N-Alkyltrimethylammonium bromides

TABLE 2 81Br NMR parameters of n-alkyltrimethylammonium bromide salts averaged over a range of MAS frequencies 6... 

Ryoo[189] found that the structural order of MCM-41 can be improved remarkably if mixed surfactants of n-alkyltriethylammonium bromides (CrcTEAB, n = 12,14,16,20 and 22), and n-alkyltrimethylammonium bromides (CrcTMAB) are used. The optimum mixing ratio can be tuned according to the length of the alkyl groups. 

Fig. 3.7.1 Variation of (a) surface tension % and (b) critical surface tension 7c of surfactant treated glass surfaces with increasing carbon content of the surfactant alkyl chain, (a) Surface tension Jb for substrates with n-alkyl monoamine layers [6]. (b) Critical surface tension for substrates with n-alkyltrimethylammonium bromide layers [7].

Alonso, B., Massiot, D., Florian, R, Paradies, H. H., Gaveau, R, and Mineva, T. (2009). N and Br. Quadrupolar nuclei as sensitive NMR probes of n-alkyltrimethylammonium bromide crystal structures. An experimental and theoretical study. J. Phys. Chem. B. 113, 11906-11920. 

Table 21 Br SSNMR parameters for n-alkyltrimethylammonium bromide salts CxH2x+i(CH3)3N Br- from Alonso et at. [44]...

Five n-alkyltrimethylammonium bromide C H2 +i(CH3)3N Br salts (x=l, 12, 14, 16, 18) were characterized by and Br MAS SSNMR in order to determine their NMR parameters and provide insight into their crystal structures (Table 21) [44]. Diffraction data and computations were also used in a complementary manner. The combined use of both and Br NMR data proved to be useful for structure refinement due to the fact that the NMR parameters were found to be strongly dependent on the chain packing among the five samples, more specifically variations in C-N-C angles and in the spatial positioning of the cations and anions. 

The Raman spectra of n-hexyl, n-octyl, n-decyl, and n-dodecyl trimethyl-ammonium bromides in the 150-600 cm" region are shown in Fig. 1. Strong Raman bands are observed for all of these in the 160-300 cm region, and these shift markedly to a lower frequency with an increase in chain length. We may assign the bands observed at 251, 208, 179, and 164 cm to the accordion modes of the n-hexyl, n-octyl, n-decyl, and n-dodecyl chains, respectively. Figure 2 shows the linear relationship between the accordion band frequency and the reciprocal number of carbon atoms (1/Cn) for the fom n-alkyltrimethylammonium bromides. We may assume that the accordion band frequencies of the n-octyl, n-decyl, and n-dodecyl chains,... 

Alkyl (Me, Et, n-Pr, n-Bu), alkyldimethyl, and alkyltrimethylammonium bromides retard the neutral hydrolysis of 1-benzoyl-1,2,4-triazole (190) to benzoic acid and the triazole (191).162 This effect is attributed to a dominant stabilization of the initial state through hydrophobic interactions with the co-solute. The effects of cetylpyridinium bromide on the hydrolysis of 2,4-dinitrochlorobenzene by hydroxide ion in water have been reported.163... 

Empirical Equations Many investigators have developed empirical equations relating the CMC to the various structural units in surface-active agents. Thus, for homologous straight-chain ionic surfactants (soaps, alkanesulfonates, alkyl sulfates, alkylammonium chlorides, alkyltrimethylammonium bromides) in aqueous medium, a relation between the CMC and the number of carbon atoms N in the hydrophobic chain was found (Klevens, 1953) in the form... 

A. Fan, P. Somasundaran, N.J. Turro, Adsorption of alkyltrimethylammonium bromides on negatively charged alumina. Langmuir 13(3), 506—510 (1997). doi 10.1021/la%07215 K. Holmberg, B. Jonsson, B. Kronbta-g, B. Lindman, Surfactants and polymers in aqueous solution, 2nd edn. (Wiley, ChichestCT, 2002). ISBN 0-47I-49883-I D. Myers, Surfaces, interfaces, and colloids Principles and applications, 2nd edn. (Wiley, New-York, 1999). ISBN 0-471-330604... 

The thermodynamic parameters change almost linearly with the total number of carbon atoms in hydrocarbon chains. The enthalpy increments for transitions are comparable with those for homologous series of n-alkanes, sodium alkyl sulfates, and long-chain alkyltrimethylammonium bromides [22,29-32,66,67], while the entropy change of melting falls within the range of those for stable bilayers of all double-chain amphiphiles, including natural lipids [19],... 

FiG.1 Raman spectra for solid -alkyltrimethylammonium bromides [(a) -hexyl, (b) n-octyl, (c) n-decyl, and (d) M-dodecyl] in the skeletal stretching region. 

V- Hexagonal MCM- lattice 41 V0S04 5H20 Fumed silica Alkyltrimethylammonium chloride or bromide (Ci6H33)(C H2 +i)(CH3)2NBr, with n= 1-22 to control pore size 100 °C, 7 days Sayari, 1995 (57)... 

Na (K) -alkyl 1-sulfates or -sulfonates Na -alkane-1-sulfonates Na -alkane-l-sulfonates Na -alkane-l-sulfonates Na n-alkyl-1-sulfates Na -alkyl-l-sulfates Na n-alkyl-2-sulfates Na p- -alkylbenzene sulfonates Na p- -alkylbenzene sulfonates /i-Alkylammonium chlorides /i-Alkylammonium chlorides /i-Alkytrimethylammonium bromides /i-Alkyltrimethylammonium chlorides (in 0.1 M NaCl)... 

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