not completely decompose in oil solution even upon heating at 423 K for 168 h and at 473 K for 72 h. The degradation of the TPPT molecule, which turned out to be a first-order reaction, started taking place after 6 h at both temperatures, leading to the breakage of the P=S bond with the formation of triphenyl phosphate. During these heating experiments, no oil-insoluble compounds were detected. The oxidation of the base oil as a result of the prolonged heating demonstrated that the TPPT molecule did not effectively act as oxidation inhibitor.

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Section: Introductionmentioning

confidence: 64%

Reactivity of Triphenyl Phosphorothionate in Lubricant Oil Solution

2009

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“…A polar interaction between the O P-O-Ph atom and the nascent iron/steel surface cannot be excluded, however, as pointed out by Koyama et al [27].…”

Section: Proposed Reaction Mechanismmentioning

confidence: 97%

“…The composition of the layer generated at 423 K was found to be dependent on the length of the alkyl chains bound to the phenyl rings: with longer chains, the phosphate concentration decreased, while the sulphur concentration increased. On the basis of these findings, a reaction mechanism was proposed: following the adsorption of the sulphur atom to the surface, as suggested by Koyama et al [27], the phosphorothionate molecules started decomposing with the scission of the P=S bond, followed by the cleavage of the C-O or P-O bond. The released sulphur was then oxidized.…”

Section: Introductionmentioning

confidence: 99%

Substituent Effect on the Reactivity of Alkylated Triphenyl Phosphorothionates in Oil Solution in the Presence of Iron Particles

2010

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The effect of the substituent attached to the phenyl rings on the reactivity of alkylated triphenyl phosphorothionates (t-butyl TPPT (b-TPPT) and p-nonyl TPPT (n-TPPT)) in oil solution at high temperature (423 and 473 K) was investigated by means of Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The FT-IR and NMR results show that the alkylated TPPTs were highly thermally stable and did not completely decompose in oil, even upon heating at 423 K for 168 h and at 473 K for 72 h, with and without steel filings and iron particles (both metallic iron and iron oxide particles). The reaction of alkylated TPPTs was found to start with the scission of the P=S bond to yield alkylated triphenyl phosphate. The kinetics of the thermooxidative reaction was slower when steel filings and iron particles were added to the oil solutions during the heating experiments. The reactivity of the unsubstituted molecule (TPPT) was higher than that of alkylated TPPTs at 423 K, while at 473 K TPPT and n-TPPT were more reactive than b-TPPT. In the case of the experiments performed at 473 K in the presence of steel filings or metallic iron or iron oxide particles, the reactivity of the alkylated TPPT molecules decreased with the length of the alkyl chain bound to the phenyl rings. The XPS results show that a reaction layer consisting of carbon, oxygen, phosphorus and iron was formed on the 100Cr6 steel filings immersed for 72 h in oil solutions containing alkylated TPPTs and heated at 473 K. Sulphur was neither detected on the surface nor in the composition vs depth profile. During the heating experiments, the base oil (PAO) was oxidized. At 423 K, the alkylated TPPTs had a strong antioxidant effect, which was found to be more pronounced upon increasing the length of the alkyl chain bound to the phenyl rings. At 473 K, the TPPTs did not inhibit the oxidation of the base oil as effectively as at 423 K.Keywords Thermo-oxidative degradation Á t-butyl triphenyl phosphorothionate (b-TPPT) Á Irgalube Ò 232 Á p-nonyl triphenyl phosphorothionate (n-TPPT) Á Irgalube Ò 211 Á Ashless anti-wear additives Á Low-SAPS additives Á FT-IR Á NMR Á XPS Á Iron particles 1 Introduction

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“…17) After minimization, molecular dynamics simulation was carried out using our in house program NEW-RYUDO. [18][19][20][21] MD simulations were carried out for 500000 steps with a step size of 0.1 fs and temperature of 298 K. Furthermore, many geometrical parameters were also analyzed throughout the simulation.…”

Section: Computational Detailsmentioning

confidence: 99%

Does Metabolism of (<I>S</I>)-<I>N</I>-[1-(3-Morpholin-4-ylphenyl)ethyl]-3-phenylacrylamide Occur at the Morpholine Ring? Quantum Mechanical and Molecular Dynamics Studies

et al. 2007

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The mechanism of Cytochrome P450 3A4 mediated metabolism of (S)-N- [1-(3-morpholin-4ylphenyl)ethyl]-3-phenylacrylamide and its difluoro analogue have been investigated by density functional QM calculations aided with molecular mechanics/molecular dynamics simulations. In this article, we mainly focus on the metabolism of the morpholine ring of substrates 1 and 2. The reaction proceeds via a hydrogen atom abstraction from the morpholine ring by Compound I on a doublet potential energy surface. A transition state was observed at an O-H distance of 1.46 Å for 1 while 1.38 Å for 2. Transition state for the rebound mechanism was not observed. The energy barrier for the hydrogen atom abstraction from 1 was found to be 7.01 kcal/mol in gas phase while 19.53 kcal/mol when the protein environment was emulated by COSMO. Similarly the energy barrier for substrate 2 was found to be 11.07 kcal/mol in gas phase while it was reduced to 12.99 kcal/mol in protein environment. Our previous study reported energy barriers for phenyl hydroxylation of 7.4 kcal/mol. Large energy barriers for morpholine hydroxylation indicates that hydroxylation at the phenyl ring may be preferred over morpholine. MD simulations in protein environment indicated that hydrogen atom at C4 position of phenyl ring remains in closer proximity to oxyferryl oxygen of the heme moiety as compared to morpholine hydrogen and hence greater chance to metabolize at phenyl ring.

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Tribochemical Reaction Dynamics of Phosphoric Ester Lubricant Additive by Using a Hybrid Tight-Binding Quantum Chemical Molecular Dynamics Method

Cited by 63 publications

References 43 publications

Reactivity of Triphenyl Phosphorothionate in Lubricant Oil Solution

Reactivity of Triphenyl Phosphorothionate in Lubricant Oil Solution

Substituent Effect on the Reactivity of Alkylated Triphenyl Phosphorothionates in Oil Solution in the Presence of Iron Particles

Does Metabolism of (<I>S</I>)-<I>N</I>-[1-(3-Morpholin-4-ylphenyl)ethyl]-3-phenylacrylamide Occur at the Morpholine Ring? Quantum Mechanical and Molecular Dynamics Studies

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