Alkyl ammonium cations

The anionic exchange reagents commonly employed in these processes are tris-alkyl ammonium cations, generally dissolved in an aromatic diluent such as xylene. Tris-isooctylamine has been used at Falconbridge Nikkeiverk in Kristiandsand, Norway for the purification of solutions derived from HC1 leaching of Ni—Cu matte for over 30 years.103... 

Exchange of organic ammonium cations. Exchange selectivity of monovalent alkyl ammonium cations in montmorillonites (40-41) and octahedrally substituted synthetic clay minerals (laponite) increases with their chain length (42) and along the series... 

Chiral crown ethers have been employed extensively (48-53, 56-60, 86, 90, 93-95, 107, no, 116, 117, 128, 143, 144, 152-155, 158-161, 163, 164, 212-227) for enantiomeric recognition of racemic primary alkyl ammonium cations including those associated with amino acid ester salts. Resolutions have been effected employing both bulk and chromatographic procedures. 

In the absence of water, none of the chemical transformations described above occurs noticeably. The low diffusion coefficient of alkyl-ammonium cations between the montmorillonite layers (2) together with the strong acid character of residual water (3, 4) in this situation might provide a favorable situation which, perhaps, does not exist on other silicate surfaces with a more open structure. 

Spherand Alkyl ammonium cation Hydrogen bonding Complex (cavitand) Spherand (CH3NH3+)... 

These hydrogen-bonded salts show distinct potential for the controlled design of new crystalline structures, and are applicable to incorporation of a wide variety of transition metal and main group metal ions. The work of Mitzi on perovskite structures in which perhalometallate layers are linked via organic alkyl ammonium cations that interact via N-H X-M hydrogen bonds shows another area of potential application [43] (see Sections 4.4.2 and 7). 

Dipolar electrostatic interactions have also been manipulated for the purposes of anion binding. Macrocyclic receptor 10 was shown to be capable of binding halide anions through interactions with the positive ends of the S = O and P = O dipoles (54). Evidence was also provided for the simultaneous binding of primary alkyl ammonium cations (to the oxygen atoms) and halide anions (to the dipoles). This topic of simultaneous cation and anion recognition is of considerable current interest. Further examples will be encountered during this chapter. 

Unfortunately, since much of human biochemistry takes place at neutral pH, a ready source of protons is not to hand and so metal ions can be used as so-called super acids to provide that source of positive charge density. Related agents that are not metal ions are alkyl ammonium cations that are also used in a support role for drug manufacturing similar to protons and metal ions. Not surprisingly, one-fifth of the drugs in the pharmacopoeia in the UK contain metals in this passive, nonspecific role. 

The binding of ammonium and alkyl ammonium cations by [18] crown-6 and C-backbone substituted derivatives proceeds via three —H - 0 hydrogen bonds to give a perching complex, although... 

In these related compounds with simple cations such as alkali metals, NO, NOj or even tetra-alkyl ammonium cations, no cationic spectra exist in case of a mono-atomic cation, whereas a non-interfering spectra with that of the anionic spectrum is observed, in a different spectral region at much higher fiequencies, in case of polyatomic cation. 

Cryptophanes also readily bind and recognize suitable cations in organic solvents.The free energies of association, at 300 K in (CD2Cl2)2, between cryptophane-E and alkyl ammonium cations ranging in size... 

Miura, M. Yuzawa, S. Takeda. M. Takeda, M. Habata, Y. Tanase, T. Akabori, S. Syntheses of aromatic bridged cryptophanes and their complexing abilities with alkyl ammonium cations. Supramol. Chem. 1996, 8, 53-66. 

Heyda J, Lund M, Onfiak M, Slavicek P, Jungwirth P (2010) Reversed of Hofmeister ordering for pairing of NH4+ vs alkylated ammonium cations with hedide emions in water J Phys Chem B114 1084310852... 

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