Fast reaction studies of carbanions and carbocations in solution

Dorfman, Leon M.; Sujdak, Richard J.; Bockrath, Bradley

doi:10.1021/ar50106a002

Cited by 45 publications

(20 citation statements)

References 28 publications

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“…3, spectrum A). The broad 370 nm is tentatively assigned to the benzyl cation by analogy with the reported spectrum for this species (17,18). The decay of both bands followed complex kinetics, a feature which is not uncommon in solid heterogeneous systems (19).…”

Section: Laser Jash Photolysissupporting

confidence: 55%

Photochemistry of dibenzylketone in Nafion membranes

Wintgens¹,

Scaiano²

1987

Can. J. Chem.

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Photolysis of dibenzyl ketone in vacuum-dried Nafion membranes leads to the detection of fluorescence from the protonated ketone and formation of modest yields of benzyl cations characterized using laser photolysis techniques. Exchange of the acid sites in Nafion by cationic surfactants leads to decreased environmental polarity and a change in mechanism towards the benzyl radical chemistry which is common in organic solvents. The decay of benzyl radicals in Nafion membranes shows magnetic field dependence which indicates that geminate processes play an important role.

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Section: Laser Jash Photolysissupporting

confidence: 55%

Photochemistry of dibenzylketone in Nafion membranes

Wintgens¹,

Scaiano²

1987

Can. J. Chem.

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“…Its decay was first-order with rate constant k 0 ffi1 10 4 s À1 (Figure 1b), unaffected by oxygen, and accelerated by azide, an excellent scavenger of cations. According to extensive literature data on arylmethyl carbocation derivatives, [13] these spectral and kinetic characteristics suggest the assignment of this transient spectrum to the 9-anthrylmethyl carbocation. It is worthy to note that the cation is completely formed within the 6 ns laser pulse, which means that its formation rate is > 1.6 10 8 s À1 .…”

mentioning

confidence: 86%

A “Dual‐Function” Photocage Releasing Nitric Oxide and an Anthrylmethyl Cation with a Single Wavelength Light

Vittorino

Cicciarella

Sortino

2009

Chemistry A European J

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A template‐directed sixfold dimerization of alkyne units is the final step in the synthesis of the title compound leading to nanoscale 2D rigid wheel‐shaped oligo(phenylene ethynylene)s. Solubilizing side groups allow full characterization by NMR spectroscopy, GPC, MALDI‐TOF MS, and STM. The distance between two peripheral tert‐butyl groups at opposite sites of the oligomer is estimated to be 7 nm.

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“…The chlorides were obtained by refluxing the corresponding alcohols with thionyl chloride in benzene for 1.5 h and were recrystallized from hexane. The alcohol precursors for salts 1 and 2 were obtained by Grignard reactions of 4-methoxy-1-naphthaldehyde (1) with phenylmagnesium bromide and p-anisaldehyde (2) with 1-naphthylmagnesium bromide. The alcohol precursors for salts 3 and 9 were prepared by sodium borohydride reduction of the commercially available ketones.…”

Section: Methodsmentioning

confidence: 99%

Laser flash photolysis studies of the formation and reactivities of phenyl(naphthyl)methyl carbocations generated from phosphonium salt precursors

Alonso¹,

Johnston²,

Scaiano³

et al. 1992

Can. J. Chem.

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The photolysis of several substituted phenyl(naphthy1)methyl triphenylphosphonium chlorides has been examined using a combination of laser flash photolysis experiments and product studies. Both carbocation and radical intermediates have been characterized in the transient experiments, with the relative yields depending strongly on the solvent. For example, in alcohols, acetonitrile, or aqueous solvents cation formation predominates while acetonitrile/dioxane mixtures (5-10%) are required for the observation of radicals. Quantum yields for cation formation vary from 0.79 in methanol to 0.093 in 1 : 4 acetonitrile/dioxane, as measured by product studies and transient experiments, respectively. The addition of perchlorate salts leads to dramatic enhancements in the cation lifetimes; the effects are particularly pronounced for acetonitrile/dioxane mixtures where the cation yields also increase by factors of 3-4. In this case the effects are attributed primarily to replacement of chloride by perchlorate in the initial ion pairs. The combined data from both solvent and perchlorate salt effects on the cation lifetimes and yields suggest that the excited state of the phosphonium salt cleaves homolytically, followed by electron transfer within the initial radical/triphenylphosphine radical cation pair to generate carbocation, as opposed to direct heterolytic cleavage. The cation yields also indicate that back reaction to regenerate starting material, as well as product formation within the initial geminate cage, occur in some solvents. The effects of solvent and added perchlorate salts on the rate constants for reaction with nucleophiles have been examined. For example, rate constants that vary by an order of magnitude have been measured for quenching by azide ion in various aqueous acetonitrile and trifluoroethanol mixtures.Faisant appel a une combinaison d'expkriences de photolyse kclair au laser et d'ktudes des produits, on a examink la photolyse de plusieurs chlorures de phCnyl(naphty1)mkthyl triphknyl phosphonium. On a caractkrisk des intermkdiaires tant cationiques que radicalaires dans les expkriences impliquant les espkces transitoires; les rendements relatifs dependent beaucoup du solvant. Par exemple, dans les alcools, l'acktonitrile ou des solvants aqueux, il y a formation prkdominante de cations alors qu'il faut un mklange d'acktonitrile/dioxane (5-10%) pour observer des radicaux. Les rendements quantiques pour la formation des cations, tels que mesurks respectivement par des ktudes de produits et des expkriences sur les espbces transitoires, varient de 0,79 dans le mkthanol a 0,093 dans un mklange 1 : 4 d'acktonitrile/dioxane. L'addition de sels de perchlorate conduit une augmentation dramatique des temps de vie des cations; les effets sont particulibrement prononcks pour les mklanges acktonitrile/dioxane dans lesquels les rendements en cations augmentent aussi par des facteurs de 3-4. Dans ce cas, on attribue les effets principalement a une substitution du chlorure par le perchlorate dans les paires d'ions ...

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Fast reaction studies of carbanions and carbocations in solution

Cited by 45 publications

References 28 publications

Photochemistry of dibenzylketone in Nafion membranes

Photochemistry of dibenzylketone in Nafion membranes

A “Dual‐Function” Photocage Releasing Nitric Oxide and an Anthrylmethyl Cation with a Single Wavelength Light

Laser flash photolysis studies of the formation and reactivities of phenyl(naphthyl)methyl carbocations generated from phosphonium salt precursors

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