DE1183901B - Process for the preparation of mixtures of isomeric trichlorobenzoic acids - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL LIBRARY DES GERMAN

PATENT OFFICE

Boarding school Class: C 07 c

Number:
File number:
Registration date:
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German KL: 12 ο-14

H 25377IV b / 12 ο
4th November 1955
December 23, 1964

The invention relates to a process for the preparation of mixtures of isomeric trichlorobenzoic acids containing a substantial amount of the 2,3,6 isomer.

Trichlorobenzyl and trichlorobenzal halides and especially the 2,6-ring-substituted isomers relatively inert and go only with great difficulty or side chain reactions not one at all. While benzyl chloride and benzal chloride do not have nuclear chlorination either or have a mono- or dichlorination on the core, for example with potassium permanganate, easily to the corresponding benzoic acids can be oxidized in high yield, this can be done with trichlorobenzyl chloride or trichlorobenzal chloride are not accomplished, especially not with such Chlorides that have a 2,3,6 or 2,4,6 nuclear orientation. Nitric acid is involved as an oxidizing agent known to some reactions, and benzyl chloride can be oxidized with very dilute nitric acid will. However, if you treat benzyl or benzal chloride with concentrated nitric acid, nitration occurs.

It is known that 2,3,4-trichlorotoluene by boiling with 60 ° / ₀ nitric acid for 16 hours under reflux in the 2,3,4-trichlorobenzoic acid can be converted. Attempts to obtain trichlorobenzoic acid in a corresponding manner from a mixture of trichlorotoluene isomers with a predominant content of 2,3,6 isomers were unsuccessful, as the following descriptions of the experiments show:

A. There were 100 g of an isomer mixture of trichlorotoluene with a content of about 64% of the 2,3,6 isomers mixed with 580 g of 60% nitric acid, and the mixture at reflux temperature heated with stirring for 9 hours. There was no noticeable reaction.

B. In another experiment, 19.5 g of the above-mentioned mixture of isomers of trichlorotoluene were used 200 ml of 70% nitric acid heated. Heating was continued at reflux temperature for 12 hours. A non-typical product weighing 0.5 g was obtained.

The method of the invention is that mixtures of isomeric chloromethyl or Brommethyltrichlorbenzole with a substantial content of 2,3,6-isomers with nitric acid having a concentration of 60 ^m to 85% of a molar ratio of nitric acid isomer mixture of at least 6: 1 oxidized at atmospheric pressure.

Process for the preparation of mixtures
isomeric trichlorobenzoic acids

Applicant:

Heyden Newport Chemical Corporation,

New York, N.Y. (V. St. A.)

Representative:

Dr. E. Wiegand, Munich 15, Nussbaumstr. 10,
and Dipl.-Ing. W. Niemann, Hamburg 1,
Patent attorneys,

Named as inventor:

Theodore Aisdorf Girard,

Wayne Township, N. J .;

Eugene Peter Dibella, Lodi, N. J. (V. St. A.)

Claimed priority:
V. St. v. America November 5, 1954
(467 242)

In a particular embodiment of the process according to the invention, the oxidation is carried out in Presence of an inert inorganic solid such as fuller's earth, bentonite or I§aolin.

The concentration of nitric acid is critical and should be in the range of 60 to 85 percent by weight lie, with the rest, apart from the usual

Like traces of contamination, consists of water. The use of nitric acid of lower concentration results in a lower or no acid output

409 759/403

3 4

loot, while the use of nitric acid 2,3,6-trichlorobenzyl chloride 71.75%

higher concentration an undesired nitration 2,3,4-trichlorobenzyl chloride 5.62%

causes. For example, 90% nitric 2,3,5-trichlorobenzyl chloride causes .. 0.43%

acid a core nitration. Preferably nitric 2,4,5-trichlorobenzyl chloride 19.78%

acid with a concentration of approximately 70 ± 2%, 5 2,4,6-trichlorobenzyl chloride 2.42% Λ

d. H. an acid with about 70% nitric acid and 30%

Water, used. which in a known manner by chlorination of a

The yield of trichlorobenzoic acid, based on the corresponding trichlorotoluene isomer mixture, the weight of the trichlorobenzyl chloride introduced, was obtained at about 205 to 210 ^° C. The generalized by a number of factors including io my procedure was that 46 g of the temperature during the reaction, the conversion (0.2 mole) of trichlorobenzyl chloride and that in the post-settling or heating period and the mole- following Table I under " Molar ratio «specified ratio of nitric acid to the starting material, number g-mol of concentrated nitric acid in one influences. In general, higher temperatures require a 500 ml bottle with a temperature, longer reaction times and a higher molar stirrer and a reflux condenser. Ratios a higher conversion to the acid. The concentration of nitric acid is given in Table I in The reaction is indicated by heating the reaction column in the "% HNO ₃ " column. The mixture was components to an elevated temperature and preferential then under reflux at atmospheric pressure (at instruct to a temperature of at least 95 ° C excluded approaching 120 ⁰ C) performs during the given in Table I. Optimal results are allowed to cook by heating the 20 number of hours. A vigorous evolution of atmospheric pressure was achieved during the reaction components at reflux temperature with heating period. Held at temperatures below nitrogen oxides. At the end of the 95 ^° C. heating, the yield is significantly reduced. or conversion time, the reaction

The response time, i.e. H. the period of time during which the reaction mixture is heated softer by mixing with stirring in approximately 400 ml of water can be poured into as. This was then extra pureed with 200 ml of benzene wide range can be changed and z. B. here. The benzene layer was separated and two between 6 and 88 hours lie. Preferably washed times with an equal volume of water the heating time is about 12 hours or and then with 200 ml of water containing 10 g more sodium, what contained, to a certain extent, other conditional hydroxide, extracted. Thereupon was the wetting is dependent. 30 inch layer with a small amount of water

Wash the theoretically required amount of nitric acid, which was combined with the alkaline extract, 4 moles per mole of trichlorobenzyl or trichloro. The benzene layer then became a benzal halide; the nitric acid, however, acts as an evaporated oily residue, the weight of which in the solvent, if no other solvent is given in Table I under "By-product". Wears out, and there will usually be at least a 35 from Run F that by-product molar ratio of 6: 1 was used. Generally not a nitration product. In the experiment, F, at optimum conversions with a higher which 90% ig ^e nitric acid was used, was a molar ratio of at least 12: 1 achieved. However, nitration can take place and the by-product can also be used in much higher molar ratios. contained, as was found, 51.3% Cl and 5.11. In the information on the molar ratio, the 40 is 5.04% N. Calculated contains -C ₇ H ₃ Cl ₄ NO ₂ 51.64% Cl, the actual amount of nitric acid present in and 5.09% N.
Considered. The separated aqueous alkaline layer became

The yield of trichlorobenzoic acid is then poured into 100 ml of concentrated hydrochloric acid while stirring, the above finely divided, inert inorganic material made of fuller's earth, 45 in order to precipitate the trichlorobenzoic acids, 45 This mixture was increased in an ice bath for 2 hours bentonite or kaolin. The amount of inert material left to stand, whereupon it is filtered off, can vary within a wide range; and finally dried to a constant weight, it is related to in a vacuum oven at 45 to 5O ⁰ C dried the weight of the Trichlorbenzyl- or Trichlorbenzal- was preferably at least 0.5%>. The yields of the trichlorobenzoic acid halide used while the optimum with a few mixes given in Table I is at least about 10%. There is no excess on this dry weight and the weight of Trischadlich. based on chlorobenzyl chloride mixture.

Catalytic amounts of catalysts can be used. Experiment N in Table I differs

However, the use of catalysts is not essential in that the reagents are 2% analyzers. For example, a 55 iodine, based on the weight of Trichlorgeringe amount of iodine, approximately _2/0 ° benzyl chloride as a catalyst at tri-, contained to the yield heights to erchlorbenzyl- or Trichlorbenzalchlorid used.

in order to increase the yield of trichlorobenzoic acid.

raise. acid was a mixture of isomers, since the trichloro

60 benzyl chloride comprised a mixture of isomers. At-

Example 1, for example, had this in Experiment N of Table I.

received product following analysis:

A series of tests was carried out for the um- 2,3,6-trichlorobenzoic acid 53.3%

Conversion of trichlorobenzyl chloride into trichloro-6 ₅ 2,3,4-trichlorobenzoic acid 10.1%

benzoic acid. The trichlorobenzyl chloride 2,3,5-trichlorobenzoic acid 2.6%

consisted of an isomer mixture of the combined 2,4,5-trichlorobenzoic acid 33.8%

release of about 2,4,6-trichlorobenzoic acid 0.2%

Table I.

attempt
No. ENT ₃ Mole
relationship Time Fuller's earth yield Cl Acid number Next to
product ° / o hours G ° / o % G A. 70 6: 1 8th 11.0 47.3 39.0 B. 70 12: 1 8th - 18.5 47.26 - 28.5 C. 70 32: 1 24 - 48.0 - 237.4 - D. 70 100: 1 24 - 27.6 45.6 234.7 3.2 E. 80 6: 1 8th - 16.0 47.23 250.0 31.5. F. 90 6: 1 8th - 16.7 46.99 246.0 39.4 G 35 5: 1 9 - 0.0 .—. - - H 70 6: 1 16 - 21.2 - 25.8 J 70 6: 1 24 - 27.6 46.97 242.0 21.3 K 70 12: 1 8th 5.0 41.0 43.41 228.0 19.1 L. 70 12: 1 24 5.0 60.3 45.2 222.0 11.0 M. 70 12: 1 8th 5.0 51.6 47.24 247.9 16.6

Example 2

A number of attempts were made to convert trichlorobenzal chloride to trichlorobenzoic acid. These experiments are shown in Table II. In each experiment the trichlorobenzal chloride used was a mixture of isomers containing approximately 70% of the 2,3,6 isomer. The trichlorobenzal chloride and concentrated 70% nitric acid were placed in a bottle which was equipped with a thermometer, a stirrer and a reflux condenser and heated there to the specified temperature, generally the reflux temperature. The upper part of the condenser was connected to a washing device for separating off the nitrogen oxides. In each experiment 0.2 mol trichlorobenzal chloride was used along with the amount of nitric acid necessary to provide the molar ratio given in the table. The heating continued for the specified period of time. In some experiments, fuller's earth was added to the reagents. At the end of the heating period, the reaction mixture was cooled, poured into 500 ml of water and then extracted with 500 ml of benzene. The benzene solution was washed with two portions of 50 ml water and then with 200 ml of a 5% strength sodium hydroxide solution, extracted ^s. The alkaline extract was added slowly with stirring to 50 ml of concentrated hydrochloric acid, cooled to 2O ⁰ C and filtered. The trichlorobenzoic acid mixture was washed with 50 ml of water, dried at 55 ° C in a vacuum oven and weighed. The percentage yield as reported in Table II is based on the weight of the trichlorobenzal chloride charged.

Table II

attempt
No. Fuller's earth
G Molar ratio temperature
⁰ C Time
hours yield Acid number A. O 6: 1 Reflux 8th 23.3 B. 5.0 6: 1 Reflux 24 36.3 247.8 C. 0 12: 1 Reflux 8th 38.9 - D. 5.0 12: 1 Reflux 24 58.0 241.5 E. 0 32: 1 Reflux 3 27.4 215 F. 0 12: 1 Reflux 88 38.9 - G 5.0 12: 1 75 to 80 24 25.3 247 H 0 12: 1 95 16 50.4 228.4

The trichlorobenzoic acid obtained in Experiment D of the Tables was as follows Analysis:

2,3,6-trichlorobenzoic acid 52.5%

2,3,4-trichlorobenzoic acid 8.1%

2,3,5-trichlorobenzoic acid 3.6%

2,4,5-trichlorobenzoic acid 33.1%

2,4,6-trichlorobenzoic acid 2.7%

Example 3

In a three-neck, round-bottom bottle with a capacity of 11, which was equipped with a stirrer, a thermometer and a condenser, HOg (0.4 mol) of a trichlorobenzyl bromide isomer mixture containing approximately 70% of the 2,3,6- Isomers, 432 g (4.8 moles, expressed as 100% HNO ₃ ) 70% nitric acid and 10 g fuller's earth introduced. The mixture was heated for 24 hours at (80 to 120 ^° C.) while stirring continuously.

The reaction mixture was then cooled to approximately 20 ° C and sintered through a funnel with a Filtered glass. The gummy precipitate was washed out with 500 ml of water. This gummy precipitate, crude trichlorobenzoic acid isomer mixture, was in 400 g of a 10% strength Dissolved sodium hydroxide solution and filtered to remove insoluble impurities. The filtrate was acidified with 200 ml of 37% hydrochloric acid to

10

to precipitate the trichlorobenzoic acid. The gummy precipitate was filtered off and washed with two 100 ml aliquots of water, then pressed as dry as possible and allowed to air dry. This Rohsäuregemisch was suspended in 50 ml of benzene, 200 ml of petroleum ether (b.p. 30 to 6O ⁰ C) was added and the mixture filtered to give 18 g of a white solid were obtained, whose analysis gave the following values:

Calculated for

C ₇ H ₃ Cl ₃ O ₂ acid number: 248.5 mg KOH / g;

Acid number found: 221.9 mg KOH / g.

The benzene-petroleum ether filtrate was evaporated to dryness and the solid residue was initially with 50 ml of 15% hydrochloric acid and then washed with 50 ml of water. The product was filtered off and on the Air dried. 26 g of an off-white solid were obtained, the analysis of which was as follows resulted in: ao

Calculated for

C ₇ H ₃ Cl ₃ O ₂ acid number: 248.5 mg KOH / g; _{Publications taken into consideration} :

Sending acid number: 225.6 mg KOH / g. _B ei 1stein, Handbook of Organic Chemistry,

The total yield of trichlorobenzoic acids (be 35 Hauptwerk, Vol. 9, p. 345/346 (1926); correct on the basis of acid numbers) was approximately Journal of Chemical Society, 1208 ff. (1951).

44%) based on the weight of the trichlorobenzyl bromide introduced.

Claims (3)

Patent claims: 1. A process for preparing mixtures of isomeric Trichlorbenzoesäuren with a substantial content of the 2,3,6-isomer, characterized in that mixtures of isomeric chloromethyl or Brommethyltrichlorbenzole with nitric acid at a concentration of 60 to 85% i ⁿ a molar ratio of nitric acid -Isomer mixture of at least 6: 1 oxidized at atmospheric pressure. 2. The method according to claim 1, characterized in that the oxidation in the presence an inert inorganic solid such as fuller's earth, bentonite or kaolin. 3. The method according to claim 1 or 2, characterized in that the reaction is carried out in the presence of iodine. 409 759/403 12.64 © Bundesdruckerei Berlin