A comparative VCD study of methyl mandelate in methanol, dimethyl sulfoxide, and chloroform: explicit and implicit solvation models
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Bibliographic record
Abstract
Vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra of methyl mandelate, a prototype chiral molecule, in a series of organic solvents, namely methanol (MeOH-d(4)), dimethyl sulfoxide (DMSO-d(6)), and chloroform (CDCl(3)), have been measured in the finger print region from 1800 to 1150 cm(-1). Implicit solvation models in the form of polarizable continuum model and explicit solvation models have been employed independently and simultaneously. The goal is to evaluate their efficiencies in dealing with solvent effects in each solution and to establish a general strategy to adequately account for effects of solvents. Molecular dynamics (MD) simulation and radial distribution function analysis have been performed to aid the construction of the explicit solvation models. Initial geometry searches have been carried out at the B3LYP/6-31G(d) level for the methyl mandelate monomer and its explicit 1 : 1 and 1 : 2 solute-solvent hydrogen-bonded complexes. B3LYP/cc-pVTZ has been used for all the final geometry optimizations, the vibrational frequency, VA and VCD intensity, and optical rotation dispersion (ORD) calculations. The results show that inclusion of solvent explicitly and implicitly at the same time has significant impacts on the appearance of the VA and VCD spectra, and is crucial for reliable spectral assignments when solvents are capable of hydrogen-bonding interactions with solutes. When no strong solvent-solute hydrogen-bonding interactions in the case of chloroform are expected, the gas phase monomer model is adequate for spectral interpretation, while inclusion of implicit solvation improves the frequency agreement with experiment. ORD spectra of methyl mandelate in the aforementioned solvents at different concentrations under 5 excitation wavelengths have also been measured. The comparison between the calculated and the experimental ORD spectra supports the conclusions drawn from the VA and VCD investigations.
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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) | 0.001 | 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 | 0.000 | 0.001 |
| 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