Alkylammonium metal alkyl

Upon replacing the hydrated metal cation from the interlayers in the pristine layered silicates with organic cations such as an alkylammonium or an alkyl-phosphonium, the layered silicate attains a hydrophobic/organophillic character... 

In the case of HDN, an additional interesting possibility also consistent with the heterolytic mechanism arises, since substrates like the pyridines -or intermediate alkyl or aryl amines- are sufficiently basic to promote the activation of hydrogen so as to form a metal hydride plus a protonated base (e.g. a pyridinium or an alkylammonium cation). Furthermore, some of the most widely accepted amine HDN mechanisms include the initial protonation of the amine nitrogen, followed by elimination of ammonia from the ammonium cation. Therefore, it is very easy to combine the idea of a heterolytic hydrogen activation promoted by, say n-pentylamine, with a subsequent degradation by a Hoffmann mechanism, to conform a reasonable HDN catalytic cycle. A simplified representation of this idea is given in Fig. E4. 

The most common ionic liquids include alkylammonium, alkylphosphonium, A/-alkylpyridinium, and A/A/ -dialkylimidazolium cations. Two general methods for their preparation are acid-base neutralization reactions and metathesis of halide salts with a metal or ammonium salts. Alkylammonium, pyridinium, and imidazo-lium halides can be prepared by the reaction of the appropriate alkyl halide and amine. Preparation of l-ethyl-3-methylimidazolium chloride [emimjCl requires a sealed tube since it has a low boiling point. On the other hand, synthesis of [bmim] Cl can be achieved under conventional reflux conditions [33, 34]. 

Naked enolates without any complexation can be made from silyl enol ethers using fluoride ion, a very selective nucleophile for silicon 49, and a non-metallic cation, usually a tetra-alkylammonium ion. The commonest reagent is TBAF (TetraButylAmmonium Fluoride Bu4N+ F ). In this way the naked enolate 50 was made. It proved to be acylated with acetic anhydride exclusively at oxygen to give the enol acetate 53 and alkylated with Mel at carbon to give the ketone 51 in 84% isolated yield.18... 

One effective method of pre-determining the type of zeolite structure that will be formed is the use of template molecules of the appropriate size. Using bulky tetra-alkylammonium hydroxides rather than alkali metal hydroxides to increase the pH gives more open structures. For example, if a short-chain alkyl trimethylammonium surfactant (detergent), C6Hi3N+(CH3)3, is used in the reaction mixture, this provides a template of a suitable size for the formation of the medium-pore zeolite ZSM-5 (Zeolite Synthesized by Mobil, number 5). 

For M = Co and Zn, the structures are of the same type, but the alkyl chains (n = 9-17) are perpendicular to the ionic layers with intercalation of chains between successive layers in the low-temperature, solid phase (Figure 68b). However, in these cases, the coordination about the metal is tetrahedral so that extended anions are not formed and the chains of successive layers are able to intercalate. Note that the liquid-like order of the alkyl chains in the high-temperature phase of all these compounds has been proved by X-ray diffraction and infrared studies. Similar pohmiorphic behavior was observed for a series of bis(alkylammonium) tetrabromozincates ( = 10-16). It was shown by X-ray diffraction and infrared, NMR, and NQR techniques that the transition from the ordered solid to the disordered solid is accompanied by a conformational... 

Alkylthiocyanates have been prepared in higji yield by reaction of alkali metal thiocyanates with various primary and secondary alkyl halides under phase transfer conditions. Quaternary alkylammonium salts [12—14], crown ethers [15], cryptates [16], and tertiary amines [14] have all proved effective phase transfer catalysts for this reaction (Eq. 13.7 and Table 13.4). The mechanism of the thiocyanate displacement is probably similar to that of the cyanide displacement reaction (see Sect. 7.2). 

New diester/diamide-calix[4]aienediquinones and a diamide-benzo-15-crown-5-calix[4]arene receptor molecule have been prepared and shown to complex Group 1 and 2 metal, ammonium and alkylammonium cations with association constants up to 4.8 X 10 with Ba + and (3) in acetonitrile solution. The redox-active quinone containing receptors electrochemically recognise these cationic guest species, including for the first time, the amperometric detection of an alkyl ammonium cationic guest species by a redox-active ionophore. 

In order to make the solution electrically conductive and to enable the electrolytic process it is necessary to add an indifferent electrolyte to the solution. As a rule salts of alkali metals or alkyl-ammonium bases are used. The concentration of these salts in the investigated solutions amounts to 10 mole /liter. It is comparatively easy to create such a concentration of indifferent electrolyte in aqueous media by alkali metal salts. In nonaqueous solvents this is not always possible for alkali metal salts various alkylammonium salts, which have better solubility, are therefore used instead. 

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