Dissociation Reactions of Low-Energy Pentenyl Methyl Ether Radical Cations C <sub>5</sub> H <sub>9</sub> OCH <sub>3</sub> <sup>•+</sup>
Bibliographic record
Abstract
The dissociation chemistry of the low-energy C 5 H 9 OCH 3 •+ ions generated from the 13 isomeric pentenyl methyl ethers derived from stable alkenols has been studied. This was done by examining their metastable ion characteristics, in conjunction with 2 H and 13 C-labelling as well as collision-induced dissociation and neutralisation–reionisation experiments. The influence of the position and substitution pattern of the double bond on the chemistry of these C 6 H 12 O •+ species is considered. The closely similar reactions of C 2 H 5 CH=CHCH 2 OCH 3 •+ , 3 •+ , CH 2 =CH–CH(C 2 H 5 )OCH 3 •+ , 4 •+ , and CH 2 =C(C 2 H 5 )CH 2 OCH 3 •+ , 13 •+ , point to a common chemistry, which is rationalised in terms of facile 1,2-H and 1,2-C 2 H 5 shifts via distonic ions. Each of the other isomers displays a distinct, though often related, chemistry. The eight allylic ionised ethers easily lose CH 3 • to produce C 5 H 9 O + oxonium ions, whose structure was established by CID experiments; ions 3 •+ / 4 •+ / 13 •+ also readily expel C 2 H 5 • to give C 4 H 7 O + ions of structure CH 2 =CH–C + (H)OCH 3 . Elimination of CH 3 OH is also significant for 3 •+ / 4 •+ / 13 •+ and for (CH 3 ) 2 C=CHCH 2 OCH 3 •+ , 8 •+ , and CH 3 CH=C(CH 3 )CH 2 OCH 3 •+ , 11 •+ . Besides expelling CH 3 • and/or C 2 H 5 • and CH 3 OH, the three homoallylic isomers undergo dissociations which are (almost) absent for their allylic counterparts: thus, both CH 3 CH=CH(CH 2 ) 2 OCH 3 •+ , 2 •+ , and CH 2 =CH–CH(CH 3 )CH 2 OCH 3 •+ , 10 •+ , lose H • and H 2 O, whereas CH 2 =C(CH 3 )CH 2 CH 2 OCH 3 •+ , 7 •+ , is unique in predominantly losing CH 2 O. For the losses of CH 2 O and H 2 O mechanisms are proposed in which ion–neutral complexes of the type [C 5 H 10 •+ / CH 2 O] and [C 6 H 10 •+ / H 2 O] are key intermediates. The behaviour of the non-(homo)allylic isomer, CH 2 =CH(CH 2 ) 3 OCH 3 •+ , 1 •+ , is similar to that of 2 •+ but the reactions occur in different proportions. A mechanism for the facile loss of an alkyl radical from 1 + is proposed in which 1,4-H shifts and distonic ions as well as communication with ionised cyclopentyl methyl ether, 14 •+ , play an important role.
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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) | 0.004 | 0.001 |
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".