Benzoic acid extraction procedure

On standing, diphenyldiazomethane decomposes to yield benzophenone azine. In one of the checkers runs the product was stored at room temperature after 2 days, crystals of the azine were visible. The product at this stage was assayed by treatment with benzoic acid addition of 6.8 g. of the diazo compound in a thin stream to a solution of 17 g. of benzoic acid in 90 ml. of ether, and, after 30 minutes, extraction of the excess benzoic acid with dilute sodium hydroxide followed by distillation of the ether, gave 7.4 g. (75%) of crude benzohydryl benzoate melting at 83-85°. In the same procedure the freshly prepared diazo compound gave a quantitative yield of the crude ester. 

There is a recent trend towards simultaneous CE separations of several classes of food additives. This has so far been applied to soft drinks and preserved fruits, but could also be used for other food products. An MEKC method was published (Lin et al., 2000) for simultaneous separation of intense sweeteners (dulcin, aspartame, saccharin and acesulfame K) and some preservatives (sorbic and benzoic acids, sodium dehydroacetate, methyl-, ethyl-, propyl- and isopropyl- p-hydroxybenzoates) in preserved fruits. Ion pair extraction and SPE cleanup were used prior to CE analysis. The average recovery of these various additives was 90% with good within-laboratory reproducibility of results. Another procedure was described by Frazier et al. (2000b) for separation of intense sweeteners, preservatives and colours as well as caffeine and caramel in soft drinks. Using the MEKC mode, separation was obtained in 15 min. The aqueous phase was 20 mM carbonate buffer at pH 9.5 and the micellar phase was 62 mM sodium dodecyl sulphate. A diode array detector was used for quantification in the range 190-600 nm, and limits of quantification of 0.01 mg/1 per analyte were reported. The authors observed that their procedure requires further validation for quantitative analysis. 

An exceptionally simple procedure was developed for the catalytic carbonylation of chloroarenes using [PdCl2(PCy3)] as catalyst. According to this method the neat chloroanene, e.g. m-chlorotoluene and the catalyst are stirred with 20 % (w/w) aqueous KOH at reflux temperature with bubbling CO. The benzoic acids are extracted from the aqueous phase after... 

Cleavage of phenacyl esters (typical procedure)f To a solution of NaHTe (prepared by heating powdered tellurium (1.28 g, 10 mmol) and NaBH4 (0.75 g. 15 mmol) under Nj in DMF at 80-90°C for 30 min, and then cooling at room temperature) is added a solution of phenacyl benzoate (1.92 g, 8 mmol) in DMF (30 mL). An instantaneous reaction takes place and the mixture is stirred at room temperature for 20 min. The solvent is evaporated and the mixture poured into H2O (100 mL) and fdtered to remove the tellurium. The basic filtrate is washed with ether and then the aqueous solution is acidified with 6 N HCl and extracted with ether (3x50 mL). The ether extract is dried (MgS04) and evaporated to give benzoic acid (1.11 g (91%) m.p. 121-122°C). 

Mannio and Cosio (78) described a sensitive, specific, and rapid chromatographic procedure to determine BA and SA in different food products. Benzoic acid and SA were extracted from foods by a microdialysis probe connected online to an HPLC column that allows separation of BA and SA. Detection was done at 228 and 260 nm for BA and SA, respectively. The procedure was linear from 1 to 80 ppm, with a detection limit of 1 ppm for SA and 2 ppm for BA. The assay was successfully applied to soft drinks, fruit juices, and dairy products (cheese, yogurt, and cream). 

One of the older methods used to detect the presence of preservatives in soft drinks and juices is thin-layer chromatography (Woidich el al., 1967). This provides a useful method to detect benzoic and sorbic acids as well as the substituted benzoic acids. The first stage involves the extraction of the preservatives with diethyl ether prior to their chromatographic separation on polyamide plates. Although it is difficult to use this procedure to quantify the level of these preservatives in a sample, it is not impossible. This approach can still be used today by a laboratory that does not have access to HPLC. 

Three spectrophotometric procedures are given in the AOAC compendium of methods (960.22, 962.13 and 967.11) for the analysis of caffeine, all of which have an extraction stage followed by a quantification procedure. There is also an HPLC method, discussed earlier, which was designed to measure saccharin, benzoic acid and caffeine at the same time (AOAC, 978.08). Again, the HPLC method, EN 12856 1999 (Anon, 1999a), can be used for the analysis of caffeine, but this analyte was not included in the collaborative study. 

Method. 4 ml of pyridine are added to a test-tube containing the steroid. This is followed by a three-fold molar excess of benzoyl chloride or p-nitrobenzoyl chloride (taking into consideration the number of hydroxyl substituents in the steroid). The mixture is shaken vigorously for 5 min and placed in a water bath at 80 °C for 15 min. The mixture is cooled and poured into a separating funnel containing 50 ml of 0.1 N hydrochloric acid and 50 ml of diethyl ether. The contents are shaken and the aqueous phase is removed. The separation procedure is repeated twice with fresh portions of acid. The diethyl-ether phase is neutralized by washing with distilled water and extracted with two 50-ml volumes of saturated sodium bicarbonate in order to remove excess of benzoic acid. After a final... 

There is no standard, universal, procedure for the Birch reduction. Experiment 7.19 illustrates some of the variants which have been reported in the literature. The original Birch procedure is to add small pieces of sodium metal to a solution of the aromatic compound in a mixture of liquid ammonia and the proton source (ethanol).18 After completion of the reaction, which is usually indicated by the disappearance of the blue colour, it is quenched by the addition of ammonium chloride and the ammonia allowed to evaporate before the cautious addition of water, and isolation of the product by ether extraction. In a modified procedure a co-solvent (ether, tetrahydrofuran, etc.) is initially added to the solution of aromatic compound/liquid ammonia prior to the addition of metal lithium metal is often used in place of sodium.19a,b In general these latter procedures are used for substrates which are more difficult to reduce. Redistilled liquid ammonia is found to be beneficial since the common contaminant iron, in collodial form or in the form of its salts, has a deleterious effect on the reaction.20 A representative selection of procedures is given in Expt 7.19 for the reduction of o-xylene, anisole, benzoic acid, and 3,4,5-trimethoxybenzoic acid. 

Amides may be hydrolysed by boiling with 10 per cent sodium hydroxide solution to the corresponding acid (as the sodium salt). The alkaline solution should be acidified with dilute hydrochloric acid the liberated acid if sparingly water-soluble is isolated by filtration, otherwise any water-soluble acidic component may be isolated by extraction with ether or by distillation from the acidic aqueous solution. The procedure is illustrated by the following experimental details for benzamide. Place 1.5 g of benzamide and 25 ml of 10 per cent sodium hydroxide solution in a 100-ml conical or round-bottomed flask equipped with a reflux condenser. Boil the mixture gently for 30 minutes ammonia is freely evolved. Detach the condenser and continue the boiling in the open flask for 3-4 minutes to expel the residual ammonia. Cool the solution in ice, and add concentrated hydrochloric acid until the mixture is strongly acid benzoic acid separates immediately. Leave the mixture in ice until cold, filter at the pump, wash with a little cold water and drain well. Recrystallise the benzoic acid from hot water. 

A new type of pyrrolizidine alkaloid has been isolated from the leaves of Ehretia aspera Willd. by Suri et al.n The structure (39) for ehretinine was established by spectroscopic evidence and by hydrolysis to give retronecanol and p-methoxy-benzoic acid. Confirmation of the structure (39) was obtained by synthesis of ehretinine from retronecanol and pmethoxybenzoyl chloride. This is the first reported occurrence of a retronecanol ester, although it should be pointed out that retronecanol esters can be produced by hydrogenolysis of retronecine diesters. The authors do not appear to have considered the possibility that ehretinine could have been formed by hydrogenolysis of the common type of ester (40) on treatment with the zinc and sulphuric acid that are used in their extraction procedure. 

This difference in acid—base chemistry can be used to separate benzoic acid and cyclohexanol by the stepwise extraction procedure illustrated in Figure 19.10. This extraction scheme relies on two ba.sic principles ... 

Separation of benzoic acid and cyclohexanol by an extraction procedure... 

How would you separate toluene (C6H5CH3), benzoic acid (CeHsCOOH), and aniline (CeH5NH2) by an extraction procedure ... 

A mixture of equal proportions of benzoic acid, 2-naphthol, and hydroqui-none dimethyl ether (1,4-dimethoxybenzene) is to be separated by extraction from ether. Note the detailed directions for extraction carefully. Prepare a flow sheet (see Fig. 2) for this sequence of operations. In the next experiment you will work out your own extraction procedure. 

Mota, F.J.M., Ferreira, I.M.P.L., Cunha, S.C., Beatriz, M., and Oliveira, PP 2003. Optimisation of extraction procedures for analysis of benzoic and sorbic acids in foodstuffs. Food Chemistry 82 469-473. 

In a dried vial 1 (2 equiv., 1 mmol), benzoic acid (0.025 equiv) and aldehyde (1 equiv., 0.5 mmol) were mixed and stirred at 20 °C. The reaction was quenched with water (2 mL) and the organic layer extracted in Et20 (3x5 mL). The crude product was desilylated by Kruger and Carreira s procedure and the resulting mixture purified by silica gel chromatography (eluent CHC13-Et20 9/1). 

Pyridine has also been used as the basic catalyst and chloride acceptor for benzoylation reactions. In one procedure, amines, volatile alcohols or thiols isolated by benzene extraction, are benzoylated with pyridine (1 ml) and benzoyl chloride (0.5 ml) by shaking intermittently at room temperature for several hours. The pyridine phase is extracted with 2 M HCl and the excess benzoyl chloride is hydrolysed with water for 12 hours. After shaking with 2 M sodium carbonate to remove benzoic acid, the benzene solution is dried and concentrated for analysis [144]. Aminoglycoside antibiotics are derivatized to the benzoyl derivatives in a similar reaction using 90 fi of pyridine and 10 /il of benzoyl chloride at 80 °C for 30 minutes. The pyridine is evaporated in a stream of nitrogen and excess benzoyl chloride is converted to methyl benzoate with methanol, again at 80°C, for 10 minutes. The product is cleaned up for analysis by a rather involved solvent extraction procedure [145]. 

In the experimental procedures that follow, three types of separations of neutral, acidic, and basic compounds are described. The first involves separating a mixture of benzoic acid (5) and naphthalene (7), using aqueous hydroxide for the extraction. The flow chart for this separation corresponds to that of Figure 5.1. The second procedure involves separating a mixture of 5,7, and 2-naphthol (11). In this case, 5 is first selectively removed from the solution by extraction with aqueous bicarbonate, which does not deprotonate 11. A second basic extraction using aqueous hydroxide removes 11 from the organic solution. The flow chart for this sequence is depicted in Figure 5.3. 

Purpose. This experiment illustrates the simultaneous oxidation and reduction of an aromatic aldehyde to form the corresponding benzoic acid and benzyl alcohol. The experiment further demonstrates the techniques for separation of a carboxylic acid from a neutral alcohol. For a detailed discussion of this extraction procedure, see Experiment [4C]. 

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