Bisulphate ion

The mechanism of the aromatic substitution may involve the attack of the dectrophilic NOj" " ion upon the nucleophilic aromatic nucleus to produce the carboniiim ion (I) the latter transfers a proton to the bisulphate ion, the most basic substance in the reaction mixture... 

In originally considering the 5 3 mechanism, involving base catalysis, Bennett, Brand, James, Saunders and Williams were trying to account for the small increase in nitrating power which accompanies the addition of water, up to about 10%, to sulphuric acid. The dilution increases the concentration of the bisulphate ion, which was believed to be the base involved (along with molecular sulphuric acid itself). The correct explanation of the effect has already been given ( 2.3.2). 

The kinetics of the Ce(IV) sulphate oxidation of oxalic acid are simple second order although the rate coefficient is inversely proportional to both hydrogen and bisulphate-ion concentrations, and it is also reduced at very high oxalic acid concentrations. Values of the activation energy from 13.4+1.5 (ref. 411) to 16.5+0.4 (ref. 409) kcal.mole have been reported. An intermediate has been detected spectroscopically " this decays in first-order fashion with E = 10.5+0.5 kcal.mole" and with a rate independent of acidity. However, the extent of formation of this complex is reduced as the acidity is increased ", and it appears that a less reactive dioxalato complex is formed at higher substrate concentrations ". 

When ion-exchange resin containing zirconium hydroxide comes into contact with acidic brine in the RNDS , zirconium hydroxide adsorbs bisulphate ions thus sulphate is removed from brine. For regeneration of the ion-exchange resin, a basic solution is supplied and when it comes into contact with the resin, sulphate desorption starts. 

In the operating commercial plant, columns are filled with ion-exchange resin containing zirconium hydroxide. Acidic brine is supplied to the column from the bottom, where bisulphate ions are adsorbed, by way of a fluidised bed arrangement, based on the equations ... 

Direct evidence that hydrolysis reactions going by the Aac1 mechanism are kinetically first-order can be obtained, at least in principle, for reactions in strongly acidic solution, because the activity of water varies significantly with the acid concentration. Graham and Hughes 7 showed that the hydrolysis of methyl benzoate in sulphuric acid at 20°C is first-order with respect to ester concentration, but zeroth-order with respect to water in concentrations up to 1 M. Leisten6 showed further that the first-order rate coefficient for this reaction is almost independent of the initial concentration of the ester, and thus ruled out the possibility that a bimolecular attack by bisulphate ion is involved, since the ester is completely protonated in 100% sulphuric acid and tfe concentration of bisulphate ion depends on the concentration of the ester, viz. 

In practice, the bisulphate ion, HS04, is a rather weak acid (pKa = 1.99 at 25°C), so that for the sulphuric acid concentrations used in practical cells, the reactions... 

Formerly the formation of persulphate was attributed to the polymerization of HS04 radicals, formed by the discharge of bisulphate ions ... 

The mechanisms of two other reactions described in Sect. 2.2 involve slow proton transfer to unsaturated carbon. The general acid catalysed cleavage of vinyl mercuric halides [42, 50] for example, allyl mercuric iodide, CH2=CHCH2HgI (XXII), gives Bronsted exponents around 0.7. Linear Bronsted plots are obtained with carboxylic acid catalysts but, as observed in other A—SE 2 reactions, general acids of different structural types (for example, hydronium ion or bisulphate ion) show substantial deviations. Bronsted catalysis of the hydrolysis of diazo compounds (N2 =CR X) has been studied by the groups of Albery and Kreevoy. With... 

Other Oxyanions of Sulphur. The effect of pressure on the dissociation of aqueous solutions of the bisulphate ion has been studied182 by measuring the Raman spectra of sulphate at 982 cm-1 and bisulphate at 1052 cm-1. An increase in the intensity of the sulphate peak was observed with increasing... 

Treatment of salt 24 with additional TPPP, however, generates a new species in addition to 24. The new species lacks the iminium proton signal at 9.3 ppm in the H NMR spectrum instead, a new signal at 6.35 ppm is visible. This new species is rather unstable and decomposes relatively quickly ( 30 min at 30 °C), but as soon as it is detectable, the addition of the alkene leads to immediate and very rapid epoxide formation. We have previously shown that TPPP does not itself promote epoxidation. Two possible structures for this intermediate may immediately be postulated, both arising from nucleophilic attack of peroxybisulphate at the iminium carbon atom a neutral intermediate 47, the product of simple addition, and the corresponding oxaziridium salt 48, produced by addition and cyclization with expulsion of bisulphate ion (Scheme 5.25). 

The major reactants are bromate (Br0 ) and malonic acid (CH2(COOH>2 = MA) They are used up slowly and monotonically. In IM sulphuric acid, hydrogen ions (H ) are present in great excess and buffered by the bisulphate ion (HSO ), so [H ] is not changed appreciably by the reaction. Cerium is a catalyst, that is, it facilitates the conversion of reactants to products without being itself transformed. 

In the reaction with hydroxylamine, under the same highly acidic conditions, the oxidation has been found to be first order in cobalt(m) and zero order in substrate, with a rate dependence on cobalt(n). Addition of bisulphate ions increases the rate, with the possibility of another reaction path involving the complex ion C0SO4+. 

Presence of HCl prevents precipitation of chromates, carbonates and phosphates which are insoluble in neutral solutions. Also the precipitate fanned in presence of HCl is coarse and consists of large crystals which are more readily filtrable. But excess of HCl should be avoided as solubility of BaS04 increases due to the fonnation of bisulphate ion ... 

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