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Electrophiles reaction, electrochemical

Benzofurazan, 7-chloro-4-nitro-, 6, 394 as fluorigenic agents, 6, 410, 426 Benzofurazan, 4-chloro-7-sulfo-ammonium salt properties, 6, 426 Benzofurazan, 4-nitro-synthesis, 6, 408 Benzofurazans, 6, 393-426 Beckmann fragmentation, 6, 412 biological activity, 6, 425 bond angles, 6, 396 bond lengths, 6, 396 diazo coupling, 6, 409 dipole moments, 6, 400 electrochemical reduction, 5, 73 electrophilic reactions, 6, 409-410 ESR spectroscopy, 6, 400... [Pg.549]

The mles of electrochemical promotion follow directly from Table 6.1 For example, as shown in Table 6.1 all purely electrophobic reactions are positive order in D and zero or negative order in A. All purely electrophilic reactions are positive order in A and zero or negative order in D. Volcano-type reactions are always positive order in one reactant and purely negative order in the other. Inverted volcano-type reactions are positive order in both reactants. [Pg.285]

Figure 6.19. Model predicted electrochemical promotion kinetic behaviour (a) and (b) electrophobic reaction, (c) and (d) electrophilic reaction. Figure 6.19. Model predicted electrochemical promotion kinetic behaviour (a) and (b) electrophobic reaction, (c) and (d) electrophilic reaction.
Consequently the proven functional identity of classical promotion, electrochemical promotion and metal-support interactions should not lead the reader to pessimistic conclusions regarding the practical usefulness of electrochemical promotion. Operational differences exist between the three phenomena and it is very difficult to imagine how one can use metal-support interactions with conventional supports to promote an electrophilic reaction or how one can use classical promotion to generate the strongest electronegative promoter, O2, on a catalyst surface. Furthermore there is no reason to expect that a metal-support-interaction-promoted catalyst is at its best electrochemically promoted state. Thus the experimental problem of inducing electrochemical promotion on fully-dispersed catalysts remains an important one, as discussed in the next Chapter. [Pg.510]

J.A. Boon, S.W. Lander, J.A. Levisky, J.L. Pflug, L.M. Skrynecki-Cooke and J.S. Wilkes Catalysis and reactivity of electrophilic reactions in room-temperature chloroaluminate molten-salts, J. Electrochem. Soc., 134,510,(1987). [Pg.1482]

Depending on the rate behaviour upon variation of the catalyst potential UWr and, equivalently work function , a catalytic reaction can exhibit two types of behaviour, electrophobic or electrophilic. These terms, introduced since the early days of electrochemical promotion, are synonymous to the terms electron donor and electron acceptor reaction introduced by Wolkenstein113 in the fifties. Electrochemical promotion permits direct determination of the electrophobicity or electrophilicity of a catalytic reaction by just varying UWr and thus 0. [Pg.151]

Thus in Table 4.3 we add to Table 4.2 the last, but quite important, available piece of information, i.e. the observed kinetic order (positive order, negative order or zero order) of the catalytic reaction with respect to the electron donor (D) and the electron acceptor (A) reactant. We then invite the reader to share with us the joy of discovering the rules of electrochemical promotion (and as we will see in Chapter 6 the rules of promotion in general), i.e. the rules which enable one to predict the global r vs O dependence (purely electrophobic, purely electrophilic, volcano, inverted volcano) or the basis of the r vs pA and r vs pD dependencies. [Pg.158]

Figure 6.21. Model predicted electrochemical promotion behaviour for a monomolecular reaction (a) electrophobic (b) electrophilic. Figure 6.21. Model predicted electrochemical promotion behaviour for a monomolecular reaction (a) electrophobic (b) electrophilic.
Reactions involving the catalytic reduction of nitrogen oxides are of major environmental importance for the removal of toxic emissions from both stationary and automotive sources. As shown in this section electrochemical promotion can affect dramatically the performance of Rh, Pd and Pt catalysts (commonly used as exhaust catalysts) interfaced with YSZ, an O2 ion conductor. The main feature is strong electrophilic behaviour, i.e. enhanced rate and N2 selectivity behaviour with decreasing Uwr and , due to enhanced NO dissociation. [Pg.411]

The parameter a in Equation (11.6) is positive for electrophobic reactions (5r/5O>0, A>1) and negative for electrophilic ones (3r/0Oelectrochemical promotion behaviour is frequently encountered, leading to volcano-type or inverted volcano-type behaviour. However, even then equation (11.6) is satisfied over relatively wide (0.2-0.3 eV) AO regions, so we limit the present analysis to this type of promotional kinetics. It should be remembered thatEq. (11.6), originally found as an experimental observation, can be rationalized by rigorous mathematical models which account explicitly for the electrostatic dipole interactions between the adsorbates and the backspillover-formed effective double layer, as discussed in Chapter 6. [Pg.501]

This is the first and obvious application of Electrochemical Promotion, which was already proposed in 1992.2 Electrochemical promotion allows one to quickly and efficiently identify the electrophobic or electrophilic nature of a catalytic reaction and thus (Rules G1 to G4, Chapter 6) to immediately decide if an electronegative or electropositive, respectively, promoter is needed on a conventional catalyst. It also allows one to identify the optimal coverage, Op, of the promoting electronegative or electropositive species. [Pg.516]

Electrochemical methods allowed to shed light on the different reaction mechanisms, both in homogeneous and heterogeneous (Ag20 promoted) systems. Furthermore, electroreduction reverses the C-Br bond polarity, allowing the formation of a C-C bond with an electrophile (f.ex. CO2). [Pg.169]


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