Gas Phase Oxidation of Nicotine by OH Radicals: Kinetics, Mechanisms, and Formation of HNCO
Bibliographic record
Abstract
Cigarette smoke is recognized as having harmful health effects for the smoker and for people breathing second-hand smoke. In an atmospheric chemistry context, however, little is known about the fate of organic nitrogen compounds present in cigarette smoke. Indeed, the atmospheric oxidation of nicotine, a major nitrogen-containing component of cigarette smoke, by OH radicals has yet to be investigated. We measured the first rate coefficient between OH and nicotine to be (8.38 ± 0.28) × 10 –11 cm 3 molecule –1 s –1 at 298 ± 3 K. We use an online proton-transfer-reaction mass spectrometer (PTR-MS) to quantify nicotine’s oxidation products, including formamide and isocyanic acid (HNCO). We present the first evidence that HNCO is formed from nicotine’s gas phase oxidation, and we highlight the potential for this toxic molecule to be an indoor air pollutant after smoking has ended. Mechanistic pathways for the oxidation of nicotine by OH radicals were investigated by theoretical calculations at the M06-2X level of theory, and we find that there are many competitive H-abstraction sites on nicotine. Our findings suggest that the atmospheric removal of nicotine by OH radicals may compete with surface deposition and air exchange and may be a source of HNCO in indoor air.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".