Titration with benzoic acid

Methyll ithium was purchased from Aldrich Chemical Company, Inc., and standardized by double titration with benzoic acid in aqueous ethanol and with allyl chloride. ... 

After the solution has been cooled in an ice bath, 120 ml. of the ethereal solution containing 0.039 mole of diazomethane is added, the flask is stoppered loosely with a cork, and the reaction mixture is stirred vigorously at 0° for one hour. The lower deuterium oxide layer is removed with a pipette and a fresh 11-ml. portion of the sodium deuteroxide solution is added. This mixture is then stirred for one hour at 0°, and the process is repeated until a total of four exchanges have been performed. The ethereal diazomethane solution is then decanted into a clean, dry 250-ml. Erlenmeyer flask and dried over 10 g. of anhydrous sodium carbonate. The resulting solution (approximately 110 ml.) contains (spectrophotometric analysis, Note 4, or titration with benzoic acid, Note 3) 0.020-0.022 mole (51-56%) of dideuteriodiazomethane which is 98-99% deuter-ated (Note 6). 

Figure 3. Values of H0 for alkaline earth metal oxides titrated with benzoic acid in benzene, using nitroaniline indicators. Key a, MgO b, CaO and c, SiO. (Reproduced, with permission, from Ref. 11.

Solutions of diazomethane in ether were titrated with benzoic acid. 

Sodium hydroxide pellets (3.98 g, 100 mmol) are dissolved in CO2/O2-free water ( 300 ml) and stored under nitrogen. The NaOH solution is titrated with benzoic acid as a standard using phenolphthalein as the indicator. 

When acid inidicator is added the colour of the indicator changes to that of its conjugate base. It is titrated with benzoic acid of O.OIM in dry benzene to restore its original acidic colour. In the present study six acid indicators of varying pKa were used and these are given in Table 2. 

Basic properties of alkaline earth oxides have been measured by different methods such as titration with benzoic acid, adsorption of CO2, and others. Basicity distributions measured by the titration of outgassed samples of MgO, CaO and SrO are shown in Fig. 3.5. Magnesium oxide and CaO possess base sites stronger than H =26. 

Preparation of TMPMgCI LiCI (64) A dried and argon-flushed 2 L 5c/i/e -flask, equipped with a magnetic stirring bar and rubber septum, was charged with /-PrMgCl LiCl (1.31 M in THF, 850 mL, 1.11 mol). Then, 2,2,6,6-tetramethylpiperidine (161 g, 194 mL, 1.14 mol, 1.02 equiv.) was added at once and the mixture was stirred until gas evolution ceases (48 h). Titration with benzoic acid using 4-(phenylazo)diphenylamine as indicator prior to use showed a concentration of 1.15 M. 

Of great interest is the study of Gur yanova and Beskina74 on dielectrometric and cryoscopic titrations of benzoic acids in benzene with amines they concluded that benzoic acid reacts as a dimer (HX)2 yielding with primary and... 

In the titration of benzoic acid with TMG, the inflection point at halfneutralization agrees, as mentioned previously for carboxylic acids in general with a complex B(HX)2. 

More detailed information on the reaction course of the three-step functionalization of an HHPA polyesteramide resin was obtained by functionalization with benzoic acid, after the polycondensation step. The reaction proceedings were monitored by multiple detector GPC (UV/RI) and titration. In the UV detector of the GPC the absorption of the aromatic acid is very dominant over the ahphatic resin itself, so that differentiation between free benzoic acid and benzoate-functionalized resin is feasible. It was observed that the titrated total acid concentration decreased much slower than the amount of free benzoic acid (Fig. 11). 

Ageneraiized, weighted, noniinear ieast squares procedure is deveioped, based on pH titration data, for the refinement of octanoi-water partition coefficients (iog P) and ionization constants (pKa) of multiprotic substances. Ion-pair partition reactions, self-association reactions forming oligomers, and formations of mixed-substance complexes can be treated with this procedure. The procedure allows for CO2 corrections in instances where the base titrant may have CO2 as an impurity. Optionally, the substance purity and the titrant strength may be treated as adjustable parameters. The partial differentiation in the Gauss-Newton refinement procedure is based on newly derived analytical expressions. The new procedure was experimentally demonstrated with benzoic acid, 1-benzylimidazole, (+)-propranolol, and mellitic acid (benzenehexacarboxylic acid, AH6). 

Specific surface areas of the catalysts used were determined by nitrogen adsorption (77.4 K) employing the BET method with Sorptomatic 1900 (Carlo-Erba). X-ray diffraction (XRD) patterns of powdered catalysts were carried out on a Siemens D5(K) (0/26) diffractometer with Cu Ko monochromatic radiation. The total amount of surface basic sites was determined via surface titration by benzoic acid from dry hexane solution as reported elsewhere [14]. Before the titration catalyst samples were dried at 300°C for 2 hours. 

The deprotection process illustrated in Figs. 5 and 6 was followed by solid-state CP/MAS NMR spectroscopy. As illustrated in Fig. 7, the carbonyl (158.2 ppm), aromatic (128.2 and 137.4 ppm), and benzylic (67.4 ppm) resonances decreased due to cleavage of those functional groups by the carbamate deprotection. However, the propyl tether resonances at 10.5, 23.1, and 43.2 ppm remained intact (Fig. 7b). Incomplete hydrolysis left a small amount of residual ethoxy moieties at 54.1 and 17.5 ppm. The degree of deprotection achieved in the material resulted in an amine number density of approximately 0.25mmol/g, as ascertained by nonaqueous titration of the amines with benzoic acid [42]. 

Reference to Tables 2.2 and 2.3 on p. lb and n will confirm that there is no difference in the lesults obtained (in 0 01 molai solutions) for benzoic acid when titrated with sodium hydroxide or for sodium benzoate when titrated with hydrochloric acid. The latter method, which is essentially the titiation of an anion, is advantageous for spaiingl) stduble acids which ma> decompose when heated to effect dissolution these should be dissolved in exacth 1 mole equivalent of cold sodium hydroxide so that the... 

To determine the exact diazomethane content, allow an aliquot portion of the ethereal diazomethane solution to react with an accurately weighed amount (say, about 1 g.) of A. R. benzoic acid in 60 ml. of anhydrous ether. The solution should be completely decolourised, thus showing that the benzoic acid is present in excess. Dilute the solution with water and titrate the excess of benzoic acid with standard 0 IN alkali using phenolphthalein as indicator. 

An alcohol-free solution of diazomethane in ether is prepared as in Chapter 17, Section III. This solution is approximately 0.5 M in diazomethane and may be standardized by titration as follows benzoic acid (0.6 g, approx. 0.005 mole) is weighed accurately into an Erlenmeyer flask and suspended in 5 ml of ether. The diazomethane solution (approx. 5 ml) is added from a buret with swirling, care being taken that an excess of unreacted benzoic acid remains (the yellow color of the diazomethane should be completely discharged). The excess benzoic acid is now titrated with standard 0.2 N sodium hydroxide solution, and the concentration of diazomethane is calculated. 

Benzoic acid is sparingly soluble in water (which is a disadvantage) and must therefore be dissolved in 95 per cent ethanol. The mode of use is similar to that already described for potassium hydrogenphthalate (Section 10.27, Procedure B). For a 0.1 M solution, of, say, sodium hydroxide, weigh out accurately 0.4 g portions of the acid into a 250 mL conical flask, add 10- 20 mL of ethanol, shake until dissolved, and then titrate the solution with the strong alkali using phenolphthalein as indicator. A blank test should be made with the same volume of ethanol and the indicator deduct, if necessary, the volume of the alkali solution consumed in the blank test. 

The theory of titrations between weak acids and strong bases is dealt with in Section 10.13, and is usually applicable to both monoprotic and polyprotic acids (Section 10.16). But for determinations carried out in aqueous solutions it is not normally possible to differentiate easily between the end points for the individual carboxylic acid groups in diprotic acids, such as succinic acid, as the dissociation constants are too close together. In these cases the end points for titrations with sodium hydroxide correspond to neutralisation of all the acidic groups. As some organic acids can be obtained in very high states of purity, sufficiently sharp end points can be obtained to justify their use as standards, e.g. benzoic acid and succinic acid (Section 10.28). The titration procedure described in this section can be used to determine the relative molecular mass (R.M.M.) of a pure carboxylic acid (if the number of acidic groups is known) or the purity of an acid of known R.M.M. 

Dissolve 20 g of tetra-n-butylammonium iodide in 100 mL of dry methanol and pass this solution through the column at a rate of about 5 mL min - L the effluent must be collected in a vessel fitted with a Carbosorb guard tube to protect it from atmospheric carbon dioxide. Then pass 200 mL of dry methanol through the column. Standardise the methanolic solution by carrying out a potentiometric titration of an accurately weighed portion (about 0.3 g) of benzoic acid. Calculate the molarity of the solution and add sufficient dry methanol to make it approximately 0.1M. 

In the case of an acid HX titrated with a quarternary ammonium base R4NOH there are a few complications as a consequence of some additional equilibrium constants and of a certain degree of instability of the titrant tetramethylammonium hydroxide (TMAOH) in pyridine for this reason the titrant solution was standardized against benzoic acid and used only on the day of preparation. Now, in addition to KHX and ifHX > we had to deal with... 

The substance is hydrolysed by boiling under reflux with 50 per cent sulphuric acid and the acetic acid or benzoic acid produced is distilled in steam and titrated with sodium hydroxide solution, using phenolphthalein as indicator. 

Determination of the Diazomethane Content of Solutions (according to Marshall and Acree, Ber., 1910,43, 2324).—An aliquot portion of the solution (about one-twentieth) diluted with absolute ether is run with shaking into an ice-cooled 0-2 N ethereal solution of benzoic acid. This latter solution, which must contain an excess of acid with respect to the diazomethane, is prepared by dissolving 1-22 g. of purest benzoic acid in absolute ether in a 50 c.c. measuring flask. The presence of an excess of acid is proved by the continued evolution of nitrogen, until the last portions of diazomethane have been added, when the solution should remain colourless. The excess of benzoic acid is titrated with 0-1 A-sodium hydroxide solution. 

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