DE1445928B2 - Process for the preparation of 4,4 'bipyndyl from pyridine - Google Patents

Description

between 10 and 15 molar parts per gram atom of aluminum. If desired, larger Amounts are used, however, this is because of the larger amounts of unreacted pyridine that must be recovered, less economical. If desired, the reaction can be interrupted before all of the existing aluminum has been used up. Anything not implemented Any aluminum or pyridine that remains does not necessarily need to be removed before the oxidation of the reaction product is carried out.

The course of the oxidation of the aluminum / pyridine reaction product is unclear, and thus the term oxidation is used here in the sense that it is intended to include herein any process whereby removal of hydrogen or electrons is effected from the aluminum / pyridine reaction product. The oxidation can be done with the help of Oxygen or mixtures thereof with an inert diluent gas such as nitrogen, be performed. It can be done in that oxygen, for example in the form of air or any another mixture of oxygen and nitrogen, through the reaction product with vigorous stirring is introduced in order to bring about an intimate contact between the gas and the liquid. It has been found that the oxidation can also be achieved using chlorine alone or in admixture with an inert diluent gas can be carried out. Oxidation can also be achieved by adding Hypochlorites, nitric acid (in the form of the free acid or neutralized with an organic base, like a pyridine) or a water-soluble inorganic peroxygen compound (especially hydrogen peroxide), preferably in the form of aqueous solutions.

The oxidation can be carried out at any desired temperature. In each case the optimum temperature and the time required for complete oxidation depends for example on the oxidation conditions that are used. You can do a simple preliminary experiment to be determined. The oxidizing conditions should not be so severe that bipyridyl by itself too strong oxidation is lost. The termination of the oxidation is indicated by the fact that with further Addition of oxidizing agent no longer takes place, or because of the fact that a change in color of the reaction mixture (usually from dark blue to brown) occurs.

It has been found to be beneficial to the viscosity to reduce the reaction mixture for oxidation by adding a liquid diluent. If this does not happen, a gelatinous one usually forms during the oxidation Mixture which, under certain circumstances, prevents further oxidation from taking place. One such diluent can consist of water, for example in a ratio of 2 parts water per part applied Aluminum. Other suitable diluents are alcohols, such as. B. methanol, and hydrocarbons, such as B. Petroleum fractions and alkylated benzenes.

The process results in a product consisting primarily of 4,4'-bipyridyl. There are only 2 to 10% of 2,4'-bipyridyl. 2,2'-Bipyridyl can often not be determined at all. That with the invention Process used pyridine should be free of other components as much as possible or impurities (for example piperidine) that are undesirable with the metal or the initiator Can lead to side reactions. The method is particularly applicable to pyridine itself.

The bipyridyls can be obtained from the product obtained in the oxidation step by known methods be deposited, for example by fractional distillation under reduced pressure, extraction with organic solvents or combinations of these working methods. Generally will the bipyridyls first of all by pre-distillation at atmospheric pressure from the largest amount of the Excess pyridine and any volatile diluent applied and then freed fractional distillation under reduced pressure separated from terpyridyls and other substances. If desired, the reaction mixture can before or after a pre-distillation with a solvent extracted to remove any aluminum hydroxide present. Suitable solvents these are methylene chloride and benzene.

4,4'-Bipyridyl itself can be obtained from the mixture of the bipyridyls in essentially pure form as the hydrochloride to be deposited. This can preferably be done in that the mixed bipyridyls in hot methanol, after which the solution is treated with dry hydrogen chloride and then is cooled, the 4,4'-bipyridyl dihydrochloride separating out. The solid hydrochloride is filtered off and treated with an alkali metal compound, for example potassium bicarbonate, Sodium carbonate or sodium hydroxide, converted into the free 4,4'-bipyridyl. If so desired but the mixed bipyridyls can also be converted into the hydrochloride by adding for example dissolved in ether and treated with dry hydrogen chloride. The mixed ones Hydrochlorides are then washed with methanol or ethanol to produce the 4,4'-bipyridyl dihydrochloride separated from the more soluble isomers. Influence higher polypyridyls, for example terpyridyls this purification method does not, so the mixed polypyridyls with a solvent such as

e.g. ether, can be extracted directly from the oxidation product, whereupon the 4,4'-bipyridyl dihydrochloride is isolated in the manner described above. 2,4'-Bipyridyl can be extracted by making use of its greater solubility in water or its higher volatility is made.

The method according to the invention has the advantage of rapid implementation and easy control. It gives excellent yields of 4,4'-bipyridyl without the need for a highly reactive one Alkali metal such as B. sodium, apply. The oxidation stage occurs in the present process light and smooth without it being a result of the formation of a gelatinous reaction mixture comes to difficulties. This is of particular concern when that Process is carried out on a large scale.

The ¹ 4,4'-bipyridyl produced is suitable as an intermediate in chemical synthesis processes, for example for the production of agricultural chemicals.

The invention is illustrated in more detail by the following examples. The parts and percentages relate focus on the weight.

5 6

continued for another 3 hours, after which again

Example! ^ qx _e ji _e pyridine were added. The overall

13.5 g of aluminum foil (0.5 atom) were mix was then incubated at 80 ⁰ C is oxidized by

Reflux with 100 g of pyridine and 0.25 g of mercury chloride 54.6 parts of an aqueous 15% sodium hypo-

heated, and as soon as the reaction had started, 5 chloride solution were added. That in a lot

An additional 137 g of pyridine was added to give an end product of 260 g containing 22.4 parts

To have a total of 3 moles of pyridine. 4,4'-bipyridyl, 1.5 parts 2,4'-bipyridyl and 1.5 parts

The mixture refluxed 2,2'-bipyridyl for 6 hours.

cooked, under a stream of nitrogen, and Example 5 then a further 158 g of pyridine (2 mol) were added, io

and the treatment was continued for a further 4 hours. A mixture of 10 g of aluminum powder and 440 g

continued. In order to reduce the viscosity of the dry pyridine was heated under reflux,

27 g of water were added to the reaction mixture, the reaction being carried out by initially adding 2 g

and the mixture was at 70 ° C by bubbling through mercuric chloride and then 5 minutes later by Na-

an air stream at a rate of 15 trium (1 g as a 33 ° / _o dispersion in

Oxidized 20 liters per hour for 5 hours. The trimethylbenzene) was initiated, and the treatment

Final product was obtained in an amount of 410 g. It was continued for 5.5 hours. The resulting

and contained 20.1 g of 4,4'-bipyridyl, less than 0.5 g of the mixture was then mixed with sodium hypochlorite in

2,4'-bipyridyl, no 2,2'-isomer being detectable. The form of 25 g of a 15 ° / _o aqueous solution loading

20 acts. The end product contained 18 g 4,4'-bipyridyl,

Example 2 _{was e} j _ner utilization of 21 ° / ₀ of the used AIu-

40.5 g of aluminum powder (1.5 atom) were under miniums and 23% of the pyridine used corresponded.

Reflux with 300 g of pyridine (3.8 mol) and 1.5 g of mer- Was the procedure of this example using

curichlorid in a mixing device consisting of 2 g of mercury chloride and 2 g of sodium

allowed bottle is warmed up, nitrogen being added (in the form of a 33% dispersion in trimethyl

was passed through. The mixture was repeated under benzene) as initiators, so a reaction

Heated reflux for 10 hours, and then tion product was obtained, which consists of 24.4 g of 4,4'-bipyridyl

1210 g (15.3 mol) of pyridine added in portions, held what a utilization of the set aluminum

was taking care that the flask contents sulphonates of 29 ° / ₀ and the next. Pyridines of

remained in a flowable state. The reaction -3 ° 31 ° / ₀ corresponded.

mixture was then cooled and at 60 ° C with.

50 1 of air per hour oxidized until the black color expression of 4 g of sodium (as a 33 ° / _o by weight

the mixture was gone. The end product dispersion in trimethylbenzene) as an initiator, however

was obtained in an amount of 1494 g and contained without mercury chloride, repeated to give a Reak-100 g of 4,4'-bipyridyl, 2.5 g of 2,4'-bipyridyl, and there was obtained 35 tion product containing 6.3 g of 4,4'-bipyridyl

no 2,2'-isomer detectable. held what a utilization of 7% of the set

Aluminum or pyridine corresponded.

B is ρ ie 1 3 ' ^F

5 parts of aluminum foil (0.185 atom) were determined with B e i s ρ i e 1 6 100 parts of pyridine (1.27 mol) heated to reflux. 40

There were added 1 part of a sodium dispersion (33 ° / ₀ A mixture of 10 g of aluminum powder and 528 g

Sodium metal in trimethylbenzene), 0.25 part of Magne-pyridine was refluxed for 2.5 hours

sium filings and 0.25 parts of a powdered alloy warms up after the implementation by adding

tion added, the 50% magnesium and 50% aluminum 1 g of mercury chloride and 2 g of sodium (in the form of a contained minium, and the mixture was then introduced into 45 33% dispersion in trimethylbenzene)

under reflux in a stream of nitrogen for 90 minutes. Through the reaction mixture was

river treated. Then another 50 parts for 6 hours were a stream of air / nitrogen

Pyridine was added and the treatment was still carried out by mixing in the ratio of 1: 1. That

Continued for 30 minutes, after which the final product again contained 21.6 g of 4,4'-bipyridyl, which was a

50 parts of pyridine were added and the treatment 50 utilization of 25% of the aluminum used

was extended to a total of 5 hours. Then or 26% of the pyridine used corresponded to,

50 parts of pyridine were added and the mixture " _{J (} . ,,

was oxidized at 60 ° C by adding ¹ 15; 2 parts of an aqueous 15% sodium hypochlorite solution

became. The 55 obtained in an amount of 268 parts The reaction of a mixture of 399 g of pyridine

The end product contained 10.5 parts of 4,4'-bipyridyl, 0.3 parts and 10 g of aluminum powder was obtained by adding

2,4'-bipyridyl and no 2,2'-isomer was detectable. 3 g of mercuric chloride introduced, and the mixture

'' Was refluxed for 3.75 hours. the

Example 4 Mixture was then introduced by introducing an air /

A powdered alloy of 50% aluminum 60 nitrogen flow (1: 1) in the described in example 6 and 50% magnesium was oxidized in an amount similar to that. Pas end product was in a Obtained 13.5 parts with 100 parts of pyridine (1.27 mol) in the amount of about 434 g, and of these Heated to reflux. 1 part of a sodium dispersion was mixed with 371 g with 540 g of water and with (33% sodium metal in trimethylbenzene) and 0.5 part of 900 ecm chloroform extracted. The chloroform-magnesium filings were added, and the mi-65 extract was fractionally distilled, leaving 289 g Schung was obtained under a stream of nitrogen for 5 hours pyridine and 11 g of a crude bipyridyl fraction treated under reflux for a long time. Then more became, from the 8.6 g of 4,4'-bipyridyl by crystallization-50 Parts of pyridine were added, and the treatment was isolated from petroleum ether.

Example 8

The reaction of a mixture of 400 parts of pyridine and 10 parts of aluminum powder was carried out Addition of 1 part of mercuric chloride and then 1 part of sodium was initiated, and the mixture was 6 hours heated under reflux for a long time and finally by blowing in a stream of air / nitrogen (1: 1) in the im Example 6 oxidized manner. The final product was treated with 40 parts of water and then fractionally distilled, initially under atmospheric pressure, with 319 parts of pyridine and then under a pressure of 1 to 2 mm, taking a crude bipyridyl fraction in an amount of 125 parts was obtained, from which 16 parts of pure 4,4'-bipyridyl were isolated by crystallization from petroleum ether.

Example 9

A mixture of 10 parts of aluminum powder and 400 parts of pyridine was refluxed for 2.75 hours after the reaction was initiated by the addition of 3 parts of mercuric chloride. The resulting mixture was then oxidized in the manner described in Example 6 by introducing a stream of an air / nitrogen mixture (1: 1). An analysis of the final product by gas-liquid chromatography showed that it contained 17 parts of 4,4'-bipyridyl contained, representing a utilization of 19% of the next aluminum or 22 ° / ₀ of the attached corresponded pyridine.

The procedure of this example was followed using 1.5 parts of mercuric chloride and 1.5 parts Sodium repeated as initiators, an end product was obtained which, after analysis, was 28.4 parts 4,4'-Bipyridyl contained, which corresponds to a utilization of 32% of the aluminum used or 34% of the used Pyridins corresponded.

B e i s ρ i e 1 10

A mixture of 10 parts of aluminum powder and 444 parts of pyridine was heated for 2 hours at 100 ⁰ C after the reaction by the addition of 2 parts of mercuric chloride and 2 parts of sodium had been initiated. The resulting mixture was then oxidized by adding 140 parts of nitrobenzene. The end product obtained contained 24 parts of 4,4'-bipyridyl, which corresponded to a utilization of 27.4% of the aluminum used and 34.3% of the pyridine used.

A repetition of the procedure of this example with the modification that the aluminum-pyridine reaction Was carried out for 17 hours at 30 ° C and the oxidation by adding 66 parts Nitrobenzene was carried out, gave 17.3 parts of 4,4'-bipyridyl, which corresponds to a utilization of 20% of the aluminum used and 29% of the pyridine used corresponded.

Example 11

The reaction of 10 parts of aluminum powder with pyridine under reflux was carried out by adding Introduced 2 parts of mercury chloride and then 2 parts of sodium. The amount of pyridine added was changed in order to avoid too high a viscosity of the mixture, and the reaction times were also changed according to the following table. The resulting reaction mixture was through Introducing an air / nitrogen mixture in the manner described in Example 6 is oxidized.

Implementation time 24 hours hour 4.5 hours 528 352 528 12.7 8th 9.9 15th 9 11th 18th 18th 12 "

Used pyridine (parts)

4,4'-Bipyridyl formed (parts).
Utilization of aluminum (%)
Utilization of pyridine (%) ...

Example 12

The reaction of 10 parts of aluminum powder and 399 parts of pyridine was initiated by the addition of 3 parts of mercuric chloride, and the reaction was conducted for 3.75 hours long _r .for 116 ° C. The reaction mixture was then oxidized in the manner described in Example 6 by introducing an air / nitrogen mixture (1: 1). Analysis of the end product showed that it contained 14.3 parts of 4,4'-bipyridyl, which corresponded to 16% utilization of the aluminum or 17.4% utilization of the pyridine.

The procedure of this example was repeated with the modification that 150 parts of pyridine were used and 150 parts of Ν, Ν-dimethylaniline were added to the mixture after initiation of the reaction. 1.7 parts of 4,4'-bipyridyl were obtained, which corresponds to a 2% utilization of the aluminum or 7% utilization of the pyridine corresponded.

The procedure has been repeated under nochffiajs Use of a mixture of 150 parts of pyridine and 250 parts of Ν, Ν-dimethylaniline in place of the 399 parts of pyridine. In this way, 2.9 parts of 4,4'-bipyridyl were obtained, which is one of the utilizations 3% of the aluminum used or 5% of the> <pyridine used corresponded.

309 545/532

Claims (15)

1 2 on while sodium is about the formation of free Claim: Radicals in the aluminum / pyridine mixture are effective. If the initiator is a metal, then this is Process for the preparation of 4,4'-bipyridyl from moderately finely ground or dispersed form Pyridine, characterized in that 5 turns, preferably in an inert mixture one excess pyridine at a temperature thinner, which the oxidation of the metal between about 100 ⁰ C and the boiling point of the surface prevents and the initiator in an ac- Pyridins with the prevailing pressure with alumi- tive condition. It can be a sodium dispersion nium that are used with mercury, mercury compounds, such as those used by gene and / or sodium is activated, converts mechanical stirring or ultrasonic stirring of the and then oxidizing the reaction product. molten metal in an inert diluent is obtained. Since mercury and mercury compounds do not promote the conversion too much, it is particularly preferred to use a combination of 15 mercury or a mercury compound and Use sodium. Here, however, it is preferred to use the mercury or the mercury compound to be added first to remove the oxide film. 4,4'-Bipyridyl is a valuable intermediate product, whereupon only the sodium, which is free for the manufacture of herbicidal agents, is broken down. The so far generated 20 radicals, is added,
known processes for the production of this substance. The amount of initiator added can, however, have the disadvantage that mixtures of iso- lent vary. In general, the corresponding meric bipyridyls are formed, from which the desired amount _{must be separated off at at least 2 ° / 0} and preferably min-4,4'-isomer. A known at least 5 percent by weight, based on aluminum, method for producing this substance is in the 25 which is reacted in the mixture. In certain German patent 358 397 and in the USA. Cases larger amounts may be necessary, described in patent 2,773,066. For example, when the metal is not pure or when driving, pyridine is reacted with sodium and the pyridine / metal mixture is not dry. The reaction product obtained is then oxidized. under extreme conditions, quantities of 20% can be required. This process not only has the disadvantage of 3 ° or more, based on the aluminum used, formation of mixtures of isomeric bipyridyls. The upper limit is to a large extent but it also has the disadvantage that it is extremely reactive and the rate of conversion depends on economic considerations and the desired sodium metal. In certain cases, therefore, when implementing special precautions, smaller amounts may be sufficient to have to be taken. 35, for example, if the reactants are very pure. It has now been found that in the process mentioned last, a reaction product is obtained as an initiator, so that after the reaction, which consists predominantly of 4,4'-bipyridyl and has started once, another reaction product is obtained Additions of metal only small amounts of undesirable isomeric bi- and / or pyridines can be made without containing pyridyls if the addition of further initiator is necessary instead of sodium with 40. It works a special activated aluminum. it is usually appropriate to carry out the reaction in the subject of the invention is a process for atmospheric pressure, but it is possible to produce 4,4'-bipyridyl from pyridine, which, if desired, is also characterized by higher or lower pressures being used : ' Pyridine at a temperature between about 100 ° C and 45 The time required for the reaction the boiling point of the pyridine at the prevailing depends on the substances and the implementation Pressure with aluminum that with mercury, mercury conditions that are applied and it is longer, silver compounds and / or sodium activated when low reaction temperatures are used is, reacted and the reaction product will then be. Implementation can be done in just 30 minutes oxidized. 5 ° be the end; but it can also be 10 or 12 hours The aluminum can be in any suitable need. Form are used, preferably in. The reaction can be carried out in the presence of a diluent a shape that has a large surface area, e.g. B. liquid is carried out »; that preferably Turning chips, foils or powder. Pure aluminum can be used as a solvent for bipyridyls and the aluminum / minium or an alloy of aluminum which is 55 pyridine reaction product. An excess of contains small amounts of other metals, pyridine can also be used as a diluent. will. Alloys of aluminum can also be used. This avoids that with other metals, such as magnesium, possibly a covering fine on the aluminum or sodium, which also reacts with pyridine, separates the reaction products, and another can be applied. Because the implementation of the aluminum 60 prevents implementation. starts badly with pyridine, and evidently the course of the reactions, which occurs with daring That which usually takes place on aluminum surfaces in accordance with the invention is not entirely clear Oxydfilms, one must clear the implementation through. It appears that at least 3 parts by mole of pyridine a small amount of an initiator in the pyridine-aluminum per gram atom of that consumed in the reaction Introduce minium mixture. Suitable initiators are 65 aluminum are required. Preferably, however Mercury and mercury compounds and Na- an excess of pyridine is used, for example as trium. Mercury and mercury compounds diluents. Accordingly, the proportion of break the oxide film on the aluminum surfaces applied pyridine up to 15 and preferably