Benzoate ion

Step 4 Proton transfer steps to yield ethanol and benzoate ion... 

Aromatic diacyl peroxides such as dibenzoyl peroxide (BPO) [94-36-0] may be used with promoters to lower the usehil decomposition temperatures of the peroxides, although usually with some sacrifice to radical generation efficiency. The most widely used promoter is dimethylaniline (DMA). The BPO—DMA combination is used for hardening (curing) of unsaturated polyester resin compositions, eg, body putty in auto repair kits. Here, the aromatic amine promoter attacks the BPO to initially form W-benzoyloxydimethylanilinium benzoate (ion pair) which subsequentiy decomposes at room temperature to form a benzoate ion, a dimethylaniline radical cation, and a benzoyloxy radical that, in turn, initiates the curing reaction (33) ... 

Sodium and potassium benzoate are employed in a wide range of preservative appHcations because they provide an effective combination of antimicrobial action, low cost, and safety. Although sodium and potassium benzoate are the preservatives offered in the marketplace, the actual active ingredient being sold is free (or undissociated) benzoic acid. The benzoate ion has essentially no antimicrobial properties. Since it is the undissociated (free) benzoic acid that provides the antimicrobial action, sodium benzoate and potassium benzoate are recommended for use in appHcation areas where the pH is at 4.5 or lower (Table 8). 

Sodium benzoate is also finding increasing appHcation as a corrosion inhibitor. It is incorporated into paper wrapping materials for the prevention of mst or corrosion in the production of such diverse items as razor blades, engine parts, bearings, etc. It is also used in the automotive industry as a corrosion inhibitor in engine cooling systems (at 1.5%), mainly in Europe and Japan. Unlike in its appHcation as a preservative where free benzoic acid is required to provide antimicrobial action, it appears to be the benzoate ion that provides the corrosion protection. 

An example of this reaction is the reaction of cyclohexene with t-butyl perbenzoate, which is mediated by Cu(I). " The initial step is the reductive cleavage of the perester. The t-butoxy radical then abstracts hydrogen from cyclohexene to give an allylic radical. The radical is oxidized by Cu(II) to the carbocation, which captures benzoate ion. The net effect is an allylic oxidation. 

Other corrosion inhibitors also enhance passivity without electrochemical reduction, by depositing insoluble oxidation products into the passivating film. For example benzoate ions cause deposition of ferric benzoate into the oxide, but do not provide any cathodic reaction. 

Participation in the electrode reactions The electrode reactions of corrosion involve the formation of adsorbed intermediate species with surface metal atoms, e.g. adsorbed hydrogen atoms in the hydrogen evolution reaction adsorbed (FeOH) in the anodic dissolution of iron . The presence of adsorbed inhibitors will interfere with the formation of these adsorbed intermediates, but the electrode processes may then proceed by alternative paths through intermediates containing the inhibitor. In these processes the inhibitor species act in a catalytic manner and remain unchanged. Such participation by the inhibitor is generally characterised by a change in the Tafel slope observed for the process. Studies of the anodic dissolution of iron in the presence of some inhibitors, e.g. halide ions , aniline and its derivatives , the benzoate ion and the furoate ion , have indicated that the adsorbed inhibitor I participates in the reaction, probably in the form of a complex of the type (Fe-/), or (Fe-OH-/), . The dissolution reaction proceeds less readily via the adsorbed inhibitor complexes than via (Fe-OH),js, and so anodic dissolution is inhibited and an increase in Tafel slope is observed for the reaction. 

Conversely, the adsorption of anions makes the potential more negative on the metal side of the electrical double layer and this will tend to accelerate the rate of discharge of hydrogen ions. This effect has been observed for the sulphosalicylate ion and the benzoate ion . 

Notice that [H+] is less than 10% of [C6H5COOH], verifying our assumption that very little of the acid reacted.) Now we know two of the concentrations in expression (43) and, to complete the calculation, we must know the concentration of benzoate ion, [CsHsCOO-]. Since the benzoic acid was dissolved in pure water, the only source of GHsCOO- is reaction (42). This is also the source of hydrogen ion, H+(aq). Since these two ions are both produced only by reaction (42), their concentrations must be equal in this solution. That is,... 

Sodium benzoate is a strong electrolyte its aqueous solutions contain sodium ions, Na+f ql, and benzoate ions, QHtCOO faqJ. Hence the equilibrium involved is the same as before ... 

First, let us assume that very little [H+] is Formed through dissociation of benzoic acid. This assumption implies that the concentrations of benzoate ion and benzoic acid are very little affected by reaction (42). Assuming this, we see that two of the concentrations in (39) are already specified ... 

The calculation cannot be considered complete until we check the assumption. Was it reasonable to assume that the concentrations of benzoate ion and benzoic acid were not changed by reaction (42)1 To decide, we compare the magnitude of [H+], 2.2 X 10 M, to the benzoate ion and benzoic acid concentrations. We find that [QHtCOOH] = 0.010 M is about 300 limes larger than the concentration change necessary to form 2.2 X 10- A3 H+. The same argument applies to [QH6COO ]. The assumption is valid. 

Urea possesses negligible basic properties (Kb = 1.5 x 10 l4), is soluble in water and its hydrolysis rate can be easily controlled. It hydrolyses rapidly at 90-100 °C, and hydrolysis can be quickly terminated at a desired pH by cooling the reaction mixture to room temperature. The use of a hydrolytic reagent alone does not result in the formation of a compact precipitate the physical character of the precipitate will be very much affected by the presence of certain anions. Thus in the precipitation of aluminium by the urea process, a dense precipitate is obtained in the presence of succinate, sulphate, formate, oxalate, and benzoate ions, but not in the presence of chloride, chlorate, perchlorate, nitrate, sulphate, chromate, and acetate ions. The preferred anion for the precipitation of aluminium is succinate. It would appear that the main function of the suitable anion is the formation of a basic salt which seems responsible for the production of a compact precipitate. The pH of the initial solution must be appropriately adjusted. 

Any strong acid that may be present is first neutralised. Then, by selecting an appropriate base, whose conjugate acid has a Ka of about 10 5, the equilibrium for the tripositive cations will be forced to the right the base is too weak, however, to remove the hydroxonium ions from the equilibrium of the dipositive cations. Since a large excess of the basic ion is added, a basic salt of the tripositive metal usually precipitates instead of the normal hydroxide. Acetate or benzoate ions (in the form of the sodium salts) are the most common bases that are employed for this procedure. The precipitation of basic salts may be combined with precipitation from homogeneous solution, and thus very satisfactory separations may be obtained. 

It lias also been suggested that photoexcited benzoyl peroxide is somewhat more susceptible to induced decomposition processes involving electron transfer than the ground state molecule. Rosenthal et c//.15 reported on redox reactions with certain salts (including benzoate ion) and neutral molecules (e.g. alcohols). 

Correlation analyses of this type have also been carried out in connection with the kinetics of the reaction of ortho-substituted benzoate ions with para-substituted phenacyl bromides164 and of ortho-substituted benzoate ions with ethyl bromoacetate165. In all cases it is possible to include 0-SO2Me among the basic set of well-behaved substituents. 

Self-Test 11.4B Calculate the ratio of the molarities of benzoate ions and benzoic acid (C6H,COOH) needed to buffer a solution at pH = 3.50. The pKa of C6H,COOH is 4.19. 

On the other hand, if substitutions of 37 were conducted with benzoate ions, instead of acetate ions, direct Sn2 reactions occurred predominantly, and carba-y -DL-mannopyranose pentaacetate (41) was obtained. ... 

As an alternative reaction process, nucleophilic substitution reactions of (1,3/2,4,6)-4-bromo-6-(bromomethyl)-l, 2,3-cyclohexanetriol triacetate (51) with benzoate ions furnished 49 in poor yield after exchange of the protective groups. ... 

Construct a table of initial concentrations, changes in concentration, and equilibrium concentrations for each species that appears in the equilibrium constant expression. The equilibrium concentrations from the last row of the table are needed to find Kgq. Start by entering the data given in the problem. The initial concentration of benzoic acid is 0.125 M. Pure water contains no benzoate ions and a negligible concentration of hydronium ions. The problem also states the equilibrium concentration of hydronium ions, 0.0028 M. 

The equilibrium constant has a small value (10 ). This suggests that we can make an approximation by assuming that the change required to reach equilibrium (x) is very small. This situation is like that shown in Figure 16-12a. As shown in the concentration table, the concentration of benzoate ion is (0.135 - Jt) M at equilibrium. Knowing that x is small, we make the approximation that x can be neglected relative to 0.135 ... 

Compared with esters, acid halides and anhydrides are more reactive and are hydrolyzed more readily. It is interesting to note that there is a substantial lifetime for these acid derivatives in aqueous media. Acid halides dissolved in PhCl or in PhBr shaken at a constant rate with water shows that hydrolysis occurs at the boundary between the two liquid phases.35 The reaction of benzoyl chloride (PhCOCl) and benzoate ion with pyridine A-oxide (PNO) as the inverse phase-transfer catalyst yields both the substitution product (benzoic anhydride) and the... 

Catalysis in Transacylation Reactions. The principal objective of the study was to evaluate 4 as an effective organic soluble lipophilic catalyst for transacylation reactions of carboxylic and phosphoric acid derivatives in aqueous and two-phase aqueous-organic solvent media. Indeed 4 catalyzes the conversion of benzoyl chloride to benzoic anhydride in well-stirred suspensions of CH2CI2 and 1.0 M aqueous NaHCC>3 (Equations 1-3). The results are summarized in Table 1 where yields of isolated acid, anhydride and recovered acid chloride are reported. The reaction is believed to involve formation of the poly(benzoyloxypyridinium) ion intermediate (5) in the organic phase (Equation 1) and 5 then quickly reacts with bicarbonate ion and/or hydroxide ion at the interphase to form benzoate ion (Equation 2 and 3). Apparently most of the benzoate ion is trapped by additional 5 in the organic layer or at the interphase to produce benzoic anhydride (Equation 4), an example of normal phase-... 

Generally, primary aliphatic alcohols are oxidized to their respective aldehydes, secondary aliphatic and aromatic alcohols to the corresponding ketones, and allyl and benzyl alcohols to their carboxylic acid or carboxylate ions. For instance, 2-propanol, acetaldehyde, and methyl-benzoate ions are oxidized quantitatively to acetone, acetate, and terephtalate ion respectively, while toluene is converted into benzoate ion with an 86% yield. Controlling the number of coulombs passed through the solution allows oxidation in good yield of benzyl alcohol to its aldehyde. For diols,502 some excellent selectivity has been reached by changing the experimental conditions such as pH, number of coulombs, and temperature. 

The molecular natures of salts crystallized from salbutamol base have been assessed by FT-Raman spectroscopy [66]. Variations in vibrational frequencies due to electron-withdrawing or -donating substituents were clearly evident the CCO stretching vibration shifted from 776 cm-1 in the free base to 756 cm-1 in the benzoate salt. The C=C stretching frequency also shifted from 1610 cm-1 to 1603 cm-1 with the benzoate ion but showed an increase to 1616 cm-1 with sulfate ion. Clearly, the choice of salt affects the molecular nature of the drug, with obvious implications for its physicochemical properties. 

Acetic acid is a weaker acid than benzoic acid since the Ka for acetic acid (1.8x10"5) is less than the Ka for benzoic acid (6.5 x 10 5). Therefore, when the relative base strengths of their conjugate bases are compared, the acetate ion, CH3COO , is a stronger base than the benzoate ion, CgHsCOO . In other words, a 0.12 M solution of the benzoate ion is more acidic (less basic) than a 0.12 M solution of the acetate ion. 

Based on empirical observation, a general statement about overtones and combination bands might be Overtones do occur, but they are very weak. Combination bands are seldom observed. Kirtley, for example, says that overtones are about a factor of 200 weaker than fundamentals in the case of the benzoate ion [47, 53]. Ramsier, Henriksen, and Gent identify a single clear overtone in the tunneling spectrum of the phosphite ion (HPO3 2) [54], The fundamental associated with... 

Although the reaction with thiosulfate and with iodide ions may be a mere reduction of the halide, the reaction with sodium benzoate would appear to be a radical dissociation induced by the attack of a negative ion. The fate of the benzoate ion is unknown. Tris-( -nitrophenyl)-methyl benzoate is a stable substance which does not dissociate into radicals.23... 

In photochemical reactions, the role of DBPO will undoubtedly be that of an electron acceptor from an excited state species, as shown in reaction (51). Thus, inverted spin trapping will be feasible and an unambiguous interpretation of the appearance of PhCOO—ST will be difficult. In HFP the very strongly attenuated reactivity of benzoate ion should, however, make the homolysis mechanism predominate, as indicated by the appearance of both PhCOO—ST and Ph-ST (ST = PBN or DMPO) in the photolysis of DBPO and ST (Eberson et al., 1996a). 

Recent studies of kinetic acidity involving nitrocarbon acids have included the following benzoate ion-promoted deprotonation of (3- or 4-nitrophenyl)nitromethane and (3,5-dinitrophenyl)nitromethane187 the deprotonation by various bases of a series of... 

Fig. 25. An example of an anaerobic food chain showing the formation of simple compounds from benzoate ion by a population of anaerobic bacteria and the subsequent utilization of the newly available substrate by a second anaerobic population (the methanogenic bacteria)...

---