Comparison of Copper and Vanadium Homogeneous Catalysts for Aerobic Oxidation of Lignin Models
Bibliographic record
Abstract
The reactivity of copper and vanadium catalysts toward the aerobic oxidation of lignin models has been explored. Both (dipic)V V (O)(O i Pr) ( 3 ) (dipic = dipicolinate) and CuCl/TEMPO (TEMPO = tetramethylpiperidine N -oxide) catalyzed the aerobic oxidation of the lignin model compound 1,2-diphenyl-2-methoxyethanol ( 2 ). The vanadium catalyst 3 produced benzoic acid (85%) and methyl benzoate (84%) as the major products via the intermediate ketone benzoin methyl ether ( 4 ). The copper catalyzed reaction afforded benzaldehyde (84%) and methylbenzoate (88%) directly, with no intermediate formation of 4 . The more complex lignin model system 1-(3,5-dimethoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol-[2,3- 13 C 2 ] ( 5 - 13 C 2 ) was oxidized under air by vanadium catalyst 3, affording ketone 7 - 13 C 2 (65%), dehydrated ketone 8 - 13 C 2 (5%), alkene product 9 - 13 C 2 (14%), 3,5-dimethoxybenzoic acid (11%), 3,5-dimethoxybenzaldehyde (2%), 2-methoxyphenol, and formic acid- 13 C 1 (4%). Aerobic oxidation of ketone 7 - 13 C 2 using catalyst 3 produced dehydrated ketone 8 - 13 C 2, 3,5-dimethoxybenzoic acid, and formic acid- 13 C 1, suggesting that 7 is further oxidized under the catalytic conditions. In contrast, oxidation of β-O-4 model 5 - 13 C 2 using CuCl/TEMPO affords 3,5-dimethoxybenzaldehyde (43%), 3,5-dimethoxybenzoic acid (13%), 2-methoxyphenol (7%), formic acid- 13 C 1 (7%), ketone- 7 13 C 2 (1%), dehydrated ketone 8 - 13 C 2 (2%), and a number of higher molecular weight products, as determined by 1 H and 13 C NMR, GC-MS, and LC-MS. Attempted oxidation of ketone 7 using CuCl/TEMPO yielded primarily dehydrated ketone 8, indicating that the ketone is not an intermediate in the formation of the aldehyde product. The reactivities of the copper and vanadium catalysts in the oxidation of lignin model compounds 2 and 5 are discussed. Remarkably different selectivities were observed for the vanadium and copper catalyzed reactions, suggesting the potential of homogeneous catalysts for controlling selectivity in the aerobic oxidation of lignin.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".