Tetra-n-butylammonium perchlorate

Tetra-n-butylammonium perchlorate [1923-70-2] M 341.9", m 210"(dec). Crystd from EtOH, ethyl acetate, from n-hexane or diethyl ether/acelone mixture, ethyl acetate or hot CH2CI2. Dried in vacuum at room temperature over P2O5 for 24h. [Anson et al. J Am Chem Soc 106 4460 1984 Ohst and Kochi J Am Chem Soc 108 2877 1986 Collman et al. J Am Chem Soc 108 2916 1986 Blau and Espenson J Am Chem Soc 108 1962 1986 Gustowski et al. J Am Chem Soc 108 1986 Ikezawa and Kutal J Org Chem 52 3299... 

Heptyl 3-Phenylpropyl Ether [Electrogenerated Acid-Promoted Reduction of an Aldehyde to an Unsymmetrical Ether].333 A mixture of 1-heptanal (1.0 mmol), 3-phenylpropoxytrimethylsilane (1.2 mmol), tetra-n-butylammonium perchlorate (0.1 mmol), and lithium perchlorate (0.1 mmol) was dissolved in CH2CI2 (3 mL) in an undivided cell. The mixture was electrolyzed under constant current (1.67 mA cm-2) with platinum electrodes at ambient temperature. After 5 minutes, dimethylphenylsilane (1.2 mmol) was added drop-wise and the electrolysis was continued (0.06 Faraday/mol). After completion of the reaction, one drop of Et3N was added and the solution was concentrated. The residue was chromatographed on Si02 to give 1-heptyl 3-phenylpropyl... 

Redox potentials for i-2 were determined in butyronitrile containing O.IM tetra-n-butylammonium perchlorate using a Pt disc electrode at 21. These potentials were measured relative to a saturated calomel electrode using ac voltammetry.(lQ) Both the one electron oxidations and reductions of i-2 exhibited good reversibility. The half-wave potentials for the one-electron oxidation and reduction of i-2, ZnTPP, and two model quinones are given in Table I. 

Fulleride anions are often more soluble, especially in more polar solvents, than the parent fullerenes. For example, in bulk electrolysis experiments with tetra-n-butylammonium perchlorate (TBACIO4) as supporting electrolyte, carried out in acetonitrile where Cjq is completely insoluble, fairly concentrated, dark red-brown solutions of 50 can be obtained [81]. Upon reoxidation, a quantitative deposition of a neutral Cjq film on the surface of a gold/quartz crystal working electrode takes place. This Cjq film can be stepwise reductively doped with TBA, leading to (Cjo )... 

By media variables we mean the solvent, electrolyte, and electrodes employed in electrochemical generation of excited states. The roles which these play in the emissive process have not been sufficiently investigated. The combination of A vV-dimethylformamide, or acetonitrile, tetra-n-butylammonium perchlorate and platinum have been most commonly reported because they have been found empirically to function well. Despite various inadequacies of these systems, however, relatively little has been done to find and develop improved conditions under which emission could be seen and studied. Electrochemiluminescence emission has also been observed in dimethyl sulfite, propylene carbonate, 1,2-dimethoxyethane, trimethylacetonitrile, and benzonitrile.17 Recently the last of these has proven very useful for stabilizing the rubrene cation radical.65,66 Other electrolytes that have been tried are tetraethylam-monium bromide and perchlorate1 and tetra-n-butylammonium bromide and iodide.5 Emission has also been observed with gold,4 mercury,5 and transparent tin oxide electrodes,9 but few studies have yet been made1 as to the effects of electrode construction and orientation on the emission character. 

Certain aromatic hydrocarbons luminesce when raised to an excited electronic state by electrochemical energy. This phenomenon is called electroluminescence (eel) and is shown by some benzo[c]furans. The eel emission was examined in V,V -dimethylformamide as solvent with tetra-n-butylammonium perchlorate as electrolyte. - The emission was identical with the normal fluorescence emission. Cyclic voltammograms were measured under the same conditions as used for the eel studies slowest scan rates at which rereduction of the cation or reoxidation of the anion... 

In the interests of improved electrochemical background limits and reactant stability, it is important to employ solvents that are as free as possible of nucleophiles and proton sources. Special attention always goes to the removal of water. The most important media are carefully purified acetonitrile, dimethyl-formamide, benzonitrile, and tetrahydrofuran. Popular supporting electrolytes are tetra-n-butylammonium perchlorate (TBAP) and fluoroborate (TBABF4). Solutions are usually prepared by vacuum-line methods (Chap. 18) or in a dry box (Chap. 19) to exclude oxygen from the systems and to avoid contamination by water. 

The effect of added tetra-n-butylammonium perchlorate on the rate of reaction (21) (X = Cl) was also studied. It was found30 that the perchlorate greatly increased the value of the second-order rate coefficient, and that this positive kinetic salt effect was more marked the lower was the solvent dielectric constant. The salt effects were analysed in terms of the equation... 

Second-order rate coefficients for reaction (21) (X = I and OAc) were also reported by Abraham and Behbahany30 and are given in Table 20. Kinetic salt effects of added tetra-n-butylammonium perchlorate were studied for reaction (21) (X = I and OAc) both with solvent methanol and solvent tert.-butanol. Reaction (21) (X = 1) was accelerated in both solvents to about the same extent as was reaction (21) (X = Cl), and mechanism SE2(open) was therefore suggested. The reaction of tetraethyltin with mercuric acetate was subject to very large positive salt effects in methanol, perhaps due to anion exchange, but was unaffected by the electrolyte in solvent /er/.-butanol. Abraham and Behbahany30 considered that it was not possible to deduce the mechanism of the acetate reaction and that further work was necessary to decide between mechanism SE2(open) and mechanism SE2(cyclic). 

Reaction (21) (X = Cl, I, OAc) has been studied by Abraham and Hogarth31 using acetonitrile as solvent. Rate coefficients and activation parameters are in Table 21. Tetra-n-butylammonium perchlorate and also lithium perchlorate accelerate reaction (21) (X = Cl) application of equation (22) yielded values for Z2d of 0.652 (Bu"4NC104) and 0.674 (LiC104). If c/ is taken as 3.1 A, as before, these values correspond to 0.46 and 0.47 for Z. Although Z is much less than observed when hydroxylic solvents are used (see Table 19), Abraham and... 

Hogarth31 considered the values of Z more compatible with mechanism SE2(open) than with mechanism SE2(cycIic). Added tetra-n-butylammonium perchlorate also accelerates reaction (21) (X = I), and mechanism SE2(open) was again suggested to obtain. 

An examination of Table 2 reveals that although mercuric acetate and mercuric nitrate have often been used as electrophilic reagents, there are but few instances in which independent evidence as to their mechanism of reaction has been put forward. Positive kinetic salt effects have been observed in the substitution of sec.-butylmercuric acetate by mercuric acetate (with lithium nitrate in solvent ethanol)2, the substitution of di-sec.-butyl mercury by sec.-butylmercuric nitrate (with lithium nitrate in solvent ethanol)11, and the substitution of tetraethyltin by mercuric acetate (with tetra-n-butylammonium perchlorate in methanol)7. In the latter case, it was suggested7 that the observed very large positive kinetic salt effect was possibly due to anion exchange between mercuric acetate and the perchlorate ion. 

Fig. 7.21 (continued) reverse scans. EE SS = —2.6V (vs. Ag), sw = 25mV, A s = 10mV. The values of the kinetic parameters and formal potential extracted in each case are given in Table 7.2. Test solution 2 mM 2-methyl-2-nitropropane, 0.1 M tetra-n-butylammonium perchlorate in acetonitrile. Reproduced from [30] with permission... 

Tetra-n-butylammonium perchlorate. A saturated aqueous solution of 8.4 g (25 mmol) of ( -Bu)4NBr in 18 mL of water is treated with 2.1 mL ( — 26 mmol) of aqueous 70-72% HC104. After the resulting insoluble perchlorate salt has been collected, washed with cold water, and dried, the yield is 8.0 g (94%) MP 197-199°C. Two recrystallizations from an ethyl acetate-pentane mixture yield 7.6 g (90%) of pure (n-Bu)4NC104 as white needles that are dried at 100°C under reduced pressure MP 212.5-213.5°C. 

Since contact ion pairs can be separated by the deliberate addition of an inert salt (such as tetra-n-butylammonium perchlorate or hexafluorophosphate) [132], (Eq. 11) ... 

Pyridinecarboxylic acid with [Ru3(CO)i2l in toluene forms the chelate mononuclear complex 249 (99JOM(585)246). 2-Pyridinecarboxylic acid (HL) with [Ru(CO)2Cl2]n and further with tetraethylammonium perchlorate or tetra-n-butylammonium perchlorate yields (R4 N)LRu( 2 (N,0)-L)(C0)2C12] (R = Et, m-Bu) (03JOM(665)107). The reaction of the same ligand with [Ru(bipy)(CO)2Cl2] and silver nitrate in water and... 

Solutions of I in CH3CN with 0.1 M tetra-n-butylammonium perchlorate (TBAP) were subjected to polarographic and cyclic voltammetric examination. The results were as follows ... 

Figure 17.2.9 Resonance Raman spectra of TCNQ and electrogenerated TCNQ , which was coulometrically produced by reduction at —0.10 V V5. SCE. Initially, TCNQ was present at 10.9 mM in acetonitrile containing 0.1 M tetra-n-butylammonium perchlorate. Excitation wavelengths are indicated. Abscissa shows frequency shift with respect to excitation line. S denotes a normal Raman band of the solvent. [Reprinted with permission from D. L. Jeanmaire and R. P. Van Duyne, J. Am. Chem. Soc., 98, 4029 (1976). Copyright 1976, American Chemical Society.]...

In their electrochemical. studies. Webb ei al. noted that the stereochemi.stry can be influenced by almost every parameter involved in the reaction. i.e.. solvent, electrolyte, electrode, leaving group (Br, 1, HgX), extent of reaction, and substituents at the reaction site (147]. Thus, reductions of l-bromo-l-methyl-2,2-diphenylcyclopropane in DMEi/tetra-n-butylammonium perchlorate give high yields of racemic RH. while similar reactions in acetonitrile and N. A-diniethylforniamidc give 25% retention. The presence or absence of iodide-ion also affects the optical purity of RM. 

Electrochemical methods have played an important role in the recognition of cation radicals as intermediates in organic chemistry and in the study of their properties. An electrode is fundamentally an electron-transfer agent so that, given the proper solvent system, anodic oxidation allows formation of the cation radical without any associated proton or other atom transfer and without the formation of a reduced form in the immediate vicinity of the cation radical. Moreover, because the potential of the electrode can be adjusted precisely, its oxidizing power can be controlled, and further oxidation of the cation radical can often be avoided. Finally, the electrochemical experiment can involve both production of the cation radical and an analysis of its behavior, so that information about the thermodynamics of its formation and the kinetics of its reaction can be obtained, even if the cation radical lifetime is as short as a few milliseconds. There are some limitations, however, in the anodic production of cation radicals. The choice of solvent is limited to those that show reasonable conductivity with a supporting electrolyte (e.g. tetra-n-butylammonium perchlorate, TBAP). Acetonitrile, methylene chloride and nitrobenzene have been employed as solvents, but other favorites, such as benzene and cyclohexane, cannot be used. The relatively high dielectric constant of the suitable... 

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