Benzoic anhydrides

In a 5-I. flask, provided with a two-hole stopper fitted with a 90-cm. fractionating column uand a dropping funnel, are placed 1500 g. of benzoic acid, 1500 g. of acetic anhydride, and 1 cc. of syrupy phosphoric acid. The mixture is very slowly distilled, at such a rate that the temperature of the vapor at the head of the column does not exceed 120° (Note 1). When 250 cc. of distillate has been collected, 250 g. of acetic anhydride is added, and distillation is continued. This process is again repeated, so that in all 2000 g. of acetic anhydride has been taken. Fractionation is then continued, fractions which distil respectively below 1200, at 120-130°, and at 130-140° being collected. Heating is continued until the temperature of the reaction mixture in the flask reaches 270°. 

The residue is fractionally distilled under reduced pressure, resulting in the collection of fractions which boil respectively below 165°, at 165-210°, and at 210-220°, all under 19-20 mm. pressure (Note 2). The lower fractions are mixed with the fraction which boils at 120-130°, and distilled as before after the addition of one drop of phosphoric acid, when a further quantity 

The fraction which boils at 120-130° under atmospheric pressure is redistilled, yielding further quantities of acetic acid (below 1200) and acetic anhydride (130-140°). 

As it is probable that the equilibria between the two acids and the three anhydrides are established in reactions of relatively low velocity, the distillation must be carried on very slowly, in spite of the catalytic action of the phosphoric acid. The intermediate fractions contain the mixed anhydride, detectable by its odor, which resembles that of acetophenone. 

Owing to the high boiling-point of the end-product, the second stage must be conducted under reduced pressure. The 

180g Tropine or pseudotropine is dissolved in a mixture of 70 g of concentrated sulfuric acid and 650 g water. This solution is brought into the anode region of an electrolytic apparatus which can be cooled, whose cathode area is separated by a diaphragm contains diluted sulfuric acid. The current which can be introduced now is to possess a density of 3 A/qdm anode surface, but is still well applicable also higher and low current densities. After the passage of the necessary ampere hours the current is interrupted. The developed tropinone can be isolated then in well-known way. Source Merck 1901 

Method B 180 g tropine or pseudotropine is dissolved with 70 g ammonium sulphate in 720 g water, on which sulfuric acid up to the neutralization is added. This solution is made alkaline with ammonia poured into the anode region of the electrolytic reduction apparatus, while in the cathode area a solution of 280 g ammonium sulfate in 800 g water. The further procedure is then exactly the same, as described 1 in the example. Source Merck 1901 

Tropine mixed with tropic acid can be obtained from atropine by hydrolysis with hydrochloric acid or a barium hydroxide solution. 

Prepared by H. T. Clarke and E. J. Rahrs Checked by Roger Adams and P. K. Porter 

IN a 5-L. flask, provided with a two-hole stopper fitted with a 90-cm. fractionating column (1) and a dropping funnel, are placed 1500 g. of benzoic acid, 1500 g. of acetic anhydride, and 1 cc. of syrupy phosphoric acid. The mixture is very slowly distilled, at such a rate that the temperature of the vapor at the head of the column does not exceed 

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In the distilling-flask remains a very small high-boiling fraction of benzoic anhydride (b.p. 366 ), formed by the dehydrating action of the thionyl chloride on the benzoic acid ... 

Thus benzoic anhydride and o chlorobenzoic anhydride (m.p. 79°) can bo readily prepared by this method (compare n-Heptoic anhydride, Section 111,91). It is sometimes convenient to use pyridine as the reaction medium. 

Benzoic anhydride (carboxylic acid - acetic anhydride method). 

Phenolsulphonephthalein (phenol red). Mix 10 g. of o-sulpho-benzoic anhydride (Section VIII,9), 14 g. of pure phenol and 10 g. of freshly fused zinc chloride in a small conical flask. Place a glass rod in the flask and heat gently over a flame to melt the phenol. Then heat the flask containing the well-stirred mixture in an oil bath at 135-140° for 4 hours. Stir from time to time, but more frequently during the first hour if the mixture froths unduly, remove the flask from the bath, cool and then resume the heating. When the reaction is complete, add 50 ml. of water, allow the water to boil and stir to disintegrate the product. Filter the crude dye with suction and wash it well with hot water. Dissolve the residue in the minimum volume of warm (60°) 20 per cent, sodium hydroxide solution, filter, and just acidify the filtrate with warm dilute hydrochloric acid (1 1). Filter the warm solution, wash with water, and dry upon filter paper. The yield of phenol red (a brilliant red powder) is 11 g. 

Formation - benzoyl chloride, benzoic anhydride, benzoyl cyanide (TL 1971, 185), benzoyl tetrazole (TL 1997, 38, 8811)... 

The kinetics of nitration of benzene in solutions at c. 20 °C in carbon tetrachloride have been investigated. In the presence of an excess of benzene (c. 2-4 mol 1 ) the rate was kinetically of the first order in the concentration of benzoyl nitrate. The rate of reaction was depressed by the addition of benzoic anhydride, provided that some benzoic acid was present. This result suggested that benzoyl nitrate itself was not responsible for the nitration, but generated dinitrogen pentoxide... 

Because of the chemical similarity between benzoyl nitrate and the acetyl nitrate which is formed in solutions of nitric acid in acetic anhydride, it is tempting to draw analogies between the mechanisms of nitration in such solutions and in solutions of benzoyl nitrate in carbon tetrachloride. Similarities do exist, such as the production by these reagents of higher proportions of o-substituted products from some substrates than are produced by nitronium ions, as already mentioned and further discussed below. Further, in solutions in carbon tetrachloride of acetyl nitrate or benzoyl nitrate, the addition of acetic anhydride and benzoic anhydride respectively reduces the rate of reaction, implying that dinitrogen pentoxide may also be involved in nitration in acetic anhydride. However, for solutions in which acetic anhydride is also the solvent, the analogy should be drawn with caution, for in many ways the conditions are not comparable. Thus, carbon tetrachloride is a non-polar solvent, in which, as has been shown above,... 

Benzoic anhydride has been prepared in excellent yield by... 

First prepared by C. F. Gerhardt from ben2oyl chloride and carefully dried potassium acetate (1), acetic anhydride is a symmetrical iatermolecular anhydride of acetic acid the iatramolecular anhydride is ketene [463-51-4]. Benzoic acetic anhydride [2819-08-1] undergoes exchange upon distillation to yield benzoic anhydride [93-97-0] and acetic anhydride. 

Benzoic anhydride is not manufactured on a large scale. Its primary use is as a benzoylating agent in the manufacture of pharmaceuticals and chemical intermediates. 

B. p-Chlorobenzoic anhydride benzoic anhydride, p,p -di-ckloro-). A mixture of 17.5 g. (0.1 mole) of j -chlorobenzoyl chloride (Note 6) and 50 ml. (0.6 mole) of pyridine in a loosely stoppered 200 ml. flask is warmed on the steam bath for 5 min-... 

The procedures as outlined are applicable to both the aliphatic and aromatic series. They are superior to the common interchange method in that they avoid the fractional distillation which is very troublesome in the aliphatic series. They have been used in numerous instances and can be adapted to give mixed anli3"drides. Benzoic anhydride has been obtained, by closely related procedures, from benzoic acid and benzoyl chloride by heating under reduced pressure or in the presence of zinc chloride. 

Propionic acid [79-09-4] M 74.1, b 141 , d 0.992, n 1.3865, n25 1.3843, pK 5-6.8 (Ho scale, aq H2SO4), pK2 4.88. Dried with Na2S04 or by fractional distn, then redistd after refluxing with a few crystals of KMn04. An alternative purification uses the conversion to the ethyl ester, fractional distn and hydrolysis. [Bradbury J Am Chem Soc 74 2709 1952.] Propionic acid can also be heated for 0.5h with an amount of benzoic anhydride equivalent to the amount of water present (in the presence of Cr03 as catalyst), followed by fractional distn. [Cham and Israel 7 C/iem 5oc 96 I960.]... 

Diversine, C2oH2,05N Pamsinomenine). This base was obtained by Kondo, Ochiai and Nakajima as an amorphous, yellow substance, m.p. 80-93°, [a]n ° + 6-98°. It reduces solutions of gold or silver salts. The hydrochloride is amorphous, m.p. 135-140° (dec.), as is also the methio-dide. The alkaloid contains two methoxyl groups and one methylimino-group, and with benzoic anhydride yields a mixture of mono- and dibenzoyl derivatives. For another diversine, see p. 350. 

A ( )-Enol-l 1-acetates are formed by distillation of acetic anhydride in the presence of / -toluenesulphonic acid. Another procedure employed for the synthesis of enol benzoates involves treatment with benzoic anhydride and triphenyl methyl sodium or ethynyl sodium. Suitable procedures utilizing a diluent have been developed for the enol esterification of a 20-ketone without affecting an 11-ketone. 

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