Coupling 31P NMR with the Mannich Reaction toward the quantitative analysis of lignins
Bibliographic record
Abstract
The reactivity of lignin model compounds under Mannich conditions with piperidine and formaldehyde was studied.The piperidinomethyl group was confirmed to be introduced quantitatively at sterically unhindered positions ortho to a phenolic hydroxyl when the substrate was allowed to react under ambient conditions.The sequential application of the Mannich reaction followed by quantitative 31 P NMR on a variety of lignin samples allowed the amounts of various aromatic groups bearing free phenolic hydroxyls to be determined.More specifically, the technique allowed the quantification of para-hydroxyl phenols, catechols, guaiacols, and phenols bearing C 5 or C 6 substituents.The quantitative reliability of the technique was also examined with a series of dissolved kraft lignins, isolated at various degrees of delignification.The data were found to favourably compare to those obtained by permanganate oxidation.
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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 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 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".