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Anthracene nucleophilic attack

The EH-catalyzed hydration of the enantiomers of the K-region epoxides of BaA, CR, and BcPh allows informative comparisons to be made [92 - 94], With four among the six substrates, nucleophilic attack is selective for the oxirane C-atom with (5)-configuration (Fig. 10.12). This is, for example, true for the two enantiomers of chrysene 5,6-oxide. Looking at the data in another way, it is also apparent that, irrespective of the enantiomer, nucleophilic attack occurs preferentially at C(5) for benz[a]anthracene 5,6-oxide, but at C(6) for benzo[c]phenanthrene 5,6-oxide. In other words, the regio- and... [Pg.628]

The main features of the chemiluminescence mechanism are exemplarily illustrated in Scheme 11 for the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of imidazole (IMI-H) as base catalyst and the chemiluminescent activators (ACT) anthracene, 9,10-diphenylanthracene, 2,5-diphenyloxazole, perylene and rubrene. In this mechanism, the replacement of the phenolic substituents in TCPO by IMI-H constitutes the slow step, whereas the nucleophilic attack of hydrogen peroxide on the intermediary l,l -oxalyl diimidazole (ODI) is fast. This rate difference is manifested by a two-exponential behavior of the chemiluminescence kinetics. The observed dependence of the chemiexcitation yield on the electrochemical characteristics of the activator has been rationalized in terms of the intermolecular CIEEL mechanism (Scheme 12), in which the free-energy balance for the electron back-transfer (BET) determines whether the singlet-excited activator, the species responsible for the light emission, is formed ... [Pg.1189]

It might seem surprising that a nucleophilic reaction with water competes with proton loss from the phenanthrenonium ion considering the stability of the aromatic product. As discussed by Richard24 (and considered further below) this reflects a higher intrinsic reactivity of the cations toward nucleophilic attack which compensates for the thermodynamic disadvantage of this reaction. For the phenanthrenonium ion the ratio of rate constants for deprotonation and nucleophilic attack on the cation (kp/kH2o) is 25 25 for the 1-protonated naphthalene it is 1600,106 for 9-protonated anthracene, 1.8.75... [Pg.40]

The mechanism for the photo-amination is reasonably suggested to involve nucleophilic attack of the amine on to the cation radical of the arene which is generated by photo-induced electron transfer to the dicyanobenzene. Irradiation at wavelengths longer than 500 nm of dichloromethane solutions of the charge-transfer complexes of various anthracenes with tetranitromethane leads to rapid... [Pg.289]

For instance, NOBF4 oxidation of benzo[a]pyrene (BP, the additional benzene ring is fused at positions 7 and 8 of pyrene) generates the BP+ BF4 salt. When this cation-radical salt is attacked with nucleophiles of various strengths, the pattern of nucleophilic substitution reflects the distribution of a positive charge in the cation-radical part of the salt. This positive charge is localized mainly at the meio-anthracenic position, that is, at the C-6 atom. Nucleophiles (Nu ) such as OH , AcO , and F enter this position (Scheme 3.68). [Pg.187]

A general theory of attack, which is supported by work from the University of Texas, is deduced from the ideas of many people. A two-step attack is proposed. The first step is electrophilic and is made by a terminal oxygen atom. The central atom, which is nucleophilic, completes the attack. The position of attack on anthracene and the specificity of attack which occurs with unsymmetrical olefins support this theory. [Pg.143]

What is the mechanism of attack of nucleophiles on radical cation species such as anthracene or thianthrene radical cations Extensive studies by a number of groups have been conducted on the reaction of radical cations with nucleophiles (6, 23, 24). Two main mechanisms have been proposed the disproportionation pathway, equations 6 and 7, in which the nucleophile,... [Pg.324]

Although the attack on (or by) the aromatic ring that leads to substitution can be brought about by free radical, electron-rich (nucleophilic) or electron-poor (electrophilic) reagents, the surfeit of electrons associated with aromaticity provides a richness that dictates that the latter should be most common. Nonetheless, aU three substitution pathways will be considered. Indeed, the three that will be examined are benzene (CeHe) and the polycyclic arenes (naphthalene [CioH ], anthracene [C14H10], and phenanthrene [CmHjo]). [Pg.424]


See other pages where Anthracene nucleophilic attack is mentioned: [Pg.163]    [Pg.276]    [Pg.153]    [Pg.153]    [Pg.887]    [Pg.141]    [Pg.153]    [Pg.1194]    [Pg.51]    [Pg.266]    [Pg.163]    [Pg.295]    [Pg.37]    [Pg.323]    [Pg.90]    [Pg.624]    [Pg.59]    [Pg.86]    [Pg.213]    [Pg.59]    [Pg.86]    [Pg.931]    [Pg.361]    [Pg.295]    [Pg.249]   
See also in sourсe #XX -- [ Pg.138 ]




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