Sulfonic ion-pairing

To determine secondary alkanesulfonates in sewage wastewaters, solid phase extraction (SPE) and a single-step procedure which combines elution and injection port derivatization for analysis with GC-MS were developed [36]. Again a tetrabutylammonium ion pair reagent was employed both to elute the secondary alkanesulfonates as their ion pairs from CI8-bonded silica disks and to derivatize sulfonate ion pairs under GC injection port conditions. Secondary alkanesulfonates were effectively recovered from samples of raw sewage (>92%) and from primary (>98%) and secondary (>85%) effluents. No... 

Crystal structures are available for many (N)4Co-amino acid complexes (Table I). Many of the diastereomers (AS, AS) in the bis-en series have been resolved using classic crystallization (usually via bromocamphor sulfonate, arsenyl-, or antimonyl-tartrate salts) or ion exchange methods (Table II). Reversed-phase ion-pair HPLC, using aryl phosphate or aryl/alkyl sulfonate ion pairing reagents in MeOH/ H20 eluent, has allowed diastereomer separations to be carried out on analytical amounts (28) (Table II). 

The value of 0.05 M from equation (7) is consistent with values of A as < 1 and ( /fes) < 1 for reactions in water. For example, = 0.3 gives (Jdjki ) = 0.17 for the relative rate constants for addition of solvent to the carbocation-anion pair and free carbocation. By comparison, the three-fold smaller rate constant for addition of water to an intramolecular trityl carbocation-sulfonate ion pair compared with addition to the analogous substituted trityl carbocation o-sulfonyl methyl ester has been used to estimate a value of (kjk ) = 0.33. " ... 

Catecholamines, nerve transmitters monitored in brain and heart patients, are separated on C18 using octane sulfonate ion pairing in 6% An/water (pH 3) with added EDTA and phosphate. Detection can be at UV, 270 nm, or by electrochemical detection at +0.72 V for maximum sensitivity. Other tyrosine and tryptophan metabolite neurotransmitters such as serotonin, VMA, and HMA can be analyzed with ion pairing and EC detection. 

Several mechanisms for the catalytic action of Cu(I) and Ag(I) have been considered6. Among these, the metal-assisted addition-elimination sequence shown in equation 85 and illustrated with cuprous triflate was deemed most consistent with various control studies. A mechanism not discussed but equally plausible is the metal-assisted MC sequence depicted in equation 86. The greater separation of iodonium-sulfonate ion pairs in acetonitrile versus benzene should provide the tosylate (or mesylate) ions with sufficient mobility to add to the /7-carbon atom of the alkynyliodonium ion. 

An ambident anion is one with different kinds of atoms which may become attached to a carbocation. Isomerization of the anionic portion permits detection of ion pair return in close analogy to the equilibration of 180 labeled benzoate or sulfonate esters. The isomerization of thiocyanates (112) to isothiocyanates (113) is the most studied of these ambident rearrangements 5, "6 In some respects these reactions differ from the return processes of carboxylate or sulfonate ion pairs ... 

These methods form an adjunct to reversed-phase chromatography and are based on the addition of compounds, e.g., sodium hexane sulfonate (ion-pair) or H (ion-suppression/ion-enhancement) to the mobile phase, which will influence the equilibrium... 

Issa YM, Badawy SS, El-Hawary WF, Ashour MS (1999) Cetyltrimethylammonium-selective PVC electrode based on its trinitrobenzene sulfonate ion-pair. Electroanalysis 11 1063-1067... 

Racemization, however, does not alwiys accompany isotopic scrambling. In the case of 5ec-butyl 4-bromobenzenesulfonate, isotopic scrambling occurs in trifluoroethanol solution witiiout any racemization. Two mechanisms are possible. Scrambling may involve an intimate ion pair in which the sulfonate can rotate with respect to the caibocation without allowing migration to die other face of the caibocation. The alternative is a concerted mechanism, which avoids a caibocation intermediate but violates the prohibition of front-side displacement. ... 

Because a neutral molecule is eliminate4 rather than an anion, there is no electrostatic attraction (ion pairing) between the products of the dissociation step. As a result, the carbocations generated by diazonium-ion decomposition frequently exhibit somewhat different behavior from those generated from halides or sulfonates under solvolytic conditions. ... 

In some cases the use of nitrosylsulfuric acid may be avoided if 1-naphthalenesul-fonic acid is added to moderately concentrated sulfuric acid (20-60%). This greatly reduces the evolution of nitrous fumes compared with a solution of pure sulfuric acid of the same hydrogen ion concentration. It has not yet been investigated whether the phenomenon is due to the formation of an ion pair, [C10H7 —SO NO+], or whether it is simply a solubility effect. In any case, the total acidity range of 4-12 m has thereby become available for diazotization technically crude sulfonation mixtures are used after dilution with water, for example, a solution of total acidity 4 m, of which 2.7 m is due to sulfuric acid. A further advantage of the method lies in the stabilizing effect of the naphthalenesulfonic acid on the diazonium compounds formed (see Sec. 2.3). 

The ion pair mechanism initially suggested by Darwish and McLaren28 (equation 2) has received further support from related studies conducted by several other investigators38-42. For example, Fava and coworkers38 have reported that during isomerization in acetic acid, optically active benzhydryl p-toluenesulfmate loses optical activity at a rate which is about two and a half times faster than the rate of sulfone formation, thus indicating that return from an ion-pair species is occurring (equation 3). 

Since the ratio of the two sulfones 2 and 3 increases with the polarity of the solvent (from 1 4 in benzene to 16 1 in formamide) a possible concerted [2,3]sigmatropic rearrangement for the formation of sulfone 3 was first considered. However, other evidence such as the effects of solvent and added salts seem to support an ionization mechanism, with the formation of the two sulfones by recombination from two different ion-pair species40. 

The evidence presented so far excludes the formation of dissociated ions as the principal precursor to sulfone, since such a mechanism would yield a mixture of two isomeric sulfones. Similarly, in the case of optically active ester a racemic product should be formed. The observed data are consistent with either an ion-pair mechanism or a more concerted cyclic intramolecular mechanism involving little change between the polarity of the ground state and transition state. Support for the second alternative was found from measurements of the substituent and solvent effects on the rate of reaction. 

An interesting sulfone to sulfinate rearrangement has been observed by Schank and Schmitt100 in the thermal fragmentation of a-alkoxysulfones, and is believed to involve an ion-pair mechanism (equation 32). 

Recently, a study of this rearrangement has been repeated and extended in order to determine the influence of a- and y-substitution on the position of the 68-69 equilibrium in the presence of silica, and the utility of this reaction for a novel and convenient synthesis of highly substituted a, / -unsaturated ketones, by subsequent treatment with CuCl2 in methanol-water136. An ion-pair mechanism can also be suggested for the facile rearrangement of sulfone 70 to 71, a key intermediate in the Hoffmann-La Roche Sulfone Route to Vitamin A137. 

The electron transfer reaction from fluorenyl carbanions adjacent to sulfoxide or sulfone (9) to fluorenone (FIO) has been studied by means of flash photolysis37. For n — 1 as well as n — 2 the transient F10T, M + (contact ion pair) appeared in THF and F10T(free ion)... 

Finally, ion chromatography can be used to determine the a-sulfo fatty acid esters. The chromatographic column is a nonpolar poly sty rene/divinylbenzene column and the ion pair reagent is 0.005 M ammonia. In order to reduce the elution time, acetonitrile is added as a modifier with increasing concentration. This gradient technique makes it possible to separate simultaneously ester sulfonates and disalts by chain length. Determination is achieved by standards with defined chain length [107]. 

An immersion time less than 1 min, the neutralization with ammonium hydroxide (it extracts the hydrogen from the sulfonic acid and leaves stabilized S03 NH4 ion pair), and the high concentration of the sulfuric acid (95 wt%) are essential to produce adequate effectiveness of the treatment. H2SO4 treatment increases the T-peel strength of treated TR or SBR-polyurethane adhesive joints (Figure 27.2). 

Polyphosphazenes sulfonates XIX with the anion covalently attached to the polymer are a new class of cation conductors that have been synthesized by Shriver [625]. They were obtained by reaction of Na0C2H4S03Na with an excess of polydichlorophosphazene in the presence of 15-crown-5, followed by the reaction of the partially substituted product with the sodium salt of poly(ethylene glycol methyl ether). The conductivity at 80 °C of the polymer with x=1.8, m=7.22 is 1.7x10 S cm This low conductivity can be attributed to an extensive ion pair formation between the sodium and sulfonate ions. 

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