Solvent, Substituent, and Temperature Effects on the Absolute Rate Constants for Addition of Methoxytrimethylsilane to 1,1-Diarylsilenes
Bibliographic record
Abstract
Absolute rate constants have been measured for the reaction of methoxytrimethylsilane with a series of transient, para-substituted 1,1-diphenylsilenes (H 2 C Si(C 6 H 4 X) 2, where X = H, Me, F, Cl, and CF 3 ) in hexane solution at room temperature. The data correlate with Hammett substituent constants, affording the reaction constant ρ = +0.9 ± 0.2. For the parent compound and the 4,4‘-bis(trifluoromethyl) derivative, rate constants have been determined over the 0−60 °C temperature range in hexane, 1,2-dichloroethane, and acetonitrile solution. The rate constants for reaction of the parent compound increase in the order hexane ≈ 1,2-dichloroethane < MeCN, but are relatively insensitive to solvent in the other case. However, differences are revealed in the Arrhenius activation energies for reaction, which are negative for both compounds in all three solvents. Those for the 4,4‘-bis(trifluoromethyl) compound in particular change to more positive values with increasing solvent polarity. The data are consistent with a two-step mechanism involving reversible preassociation of the silene and the alkoxysilane to form a Lewis acid−base complex, which collapses to product by intramolecular transfer of trimethylsilyl from oxygen to the silenic carbon.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".