DD144759A1 - METHOD FOR PRODUCING BENZIL - Google Patents

Abstract

Benzil is prepared by reacting in an anhydrous or hydrous aliphatic carboxylic acid and optionally in the presence of a mineral acid with the introduction of air or oxygen benzion in the presence of a small amount of a cheap heavy metal, heavy metal oxide or heavy metal salt at 40 to 110 degrees C, preferably at 75 to 90 Grade C, ocidiert. As a result, the addition of this catalyst, the reaction time can be significantly shortened.

Description

Title of the invention

Process for the preparation of benzil

Application area of the invention

The invention relates to a process for the preparation of benzil, which is an important intermediate for the preparation of medicaments, such as 5,5-diphenylhydantoin and of 1, 3,4,6-tetrachloro-7,8-diphenyl-acetylenediurein ·

Characteristic of the known technical solutions

Ea is known to produce benzil by oxidation of benzoin. "Many variants have been described for this reaction.

For example, benzoin can be oxidized to benzil with concentrated nitric acid (Gattermann "Praxis der organischen Chemiker", 1.95,4, page 194).

According to US Patent No., 2,377,749 (see also Organic Synthesis, Coll, "Vol. I, page 87) are equivalents sulfate amounts of copper (II) for the oxidation of benzoin required and after W _e Rigby (J" Chem «Soc» JT952, page 793), expensive bismuth (III) .- carbonate is used for the oxidation of benzoin *

- c.

These processes have the following disadvantages: * Nitric acid has an extremely strong corrosive effect, which is why the equipment and plant components must be made of special materials. »Nitroxide gas is produced as a by-product during nitric acid oxidation due to environmental protection requirements with special absorption systems from the exhaust air must be absorbed "The processes based on copper (II) sulfate and bismuth (III) carbonate are ruled out due to economic considerations, since these two oxidants are very expensive and are needed in equivalent amounts."

It is also known that the oxidation of benzoin in the presence of catalytic amounts of copper (II) sulphate (US Pat ent ~ writing Ir "2658920; M ₉ Weiss and _Μ β Appel, J _{e e} Amer Chem Soc" 70, Page 3666 (1948)) or bismuth (III) carbonate (B ₀ Holden, W. Rigby, J. Chem _e Soc., 1924) also expires,

In these two processes, the spent catalyst must be constantly regenerated. In the case of bismuth (III) carbonate, the regeneration is achieved with air and in the case of copper (II) sulfate with ammonium nitrate »

This latter process is not easily controllable. "Ammonium nitrate is reduced in this process to ammonium" nitrite, which in the acetic acid solution decomposes into nitrogen and water. "This reaction sometimes jumps, but then spontaneously, so that the process "Since ammonium nitrate is also used for the production of safety explosives and in the presence of organic substances according to the Explosives Act of the GDR all explosives are not easily controlled on a small scale."

Because of its hazardous nature, this process can not be transferred to large-scale production

The Preparation of Benzil by Oxidation of Benzoin in Dry Dioxane with 1.2 Equivalents of Hatrium Antimony (V) Acetate According to P, Uerdel (Chem, Ber. *. ) (1), 124, 131, (1964)) has only academic interest because it is too expensive »

Bach of the USSR sponsor Ur. 224 507 (Y. A, Ostrovskaya, A, I "Adamovich, A. S _e Sarenko and U. P, Mikhailowa) benzil is oxidized with ammonium nitrate at 100 - 11O ⁰ C in the presence of a catalyst. This method is eliminated due to the use of ammonium nitrate and has the disadvantages already described above.

The oxidation of benzoin with N-bromo-succinimide in the presence of pyridine as described by R · Heilmann and P _e Baret (C. R _e Acad. Sci., Paris, C. 1968, 267 (8), 579 - 81) is likewise disclosed economically unacceptable »

Hach Ρ "Manos (. US Patent 3,595,922 Hr) is benzoin at 35 - 4O ⁰ C oxidized in methanolic solution in the presence of 0.14 equivalents of copper benzoate as a catalyst while introducing air to benzil. The drawbacks of this process are the pressure of the discharge by coupons and the small space-time yield due to the low solubility of benzoin in methanol.

There are a number of other synthetic routes to benzil, but all these methods are economically uninteresting or unreasonable for environmental reasons (see

Z ₉ Bo Tse-Lok Ho, Chem _e Ind. (London) IjJTJi, (20) ,. 807; S, Mineo et al., Yakugaku Zassiii 197, 4-94 (9), 1180-1182; D _e Macaione P. et al _e, Synthesis 1974, 10, 716 ;. J. D _e Albright, US Pat. No. 3,901,896; P _e Girard, a? Letters 1975, '50, 4513-14; J ₉ San Filippo et al., J _e Orgv Chem. JJ377 »42 (12), 2182-83).

It is also known that benzil be prepared by benzoin in a mixture of an aliphatic carboxylic acid, water and a mineral acid while passing oxygen or air to temperatures of 60 - 110 ⁰ C, preferably 100 ⁰ C, heated '(DD patent No. 126 ^

As aliphatic ^ carboxylic acids formic acid and acetic acid and hydrochloric acid, sulfuric acid or phosphoric acid are suitable as mineral acid According to this process, benzil is obtained in excellent quality with a melting point between 90 and 95 ⁰ C and 85 to 90% yield »

This process seems favorable at first glance. However, it is problematic to finely distribute the required amount of air or oxygen in the reaction solution. In principle, this can be done either by introducing air via tailed tubes or via stirrers equipped with nozzles, in which case reaction times of 35-40 hours are required in the case of uncatalyzed oxidation, or in circulation by means of pump and radiator in which the air or the oxygen is intensively mixed in, but even under optimal conditions, 16 to 20 hours of reaction time are still required in the industrial scale. "In addition, the corro sion problems caused by the hot acidic reaction solution in this long time _e

Object of the invention

By the invention it is possible, while maintaining high yields of 90%, and the excellent quality (Pp. 92 - 95 ⁰ C) benzil provided by introducing air Einhängerohre or over with nozzles stirrer in a considerably shorter reaction time, DIE about 10 to 15 hours and thus with very reduced corrosion problems very safe, technologically simple and economically extremely low ·

Explanation of the essence of the invention:

The invention is based on the object, while maintaining the high yield of 90 % and the excellent quality of Benzil in a much shorter.: \ Reaction time and thus with greatly reduced corrosion problems very low and economically extremely low production «

According to the present invention, this is achieved by reacting benzoin in an anhydrous or hydrous aliphatic carboxylic acid, optionally in the presence of a mineral acid, and in the presence of a small amount of a heavy metal, heavy metal oxide or heavy metal salt as a catalyst while introducing oxygen or air to temperatures between 40 and 110 ⁰ C, preferably at 75 - 90 ⁰ C, heated.

The amount of catalyst used can vary within wide limits. "In general, amounts of from 0.1 to 10%, advantageously from 1 to 5%, are sufficient. * However, it is also possible to use larger or smaller amounts of catalyst, although this is disclosed in US Pat most cases hardly brings more benefits *

, 6 "

It is preferred to use aliphatic-acid carboxylic acid as acetic acid or formic acid. As mineral acids, preference is given to using sulfuric acid, hydrochloric acid or phosphoric acid. Iron salts, iron oxide or iron in the form of iron powder or iron filings are preferably used as metal catalysts. Suitable catalysts are nickel small amounts in an analogous manner, cobalt _s copper or manganese in an appropriate form suitable "

The water content of the mixture can be up to 50 % ^ with increasing water content a correspondingly larger amount of aliphatic carboxylic acid is required. »The amount of mineral acid can be from 0.1 to 3.0 moles per mole of benzoin, depending on the water content of the mixture.

EXAMPLES Example 1t

178 g of benzoin (0.88 mol) are added to a mixture of 450 ml of glacial acetic acid, 150 ml of 9% acetic acid (10 % water content), 85 ml of concentrated hydrochloric acid and 10 g of iron (II) sulfate. The reaction mixture is stirred 75 -. heated 80 ⁰ C "If the temperature reaches 80 ⁰ C, starting with vigorous stirring with the introduction of the air," times the TLC Kachweis complete conversion of benzoin (a sample is dissolved in CHCIo, Laufinlttels benzene! / Acetone 9: 1), the introduction of the air is stopped »

While stirring, allowed to run in 300 ml of water slowly * After the reaction mixture with stirring at 15 - cooled "20 ^0C. The benzil crystallizes out and is filtered off with suction, washed with water and dried

Yield: 155 g of pale yellow, citrate benzil, 88 % of theory, mp 92-95.3 ⁰ O.. ,

Example 2:.

178 g of benzoin (0.88 mol) are added to a mixture of 700 ml of 85% acetic acid (15 % water), 50 ml of concentrated sulfuric acid and 10 g of iron (II) sulfate. This reaction mixture is treated further as described under Example 1,

By weiterea diluting the mother liquor with an appropriate amount ^ ater one still gives about 10g benzil from Pp. 80 - 90 ⁰ C. This benzil is contaminated by lifting products, ζ "benzoic acid. Recrystallization of this contaminated benzene from methanol and in the presence of some activated carbon gives pure benzil. This applies to all examples.

Yield: 159 g of benzil = 90 % of theory, mp 91.7 - Ij 95.8 ⁰ C.

Example 3:

178 g of benzoin (0.88 mol) are introduced into one of 60 ml of 85% formic acid, 75 of concentrated hydrochloric acid and 10 g of iron (II) -aulfate. Ea is carried out as described in Example 1. Yield: 150 g = 85% of theory benzil, Pp, from 91 to 94.8 ⁰ C.

Example 4:

178 g of benzoin (0.88 mol) are added to a mixture of 450 ml of glacial acetic acid, 150 ml of 90% acetic acid and 0.2 g of iron (II) sulfate

treated in the manner described in Example 1 ". Yield: 132.5 g of benzil, 75% of theory · mp 92.7 96.1 ⁰ C .-.

Example 5:

173 g of benzoin (0.88 mol) are introduced into a mixture of 450 ml of glacial acetic acid, 150 ml of 90% acetic acid (10% water content), 100 ml of concentrated hydrochloric acid and 2 g of iron powder or egganae. The reaction mixture is treated as described in Example 1 "yield: 154 g of benzil, 87% of theoretical PP 92.3 to 95.4 ^0C.

Example 6:. ,

178 g of benzoin (0.88 mol) are added to a mixture of 450 ml of glacial acetic acid, 150 ml of 90% acetic acid (10 % water), 130 ml of V / a, 35 ml of 75% phosphoric acid and 10 g of iron (II ) -sulfate added «Continue according to example 1»

Yield: 156 g of benzil, 88.5 % of theory Fp * 91-95 ⁰ C,

Example 7:

Examples 1 to 4 and Example 6 can also be carried out in analogous manner with Eiaen (II) chloride, iron (III) chloride, iron (III) sulfate or other soluble iron salts. «

Example 8:

382 g of benzoin werden.in a mixture of 1 200 ml of glacial acetic acid, 160 ml of water, 172 ml of hydrochloric acid and o, 5 g of iron

The reaction mixture is treated as described in Example 1, yield: 157.6 g of benzil, 89% of theory • - P. 94, '8 - 95.1 ° C _e

Claims (1)

claims: 1 · Method for the production of. Benzil by oxidation of benzoin in an anhydrous or hydrous aliphatic carboxylic acid, in the presence of a mineral acid, by introducing air or oxygen at 60 to 110 ⁰ C, characterized in that the oxidation in the presence of a small amount of a cheap Sehwermetalles, Schweriuetalloxides or heavy metal salt, _{e e} B "of iron, nickel, cobalt, copper or manganese, and in the presence or absence of a ¹ mineral acid faei a temperature of 40 - 110 ⁰ C, tforziigeweise at 75 - 9O ⁰ C is performed, 2 «Process according to item 1, characterized in that acetic acid, formic acid or mixtures of these two acids are used as aliphatic carboxylic acids 3 * Method according to the points 1.; and 2, characterized in that hydrochloric acid, sulfuric acid or phosphoric acid are used as the mineral acids. 4 · Method according to points 1 to 3, characterized in that the oxygen required for the oxidation is used in the form of compressed air « 5β Process according to items 1 to 4, characterized in that the acid radical of the heavy metal salt can derive both from an organic acid and from an inorganic acid. " 6. Process according to items 1 to 55, characterized in that the water content of the solvent mixture can be up to 50 % « · - 11 - 7 · Process according to points -1 to 6, characterized in that per mole of benzoin 0.1 to 3.0 moles of ralic acid mine are used. , : 8, process according to points 1 to 7, characterized in that 0.1 to 10%, preferably 1 to 5% catalyst based on the benzoin used is set