IV-Phenylanthranilic acid

In a 1 litre round-bottomed flask, equipped with an air condenser, place a mixture of 44 g. of o-chlorobenzoic acid (Section IV,157) (1), 156 g. (153 ml.) of redistilled aniline, 41 g. of anhydrous potassium carbonate and 1 g. of cupric oxide. Reflux the mixture in an oil bath for 2 hours. Allow to cool. Remove the excess of aniline by steam distillation and add 20 g. of decolourising carbon to the brown residual solution. Boil the mixture for 15 minutes, and filter at the pump. Add the filtrate with stirring to a mixture of 30 ml. of concentrated hydrochloric acid and 60 ml. of water, and allow to cool. Filter off the precipitated acid with suction, and dry to constant weight upon filter paper in the air. The yield of iV-phenylanthranilic acid, m.p. 181-182° (capillary tube placed in preheated bath at 170°), is 50 g. This acid is pure enough for most purposes. It may be recrystaUised as follows dissolve 5 g. of the acid in either 25 ml. of alcohol or in 10 ml. of acetic acid, and add 5 ml. of hot water m.p. 182-183°. 

In a 500-cc. round-bottomed flask fitted with a water-cooled toiulenser, 50 g. (0.23 mole) of iV-phenylanthranilic acid (Org. Syn. 19, 6) [or 46 g. acridone (Org. Syn. 19, 7)] is mixed with WiO cc. (270 g., 1.76 moles) of phosphorus oxychloride (Note 1). The mixture is slowly heated (about fifteen minutes) to 85-90° on a water bath. A vigorous reaction sets in, and the flask is removed at once from the hot bath. If the reaction becomes too violent, I lie llask is immersed in a beaker of cold water for a moment. After live to ten minutes, when the boiling subsides somewhat, I lie llask is immersed in an oil bath. The temperature of the bath is then raised to 135-140°, where it is maintained for two hours. The excess phosphorus oxychloride is removed by distillation I mm an oil hath at 140 150° under a vacuum of about 50 mm. The residue, after cooling, is poured into a well-stirred mixture of... 

The fV-phenylanthranilic acid may be used without recrystallization if it has been prepared from purified o-chlorobenzoic acid. If not, the crude iV-phenylanthranilic acid must be submitted to the decolorizing treatment described in Note 4, as otherwise a greenish acridone is obtained, which, however, has the same melting point. 

The practical methods of preparation of iV-phenylanthranilic acid are the action of aniline on o-chloro- or o-bromobenzoic acid, or the action of bromobenzene on anthranilic acid, using copper or its salts in both instances. 

If iV-phenylanthranilic acid is used in place of diphenylamine, a good yield of the iV,Af-diphenylanthranilic acid is obtained 540 and the monophenyl derivative itself can be obtained by an Ullmann reaction from o-chlorobenzoic acid in about 90% yield.538,541... 

IV-Phenylanthranilic acid (52) reveals dual reactivity upon the rhodium-catalyzed annulation (Scheme 25.29) [24]. Under conditions similar to those in Scheme 25.28... 

Internal indicators suitable for use with cerium(IV) sulphate solutions include AT-phenylanthranilic acid, ferroin [1,10-phenanthroline iron(II)], and 5,6-dimethylferroin. 

Method A Standardisation with arsenic (III) oxide. Discussion. The most trustworthy method for standardising cerium(IV) sulphate solutions is with pure arsenic(III) oxide. The reaction between cerium(IV) sulphate solution and arsenic(III) oxide is very slow at the ambient temperature it is necessary to add a trace of osmium tetroxide as catalyst. The arsenic(III) oxide is dissolved in sodium hydroxide solution, the solution acidified with dilute sulphuric acid, and after adding 2 drops of an osmic acid solution prepared by dissolving 0.1 g osmium tetroxide in 40mL of 0.05M sulphuric acid, and the indicator (1-2 drops ferroin or 0.5 mL /V-phenylanthranilic acid), it is titrated with the cerium(IV) sulphate solution to the first sharp colour change orange-red to very pale blue or yellowish-green to purple respectively. 

Procedure. Weigh out accurately about 0.2 g of arsenic(III) oxide, previously dried at 105-110 °C for 1-2 hours, and transfer to a 500 mL beaker or to a 500 mL conical flask. Add 20 mL of approx. 2M sodium hydroxide solution, and warm the mixture gently until the arsenic(III) oxide has completely dissolved. Cool to room temperature, and add 100 mL water, followed by 25 mL 2.5M sulphuric acid. Then add 3 drops 0.01 M osmium tetroxide solution (0.25 g osmium tetroxide (CARE FUME CUPBOARD) dissolved in 100 mL 0.05M sulphuric acid) and 0.5 mL AT-phenylanthranilic acid indicator (or 1-2 drops of ferroin). Titrate with the 0.1 M cerium(IV) sulphate solution until the first sharp colour change occurs (see Discussion above). Repeat with two other samples of approximately equal weight of arsenic(III) oxide. 

Discussion. Copper(II) ions are quantitatively reduced in 2M hydrochloric acid solution by means of the silver reductor (Section 10.140) to the copper(I) state. The solution, after reduction, is collected in a solution of ammonium iron(III) sulphate, and the Fe2+ ion formed is titrated with standard cerium(IV) sulphate solution using ferroin or AT-phenylanthranilic acid as indicator. 

Procedure (copper in crystallised copper sulphate). Weigh out accurately about 3.1 g of copper sulphate crystals, dissolve in water, and make up to 250 mL in a graduated flask. Shake well. Pipette 50 mL of this solution into a small beaker, add an equal volume of ca AM hydrochloric acid. Pass this solution through a silver reductor at the rate of 25 mL min i, and collect the filtrate in a 500 mL conical flask charged with 20 mL 0.5M iron(III) ammonium sulphate solution (prepared by dissolving the appropriate quantity of the analytical grade iron(III) salt in 0.5M sulphuric acid). Wash the reductor column with six 25 mL portions of 2M hydrochloric acid. Add 1 drop of ferroin indicator or 0.5 mL N-phenylanthranilic acid, and titrate with 0.1 M cerium(IV) sulphate solution. The end point is sharp, and the colour imparted by the Cu2+ ions does not interfere with the detection of the equivalence point. 

Hydrogen peroxide. The diluted solution, which may contain nitric or hydrochloric acid in any concentration between 0.5 and 3M or sulphuric add in the concentration range 0.25 to 1.5M, is titrated directly with standard cerium(IV) sulphate solution, using ferroin or /V-phenylanthranilic acid as indicator. The reaction is ... 

A number of transition metals can be determined conveniently if their cations undergo a definite change of oxidation state see Oxidation Number) on titration with a standard solution of potassium permanganate, potassium dichromate, cerium(IV) sulfate, or ammonium hexanitratocerate(IV). Several visual indicators have been proposed, including diphenylamine and its derivatives, xylene cyanole FF, and especially A-phenylanthranilic acid and tris(l,10-phenanthroline)iron(II) sulfate ( ferroin ). Solutions of have been used in the determination of iron, copper, titanium, vanadium, molybdenum, tungsten, mercury, gold, silver, and bismuth, and standard solutions of and Sn F U, and and Mo have also... 

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