Allyl ions, decomposition

The yields calculated using these assumptions are in satisfactory agreement with the experimental values, as illustrated in Table 18. The observation that, among all the fragmentation processes induced by the decay, only reaction (27) is prevented by collisional deactivation, supports the view that the excitation level of the propyl ions that dissociate at 10 torr into allyl ions is low indeed, and that such decomposition is possible for its low energetic requirements. The situation is completely different in the liquid phase. This is indicated, in the first place, by the substantial decrease of the yield of HT, which provides a rough indication... 

Treatment of A-nitroso-iV-(cr5-2-phenylcyclopropyl)urea with excess sodium formate in methanol at 25 "C for 15 hours affords ( )-3-methoxy-l-phenylprop-l-ene (25%) and 3-methoxy-3-phenylprop-l-ene (60%, Table 15, entry 7). An almost identical result is obtained when the tran -isomer is used as substrate. Formation of the 2-phenylcyclopropyldiazonium ion, decomposition with loss of nitrogen to the 2-phenylcyclopropyl cation, followed by ring opening to form the phenylallyl cation, can explain the result. When [l- Hi]aminocyclopropane is subjected to deamination with nitrous acid in water at 0°C (Table 15, entry 8), allyl alcohol is obtained, which is isolated as the 4-(phenylazo)benzoate derivative in 44% yield. In this case, the deuterium is only located at the C2 allyl position. ... 

Triflate (348 X = OTf) is reputed to undergo acetolysis exclusively to (350), which in turn suffers epimerization under the reaction conditions to yield a mixture of (350) and (351). These data, coupled with the failure to detect any product with the retained skeleton, are taken to infer a fully opened allylic ion intermediate (349). In contrast to this report, decomposition of (348 X = ), generated from the cor-... 

Oxidation of the steroidal olefin (XXVII) with thallium(III) acetate gives mainly the allylic acetates (XXXI)-(XXXIII) (Scheme 15), again indicating that trans oxythallation is the preferred reaction course (19). Addition of the electrophile takes place from the less-hindered a-side of the molecule to give the thallinium ion (XXVIII), which by loss of a proton from C-4 would give the alkylthallium diacetate (XXIX). Decomposition of this intermediate by a Type 5 process is probably favorable, as it leads to the resonance-stabilized allylic carbonium ion (XXX), from which the observed products can be derived. Evidence in support of the decomposition process shown in Scheme 15 has been obtained from a study of the exchange reaction between frawr-crotylmercuric acetate and thallium(III) acetate in acetic acid (Scheme 16) (142). 

Acetylation occurs at the 2-position of allene systems (Scheme 8.14). The intermediate 7t-allyl complex breaks down via the nucleophilic displacement of the cobalt carbonyl group by the hydroxide ion to produce the hydroxyketone (7) [ 11 ]. An alternative oxygen-initiated radical decomposition of the complex cannot, however, be totally precluded. The formation of a second major product, the divinyl ketone (8), probably arises from direct interaction of the dicobalt octacarbonyl with the allene and does not require the basic conditions. 

Thermal decomposition of Zn(CH3)2 or its co-pyrolysis with other organoelement compounds has been studied mass spectrometrically ". Only two Zn-containing ions ([ZnCH3]+ and [Zn]+) were detected at 100 °C from the co-pyrolysis of an equimolar mixture of f-butyl(allyl)selenium and dimethylzinc " . The relative intensities of the peaks corresponding to the [ZnCH3]+ and [Zn]+ ions diminish as the temperature increases, becoming negligible at T > 320 °C. 

This is proved by the observation that the rate of decomposition of persulphate drops to the same low value as when allyl acetate is added in the absence of alcohol. On addition of allyl acetate, the sulphate ion radicals react with the allyl monomer rather than with the alcohol, so that no alcohol radicals are formed and reaction (VII) cannot take place. Formaldehyde is only formed in the absence of allyl acetate. It should be noted that Bartlett and Nozaki (24) could not confirm these observations. 

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Frimer, A. A., J. Org. Chem., 1977, 42, 3194—3196, footnote 7 A new method of preparation involves interaction of allylic halides in solvents with 98% hydrogen peroxide in presence of silver ion and base at ambient temperature under argon. The reactions must be run in the dark to prevent precipitation of metallic silver, which will catalyse decomposition of the hydroperoxide or excess hydrogen peroxide. In an experiment not run in the dark, the hydroperoxide from 3-chlorocy-clohexene ignited spontaneously after isolation and concentration. 

The <7-allyl complex, (Ph3P)2Pt(C3H5)2, showed a cracking pattern due to triphenylphosphine, presumably formed by thermal decomposition in the inlet ( 200°C). The main ions were Pt(C3H5)2, Pt(C3H5)+, and C3HJ PtC3HJ and Pt+ appear with lower abundances (28). 

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