A Quantum Chemical Study of the Unimolecular Decomposition Mechanisms of Zinc Dialkyldithiophosphate Antiwear Additives
Bibliographic record
Abstract
Density functional theory calculations were applied to study a set of isomerization and decomposition reactions that zinc dialkyldithiophosphate (ZDDP) engine oil antiwear additives may take part in. The products of these reactions comprise a set of chemical species that can lead to the formation of poly(thio)phosphate films that are thought to be responsible for the antiwear protection offered by ZDDPs. The specific reactions examined involved either intramolecular alkyl group transfer within ZDDP or the intramolecular elimination of olefins from this molecule. A series of substituents were employed to examine how the nature of the substituent on the ZDDP molecule affects the thermodynamic and mechanistic details of these reactions, which in turns may have ramifications regarding various aspects of antiwear film formation. It was found that qualitative and quantitative aspects of these reactions were markedly different when hydrogen atoms were used as substituents instead of alkyl groups. The details of the reactions for the H-substituted system indicated that the precursors to the antiwear films should not be formed. When alkyl groups were employed as substituents, the energetic details of the reactions considered in this study exhibited a dependence upon the nature of these groups. An examination of these details revealed that straight-chained primary alkyl ZDDPs should decompose through reactions involving alkyl group transfer, while secondary and branched primary alkyl ZDDPs should primarily undergo olefin elimination reactions to form precursors to ZDDP antiwear films. The details of the reaction pathways that these systems follow to form the precursors shed light on the observed byproducts of antiwear film formation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".