Computational (DFT and MP2) and spectral interpretations, normal coordinate analysis, force constants and barriers to internal rotations of Trimethylacetonitrile
Bibliographic record
Abstract
The Raman (3500[Formula: see text]cm[Formula: see text]100[Formula: see text]cm[Formula: see text] and IR spectra (4000[Formula: see text]cm[Formula: see text]400[Formula: see text]cm[Formula: see text] of liquid trimethylacetonitrile (C 5 H 9 N, TMA) have been obtained. In addition, the 1 H and [Formula: see text]C NMR spectra of TMA were obtained in DMSO-[Formula: see text] and CDCl 3 . The staggered conformer (C[Formula: see text] was favored using MP2 and DFT(B3LYP/[Formula: see text]B97XD) quantum mechanical calculations utilizing a 6-311[Formula: see text]G(d,p) basis set. High energy difference estimates of 4534[Formula: see text]cm[Formula: see text]5338[Formula: see text]cm[Formula: see text] (12.96[Formula: see text]kcal/mol[Formula: see text]15.26[Formula: see text]kcal/mol) were predicted, along with three imaginary torsion frequencies for the eclipsed conformer, therefore considered a transition state. The 1 H and [Formula: see text]C NMR chemical shifts were predicted with B3LYP and [Formula: see text]B97XD methods using the GIAO approximation and 6-311[Formula: see text]G(d,p) basis set. B3LYP frequencies calculation is favored herein owing to the relatively good compilation with the experimental measurements. The computed structural parameters are well correlated to those reported from electron diffraction and microwave studies. Moreover, the [Formula: see text]C[Formula: see text]H coupling constant was estimated and found consistent with that observed for the sample dissolved in DMSO-[Formula: see text]/CDCl 3 solvents. Using the observed methyl torsion at 266[Formula: see text]cm[Formula: see text] in gas phase and the kinetic parameter F number, a potential function (V[Formula: see text] of [Formula: see text][Formula: see text]cm[Formula: see text]([Formula: see text][Formula: see text]kcal/mol) was obtained, this barrier to internal rotation is well correlated to 1527[Formula: see text]cm[Formula: see text] (4.37[Formula: see text]kcal/mol) predicted from MP2/6-311[Formula: see text]G(d,p) potential surface scan. Aided by the predicted wavenumbers and their IR intensity/Raman activity, the observed IR/Raman bands were intensively discussed and therefore assigned to their corresponding fundamentals, in agreement with novel normal coordinate analysis and potential energy distributions (PEDs).
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How this classification was reachedexpand
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 | 0.000 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".