Photochemistry of alkyl halides. 3. Generation of vinyl cations

McNeely, Steven A.; Kropp, Paul J.

doi:10.1021/ja00430a056

Cited by 58 publications

(14 citation statements)

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“…In the case of 1‐iodocyclopentene, the process is thermodynamically possible in methanol and for 1‐iodocyclohexene it would be, both in dichloromethane and in methanol. This is in agreement with the results obtained by Kropp and co‐workers35 who have observed that the irradiation of 1‐iodocyclohexene in a solution of methanol or dichloromethane at 40 °C leads mainly to the formation of products coming from nucleophilic substitution, together with smaller amounts of cyclohexene derived from the reaction via radicals.…”

Section: Resultssupporting

confidence: 93%

“…In the irradiation of 1‐iodocyclopentene in dichloromethane, only cyclopentene as photoproduct was detected at 40 °C, and at −25 °C ionic products were formed in dichloromethane and methanol 35. However, in the case of 2‐iodothiophene, the process would not be thermodynamically feasible in any of the solvents considered, even in the most polar ones.…”

Section: Resultsmentioning

confidence: 96%

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The photoinduced reaction of 2‐iodothiophene in solutions of n‐heptane, dichloromethane and methanol

Herrera

Nieto

Olleta

et al. 2010

J of Physical Organic Chem

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The photoinduced reaction of 2‐iodothiophene in n‐heptane, dichloromethane and methanol was studied at room temperature from experiments carried out with degassed solutions. The photoproducts of the reaction were mainly thiophene and small amounts of iodine in all three solvents used. The concentration of 2‐iodothiophene decreases throughout photolysis, following a first‐order rate law and the pseudo‐first‐order rate constants were determined in the three solvents used. The photochemistry of the system was quantified determining the quantum yields of 2‐iodothiophene consumption and thiophene formation in n‐heptane solutions. The results show that under the experimental conditions of this research, products deriving only from the reaction of the thienyl radical were observed. To support the experimental results, calculations were performed of the ionization potential of the thienyl radical, electron affinity of the iodine atom and free energy of solvation of the corresponding iodide and carbocation in the different solvents used. Copyright © 2010 John Wiley & Sons, Ltd.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 96%

The photoinduced reaction of 2‐iodothiophene in solutions of n‐heptane, dichloromethane and methanol

Herrera

Nieto

Olleta

et al. 2010

J of Physical Organic Chem

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“…The particularly electrophilic salt ( I 3 ) can enter the p-position in anisole at 0 to 20°C. Subsequent elimination of hydrogen chloride forms the 2-chloro-2-(p-methoxypheny1)-ethylene-I -diazonium salt (42) 4 2 ) and ( 4 3 ) , isolated in an analytically pure state and free from isomers, are 61 and 56 %, respectively. The postulated intermediate ( 4 1 ) comprises a strong protonic acid and an acid-sensitive diazoalkane group united in a single molecule, but the usual displacement of nitrogen does not occur.…”

Section: Reactions Of Alkenediazoniummentioning

confidence: 99%

Alkenediazonium Salts: A New Chapter of Classical Organic Chemistry

Bott

1979

Angew. Chem. Int. Ed. Engl.

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Whereas the protonation of a-diazo-0-diketones and r-diazo-P-oxo esters with hydrogen chloride and antimony pentachloride yields the corresponding hydroxyalkenediazonium hexachloroantimonates, the "acid-sensitive'' r-diazomonocarbonyl compounds can be transformed into resonance-stabilized alkenediazonium salts by an analogous 0-alkylation with triethyloxonium hexachloroantimonate. A general route for synthesizing these compounds consists in the transformation of the p-toluenesulfonylhydrazones of a-halogenated aldehydes and ketones with Lewis acids. Alkenediazonium ions which are not resonance stabilized can be isolated at room temperature only if their decomposition at higher temperatures leads, uia evolution of nitrogen, to vinyl cations in particularly high energy levels. Facile substitution reactions at the CC double bond with anisole and methanol demonstrate the strongly electrophilic nature of alkenediazonium salts. When electron-donating substituents are attached to C2 of an ethylenediazonium ion, the bond order of the NN triple bond can be reduced to a level comparable with that in diazoacetic ester.

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“…Alkyl halides exhibit competing radical and ionic photobehaviours [1]. Iodides give predominantly ionic products.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Photochemistry of 1-Iodocyclohexene:Influence of Ultrasound on Ionic vs. Radical Behaviour

Blaškovicová

Gáplovský²,

Blaško³

2007

Molecules

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Simultaneous application of UV light and ultrasonic irradiation to a reaction mixture containing 1-iodocyclohexene is reported. The irradiation of 1-iodocyclohexene in methanol was carried out with or without addition of zinc. The effect of ultrasound or mechanical stirring on this solid-liquid system was also compared. The irradiation of 1-iodocyclohexene in methanol in the presence of zinc increases the yield of the nucleophilic trapping product, compared with the yield after irradiation in the absence of zinc. The photodegradation of 1-iodocyclohexene was slightly accelerated after addition of zinc. A rapid formation of radical product was accompanied by substantial decrease of 1-iodocyclohexene after application of ultrasound and irradiation without the zinc. The ultrasound significantly affects the photobehaviour of this reaction, predominantly its radical route. The joint application of ultrasound and zinc contributes positively to the production of radical and ionic products. The sonochemical stirring is more effective than mechanical stirring.

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Photochemistry of alkyl halides. 3. Generation of vinyl cations

Cited by 58 publications

References 0 publications

The photoinduced reaction of 2‐iodothiophene in solutions of n‐heptane, dichloromethane and methanol

The photoinduced reaction of 2‐iodothiophene in solutions of n‐heptane, dichloromethane and methanol

Alkenediazonium Salts: A New Chapter of Classical Organic Chemistry

Synthesis and Photochemistry of 1-Iodocyclohexene:Influence of Ultrasound on Ionic vs. Radical Behaviour

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