Tetramethylammonium ions

In each case, the N atom is sp hybridized, with one lone pair of electrons and three o-bonds. A quaternary ammonium ion is a tetrahedral ion of the form R4N, where as many as three of the R groups (which may all be different) can be replaced by H atoms. For example, the tetramethylammonium ion, (CH3)4N+, and the trimethylammonium ion, (CH3)3NH+, are quaternary ammonium ions. The amino group, the parent functional group of amines, is —NH2. 

When Cs in Eq. (1) was replaced by tetramethylammonium ion, TMA, the positive limit of the amplitude shifted to more negative potentials and the amplitude decreased to be 0.28 V as compared to 0.40 V with Cs. Employing tetraethylammonium ion, TEA, instead of Cs+, the oscillation was not observed regardless of the magnitude of the applied current and the concentration of TEA+TPhB or TPA" TPhB . 

To further probe the phase behavior of hydrated Nafion, Rollet et al. used a contrast matching method in the SANS analysis of Nafion membranes neutralized with tetramethylammonium ions. With 12 hydrogen atoms per counterion, the N(CH3)4+ ions... 

The above speculation [21] may be extended to include the related quaternary ammonium compounds such as xylocholine (XXXIX). It is probable that the volumes of the guanidinium ion and the trimethylammonium group are similar. The ionic radius of the guanidinium ion (IX) is about 3A the ionic radius of the tetramethylammonium ion has been estimated [300] to be 3-4A, although rather smaller values have also been proposed [301-303]. Crystallographic analyses of muscarine iodide [304], choline chloride [305] and acetylcholine bromide [306] have revealed that the carbon to nitrogen distance is about l-SA, and that a hydrogen bond (C-H-0 distance 2-87-3 07A) exists in the crystals of these compounds. 

Ion Exchange and Pyrolysis. A typical specimen of zeolite 0 contains approximately eight cations per unit cell, of which about six are sodium ions, and the remaining two are tetramethylammonium ions. The positions of these ions within the zeolitic framework can be determined by x-ray structural studies or by ion-exchange experiments if the structure of the framework is known. 

PI6.4 The tetramethylammonium ion (Me4N+) has been reported to stabilize oligonucleotides. Marky et a/.20 have studied its effect on the helix-to-coil transition in poly(dA-dT). They compared their results with similar studies conducted in solutions containing the sodium ion of the same concentration. The results are summarized below ... 

L.A. Marky, D. Patel, and K. J. Breslauer, Effect of Tetramethylammonium Ion on the Helix-to-Coil Transition of Poly(deoxyadenylylthymidine) A Nuclear Magnetic Resonance and Calorimetric Investigation , Biochemistry, 20, 1427-1431 (1981). 

Ammonium cations may also be bound by cation s interactions by large cyclophanes such as 3.102 (calixarene-derivatives - see Section 3.14). The rigid, deep-cavity tetrahydroxy receptor 3.102a is able to selectively bind tetramethylammonium ions with Kn > 104 M 1 in chloroform solution,... 

We first describe the NMR parameters for the duplex to strand transition of the synthetic DNA poly(dA-dT) (18) with occasional reference to poly(dA-dU) (24) and poly(dA- brdU) and the corresponding synthetic RNA poly(A-U) (24). This is followed by a comparison of the NMR parameters of the synthetic DNA in the presence of 1 M Na ion and 1 M tetramethylammonium ion in an attempt to investigate the effect of counterion on the conformation and stability of DNA. We next outline structural and dynamical aspects of the complexes of poly(dA-dT) with the mutagen proflavine (25) and the anti-tumor agent daunomycin (26) which intercalate between base pairs and the peptide antibiotic netropsin (27) which binds in the groove of DNA. 

The tetramethylammonium ion appears to exhibit some specificity in its binding to poly(dA-dT) since the dTjsdA and dA dT resonances are partially resolved in the presence of this counterion. This specificity is probably also reflected in the selective glycosidic torsion angle change (monitored at one sugar H-l resonance) in the poly(dA-dT) duplex on proceeding from 1 M Na+ solution to 1 M TMA " solution. 

Contrary to the resonance stabilized triphenylmethyl-4), benzyl-5) and fluorenyl-anions 8, phenyllithium did not leave the tetramethylammonium ion unaffected. Instead, it removed a proton to form trimethylammonium-methylide (<5) 19), the prototype of that interesting class of zwitter-ionic compounds for which Wittig coined the name ylides 20). 

Effect of the Structure of Organic Quaternary Ammonium Ions. The tetramethylammonium ion (N C J ), first introduced in zeolite synthesis by Barrer and Denny (30), and Kerr and Kokotailo (21) is effective in forming the cubic octameric silicate anion (Sig02Q°, cubic octamer) (2-16). In the tetramethylammonium silicate aqueous solutions at higher S3.O2 concentrations or cation-to-silica molar ratios (abbreviated to the N/Si ratios), the cubic octamer is singularly formed. 

Electroinactive species — Ions and neutral compounds that show no signal in electrochemical measurements. In this sense, -> supporting electrolyte ions are electroinactive at least in the potential window. However, note that whether a species is electroactive or not should depend on the electrode used and measurement conditions. For example, tetramethylammonium ion is electroinactive at conventional electrodes, but electroactive at the interface between two immiscible electrolyte solutions, where it gives a voltammetric wave for transfer across the interface. 

Fig. 2.42. Orientational change of a water molecule in the first hydration shell of a tetramethylammonium ion (TMA ). (a) A water molecule in the first hydration shell is attached to the TMA ion by charge-electric dipole interaction, (b) Orientational change of a water molecule in the first hydration shell is complemented by formation of another hydrogen bond to an outer water molecule. (Reprinted from Y. Nagano, H. Mizuno, M. Sakiyama, T. Fujiwara, and Y. Kondo, J. Phys. Chem. 95 2536, 1991.)...

The examples we have chosen to focus upon are again from our own work. However, other studies of aqueous solution systems that have utilized SDFs in their analyses, including such examples as aqueous tetramethylammonium ion [71], trimethylamine-N-oxide and t-butyl alcohol [72]. 

Many of the amines have a fishy smell, and as early as 1851 trimethylamine was isolated by distillation of herring with lime and was called fish-gas . Methylamine CH3NH2 Ethylamine C2H5NH2 Phenylamine QH5NH2 Dimethylamine (CH,)2NH Methylethylamine (CH3)(C2H5)NH Trimethylamine (CH3)3N R Tetramethylammonium ion (CH3>4N ... 

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