Benzoate buffer

Benzoate can be used as an anodic inhibitor and is effective at preventing waterline attack. Phosphate is also sometimes included. Sodium borate (borax) is usually added to the formulation to provide an alkalinity reserve buffer. Typically, a copper inhibitor such as benzo-triazole (BTA) or tolyltriazole (TTA) also forms part of a formulation and is used to provide yellow metal (copper and brasses) protection. 

Sodium benzoate is used as a broad-spectrum antimicrobial, inhibiting bacteria, molds, and yeasts. The high acid content of the soft drink is necessary for the preservative action. Sodium citrate buffers the acids, so the pH stays low (acidic). It also emulsifies any fats or fat-soluble compounds in the flavorings, keeping them in solution. 

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. 

The feasibility of injecting benzoate to enhance the growth of BTX degraders and establish a buffer zone downgradient of a BTX plume was also investigated. 

Benzoates TBA Silanized silica PeOH + phosphate buffer 65... 

Reduction of 2-bromo-3-pentanone at mercury affords a mixture of 3-pentanone and l-hydroxy-3-pentanone, whereas electrolysis of Q ,Q -dibromoacetone in the presence of benzoate gives a mixture of products arising from both a carbon-bromine bond cleavage and an Sn2 displacement of bromide by benzoate [94]. In an acetic acid-acetate buffer, branched dibromo ketones, such as 2,4-dibromo-2,4-dimethyl-3-pentanone, are reduced to a-acetoxy ketones however, less highly substituted compounds, such as 4,6-dibromo-5-nonanone, undergo simple cleavage of both carbon-bromine bonds [95]. Other work dealing with the reduction of Q, Q -dibromoketones has been described [96]. 

A buffer solution is prepared by dissolving 1.80 g of benzoic acid, CeHsCOOH, and 1.95 g of sodium benzoate, NaCeHsCOO, in 800 mL of water. Calculate the pH of the buffer solution. 

FIGURE 8 Analysis of the test mixture with (A) the SDS MEKC system containing 10 mM phosphate buffer (pH 7.5), 60 mM SDS, and 10% acetonitrile and (B) the CTAB MEKC system containing 25 mM phosphate buffer (pH 7.5), 10 mM CTAB, and 10% acetonitrile. Peaks I formamide 2 pyridine 3 aniline 4 meta-cresol 5 phenyl acetate 6 nitrobenzene 7 benzoic acid 8 thiamine 9 ethyl benzoate. (Reprinted from reference 270, with permission.)... 

Buffer catalysis is observed in the intramolecular tranesterification of ethyl 2-hydroxymethyl benzoate to phthalide [equation (24)] (Fife and Benjamin, 1973). There is general base catalysis by... 

Figure 25-12 Isocratic HPLC separation of a mixture of aromatic compounds at 1.0 mL/min on a 0.46 x 25 cm Hypersil ODS column (C,8 on 5-jxm silica) at ambient temperature ( 22 C) (1) benzyl alcohol (2) phenol (3) 3, 4 -dimethoxyacetophenone (4) benzoin (5) ethyl benzoate (6) toluene (7) 2,6-dimethoxytoluene (8) o-methoxybiphenyl. Eluent consisted ot aqueous buffer (designated A) and acetonitrile (designated B). The notation 90% B in the first chromatogram means 10 vol% A and 90 vol% B. The buffer contained 25 mM KH2P04 plus 0.1 g/L sodium azide adjusted to pH 3.5 with HCI.

After reaction of 6-14C-DON with glutaminase, glutamic acid (1 equivalent) and I4C-methanol (0.75 equivalent) were isolated from the reaction mixture. The initial product formed from the C-6 atom appears to be diazomethane Ha). If relatively high concentrations of a benzoic acid-benzoate buffer are included in the reaction mixture, labeled methyl benzoate is formed in addition to the methanol. Further, the relative... 

Reverse-phase chromatography has been used extensively for the determination of saccharin. Smyly et al. (30) and Eng et al. (39) used /rBondapak Cl 8 and 5% acetic acid for the determination of saccharin. Based on this work, an Association of Official Analytical Chemists (AOAC) collaborative study was conducted, and the method using a mobile phase buffered to pH 3 with sodium acetate and modified with 3% isopropanol was adopted. Webb and Beckman (61) used this method successfully for the separation of saccharin from aspartame, caffeine, sodium benzoate, and artificial colors and flavors. Veerabhadrarao et al. (27) added methanol to the mobile phase (methanol acetic acid water, 4 1 1, v/v) for improved separation of saccharin from caffeine, benzoic and p-hydroxybenzoic acids, vanillin, aspartame, acesulfame-K, and dulcin. Saccharin was also determined using LiChrosorb Cl8 and 4 6 v/v methanol phosphate buffer,... 

Nitrite is usually formulated with TTA (yellow metal protection) and borax (to provide a buffered pH of 8.0 or greater). Sometimes nitrite is formulated with benzoate, an anodic inhibitor effective at preventing waterline attack, or silicates or molybdates, to provide synergistic inhibition and to reduce corrosion risks with softer waters and multimetal systems. 

In other studies, analysis of the products of reaction between formaldehyde and guanosine at moderate pH shows a new adduct—formed by condensing two molecules of each reactant—which has implications for the mechanism of DNA cross-linking by formaldehyde,17 while the kinetics of the mutarotation of N-(/ -chlorophcnyl)-//-D-glucopyranosylamine have been measured in methanolic benzoate buffers.18 For a stereoselective aldol reaction of a ketene acetal, see the next section. 

In a second report on the cyclen analogue 34, binding of lactate to the Tb(III) complex was found to be aided by the presence of the aza-crown when compared to the TbD03A control. Studies of 34 with benzoate and salicylate in buffered solutions at pH 7.4 showed luminescence enhancements of 12-fold (log ft = 2.9) and 135-fold (log f) = 3.9), respectively. When compared to Tb D03A, with luminescence enhancements of only 14-fold (log ft = 2.7)... 

Ribose may be identified through the benzimidazole from ribonic acid, 2-(D-n6o-tetrahydroxybutyl)benzimidazole52 53 54 and its picrate and hydrochloride. However, caution must be used at two points in this procedure. In the first place, the customary oxidation of ribose with alkaline hypoiodite produces both ribonic and arabonic acids, the latter being formed by the alkali-induced epimerization of the former. While this epimerization may be avoided by using a buffered oxidizing mixture such as bromine-barium benzoate,65 there is, in the second place, further risk of epimerization during the condensation of the aldonic acid with o-phenylenediamine, particularly if there is insufficient acid present.9 10-11... 

D-ribonate. In critical cases, such as the study of a mixture in which the presence of small quantities of D-arabinose is being considered, oxidation with bromine and a barium benzoate buffer according to Hudson and Isbell27 may be substituted, even though the procedure becomes more complicated if one wishes to fractionate the aldonic acids through their potassium and barium salts. While other examples of epimerization under these alkaline conditions have not been reported, the possibility of such rearrangements must always be kept in mind. 

If the hydrolysis of methyl orthobenzoate in weakly acidic solution is carried out in the presence of various amounts of added nucleophiles, such as hydroxylamine or semicarbazide, a considerable fraction of the orthoester is transformed to the product of the reaction with the amine rather than to methyl benzoate, while the rate coefficient remains unchanged [183]. Similarly, the rate of hydrolysis of ethyl orthocarbonate in aqueous cacodylic acid buffer is the same in the presence of 0.04 M NaC104 and of 0.04 M Nal [192]. Thus, nucleophilic catalysis is absent even under conditions when general acid catalysis is effective. 

Hudson and Isbell developed the buffering action further. Calcium or barium benzoate was employed to maintain the oxidation solution at a pH of 5-6, and the reaction mixture was kept in the dark. Lactose was converted to lactobionic acid without hydrolysis, and 96 and 90% yields of calcium D-gluconate and cadmium D-xylonate-cadmium bromide were reported by the use of this method. Isbell and Pigman developed this method later into a valuable tool for the study of the mechanism of bromine oxidation and for the study of the structure of various aldoses (see pages 171, 182). 

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