Primary alkylammonium ions

The ability of [18]crown-6 derivatives to complex primary alkylammonium ions has been elegantly exploited in the protection of primary amines (80CC300). In the presence of primary amines, secondary amines can be acylated selectively by adding [18]crown-6 and a proton source. This strategy has obvious advantages over normal amine protecting groups which require a deprotection step. 

Four examples are known of calix[6]arene derivatives which have been used as receptor molecules in potentiometric measuring devices. Calix[6]arene 36 functionalized with six ethylester moieties showed a moderate selectivity for hexylammo-nium ions in the presence of smaller primary alkylammonium ions (logA = —1.0 to — 1.4) in ion-selective electrodes [140]. The same derivative 36 also proved to be sensitive towards Cs ions [141]. CHEMFETs with calix[6]arenes, functionalized with three diethylamido moieties (37) or with three phosphate moieties (38), are selective for guanidinium ions [142]. The fourth example is calix[6]arene 39 functionalized with two thiophosphoryl groups which is selective for Pb " ions... 

An amine and its ammonium ion (eq. 11.14) are related as a base and its conjugate acid. For example, RNH3 is the conjugate acid of the primary amine RNH2. It is convenient, when comparing basicities of different amines, to compare instead the acidity constants (pK s) of their conjugate acids in water. Equation 11.15 expresses this acidity for a primary alkylammonium ion. 

The year after Fukazawa s report on fullerene recognition [7], S. Pappalardo and coworkers, following up earlier studies on calix[5]arene crown-5 derivatives [23], noticed that p-teri-butylcalix[5]arenes - locked in a cone conformatirMi [24] - act as very selective receptors of linear primary alkylammonium ions [25]. Owing to the... 

For scientific studies primary alkylammonium ions RNH and alkylpyridinium ions n-r are often used. 

Surfactant cations are difficult to displace from the clay mineral surface. Quaternary alkylammonium ions are easier to exchange than primary alkylammonium ions. Primary alkylammonium ions are removed by hydrolysis into the amine in alkaline medium [47]. The mutual exchange of surfactants in non-aqueous dispersions was studied by Me Atee [48, 49], Solvent was a mixture of isooctane and isopropyl alcohol. The alcohol served two functions as a solvent for the surfactant chloride salts and the dispersing agent for the clay mineral surfactant particles. An effective agent to displace quaternary alkylammonium ions (dodecyl trimethylammonium ions) is paraquat [50],... 

Perraud O, Lefevre S, Robert V, Martinez A, Dutasta J-P (2012) Hemicryptophane host as efficient primary alkylammonium ion receptor. Oig Biomol Chem 10 1056-1059... 

Recently, the abilities of primary to tertiary alkylammonium ions with Me, Et, and -Bu groups to transport water to NB have been studied [48]. As the result of careful consideration of the ion-pair formation, it has been shown that the hydration numbers (w ) of the ammonium ions in NB, being little affected by the alkyl chain length, are simply dependent on the class of the ammonium ion % = 1.64, 1.04, 0.66, respectively, for the primary, secondary, and tertiary ammonium ions. 

Figure 4. Log k °j for tributylamnanium CWEs vs. carbon number for various alkylammonium ions < > = primary ammonium ions, = secondary amnonium ions, = tertiary amnonium ions, S = quaternary amnonium ions.

All chiral crown ethers incorporating one carbohydrate subunit possess two diastereo-topic faces of the macrocyclic ring. They are able to form diastereoisomeric complexes with primary alkylammonium cations. Since nonbonding interactions are responsible of the chiral recognition of optically active species, it would be desirable to form monofacial ligands in which the inclusion of a chiral molecule (or chiral ion) could proceed from the sterically hindered side only. This special molecular architecture may be followed by the fusion of the cryptand framework and the chiral unit. 

Two chiral [2.2.1]cryptands, one incorporating the methyl 4,6-O-benzylidene-a-D-mannopyranoside unit (70), the other the methyl 4,6-0-[(S)-phenylethylidene]-a-D-mannopyranoside unit (77), may exhibit the same two different modes of complexa-tion as before binding of primary alkylammonium cations via hydrogen bonds between the NH-f group and the heteroatoms of the ligand or cascade complexation of ion pairs. Chart 2 shows the constitutions of the two cryptands 70 and 77 and is also indicative that the approach of guest molecules may occur from the more sterically hindered side. 

In the NB-W system, primary to tertiary ammonium ions with methyl (Me), ethyl (Et), and -butyl ( -Bu) groups were distributed with DPA and TPB, and the number of water molecules being coextracted to NB by an alkylammonium ion (R NH4 ) was measured by the Karl Fischer method [16]. 

Even this is not all The alkylation steps keep going, forming the secondary and tertiary amines, and stopping only when the non-nucleophilic tetra-alkylammonium ion R4N+ is formed. The problem is that the extra alkyl groups push more and more electron density onto N, making each product more reactive than the previous. The quaternary ammonium salt could probably be made cleanly if a large excess of alkyl halide RX is used, but other more controlled methods are needed for the synthesis of primary, secondary, and tertiary amines. 

Primary alkyl amines, when exposed to acidic medium, protonate the amine function resulting in the formation of alkylammonium ions. Montmorillonite exchanged with long-chain alkylammonium ions can be dispersed in polymer matrix. 

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