Infrared spectroscopy of methanol-hexane liquid mixtures. II. The strength of hydrogen bonding
Bibliographic record
Abstract
The study by Fourier transform infrared attenuated total reflectance spectroscopy at 27 degrees C of methanol (MeOH) and hexane mixtures is presented. In the 0-0.25 and 0.75-1.00 molar fractions, the mixtures form homogeneous solutions, whereas from 0.25 to 0.75, the mixtures are inhomogeneous forming two phases. These mixtures have the near 3300 cm(-1) OH stretch band only slightly displaced throughout the whole concentration range indicating very little variation in the H-bonding condition. This result is very different from that of MeOH in CCl(4) where the OH stretch bands are scattered in a wide frequency range. Factor analysis applied to the MeOH/hexane spectra gave seven principal factors (one hexane and six methanol factors) and retrieved their principal spectra and abundances. In the inhomogeneous region, the two phase volumes changed inversely with concentration, but their factor compositions are invariable at 1:3 and 3:1 molar ratios. Five of the six principal methanol factors have the O-H and the C-O stretch bands situated near, respectively, 3310 and 1025 cm(-1) with little displacement in the whole concentration range. The sixth factor observed at 3654 cm(-1) (full width at half height<40 cm(-1)) was assigned to free methanol OH by Max and Chapados [J. Chem. Phys. 128, 224512 (2008)]. This species concentration is very low but constant at around 0.01 M in the methanol range of 0.5-2.5 M. The main OH stretch bands (approximately 3300 cm(-1)) were simulated with six Gaussian components that were assigned to different hydrogen-bonding situations. These form reverse micelles at low methanol concentrations and micelles at high concentrations that persist in pure methanol. A very different state of affairs exists in MeOH in CCl(4) where free OH groups are formed in almost all mixtures except in pure MeOH. Since hexane is a better model of a lipidic milieu than CCl(4), the results for MeOH/hexane give a better representation of the fate of alcoholic OH groups in such a milieu.
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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 | 0.000 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".