Alkylammonium halide

Whilst reaction can take place in the absence of catalysts it is more common to use such materials as tetra-alkylammonium halides and tertiary amines such as triethylenediamine. A major side reaction leads to the production of isocyanurate rings, particularly in the presence of tertiary amines. 

SURFACTANTS Quaternary alkylammonium halides Primary amines Non-ionic surfactants... 

N-Trialkyl-B-trihaloborazines can be prepared without difficulty from alkylammonium halide or alkylamine and trihaloborane 4> when the resulting alkylammonium tetrahaloborate or alkylamine-trihalo-borane is refluxed in chlorobenzene. Yields are nearly quantitative in most cases. This same observation holds true for N-triaryl-B-trihalo-borazines. Extensive studies using thermogravimetric methods in addition to preparative methods did not provide for the isolation or identification of any intermediates between the amine-trihaloborane and the borazine stage of the reaction 45 4fl>. 

Gellman and coworkers have reported the binding of ammonium ions, as well as halide ions, in methanol-chloroform by a macrocycle containing a phosphine oxide and two sulfoxide functionalities (Figure 54) [75]. Mono-alkylammonium halides (except fluoride) were found to bind via both anion and cation complexation. 

The most common emulsions used in dermatological therapy are creams. These are two-phase preparations in which one phase (the dispersed or internal phase) is finely dispersed in the other (the continuous or external phase). The dispersed phase can be either hydrophobic based (oil-in-water creams, O/W) or aqueous based (water-in-oil creams, W/O). Whether a cream is O/W or W/O is dependent on the properties of the system used to stabilize the interface between the phases. Given the fact that there are two incompatible phases in close conjunction, the physical stability of creams is always tenuous, but may be maximised by the judicious selection of an appropriate emulsion stabilizing system. In most pharmaceutical emulsions, stabilizing systems are comprised of either surfactants (ionic and/or non-ionic), polymers (non-ionic polymers, polyelectrolytes or biopolymers) or mixtures of these. The most commonly used surfactant systems are sodium alkyl sulphates (anionic), alkylammonium halides... 

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. 

Throughout this paper we represent all alkylammonium halides according to a notation CnX, in which n is the number of carbon atoms in the long chain and X is the halide anion. If water be present in the crystal lattice, the notation CnX.H20 refers to the monohydrate forms. For example, C14C1 indicates Cj, and C16Br.H20 indicates Ci6H33NH+Br .H20. 

Much information on the structures and thermal behaviour of alkylammonium halides is available in the crystallographic literature. As compounds with short... 

Two major experimental techniques available for the investigation of the polymorphism of -alkylammonium halides are X-ray diffraction and thermal analysis. X-ray diffraction is the most informative technique because it provides detailed information on the molecular conformation and the packing of polymorphs. 

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. 

Alkane molecules in crystals that are stable at room temperature normally exist in an extended all-fran conformation. For all known crystal structures of the -alkylammonium halides, the long-chain molecule deviates from the ideal all-trans conformation because of hydrogen-bonding interactions. In some structures this deviation is severe, and results in gauche bonds in the molecular chain (Figures 10-9 and 10-11). The long-chain molecule remains mostly in the trans conformation for all known structures. 

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

We thank Professor Erie Reynhardt and Ms. Rosalie Scholtz for introducing us to the alkylammonium halides. 

The complex mechanism and the various processes (Fig. 10.17) are responsible for the strong influence of the reaction conditions and parameters. Additives play an important role. Thus the performance of different catalysts can be improved by (defined) small amounts of oxidizing as well as reducing agents [64, 143, 172], by a variety of additives (in particular by alkylammonium halides) and is strongly influenced by the nature of solvent and base. Note, that these parameters also influence the Pd leaching in an analogous manner. In particular for the activation... 

One of the most important transformations catalysed by palladium is the Heck reaction. Oxidative addition of palladium(O) into an unsaturated halide (or tri-flate), followed by reaction with an alkene, leads to overall substitution of a vinylic (or allylic) hydrogen atom with the unsaturated group. For example, formation of cinnamic acid derivatives from aromatic halides and acrylic acid or acrylate esters is possible (1.209). Unsaturated iodides react faster than the corresponding bromides and do not require a phosphine ligand. With an aryl bromide, the ligand tri-o-tolylphosphine is effective (1.210). The addition of a metal halide or tetra-alkylammonium halide can promote the Heck reaction. Acceleration of the coupling can also be achieved in the presence of silver(I) or thallium(I) salts, or by using electron-rich phosphines such as tri-tert-butylphosphine. ... 

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