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Tetra-alkylammonium functionality

One of the earliest reports on the use of dendrimers in catalysis is the unimolecu-lar decarboxylation of 6-nitro-benzisoxazole-3-carboxylate in the presence of a dendrimer comprising ether dendrons which are functionalized at their periphery with tetra-alkylammonium cations (e.g. 20, Scheme 21) [30]. In aqueous media, the quaternary ammonium groupings promote the reactivity of organic anions which presumably bind in high concentration to the polycationic periphery of the dendrimer. The latter species enhances the rate of the bimolecular hydrolysis of p-nitrophenyl diphenyl phosphate catalyzed by o-iodosobenzoate ion. [Pg.503]

As a rather strongly hydrophilic anion, nitrate requires an ISE membrane containing a strongly hydrophobic cation, as described on p. 169. This function was fulfilled in the first nitrate electrode from Orion Research by cation V [180] in nitro-p-cymene 5. The electrode can be used in the pH range 4-7. In other commercial electrodes, the ion-exchanger ion is a tetra-alkylammonium salt, for example in the electrode from Coming Co., substance XIII in solvent 6 [27]. An ISE with a renewable membrane surface was found to be very useful (see section 4.1 and fig. 4.4), in which the ion-exchanger solution contains the nitrate of crystal violet VII dissolved in nitrobenzene [191]. The NOj ISE also responds to nitrites that can be removed by addition of aminosulphonic acid. [Pg.191]

Fig. 11. Inhibitory constants of tetra-alkylammonium salts, R4N, as function of n, the number of carbon atoms in the four substituents together (according to Table IV and V). O------O Eel esterase. ------ Human plasma ChE. Fig. 11. Inhibitory constants of tetra-alkylammonium salts, R4N, as function of n, the number of carbon atoms in the four substituents together (according to Table IV and V). O------O Eel esterase. ------ Human plasma ChE.
Laidler has pointed out [11, 242] that Eq. (5-88) is best considered as a semi-quantitative formulation, which gives only a rough prediction of the effect of a change in fir on the rate of dipole-dipole reactions. This also applies to Eqs. (5-87) and (5-90). Nevertheless, in many cases a satisfactory correlation between rate constants and function of solvent relative permittivity has been obtained, as, for instance, in the Men-schutkin reaction between trialkylamines and haloalkanes forming quaternary tetra-alkylammonium salts [2, 56, 58, 60, 61, 64, 65, 245-247]. [Pg.227]

Figure 15 shows the change in the ionic diffusion coefficients of tetra-alkylammonium ions in strong acid cation resins as a function of mean effective pore diameter of the resins.l As the pore diameter is increased, the penetrability of the resins with respect to the large ions also increased. [Pg.411]

Figure 3.14. The eomparison of the values of the limiting ionic conductivity (Aq) in water of rigid monopositive ions with the prediction of the molecular theory that takes into account the ultrafast sub-50 fs SD in liquid water. Here (Aq) is plotted as a function of the inverse ionic radius in water at 298 K. The solid line represents the predictions of the microscopic theory. The open circles denote the experimental results. Here, the tetra-alkylammonium ions are represented by C1-C4, where C = (C H2 +i)4N, n being 1,2,3, or 4. Adapted with pennission from cc. Chem. Res., 31(1998), 181. Copyright (1998) American Chemical Society. Figure 3.14. The eomparison of the values of the limiting ionic conductivity (Aq) in water of rigid monopositive ions with the prediction of the molecular theory that takes into account the ultrafast sub-50 fs SD in liquid water. Here (Aq) is plotted as a function of the inverse ionic radius in water at 298 K. The solid line represents the predictions of the microscopic theory. The open circles denote the experimental results. Here, the tetra-alkylammonium ions are represented by C1-C4, where C = (C H2 +i)4N, n being 1,2,3, or 4. Adapted with pennission from cc. Chem. Res., 31(1998), 181. Copyright (1998) American Chemical Society.
Batey has reported Pd-catalyzed cross-coupling reactions of tetraalkylammo-nium aryl trifluoroborate salts bearing functional groups such as acetyl, nitro and chloro with functionalized aryl bromides under mild conditions 35]. These tetra-alkylammonium organofluoroborates are prepared from the respective boronic acids using counter ion exchange protocol. They are air and moisture stable and are soluble in various organic solvents (Scheme 3.21). [Pg.57]


See other pages where Tetra-alkylammonium functionality is mentioned: [Pg.328]    [Pg.328]    [Pg.340]    [Pg.493]    [Pg.844]    [Pg.226]    [Pg.257]    [Pg.268]    [Pg.32]    [Pg.41]    [Pg.400]    [Pg.501]    [Pg.508]    [Pg.36]    [Pg.306]    [Pg.318]    [Pg.2]    [Pg.501]    [Pg.269]    [Pg.480]    [Pg.304]   
See also in sourсe #XX -- [ Pg.95 ]




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