Anion Hydration Studies

On cation exchangers (sulfonic acid-type and carboxylic acid-type), a value of = 0.0089 cm. i was observed, corresponding to the hydrated Mn(H20)6++. The effect of axial symmetry (D 9 0) was observed as evidenced by a fine structure in the hyperfine lines. A value of D however was not determined. The EPR spectrum of Mn++ on an anion exchanger studied consisted of a single unresolved broad line. A smaller A value and larger... 

Proton or sometimes alkali metal cations are used for countertransport of cationic or cotransport of anionic solutes because of their good transport properties. It is not the case with the coupling anions. In fact, for K+ transport by 18-crown-6 in a BLM, the anion effect differs by more than 100 [96]. Many studies of the anion effect on transport efficiency have been conducted [97-100]. The effects of anion hydration free energy, anion lipophilicity, and anion interactions with solvents have been mentioned, although anion hydration free energy seems to be the major determinant of transport efficiency. For example, transport of K+ with dibenzo-18-crown-6 as a carrier, decreased in the order picrate > PFr, > CIO > IO >... 

Only nuclei with a net nuclear spin will give a signal. However, this is no problem for hydration studies since it is the chemical shift of the proton, H, signal of H2O which is being measured. In certain cases the signal from in Hj O is used. In a solution the O atom is the atom closest to the cation and the H atom is the one closest to an anion. Essentially the experiment looks at the environment of the atom whose resonance is being studied. In an electrolyte solution there are three species of interest the solvated cation, the solvated anion and bulk water. Coordinated water will exchange with secondary solvation of the ion under study, with the primary and secondary solvation of the counter ion and with the bulk water. 

Although catalytic hydration of ethylene oxide to maximize ethylene glycol production has been studied by a number of companies with numerous materials patented as catalysts, there has been no reported industrial manufacture of ethylene glycol via catalytic ethylene oxide hydrolysis. Studied catalysts include sulfonic acids, carboxyUc acids and salts, cation-exchange resins, acidic zeoHtes, haUdes, anion-exchange resins, metals, metal oxides, and metal salts (21—26). Carbon dioxide as a cocatalyst with many of the same materials has also received extensive study. 

These hydrated salts contain bidentate carbonate ligands and no water molecules are bound directly to the central metal atom. The only single-crystal x-ray diffraction studies available are those for salts of (4) (52—54) and the mineral tuliokite [128706 2-3], Na2BaTh(C03)2 -6H20], which contains the unusual Th(C02) 2 anion (5) (55). 

Hydrated forms of the hydroxide ion have been much less well characterized though the monohydrate [H302] has been discovered in the mixed salt Na2[NEt3Me][Cr PhC(S)=N-(0) 3]. NaH302.18H20 which formed when [NEt3Me]I was added to a solution of tris(thiobenzohydroximato)chromate(III) in aqueous NaOH. ° The compound tended to lose water at room temperature but an X-ray study identified the centro-symmetric [HO-H-OH] anion shown in Fig. 14.15. The central O-H-O bond is very short indeed (229 pm) and is... 

In 2-hydroxy-l,3,8-triazanaphthalene (the only l,3,x-triazanaph-thalene with an acidic function that has been studied) the percentage of the hydrated species in the neutral molecule and in the anion was found to be 90 and 6, respectively. 

Fig. 8.9 Possible mechanisms of the bioluminescence reaction of dinoflagellate luciferin, based on the results of the model study (Stojanovic and Kishi, 1994b Stojanovic, 1995). The luciferin might react with molecular oxygen to form the luciferin radical cation and superoxide radical anion (A), and the latter deproto-nates the radical cation at C.132 to form (B). The collapse of the radical pair might yield the excited state of the peroxide (C). Alternatively, luciferin might be directly oxygenated to give C, and C rearranges to give the excited state of the hydrate (D) by the CIEEL mechanism. Both C and D can be the light emitter.

ESR experiments employing in situ photolytic decomposition of the peroxydisulfate anion (S20g ) have been carried out to study the reaction of S04 with aliphatic sulfoxides. In the case of dimethyl sulfoxide three radicals are detected ( CHj, CH3 S02, CH2 S(0)CH3), the proportion being pH-dependent. The reaction is assumed to proceed via an initially formed radical cation (not detected) which would be rapidly hydrated to give an intermediate identical with that generated by OH addition on the sulfoxide. Such a process parallels the rapid hydration of radical cations formed from thiophene in their reactions with SO/ and... 

The monoketone bis(2,2, /V,/V -bipyridyl)ketone forms a [CoinL2]+ complex on reaction with [Co(NH3)4(C03)]+ in water.981 As reported for a quite different Co11 complex, the ketone is hydrated to form the gem diol which binds as a monodeprotonated O-donor along with the two pyridine groups in a tridentate chelate, with very little distortion from octahedral observed in the complex. This appears to represent a facile route for this type of inherently poor donor to achieve coordination. Chelated /3-diketonate anions are long-studied examples of O-donor chelates, and continue to be examined. A simple example is the m-[Co(acac)2(NH 3)2]1 (acac = 2,4-pentane-dionate), structurally characterized and utilized to produce molecular mechanics force field parameters for /3-diketones bound to Co111.982... 

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