Some Like It Hot: Experimentally Determining ΔΔ<i>H</i><sup>⧧</sup>, ΔΔ<i>S</i><sup>⧧</sup>, and ΔΔ<i>G</i><sup>⧧</sup> between Kinetic and Thermodynamic Diels–Alder Pathways Using Microwave-Assisted Synthesis
Why this work is in the frame
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Bibliographic record
Abstract
The effects of kinetic vs thermodynamic control on endo/exo stereoisomer ratios can be observed in a simple Diels–Alder reaction between N-phenylmaleimide and furan. The use of microwave-promoted synthesis affords the cycloadducts in yields ranging from 65–100%, employing reaction times of 1–10 min at temperatures of 55–130 °C. Short reaction times enable screening of numerous reaction conditions (time and temperature) within a single lab period, where endo:exo product ratios follow the primary facets of kinetic and thermodynamic control. Analysis of product ratios obtained under kinetic control allows for the evaluation of activation parameters (ΔΔH⧧ (≈ ΔEa), ΔΔS⧧, and ΔΔG⧧) by means of the Arrhenius and Eyring equations. Values of ΔΔH⧧, ΔΔS⧧, and ΔΔG⧧ were found to be 6.4 ± 0.3 kJ mol−1, 16.5 ± 0.9 J mol−1 K−1, and 1.5 ± 0.4 kJ mol–1 (ΔΔ: exo – endo), respectively. Experimentally determined activation parameters correlate well with quantum-chemical calculations. Several key teaching points are also addressed, including frontier molecular orbital analysis, reversibility of the Diels–Alder reaction, column chromatography, and the use of 1H nuclear magnetic resonance spectroscopy to assess both stereoisomeric yield and purity.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| 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 | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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 it