DE1493025C3 - A process for the preparation of alkyl adamantanes having 12 to 15 carbon atoms by catalytic isomerization of certain tricyclic perhydroaromatic hydrocarbons having 12 to 15 carbon atoms and interrupting the reaction before the isomerization is complete - Google Patents

Description

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The carbon nucleus of adamantane contains carbon atoms which are arranged completely symmetrically and without tension, so that there are four condensed, six-membered rings and four bridgehead carbon atoms. The structure of adamantane (C ₁₀ H ₁₆ ) is generally given schematically as follows:

. ■: ■: ■■ · ■■■■:.-....... ■

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60

Adamantane has a melting point of 268 ° C, sublimes below its melting point and occurs consequently not in a liquid state. Because of the symmetrical, tension-free arrangement of the Carbon atoms and the fact that due to the bridgehead carbon atoms no hydrogen splitting can occur, adamantane is an extremely stable hydrocarbon.

Numerous derivatives of adamantane are already known. Ethyl-substituted adamantanes were also used already produced according to classical synthetic methods.

It was also already known a method for the rearrangement of perhydrogenated trinuclear aromatic hydrocarbons known, which was carried out at a relatively low temperature of -5 to +50 ⁰ C in the presence of a Aluminiumhalogenidkatalysators (US-PS 31 28 316). This known process was mainly used for the production of methyl-substituted adamantahs.

In contrast, the invention is based on the object of a process for the catalytic isomerization of to provide certain perhydroaromatic hydrocarbons that lead to the formation of ethyl-substituted adamantanes.

The invention relates to a process for the preparation of alkyl adamantanes having 12 to 15 carbon atoms by isomerizing perhydroanthracene, perhydrobenzonaphthene, perhydrofluoren, perhydroacenaphthene, perhydrophenanthrene or their alkyl homologues having 12 to 15 carbon atoms at elevated temperature in the presence of an isomerization catalyst and interrupting the reaction before completion of isomerization. The process is characterized in that, for the preparation of ethyl-substituted adamantanes, the reaction is carried out in the presence of an HF-BF ₃ catalyst at 50 to 200 ° C. until at least the greater proportion of the perhydrogenated aromatic hydrocarbon has been converted into hydrocarbons with an adamantane structure, However, the reaction is interrupted before the isomerization of a larger proportion of the alkyl adamantanes to polymethyladamantanes has taken place, and that during the reaction a weight ratio of perhydroaromatics to HF of 2 to 20: 1 and a molar ratio of HF: BF ₃ of 1: 1 to 50 : 1 complies.

In general, perhydroaromatics are used as starting compounds according to the invention not readily available. However, the corresponding aromatic hydrocarbons can be made from Sources such as direct distillates, cracked petroleum fractions or coal tar can be obtained.

Accordingly, such aromatics can be used as a suitable starting material and they can easily be converted to perhydroaromatics for the purposes of the present process by complete hydrogenation using a suitable catalyst. A catalyst suitable for this purpose is Raney nickel. Suitable hydrogenation conditions when using this catalyst are a temperature range of 200 to 275 ° C., a hydrogen pressure of 140.6 to 281.2 kg / cm ² above atmospheric pressure, a weight ratio of catalyst to hydrocarbon of 1: 4 to 1:20 and a reaction time from 2 to 12 hours. Other suitable catalysts are, for. B. platinum, cobalt molybdate, nickel tungstate or nickel sulfide — tungsten sulfide, these hydrogenation components being deposited on aluminum oxide. Commercially available platinum reforming catalysts can also be used for this purpose. These other catalysts are generally used at the same pressure, but at higher temperatures than for Raney

e
e
• s
is

Nickel, e.g. B. at 300 to 400 ⁰ C, used to achieve the complete hydrogenation of the aromatic hydrocarbon.

The aromatics used as starting material for the isomerization can also be non-cyclic Substituents such as methyl and / or ethyl groups and olefinic or acetylenic groups and can also be used in the form of a mixture. <

In order to obtain the desired ethyl-substituted products, it is extremely important to carry out the reaction interrupt at the right level, otherwise the main products dimethyladamantane, trimethyladamantane, Represent tetramethyladamantane or pentamethyladamantane, in which the methyl groups are replaced mainly at the bridgehead carbon atoms in the adamantine core. When the reaction is interrupted at the corresponding stage, generally more than 40% of the reaction product adamantanes with a single ethyl substituent and 0 to 3 methyl substituents depending on the number of carbon atoms in the starting perhydroaromatic. The substitution of the adamantane core occurs largely on the bridging carbon atoms, but can separate there are also smaller amounts of methyl or ethyl groups on the non-bridging carbon atoms. Accordingly, the following compounds can be obtained as the main products of the isomerization reaction will:

from C ₁₂ perhydroaromatics

1-ethyladamantane,
from C ₁₃ perhydroaromatics

1-methyl-3-ethyladamantane,
from C ₁₄ perhydroaromatics

1, S-dimethyl-S-ethyladamantane,
from C ₁₅ perhydroaromatic compounds

1,3,5-trimethyl-7-ethyladamantane.

30th

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The isomerization reaction is only initiated by contacting the perhydroaromatic carbon with the HF-BF ₃ catalyst at a temperature from 50 to 200 ° C., preferably from 70 to 150 ° C. and in particular at 75 to 125 ° C. As a diluent for the perhydroaromatic a saturated hydrocarbon can optionally be used, but this is generally not necessary. If a diluent is used, it is preferably an alkyl naphthalene such as methylcyclohexane or dimethylcyclohexane. The weight ratio of perhydroaromatic to HF should be in the range from 2 to 20: 1. The molar ratio of HF: .BF ₃ should be kept in the range from 1: 1 to 50: 1. The effective catalyst is apparently a complex formed _{between HF and BF 3.} The pressures in the reaction zone can vary widely depending on the temperature and the amount of BF ₃ that has been used. Pressures in the range from 15.1 to 57.2 kg / cm ² are preferred. ''^;

The reaction time for the isomerization reaction can vary widely, depending on the temperature and also on the ratio of HF ^ -BF ₃ -catalyst complex in relation to the amount of perhydroaromatic compounds supplied. As a result, the reaction time can be between 5 minutes and 100 hours. At reaction temperatures in the preferred range from 75 to 125 ° C., the reaction time is generally from 3 to 24 hours.

The reaction mechanism for the reaction, which is _{catalyzed by HF-BF 3} , comprises several isomerizations in which the end products would be polymethyladamantanes if the reaction were to take too long. The ethyl-substituted adamantanes represent an intermediate stage in the overall isomerization, as it is important that the reaction be interrupted at this stage. If the starting material is a C ₁₂ perhydroaromatic compound other than perhydroacenaphthene, isomerization to perhydroacenaphthene, which has the structure given above, takes place in the first stage. During the further isomerization, this compound is converted into ethyl adamantane. It appears that the ethyl adamantane formed first is the 2-isomer, i.e. in which the ethyl group is not located on any bridging carbon atom: However, this 2-isomer is obviously isomerized rapidly to the 1-ethyl-adamantah, so that as practical consequence the 1-isomer always seems to predominate over the 2-isomer in the reaction product. An additional isomerization leads to the conversion of Äthyladaniantans into dimethyladamantan, which is a mixture of two isomers, namely 1,2- and 1,4-dimethyl- at the beginning. adamantane, appears to be. If the reaction is allowed to continue, these compounds will be isomerized to the isomer which is completely substituted by the bridging carbon atoms, i.e. the 1,3-dimethyladamantene, which is the thermodynamically favored isomer and thus the end product when the isomerization is complete In carrying out the present invention, the reaction is interrupted before the isomerization is complete, so that the production of ethyl adamantane, mainly 1-ethyl adamantane, can be maximized. The ethyl adamantane can be isolated from the other reaction products by distillation under good fractionation conditions will.

In the case of the starting C ₁₃ -C ₁₅ tricyclic perhydroaromatic material, the first type to be formed upon isomerization is a compound of the perhydropeririaphthene type (also known as perhydrobenzonaphthene and perhydrophenals). Thus the kernel at this 1st reaction stage has the following structural formula:. · .. '■.

If the perhydroaromatic used as the starting material Has 13 carbon atoms, so is. that's first Isomerization product formed is perhydroperinaphthene itself. The first reaction product is analogous of a C ^ -ausgahgSmateriais Methylperhydröperinaphthen, while the corresponding product of a cis-starting material dimethylperhydroperinaphthene is. The further isomerization then leads to a Ädamanfänkerri, on which one Ethyl group and one, two or three methyl groups; depend, depending on the number of carbon atoms in the Source material. The ethyl group appears at the beginning

sitting on a non-bridging carbon atom, but it is quickly isomerized to a bridging position. The one methyl group from a C 1-4 hydrocarbon starting material and the two methyl groups in the case of a C ₁₄ starting material tend to occur preferentially on bridging carbon atoms. For example, a C ₁₃ starting material 1-methyl-3-ethyladamantane is produced, while a C ₁₄ charge produces 1,3-dimethyl-5-ethyladamantane. In the case of the C ₁₅ perhydroaromatic compounds, an ethyl group and 3 methyl groups are formed, the preferred substituent positions again being on the 4 bridging carbon atoms. In all of these isomerization processes, the reaction should be interrupted at the appropriate stage in order to maximize the yield of the ethyl-substituted product, otherwise the ethyl group is converted into 2 methyl groups and polymethyladamantanes are obtained. In the case of the C ₁₅ material, too long a reaction not only converts the dimethylethyladamantane into the 1,2,3,5,7-pentamethyladamantane, but also tends to crack.

The ethyl-substituted adamantanes produced by the process according to the invention have high thermal stability, they occur for saturated hydrocarbons in an unusually broad range Temperature range as liquids. They are useful as specialty coolants and as a result Lubricant., Comparatively, e.g. B. 1-Ethyladamantane a melting or boiling point of -60 or 219 ° C, while the corresponding values for its isomer, 1,3-dimethyladamantane, about -30 or 205 ° C. The melting and boiling points for 1,3-dimethyl-5-ethyladamantane are below - 80 or 235 ° C, while the corresponding values for its isomer, 1,3,5,7-tetramethyladamantane, about 67 and 215 ° C.

example 1

Acenaphthene is dissolved in methylcyclohexane and then hydrogenated at 246 ° C. under a hydrogen pressure of 36.2 kg / cm ² with the aid of a 1% platinum-aluminum oxide catalyst to give perhydroacenaphthene (C ₁₂ H ₂₀ ). After most of the methylcyclohexane has been removed by distillation, 520 g of perhydroacenaphthene, which contains 3.3% residual methylcyclohexane, are fed to an autoclave which is provided with a stirrer. 70 g of anhydrous HF are added and the autoclave is pressurized _{with 30 g of BF 3.} When the reaction mixture has been heated to 31 ° C., it is stirred at this temperature for about 3 hours, with virtually no reaction occurring. The mixture is then heated and maintained in a temperature range of 65 to 85 ° C, mainly in the region of 82 ° C, for 6.3 hours with stirring.

The reaction is then stopped and the hydrocarbon layer is removed from the catalyst layer separated and washed to remove catalyst residues. The hydrocarbon product is analyzed by separating the components with the aid of vapor phase chromatography; the main components are determined by nuclear magnetic resonance, infrared and mass spectroscopy as well as determined by carbon and hydrogen analyzes. The results are in the following Table compiled.

Methylcyclohexane Batch Reaction 0.6 J Isodecaline «%) product 20.1 1,3-dimethyladamantane 3.3 12.3 IO 1,2- and 1,4-dimethyl -. adamantan *) - 3.2 Unidentified - C ₁₂ adamantane 48.9 15th 1-ethyladamantane - 14.9 2-ethyladamantane - Perhydroacenaphthene - 100.0 - 20th 96.7 100.0

*) The two isomers occur in approximately the same amounts.

The values in the table show that the two ethyladamantanes in this reaction procedure Represent the main product and that of them represent the isomer substituted on a bridging carbon atom (1-ethyladamantane) arises by far predominantly.

Example 2

Perhydrophenanthrene is made by hydrogenating phenanthrene by essentially the same procedure produced as in example 1. Two approaches are carried out in which the hydrogenated product is isomerized in a mixture with a small amount of methylcyclohexane. One approach is mainly at about 90 ° C for 3 hours and the other substantially at about 100 ° C for 8 hours accomplished. When working up and analyzing the products as in the previous example achieved the following results:

Reaction temperature (° C) .. 90 100

Response time (hours) 3 8

Hydrocarbon charge:

Perhydrophenanthrene (g) 527 311

Methylcyclopentane (g) ... 13 13

Catalyst:

HF (g) 32 100

BF ₃ (g) 35 35

Liquid reaction product:

Methylcyclohexane 1.9 4.0

No traces of C _{8 naphthene}

C ₉ naphthene none 1.7

Qo-naphthene none 0.6

Methyladamantane traces 1.7

1,3,5,7-tetramethyladamantane 0.5 5.6

Other tetramethyl

adamantane 3.8 2.3

1,3-dimethyl-5-ethyl

adamantan 11.4 59.3

Unidentified

Adamantanes 11.0 10.1

Methyl perhydroperi-

naphthene 50.5

Perhydroanthracene 17.6

Perhydrophenanthrene .... 3.3

9.0
4.0
1.7

The values in the table show that for the batch carried out at 90 ° C., a reaction time of 3 hours is not sufficient _{to isomerize the C 14} perhydroaromatic compound used up to the stage at which dimethylethyladamantane is the main product. This approach represents an earlier stage of isomerization in which the main product has the perhydroperinaphthene structure. The other approach, carried out at a slightly higher temperature and a longer reaction time, shows the isomerization stage in which the dimethylethyladamantane is obtained almost as the main product, as can be seen from the yield of 59.3% 1,3-dimethyl-5-ethyladamantane.

The preceding examples explain the preparation of ethyl-substituted adamantanes with 12 or 14 carbon atoms. In the same way, ethyl-substituted adamantanes with 13 and 15 carbon atoms can be prepared from the tricyclic perhydroaromatics of the C ₁₃ and C ₁₅ type listed at the outset. Each of these ethyl-substituted products can be separated from the accompanying isomer by superfractionation and isolated in high purity.

509 685/17

Claims (2)

Patent claims: 1. Process for the preparation of alkyl adamantanes with 12 to 15 carbon atoms by isomerization of perhydroanthracene, perhydrobenzonaphthene, perhydrofluoren, perhydroacenaphthene, perhydrophenanthrene or their alkyl homologues with 12 to 15 carbon atoms at elevated temperature in the presence of an isomerization catalyst and with interruption of the reaction before the completion of the isomerization, characterized gek.ennzeichnet, wherein the reaction for the preparation of äthylsubstituierten adamantanes ₃ catalyst as long as carried out in the presence of a HF-BF at 50 to 200 ⁰ C, until at least the greater proportion of perhydrogenated aromatic hydrocarbon is converted into hydrocarbons with adamantane which However, the reaction is interrupted before the isomerization of a larger proportion of the alkyl adamantanes to polymethyladamantanes has taken place, and that during the reaction a weight ratio of perhydroaromatic to HF of 2 to 20: 1 and a molar ratio of HF : Complies with BF ₃ from 1: 1 to 50: 1. 2. The method according to claim 1, characterized in that the reaction is carried out at 70 to 150 ° C, in particular at 75 to 125 ° C carried out.