Conformational Stability of the Propylene Oxide−Water Adduct: Direct Spectroscopic Detection of O−H···O Hydrogen Bonded Conformers
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Bibliographic record
Abstract
The 1:1 molecular adduct of propylene oxide and water (PO-H(2)O) was studied using Fourier transform microwave spectroscopy and high level ab initio methods. Two distinct structural conformers with the water molecule acting as a proton donor were detected experimentally: one with the water on the same side as the methyl group with respect to the ether ring, i.e., syn-PO-H(2)O, the other with the water molecule binding to the O-atom from the opposite side of the methyl group, i.e., anti-PO-H(2)O. The nonbonded hydrogen is entgegen to the ether ring in both conformers. Rotational spectra of four isotopic species, namely PO-H(2)O, PO-DOH, PO-HOD, and PO-D(2)O, were recorded for the two conformers. The hydrogen bond parameters: r(O(epoxy)...H), angle(ring-O(epoxy)...H), and angle(O(epoxy)...H-O) are 1.908 A, 112 degrees, and 177 degrees for syn-PO-H(2)O, and 1.885 A, 104.3 degrees, and 161.7 degrees for anti-PO-H(2)O, respectively. The experimental results suggest that the hydrogen bond in syn-PO-H(2)O is stronger and the monomer subunits are more rigidly locked in their positions than in the ethylene oxide-water adduct. The stabilizing effect of the methyl group to the intermolecular hydrogen bond is discussed in terms of the experimentally estimated binding energies, the structural parameters, and the ab initio calculations.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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