CONFORMATIONAL LANDSCAPES OF 2-FUROIC ACID MONOMERS AND DIMERS BY ROTATIONAL SPECTROSCOPY AND DFT CALCULATIONS
Bibliographic record
Abstract
2-furoic acid (FA), a heterocyclic carboxylic acid, is a significant precursor of esters, acrylic chloride, and acid anhydride, and is often used for medical purpose, for example in an orally active antidiabetic vanadyl complex.1 FA monomer may exist in a number of possible conformations based on the orientation of the COOH group with the ring O atom and on the relative orientation of the C=O and OH in the COOH group. Some of these possible conformations were investigated before.2 In this work, we studied conformational landscapes of the FA monomer and dimer by using a chirped pulse Fourier transform microwave (FTMW) spectrometer and DFT calculations. Conformational searches were performed to identify possible conformations using a conformer-rotamer ensemble sampling tool (CREST).3 The resulting candidates were further optimized at the B3LYP-D3(BJ)/def2-TZVP level of theory. Three FA conformers and four (FA)2 conformers 2-furoic acid dimers were predicted. Experimentally, rotational spectra of three monomeric conformers and two binary conformers were assigned. Two other FA dimers predicted have zero electric dipole moments. Detailed analyses of the double proton tunneling motion and conformational conversion barriers will also be presented.\n\n\n\n1 M. Yin, X. Lei, M. Li, L. Yuan, J. Sun, J. Phys. Chem. Solids, 2006, 67, 1372-1378. 2 A. Halasa, L. Lapinski, I. Reva, H. Rostkowska, R. Fausto, M. J. Nowak, J. Phys. Chem. A, 2015, 119, 1037-1047; H. Ghalla, N. Issaoui, M. V. Castillo, S. A. Brandán, H. T. Flakus, Spectrochim. Acta A Mol. Biomol. Spectrosc, 2014, 121, 623-631. 3 S. Grimme, J. Chem. Theory Comput., 2019, 15, 2847-2862.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".