Gas phase hydration, bond dissociation enthalpies, and acidity of aldehydes: A CBS-Q//B3, G4MP2, and G4 theoretical study of substituent effects
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Bibliographic record
Abstract
Abstract CBS-Q//B3, G4MP2, and G4 composite method calculations were used to estimate gas phase standard state (298.15 K, 1 atm) free energies of hydration (Δ~hydr~G°~(g)~), hydration equilibrium constants (log K~hydr,(g)~), bond dissociation enthalpies (BDEs), and enthalpies (Δ~d~H°~(g)~) and free energies (Δ~d~G°~(g)~) of aldehydic proton acid dissociation for various substituted aldehydes with electron withdrawing and electron releasing groups. Good quality log K~hydr,(g)~ correlations with the Swain-Lupton resonance effect parameters R and R^+^ were found, allowing extension of the model to predict log K~hydr,(g)~ values for 487 substituted aldehydes having available R-values and 108 substituted aldehydes having available R^+^-values. Good correlations were also found between experimental aqueous phase hydration equilibrium constants (log K~hydr,(aq)~) and summative R/R^+^-values for peripheral substituents on a range of carbonyl derivatives (aldehydes, ketones, esters, and amides), suggesting the structure-reactivity modeling approach can be extended to include all possible combinations of R~1~C(O)R~2~ carbonyl substitution in both gas and aqueous systems. Computationally derived BDEs and Δ~d~H°~(g)~ / Δ~d~G°~(g)~ were in good agreement with the limited experimental and theoretical datasets. BDEs did not generally correlate with any of the Hammett substituent constants or Swain-Lupton parameters considered. Gas phase acidities exhibited high correlation coefficients with Hammett inductive substituent constants (σ~I~) and field effect parameters (F), allowing these to be employed as surrogates for estimating the gas phase aldehydic proton acidities of a larger potential compound range.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.000 | 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