DE1070607B - Process for the preparation of nitro compounds of alkanes, cycloalkanes and aryl-substituted alkanes - Google Patents

Description

The invention relates to a new process to be carried out in the liquid phase for producing the Nitro compounds of alkanes, cycloalkanol and aryl substituted alkanes.

Some of these nitro compounds are valuable solvents. They are also of particular importance as chemical intermediates for the production of technically interesting amines. _{Up to now, HNO 3} has primarily been used as a nitrating agent for their production. However, there are considerable disadvantages associated with the processing of this acid, above all because acid-proof chrome steel containers and pipes or corresponding units lined with glass or acid-proof stones are required. The yield of nitro compounds in the reaction with HNO ₃ also leaves something to be desired, since the nitrites formed in considerable quantities in the presence of water continue to react with the nitric acid to form substantial quantities of undesirable oxidation products. Since two liquid phases are also formed from acid and hydrocarbon, an intimate mixing of the components requires intensive stirring units. Finally, there are also particular difficulties when introducing the nitro group into aryl-substituted alkanes. Here the substitution does not take place, as desired, only on the alkyl side chain, but also on the aromatic ring.

The invention overcomes all of these disadvantages. It provides a new, simple and economical process for the production of nitro compounds from alkanes, cycloalkanol and aryl-substituted alkanes, in which work is carried out in a homogeneous phase and in which only minor amounts troublesome by-products are formed. '

The process of the invention is characterized in that alkyl nitrates, in particular n-propyl nitrate or cycloalkyl nitrates, with heating, preferably to 140 to 300 ° C, and increased pressure, preferably of at least 9 kg / cm ² , with a molecular excess of the in Hydrocarbons held in the liquid phase. The pressure is expediently set by forcing in inert gases such as nitrogen, helium or CO ₂ .

According to one embodiment of the process of the invention, nitrate and hydrocarbon are fed continuously a pressure vessel under the required temperature and pressure conditions to and draws the mixture dtr sales contract

also continuously. 5 »

The new experience works without the application of Catalysts. The hydrocarbons to be converted are kept in the liquid phase. One wins in a smooth and fast way nitro compound method of making

of nitro compounds of alkanes,

Cycloalkanes and aryl-substituted ones

Alkanes

Applicant:

EI du Pont de Nemours and Company,
Wilmington, Del. (V. St. A.)

Representative:
Dr.-Ing. A. v. Kreisler, Dr.-Ing. K. Schönwald,

Dipl.-Chem. Dr. phil. H. Siebeneicher

and Dr.-Ing. Th. Meyer, patent attorneys,

Cologne 1, Deichmannhaus

Claimed priority:
V. St. v. America April 16, 1957

Charles Philip Spaeth, Woodbury, NJ (V. St. A.),
has been named as the inventor

gen as the main product. It is of particular importance that the nitro group is only on the alkyl side chain attacks aryl-substituted alkanes, while no substitution takes place on the aryl ring itself.

At pressures below 9 kg / cm ^{2 it} is generally difficult to maintain a liquid phase. The pressures to be used are also determined by the type of pressure equipment. However, work should not be carried out in the area of extremely high pressures, for example above 1000 kg / cm ² , since any technical advantages cannot be achieved as a result. If one works at temperatures above 300 ° C., resin formation occurs which reduces the yield of nitro compounds.

If, according to the invention, an excess of hydrocarbons is used, the proportion of unreacted hydrocarbons recovered in a simple manner and returned to the process will.

The implementation takes place in a short time with good results, usually a few minutes are sufficient

909 688/406

Reaction time. If the reaction is allowed to take too long, there is a risk of decomposition of the compounds formed.

The nitrating agents are n-propyl and isopropyl nitrate in the foreground. In principle, however, the process according to the invention can be used with all alkyl nitrates carry out. Also with ethyl nitrate, li-butyl nitrate, isobutyl nitrate, secondary butyl nitrates, Mixtures of amyl nitrates, hexyl nitrate and cyclohexyl nitrate gave good nitration results.

According to the invention, the nitro group can be converted into all alkanes, cycloalkanes and aryl-substituted alkanes introduce which can be kept in the liquid phase under the reaction conditions. Except the The following compounds can also be used successfully in the reactions described in the examples nitrate: η-hexane, 2,2-dimethylbutane and tsooctane. Corresponding cycloalkanes are: cycloheptane and cyclopentane. To the cycloalkanes within the meaning of the invention also include alkyl-substituted cycloalkanes, such as methylcyclohexane, etc., and also alkylated cycloheptanes and cyclopentanes. In the same way, you can also use aryl-substituted alkanes, such as toluene, ethylbenzene, Nitrate cumene, cymene, durene and diisopropylbenzene. The method of the invention can also be used transferred to nitro- or halogen-substituted hydrocarbons, i.e. to those that do not have any other Carry hydrocarbon residues. Accordingly, you can also use nitrocyclohexane, chlorodecane, bromopentane etc. as starting materials. If you start from nitro-substituted hydrocarbons, you get polynitro compounds are of course produced by nitration.

In some cases it is useful to remove the hydrocarbon to be nitrated with solvents to be diluted, which are inert towards the nitrates used under the selected operating conditions are e.g. B. with benzene or acetonitrile.

The following examples illustrate the invention. Unless otherwise stated, mean all quantities are weight.

All conversion numbers represent percentages of the theoretically possible yield of nitro compounds produced They relate to the nitrating agent used.

Example 1.

294.5 parts of methylcyclohexane were placed in a pressure vessel previously flushed with nitrogen, a pressure of 28.4 kg / cm ^{2 was} set by forcing in nitrogen and the methylcyclohexane was heated to 203.degree. A mixture of 63.0 parts of n-propyl nitrate and 785.6 parts of methylcyclohexane was then pumped into the container over the course of 7 minutes while maintaining the temperature and pressure conditions.

After all the mixture had been added, 98.2 parts of methylcyclohexane were pumped through the feed lines of the pump in the course of 2 minutes in order to remove residues of the nitrate and methylcyclohexane mixture from the lines. A total of 20 mol of methylcyclohexane were used per Mo) n-propy) nitrate.

After cooling to 30 ° C., the pressure vessel was vented. The present mixture, expanded to atmospheric pressure, was washed with dilute sodium bicarbonate solution and analyzed. It was found that the mixture of 1-methyl-1-nitrocyclohexane was present in a yield of 26% of theory, based on the n-propyl nitrate used. In addition, a secondary mononitro compound was formed in a yield of 30%, based on the n-propyl nitrate used.
5

B e i s ρ i e 1 2

252 parts of cyclohexane were introduced into a pressure vessel previously flushed with nitrogen, a pressure of 28 kg / cm ^{2 was} set by forcing in nitrogen and the methylcyclohexane was heated to 210.degree. A mixture of 63 parts of n-propyl nitrate and 672 parts of cyclohexane was then poured into the container over a period of 7 minutes while maintaining the temperature and pressure conditions

* 5 pumped.

When the addition of the mixture was complete, the feed lines of the pump were also used 84 parts of cychohexane are pumped in to remove residues of the nitrate-cyclohexane mixture to remove from the lines. A total of 20 moles of cyclohexane were used per mole of n-propyl nitrate.

After cooling to 30 ° C., the pressure vessel was vented. The present mixture was washed with dilute sodium bicarbonate solution

^a 5 and analyzed. Nitrocyclohexane was formed in a yield of 43% of theory, based on the n-propyl nitrate used.

Example 3

The procedure and conditions of Example 1 were repeated, but instead of Methylcyclohexane is now used p-xylene. Initially, 318 parts of p-xylene were added to the reactor introduced. After the nitrogen pressure had been injected, the p-xylene was heated to 203 ° C. and a Mixture of 63 parts of n-propyl nitrate and 848 parts of p-xylene are pumped into the reactor. Afterward 106 parts of p-xylene were pumped into the container. Per mole of n-propyl nitrate were in total 20 moles of p-xylene were used. It was found analytically that α-nitro-p-xylene in one yield of 22.1%, based on the amount of n-propyl nitrate used, was formed. Analytically could it can also be demonstrated that no nitration had taken place on the ring.

Example 4

Cyclohexane was reacted with isopropyl nitrate under the conditions outlined in Example 2. It the same amounts were used, with isopropyl nitrate only instead of p-propyl nitrate \ i-was used. Analysis could prove that nitrocyclohexane is formed in a yield of 33%, based on the isopropyl nitrate used had been.

Example 5

Analogously to the procedure and reaction conditions of Example 1, n-nonane was reacted with n-propyl nitrate. First, 256 parts of n-nonane were added to the container. After the nitrogen had been forced in and after heating to 203 ° C., the mixture of 63 parts of n-propyl nitrate and 768 parts of n-nonane was pumped into the container. Afterward

^ 5 128 parts of n-nonane were added to the container. 15 moles of n-nonane were used per mole of n-propyl nitrate.

Analysis could show that in a yield of 31% - based on the amount used n-propyl nitrate, a mixture of primary

and secondary mononitro-n-nonanes had been formed.

Claims (3)

Patent claims: 1. A process for the preparation of Nitroverbindungen of alkalis, cycloalkanol and aryl-substituted alkalis, characterized in that one Alkvlnitrate, in particular n-propyl nitrate or isopropyl nitrate or cycloalkyl nitrate, with heating, preferably to 140 to 300 ° C, and increased pressure, preferably of at least 9 kg / cm ² , with a molar excess of the hydrocarbons present in the liquid phase. 2. The method according to claim 1, characterized in that the pressure is adjusted _{by forcing inert gases such as nitrogen, helium or CO 2.} 3. The method according to claim 1, characterized in that one nitrate and hydrocarbon continuously a pressure vessel under the required temperature and pressure conditions supplies and the mixture of the reaction products also continuously withdraws.