N-Alkylammonium

In this study, tetra-n-alkylammonium bromides ((n-Alkyl)4NBr, QBr) were used as the phase-transfer catalysts. The reaction will proceed in the catalyst-rich liquid phase in a way... 

Potentiometric titrations of aqueous solutions of PGA with some alkali hydroxides LiOH,NaOH,KOH)a.ni. tetra-n-alkylammonium hydroxides, e.g. (C/Zj) AO//and (C Hg) NOH, were performed in three parallel determinations... 

Vansant EF, Uytterhoeven JB (1972) Thermodynamics of the exchange on n-alkylammonium ions on Na-montmorillonite. Clays Clay Mineral 20 47-54... 

Palladium clusters [51], solubilized by tetra-n-alkylammonium salts, are effective in the Suzuki coupling of phenylborinic acid with bromoarenes to produce biaryls... 

Similarly, N-alkylammonium [28] and alkylphosphonium [29] salts form lamellar phases with smectic bilayer structures. In both cases. X-ray scattering also showed the isotropic liquid not to be completely disordered and still displaying similar features to the mesophase. Buscio et al. [28] showed that in N-alkylammonium chlorides the feature was not only much broader than that observed in the mesophase but increased in width with decreasing chain length. 

The dichalcogenides of group VI do not readily form intercalates with organic molecules. But n-alkylammonium compounds can be prepared by ion-exchange reactions of the hydrated sodium intercalation compounds such as Na j(H20)o g M0S2. Alkylammonium compounds prepared by this route show lattice expansions that depend on the alkyl chain length, very similar to the MX2-n-alkylamine systems described above. This raises the fundamental question whether protonated amines are the actual intercalated species in both the cases, involving reduction of the host. In fact, this constitutes the basis of the new model for the intercalation reaction in MX2 proposed by Schollhorn (1980). 

As might be expected, the values for the tetra-n-alkylammonium ions decrease fairly regularly as the number of carbon atoms in the alkyl chain is increased. Paul and co-workers have used Xjjj values to estimate apparent solvation numbers for several singly-charged ions8S ... 

A study of the structural properties of primary n-alkylammonium haUdes enabled us to evaluate the relative importance of intermolecular forces of the two types as the polar ends of the layers form strong hydrogen-bonded networks that dominate the packing on crystallization. Here we illustrate trends in the crystal chemistry of the n-alkylammonium halides, and the investigative methods, using as examples n-octadecylammonium chloride, CigH37NH Cl , and their related bromides and iodides... 

Primary and tertiary -alkylammonium halides are widely used as surfactants. The amphiphilic nature of the molecules produces micelles in water, resulting in superior detergent properties. Some have also been shown to exhibit bactericidal properties. Despite their industrial importance, little fundamental information on the polymorphism of the primary n-alkylammonium halides was available when we began our structural investigation. Our focus here is thus on the structural properties of primary -alkylammonium halides - compounds with straight, saturated hydrocarbon chains that contain one terminal functional group. 

Figure 10-2. Long spacings of n-alkylammonium chlorides in all five polymorphic forms observed at room temperature...

Figure 10-3. Temperatures of phase transition of the epsilon form of n-alkylammonium bromides, illustrating the odd-even effect...

Figure 10-4. X-ray powder diffraction pattern of a n-alkylammonium halide. The arrows indicate how the difference between the d values is related to the lamellar thickness...

These experimental techniques are complementary to one another. Single crystal X-ray diffraction allows only the study of polymorphs of n-alkylammonium halides at specific temperatures, commonly room temperature. In contrast thermal analysis yields no information about the structural nature of compounds, but allows the determination of temperatures and sequences of phase transitions (Figure 10-8). In some instances powder diffraction fails to distinguish two polymorphic forms, but DSC scans indicate their distinction. 

Figure 10-6. TGA and DSC scans of crystals of C18Br.H20, one n-alkylammonium bromide monohydrate. Temperatures of phase transitions as observed by DSC are indicated widi dotted Unes...

Figure 10-8. Thermotropic phase transitions observed for n-alkylammonium iodides...

Figure 10-11. A cartoon of the packing patterns observed in the n-alkylammonium halides...

Materials. The methylammonium Y-zeolites (Table I) were prepared by ion-exchanging NaY (5 grams) with 4 100-ml portions of 1 N alkylammonium salt solution at 80 °C. Monomethylammonium (MMA) chloride, dimethylammonium (DMA) chloride, and tetramethylammonium (TTMA) bromide (Matheson, Coleman, and Bell) and the trimethyl-ammonium (TMA) chloride (Eastman Organic Chemicals) were used as received. 

Levy, G. C., Komoroski, R. A., and Halstead, J. A. (1974)./. Amer. Chem. Soc. 96, 5456. Solvation and Segmental Motions of n-Alkylammonium Ions. A 1 3 C Spin-Lattice Relaxation Study. 

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