DE2412110A1 - NEW ESTERS OF TETRACARBONIC PYRAZIC ACIDS, THE PROCESS FOR THEIR PRODUCTION AND THEIR USE AS THERMOSTABLE FLUIDS - Google Patents

Description

Patent Attorneys DlpL-Ing. R. BEETZ «en.
Dlpl-ing. K. LAMPRECHT

Dr.-Ing. R. 3 EETZ Jr. IMttnchen 22, Steinedorfetr. If

550-22.297P 13. 3- 1974

SOCIETE NATIONALE DES POUDRES ET EXPLQSIFS, Paris (France)

New esters of the tetracarboxylic acid pyrazine acid,

Process for their production and their use as thermostable fluids

The invention relates to new esters of the tetracarboxylic pyrazine acid, improvements in the synthesis of these esters and their Use as thermostable fluids. The synthesis of the tetracarboxylic pyrazine acid has been described in the literature, for example in the essay by H. I. X. Mager and W. Berends in "Recueil des Travaux Chimiques des Pays-Bas" (1957), vol. 76, p. 28. Nevertheless the isolation of this acid is rather difficult, and only the methyl and ethyl esters of this acid have been described in the literature, in particular by F. D. Chattaway and W. G. Humphrey in "Journal of the Chemical Society", 1929, p. 645. The invention relates to the synthesis of alkylpyrazine tetracarboxylates of the general formula

550- (B 468) -T-r (7) "

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(D

in which R is a linear or branched alkyl radical which is a or can contain several functional groups.

The synthesis is carried out according to the invention by direct reaction of the alcohol-sulfuric acid pair with a potassium salt of the acid, which in turn is produced by condensation of the orthophenylenediamine with itself under the action of ferric chloride and subsequent oxidation with potassium permanganate. This avoids the main disadvantage of the processes already known, namely the isolation of the pure acid. The invention also relates to the use of the liquid esters of the tetracarboxylic acid pyrazine acid as thermostable fluids.

According to the invention, the alkylpyrazine tetracarboxylates are synthesized (l) by the action of the alcohol-sulfuric acid mixture on the dipotassium salt of the tetracarboxylic acid pyrazine acid (2) with the formula

(2)

Q 9 H U (j / IQlB

This salt (2) itself is according to the article already cited produced by the method described by Mager and Berends; the production this salt can be represented according to the following reaction scheme:

FeCl

3- *

1) KMn 04

2) HCl

NH,

To esterify the salt (2), proceed as follows: The salt (2) and the alcohol are combined in one before the reaction Alcohol / salt molar ratio close to 6 with vigorous stirring. The concentrated sulfuric acid is poured in small portions, with the mixture is brought to a temperature close to that of reflux. According to a preferred embodiment of the invention, this is The molar ratio of the total amount of acid used to the amount of salt (2) used is almost exactly equal to 6. The sulfuric acid used should be pure and concentrated in order to have a good dehydrating effect, and should titrate at least 66 trees for this purpose.

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After all the acid has been added, the mixture is heated with stirring for several hours (in all cases more than three hours) at the reflux temperature of the alcohol-sulfuric acid mixture. It is then allowed to cool and the ester is taken up in the ethyl ether and filtered. The filtrate is with an alkali carbonate or a anhydrous alkaline earth carbonate is neutralized until the evolution of gas ceases, and then it is filtered and the ether is evaporated.

The ester is taken up again in normal hexane or in chloroform , allowed to settle in order to separate the mineral residues that precipitate, filtered, the hexane evaporated and the process started again several times; in the majority of cases it is interesting to treat the phase in the hexane with animal charcoal in order to decolorize the product. If the ester is a liquid, its purification is then completed by removing the traces of alcohol that are still in it by distillation under a strong vacuum (10 to 10 mm Hg), followed by evaporation on molecular film. If the ester is a solid, it is purified by recrystallization in petroleum ether. The product obtained has the appearance of a slightly yellowish oil when it is a liquid and that of white crystals when the ester is solid.

The esters of the tetracarboxylic pyrazine acid according to the formula (I) are prepared by the process described above, in which R is a linear or branched alkyl radical. The alkyl chain may or may not contain functional groups, whereby the radio

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tion groups are selected from the group consisting of the functions and resistant to boiling concentrated sulfuric acid in particular the ether, ketone, sulfoxide and phosphine oxide functions. According to a preferred embodiment of the invention the alcohol used is a primary or secondary alcohol to ensure that the reaction proceeds properly.

The applicant has found that the liquid esters according to the invention have, with regard to the variation in their viscosity with temperature and with regard to their thermal stability, the essential properties desired for the formation of the basic materials of thermally stable lubricants. By mutually mixing the liquid esters according to the invention with the usual additives known per se for lubricant compositions (viscosity modifiers, antioxidants, anti-corrosion and anti-foam additives, load capacity modifiers), lubricants are obtained which can be used at high temperatures (at least 250 ° C.). The solid esters can advantageously serve as plasticizers for polyolefins and polyvinyl chlorides.

Example 1: Synthesis of the n-propylpyrazine tetracarboxylate

The synthesis of the dipotassium salt of the tetracarboxylic acid pyrazine acid was carried out according to the method of Mager and Berends, of which a more detailed description is explained below as an example will.

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In one equipped with a stirring device and a pouring ampoule Glass flasks of 5 l are placed in 54 g of orthophenylenediamine dissolved in 83 ml of concentrated hydrochloric acid and 2.5 l of water. Man slowly adds a solution of 400 g of ferric chloride in 750 ml of water while stirring. After 12 hours of reaction at room temperature and If a reddish brown color occurs, the diamine-2,3 phenazine that has precipitated is filtered off. It is washed with a dilute hydrochloric acid solution . The precipitate is dissolved in warm water, then precipitated again by adding potash, filtered and washed and dried at 100 to 110 ° C. The previous filtrate is heated and glacial acetic acid up to a pH of 4 to 5 acidified. After cooling, the amino-2 hydroxy-3 phenazine is collected on the filter, washed with water and kept at 100 to 110.degree dried.

The two dried precipitates are mixed and dissolved in 4 liters of an aqueous potash solution. One stirs and adds and after 560 g of potassium permanganate, the temperature is kept in the vicinity of 95.degree. The reaction is allowed to take place for 12 hours. At the end of the reaction, the excess potassium permanganate is removed by adding ethyl alcohol. A brown solution is obtained which after filtration gives an orange filtrate. It is evaporated almost to dryness, allowed to cool and acidified with concentrated hydrochloric acid until to a pH of 2 to 3. A yellow precipitate is obtained of the dipotassium salt of tetracarboxylic pyrazine acid (2), which is filtered, washed with water and dried at 100 to 110.degree. Adds 100 g of dipotassium salt (2) of the tetracarboxylic acid pyrazine acid

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3 you add 150 g normal propyl alcohol and 100 cm sulfuric acid from 66 Baume.

After 6 hours of heating at 80 ° C., the solution is cooled, poured into 0.5 l of ethyl ether and neutralized with 1 kg of neutral sodium carbonate. After filtering, the ether phase is evaporated; the oily residue taken up in hexane is treated with animal charcoal in the heat. After distillation at ambient pressure is taken again in hexane and starts treatment with charcoal on

—3 new ones. Distillation is then carried out in vacuo (10 mm Hg) and the ester obtained has the appearance of a translucent oil, the purification of which is completed by evaporation on a molecular film.

The elementary analysis of the product shows the following results:

theoretically experimental Proportion of carbon 56.6 55.1 Proportion of hydrogen 6.6 6.9 Proportion of nitrogen 6.6 6.1

The IR spectrum shows a peak at 1750 cm accordingly of oscillation C = O and a peak at 2940 cm corresponding to oscillation C-H.

The RMN spectrum obtained using "CDC13" as the solvent and was obtained by comparison with tetram ethylsilane,

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shows a triple spectral line at 1 ppm, a six-fold spectral line at 1.8 ppm and a triple spectral line at 4.33 ppm.

The UV spectrum shows a peak at 280 myu with an extinction coefficient from 7280.

The refractive index of the product is 1.4829.

The fiscal properties of the ester are given in the table below and it is found that the viscosity index is quite good and the product has good thermal stability (the decomposition maximum under the closed capsule heated at a heating rate of 20 C / min is at 390 ⁰ C).

Viscosity viscosity viscosity

at 37.8 ° C at 98.9 ° index

24.5 cst 4.0 cst 38.1

Example 2

The purpose of this example is to illustrate the implementation of the process of the invention in the case of a low number ester of carbon atoms using a secondary alcohol. Isopropyl alcohol was used. The synthesis of the salt (2) was carried out in a manner analogous to that described in Example 1

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guided. 100 g of the dipotassium salt of the tetracarboxylic acid pyrazine

3 acid is added to 150 g of isopropyl alcohol and 100 cm of sulfuric acid. After three hours of reaction at 80 ° C., the mixture is cooled, filtered and treated in hexane and with animal charcoal. Since the product is solid, it is cleaned by recrystallization in petroleum ether. White crystals with a melting point of 110 ° C. are obtained. The yield in relation to the theoretical yield is 65 %. The elemental analysis of the product provides the following results:

theoretically experimental

Percentage of carbon 56.6 56.6

Proportion of hydrogen 6.6 6.7

Proportion of nitrogen 6.6 6.7

The IR spectrum shows a peak at 1740 cm accordingly of oscillation C = O and a peak at 2940 cm corresponding to oscillation C-H.

The RMN spectrum obtained under the conditions of Example 1 shows a double spectral line at 1.39 ppm and a seven-fold Spectral line at 5.26 ppm.

The UV spectrum shows a peak of 275 myu with a molecular extinction coefficient out of 6770.

The thermal stability under a closed capsule heated at a heating rate of 10 C / min (stability ¹¹ DSC ") shows a decomposition maximum at 375 C.

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Example 3

This example relates to the practice of the invention in the case of an <X-branched ester having 5 carbon atoms when used of a primary alcohol. Isoamyl alcohol was used. The synthesis of the ester was carried out in one of those described in Example 1 carried out in an analogous manner. 120 g of the dipotassium salt of the tetra-

3 carboxylic acid pyrazinic acid is added to 245 g of isoamyl alcohol and 100 cm of sulfuric acid. The reaction lasted 12 hours at 90 ° C. and the purification was carried out in the manner analogous to Example 1 using hexane as the solvent. A translucent oil is obtained with an output of 65 % based on the theoretical output.

The elemental analysis of the product shows the following results:

theoretically experimental

Proportion of carbon Proportion of hydrogen Proportion of nitrogen

The IR spectrum shows a peak at 1740 cm accordingly of oscillation C = O and a peak at 2920 cm corresponding to oscillation C-H.

The RMN obtained under conditions analogous to Example 1

62.7 61.2 8.2 8.3 5.2 4.4

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Spectrum shows a double spectral line at 0.95 ppm and a massive between 1 and 2 ppm.

The UV spectrum shows a peak at 275 m / a with an extinction coefficient of 6790.

The refractive index of the ester is 1.4676.

The viscometric properties are given in the following table:

Viscosity viscosity viscosity

at 37.8 ° C at 98.9 ° C index

39.6 cst 5.6 cst 82.7

The thermal stability "DSC" is 330 ^° C.

Example 4

This example concerns the implementation of the invention in the case of a linear ester having 6 carbon atoms.

The n-hexyl alcohol was used.

The synthesis of this ester was carried out in one of those described in Example 1 carried out in an analogous manner by standing for 12 hours

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at 100 C 103 g of the dipotassium salt of the tetracarboxylic acid pyrazine

acid was allowed to react with 245 g of n-hexalcohol and 80 cm of sulfuric acid. The cleaning solvent used was hexane.

An orange oil is obtained with an output of about 70% of the theoretical output.

The elemental analysis of the product gives the following results;

theoretically experimental Proportion of carbon 64.9 64.6 Proportion of hydrogen 8.8 9.1 Proportion of nitrogen 4.7 4.3

The refractive index is 1.4485.

- 1 The IR spectrum shows a peak of 1740 cm accordingly

of the oscillation C = O and a peak of 2900 cm corresponding to the oscillation CH.

The RMN spectrum obtained under the conditions of Example 1 shows a triple spectral line at 0.90 ppm, a solid centered at 1.30 ppm and two triple spectral lines at 1.8 ppm and 4.45 ppm.

The UV spectrum shows a peak at 275 m ju with an extinction coefficient of 7 100th

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The thermal stability "D.S.C." is 330 "c.

The viscometric properties are in the table below specified:

Viscosity viscosity viscosity

at 37.8 ° C at 98.9 ° C index

5.43 cst 1.78 cst 94.3

Example 5

This example illustrates the application of the invention in the case of a branched ester with 8 carbon atoms with complete β-branching. Trimethyl-2,2,4 pentanol was used.

The synthesis of this ester was carried out in one of those described in Example 1 carried out in an analogous manner by for 48 hours at 70 C 120 g of the dipotassium salt of the tetracarboxylic pyra-

Zinsic acid with 135 g of trimethyl-2,2,4-pentanol and 80 cm of sulfuric acid let react. The cleaning solvent used was chloroform. The yield was in relation to the theoretical 70%.

The product obtained has the appearance of a translucent oil, the refractive index of which is 1.4736 and its elemental analysis delivers the following results:

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theoretically experimental Proportion of carbon 68, 2 67.8 Proportion of hydrogen 9.6 9.9 Proportion of nitrogen 4.0 3.5

- 1 The IR spectrum shows a peak at 1740 cm accordingly

of oscillation C = O and a peak at 2920 cm corresponding to oscillation C-H.

The RMN spectrum obtained under conditions analogous to those in Example 1 shows a double spectral line at 0.92 ppm, a single spectral line at 1.00 ppm, a double spectral line at 1.23 ppm, a massif at 1.63 ppm and a single spectral line at 4.12 ppm.

The UV spectrum shows a peak at 275 m u with a molecular extinction coefficient from 7350.

The viscometric properties of the product are shown in the table below.

Viscosity at 37.8 ° C

Viscosity at 98.9 ° C Viscosity index Thermal stability in air ("DSC")

Maximum decomposition peak at 10 C / min heating rate

254 ,8th CSt 20th , 3 CSt 100 450 O C.

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Example 6

This example explains the invention for the case of a branched one Esters with 9 carbon atoms. Trimethyl-3,5,5-hexalcohol was used as the alcohol.

The synthesis of this ester was carried out in a manner analogous to that described in Example 1 by, during 24 Hours under reflux 100 g of the dipotassium salt of the tetracarbon

3 acidic pyrazinic acid with 90 g trimethyl-3,5,5 hexalalcohol and 50 cm Let sulfuric acid react. The cleaning solvent used was hexane. The yield in relation to the theoretical is 70%.

The product obtained has the appearance of a translucent Oil whose refractive index is 1.4670 at 25 C and whose EIe mental analysis provides the following results:

theoretically experimental

Proportion of carbon Proportion of hydrogen Proportion of nitrogen

The IR spectrum shows a peak at 1740 cm "" accordingly

- 1 corresponding to the oscillation C = O and a peak at 2900 cm

the oscillation C-H.

69.5 68.5 10.0 10.1 3.7 2.9

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The RMN spectrum obtained under conditions analogous to those in Example 1 shows three massifs at 0.9, 1.2 and 1.7 ppm.

The UV spectrum shows a peak at 275 m u with an extinction coefficient from 6300.

The viscometric properties of the product are given in the following table:

Viscosity at 37.8 ° C

Viscosity at 98.9 ° C Viscosity index Thermal stability in air ("DSC")

111 CSt 11 , 4 cst 90 425 ° C

To compare the viscometric properties of the esters according to Examples 1, 3, 4, 5 and 6 with those of two known ones The basic materials for thermostable lubricants, namely ethyl 2-hexyl sebacate and trimethylolpropane triheptanoate, are the viscometric ones Properties of these known substances are given in the following table:

Viscosity at 37.8 C Viscosity at 98.9 ° C Viscosity index Thermal stability ("DSC")

Ethyl-2 ~
hexalsebazate Trimethylol
propantri
heptanoate 15.02 cst 12.50 cst 3.50 cst 3.31 cst 129 156 309 ° C 280 ° C

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It is found that the liquid esters according to the invention have a higher viscosity at 98.9 ° C. than those currently known Have lubricant base materials, and this property in conjunction with their good thermal stability enables their use these esters according to the invention as thermostable fluids at higher temperatures than are currently known Fabrics is possible.

Example 7

This example illustrates the practice of the invention in the case of a linear ester having 9 carbon atoms. It became the n-nonyl alcohol is used.

The synthesis of this ester was carried out in a manner analogous to that described in Example 2, while 8 hours under reflux 100 g of the dipotassium salt of the tetracarbon

acidic pyrazinic acid was allowed to react with 90 g of n-nonyl alcohol and 50 cm of sulfuric acid. The cleaning solvent used was cyclohexane. The yield in relation to theory is 70 %.

The product has an appearance of a white solid, its Melting point is 51 C and its elemental analysis gives the following results:

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theoretically experimental Proportion of carbon 69.47 69.74 Proportion of hydrogen 10.00 10.08 Proportion of nitrogen 3.68 3.65

The IR spectrum shows a peak at 1740 cm accordingly

—1 corresponding to the oscillation C = O and a peak at 2920 cm the oscillation C-H.

The RMN spectrum obtained under the conditions of Example 1 reveals three massifs centered at 0.9, 1.2 and 1.7 ppm and a triple spectral line at 4.39 ppm.

The UV spectrum shows a peak at 275 nm with an extinction coefficient from 8300.

The thermal stability "D.S.C." is 265 ° C,

Example 8

This example illustrates the application of the invention in the case of a linear ester having 12 carbon atoms.

The synthesis of this ester was carried out in one of those described in Example 2 carried out in an analogous manner by standing for 48 hours at 120 C 102 g of the dipotassium salt of the tetracarboxylic acid pyra-

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3 Zinic acid react with 298 g of n-dodecanol and 100 cm of sulfuric acid let. The cleaning solvent used was chloroform. The spreading in relation to the theoretical is 75%. The product is a white solid with a melting point of 51 C and its elemental analysis brings the following results;

theoretically experimental Proportion of carbon 72.4 73.0 Proportion of hydrogen 10.8 11.1 Proportion of nitrogen 3.0 2.8

-1

The IR spectrum shows a peak at 1740 cm "accordingly

the oscillation C = O and a peak at 2900 cm corresponding to the oscillation C - H,

The RMN spectrum obtained under the conditions of Example 1 shows two massifs and at 0.83 ppm and 1.27 ppm a triple spectral line at 4.38 ppm.

The UV spectrum shows a peak at 270 mu with an extinction coefficient from 6000.

The Thermal Stability ("DSC") test on air with a heater A speed of 10 ° C / min shows a maximum decomposition at 320 ° C.

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Example 9

This example illustrates the implementation of the invention in the case of functional groups inside the hydrocarbon chains containing ester. The alcohol used is the following ether alcohol: 2 2 (2 ethoxyethoxy) ethoxy ethyl alcohol.

The synthesis of the corresponding ester was carried out in a manner analogous to that described in Example 2 by during 72 hours 220 g of the 2 2 (2 ethoxyethoxy) ethoxy ethyl alcohol

hols and 100 cm of sulfuric acid allowed to react. The cleaning solvent used was hexane. The yield in relation to the theoretical is 70 % <

The elemental analysis of the product brings the following results:

theoretically exper in enteil Proportion of carbon 53.6 53.1 Proportion of hydrogen 7.6 7.0 Proportion of nitrogen 3.1 2.8

The IR spectrum shows a peak at 1740 cm accordingly the oscillation C = O and a peak at 2900 cm corresponding to the oscillation C-H.

The RMN spectrum obtained under the conditions of Example 1 shows a triple spectral line at 1.2 ppm, a quadruple

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Spectral line at 3.52 ppm, a massif centered at 3.65 ppm and a triple spectral line centered at 4.64 ppm.

, The UV spectrum shows a peak at 275 m u with an extinction coefficient from 3080.

The thermal stability ¹¹ DSC ″ is 250 ° C.

In all the examples given, the term "ester with χ carbon atoms" means that each of the alkyl chains of the ester χ has carbon atoms; otherwise all indices of refraction measured at 25 C.

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Claims (8)

Claims Vjfy process for the synthesis of esters of the tetracarboxylic acids Pyrazinic acid of the formula in which R is a radical which has at least 3 carbon atoms and is selected from the group consisting of the linear alkyl chains, the branched alkyl chains and the hydrocarbon chains, which contain at least one functional group, which in turn is selected from the group consisting of the functions resistant to boiling sulfuric acid and in particular the etheric, Ketone, sulfoxides, and phosphine oxide functions consist, thereby characterized in that one with the dipotassium salt of tetracarboxylic acids Pyrazinic acid is made from the concentrated sulfuric acid and an alcohol of the formula ROH, in which R has the same meaning as above, existing mixture at the reflux temperature of the alcohol-sulfuric acid mixture lets react. 2. The method according to claim 1, characterized in that the molar ratio of alcohol / dipotassium salt of the tetracarboxylic acid pyrazine acid is close to 6. 3. The method according to claim 2, characterized in that the 409840/1018 Alcohol is selected from the group of primary and secondary alcohols . 4. The method according to any one of claims 1 to 3, thereby calibrated, d
Baume titrated. indicates that the sulfuric acid used is at least 66 5. The method according to claim 4, characterized in that
the molar ratio of sulfuric acid / dipotassium salt of the tetracarboxylic acid pyrazine acid is close to 6. 6. The method according to any one of claims 1 to 5, characterized in that the reaction time of the alcohol-sulfuric acid mixture with the dipotassium salt of the tetracarboxylic pyrazine acid
is at least three hours. 7. Esters of the tetracarboxylic pyrazine acid of the formula in which X is a linear or having 3 to 15 carbon atoms branched alkyl means radical. 8. Use of liquid esters of tetracarboxylic pyrazine acid the formula 409840/1018 CO _n YN CO ₀ Y CO ₂ Y in which Y is a linear or branched alkyl radical as raw materials for thermally stable lubricants. 9 _8/4 M / 1 f! 1 8