Proton sodium acetate

In contrast to this, consider next a solution of sodium acetate. From vSec. 09 we know that in such a solution the thermal agitation raises a certain number of protons from the solvent molecules to the vacant proton levels of the (CH GOO) ions. In the aqueous solution of such a salt, this process is known as the hydrolysis of the salt and is traditionally regarded as a result of the self-ionization of the water. In Fig. 36, however, it is clear that in the proton transfer... 

Robertson et al.261 measured rates of bromination of some aromatic hydrocarbons in acetic acid containing sodium acetate (to eliminate protonation of the aromatic by liberated hydrogen bromide) and lithium bromide (to reduce the rate to a measurable velocity ) at 25 °C, the second-order rate coefficients for 3-nitro-N,N-dimethylaniline and anisole being 14.2 and 0.016 respectively the former compound was thus stated to be about 1012 times as reactive as benzene (though no measurement of the latter rate coefficient, inferred to be 1.33 xlO-11, could be found in the literature) and this large rate spread gives one further indication of the unreactive nature of the electrophile. Other rates relative to benzene were ... 

The fact that protons are released through complexation makes it sometimes possible to enhance the reaction and to improve the yield by adding a base (such as sodium acetate). 

Figure 12.1 Clearance of small-molecule impurities from process buffers in a formulated protein product. Trace A the NMR spectrum of a control sample containing a mixture of three components (succinate, tetraethylammonium, and tetramethylammonium) in the final formulation buffer (sodium acetate). These three components were used in the recovery process for a biopharmaceutical product. Traces B and D the proton NMR spectra of the formulated protein product. No TEA or TMA were detected, but a small amount of succinate was observed in this sample. Traces C and E the proton NMR spectra of a formulated protein product spiked with 10 jag/ml of succinate, TEA, and TMA. Traces D and E were recorded with CPMG spin-echo method to reduce the protein signals. The reduction of NMR signals from the protein allows for better observation of the small-molecule signals.

Von Runge and Triebs used a solution of dinitrogen pentoxide in chloroform for the N-nitration of both amides and imides. Solutions of dinitrogen pentoxide in chlorinated solvents are not neutral nitrating agents when amides and imides are nitrated - the presence of acidic N-H protons in these substrates leads to the formation of nitric acid. Sodium fluoride acts like a base towards nitric acid and so its addition to these reactions can increase product yield. Sodium acetate has been used for the same purpose during the nitration of n-butyl-V, V -dimethylurea. The effectiveness of dinitrogen pentoxide for the V-nitration of ureas is further illustrated by its use in the conversion of 2-imidazolidinone to N, V -dinitro-2-imidazolidinone in 90 % yield. In the presence of sodium fluoride the yield for this reaction exceeds 90 %. 

The isomer distribution obtained from the oxidation of mesitylene in acetic acid, sodium acetate depends on the anode material. Graphite strongly favours nuclear substitution to side chain substitution in the ratio 23 1 while at platinum this ratio is 4 1. Oxidation of methyl benzenes in acetic acid containing tetrabutykmmonium fluoroborate and no acetate ion gives benzyl acetate as the major product since loss of a proton from the radical-cation is now faster than nuclear substitution by acetic acid as the only nucleophile present [39]. 

Reduction of substituted nitrobenzenes under alkaline conditions, usually with aqueous sodium acetate as electrolyte and a nickel cathode, is the classical method due to Elbs [45] for the formation of azo- and azoxy-compounds. Protons are used in the electrochemical reaction so that the catholyte becomes alkaline and under these conditions, phenylhydroxylamine reacts rapidly with nitrosobenzene to form azoxybenzene. Finely divided copper has long been known to catalyse the reduction of nitrobenzene to aniline in alkaline solution at the expense of azoxybenzene production [46]. Modem work confirms that whereas reduction of nitrobenzene at polycrystalline copper in alkaline solution gives mainly azoxybenzene, if the electrode is pre-oxidised in alkaline solution and then reduced just prior to the addition of nitrobenzene, high yields of aniline are obtained with good current efficiency... 

When sodium acetate is dissolved in water the acetate ion behaves as a base removing protons from solution. For a weak electrolyte in water KbxKa = Kw. If a 0.1 M solution of sodium acetate in water is considered ... 

It is well documented that the isoimide is the kinetically favoured product and that isomerization yields the thermodynamically stable imide when sodium acetate is used as the catalyst. High catalyst concentrations provide maleimides with low isoimide impurity. The mechanism by which the chemical imidization is thought to occur is shown in Fig. 3. The first step in the dehydration reaction may be formation of the acetic acid-maleamic acid mixed anhydride. This species could lose acetic acid in one of the two ways. Path A involves participation by the neighboring amide carbonyl oxygen to eject acetate ion with simultaneous or subsequent loss of proton on nitrogen to form the isoimide. Path B involves loss of acetate ion assisted by the attack of nitrogen with simultaneous or subsequent loss of the proton on nitrogen to form the imide. If the cyclodehydration is run in acetic anhydride in the absence of the base catalyst, isoimide is the main reaction product. 

The simple furan-3(2/f)-ones exist in the keto form but may be O-acylated with acetic anhydride and sodium acetate however, they undergo C-alkylation. They are usually stable to acid, merely being protonated. 4-Alkoxyfuran-3(2//)-ones are readily hydrolyzed to tetronic acids. Furan-3(2//)-ones are degraded by aqueous base which attacks in a conjugate fashion so that 2,5-dimethylfuran-3(2iT)-one, readily available from biacetyl, furnishes acetate and acetoin, but compounds with an ester group at the 4-position furnish tetronic acids (Scheme 109). 

The electrochemical oxidation of 2,5-dimethylthiophene in various electrolytes has been investigated (71JOC3673). In non-halide electrolytes such as ammonium nitrate or sodium acetate, the primary anodic process is the oxidation of the thiophene to the cation-radical (159). Loss of a proton, followed by another oxidation and reaction with solvent methanol, leads to the product (160) (Scheme 31). When the electrolyte is methanolic NaCN, however, nuclear cyanation is observed in addition to side-chain methoxylation. Attack by cyanide ion on the cation-radical (159) can take place at either the 2- or the 3-position, leading to the products (161)-(163) (Scheme 32). 

Protonation represents the simplest electrophilic reaction. Contrary to azulene (pKa = — 1.7)237 most pseudoazulene systems are relatively strong bases. The pK.d values are listed in Table V. Numerous pseudoazulenes can be obtained from their quaternary salts by the action of sodium acetate (see... 

Effect of pH on the addition reactions was studied from pH 4 to 10. For pH values below 7, the reaction was buffered with a 25 mM sodium acetate solution whereas for pH values above 7, a 25 mM disodium tetraborate solution was used the pH was adjusted by adding either HC1 or NaOH. The combination electrode used for the determination of experimental pH, was calibrated with National Bureau of Standards (NBS) buffers for Milli-Q water (36) and tris(hydroxymethyl)aminomethane (TRIS) buffers for seawater (37) and NaCl solutions (38) on the pHF (free proton) scale. Since the addition of reactants caused a small pH change in the buffered medium, the experimental pH values shown in the results were measured after the reactants were added to reaction bottle. Samples from low pH reaction series were adjusted topH 9 by addition of a strong borate buffer just prior to HPLC analysis. Inis was necessary because thiol analysis using o-phthalaldehyde requires this pH for optimum derivatization. 

A salt containing at least one ion which is conjugate to a weak acid or base undergoes a reaction with water of an acid-base nature. Let us look at NaC2H302, a salt produced from a strong base, NaOH, and a weak acid, HC2H3O2. The acetate ion in sodium acetate is conjugate to the acetic acid, a weak acid. The acetate ion is a base and can accept a proton from an acid or from the solvent (water) ... 

Suppose we have a weak acid solution, and to this we add its sodium salt, such as acetic acid and sodium acetate. The pH of the acetic acid solution will increase because a common ion, acetate, shifts the equilibrium of acetic acid dissociation toward its undissociated form, thus removing protons from solution and making it more alkaline. We now have a mixture of a weak acid and its conjugate base. 

The increase in concentration of the acetate ions will drive the reaction to the left, which will further inhibit the dissociation of acetic acid. Adding hydrochloric acid will have the same effect because it will increase the concentration of protons, which will also drive the reaction to the left. Sodium acetate and hydrochloric acid have two features that allow them both to cause the common-ion effect to occur. First, they are both strong electrolytes, and second they each have an ion in common with the acetic acid equilibrium. These are the key ingredients that cause the common-ion effect. 

The acetic anhydride could be attacked by either the water, the acetate, or by aniline itself. Aniline is much more nucleophilic than the other two nucleophiles but only aniline itself can attack the anhydride protonated aniline has no lone pair and is not nucleophilic. This, then, is the role of the sodium acetate—to act as a base and deprotonate the aniline hydrochloride. The pKas of the aniline hydrochloride and acetic acid are about the same, around 4.7. An equilibrium will be set up to give some neutral aniline which will then attack the acetic anhydride and form the amide. 

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