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US1994851A - Alkylation of aromatic amines - Google Patents

Alkylation of aromatic amines Download PDF

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US1994851A
US1994851A US580732A US58073231A US1994851A US 1994851 A US1994851 A US 1994851A US 580732 A US580732 A US 580732A US 58073231 A US58073231 A US 58073231A US 1994851 A US1994851 A US 1994851A
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aniline
alkyl
monoand
aromatic amines
ethyl
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US580732A
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Carleton Paul Whittier
Woodward Joseph Donald
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EIDP Inc
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EI Du Pont de Nemours and Co
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
    • C07C209/04—Preparation of compounds containing amino groups bound to a carbon skeleton by substitution of functional groups by amino groups
    • C07C209/14—Preparation of compounds containing amino groups bound to a carbon skeleton by substitution of functional groups by amino groups by substitution of hydroxy groups or of etherified or esterified hydroxy groups
    • C07C209/18—Preparation of compounds containing amino groups bound to a carbon skeleton by substitution of functional groups by amino groups by substitution of hydroxy groups or of etherified or esterified hydroxy groups with formation of amino groups bound to carbon atoms of six-membered aromatic rings or from amines having nitrogen atoms bound to carbon atoms of six-membered aromatic rings

Definitions

  • This invention relates in general to the alkylation of aromatic amines, and particularly to the alkylation of primary aromatic amines when the alkyl groups to be introduced into the amine contain more than one carbon atom. More particularly, the invention relates to the ethylation of aniline and its homologues.
  • alkyl radicals may be substituted for one or both of the hydrogens in the amino group of a primary aromatic amine.
  • an alkyl radical such as the methyl group
  • this substitution takes place quite readily.
  • aniline when heated with methanol and a relatively small amount of sulfuric acid, under elevated temperature and pressure may be converted substantially completely to dimethylaniline or mixtures thereof with monomethylaniline.
  • an alkyl alcohol of higher order than methyl is used, this procedure is unsatisfactory because of side reactions and for other reasons.
  • other disadvantages have attended previously proposed methods for alkylating aromatic amines to a higher order than methyl.
  • Our invention has as one of its objects a new and improved method of allzylating primary aromatic amines, particularly as regards alkylations of aniline or its homologues to a higher order than methyl, whereby mixtures of the monoand dialkyl substituted amines are obtained.
  • a fur ther object of the invention is the provision of a flexible process for regulating the proportions of monoand disubstituted amines produced.
  • a still further object is the ethylation of aniline to produce substantially binary mixtures of monoand diethylaniline by a method which is controllable to such an extent that a relatively small change in the conditions of ethylation will cause a marked difference in the ratio of monoand diethylaniline produced, and the amount of each product can be varied as needed.
  • An additional object of the invention is the provision of a method for ethylating primary aromatic amines which is better from the economic standpoint than any method previously proposed.
  • the invention comprises producing monoand dialkyl aromatic amines by reacting a primary aromatic amine with an alkyl alcohol, preferably of a higher order than methyl, and the corresponding allcyl chloride under elevated pressure and temperature.
  • the resultant product contains an oily mixture of monoand dialkyl aromatic amines, which may be recovered in any suitable manner, for example, by making the reaction product alkaline, whereupon the oil separates from the remainder of the liquid and may be removed by means of a conical separator or by any other convenient method.
  • the oily mixture may be used as such in certain chemical processes.
  • the monoand dialkyl amines may be separated from each other by any suitable means, for instance, by fractional distillation or by fractional crystallization of salts of the amines.
  • the invention may be well illustrated by the ethylationof aniline. This is preferably accomplished by reacting aniline, ethyl alcohol, and ethyl chloride, under autogenous pressure and at an elevated temperature, while regulating the proportions of the reactants and more particularly the amount of ethyl chloride to produce a product containing a mixture of monoand diethylaniline in desired ratios, substantially no unconverted aniline being present.
  • the resultant mixture may be recovered in any suitable manner and the two constituents separated or used as such without the difficulties and expense involved when a substantial amount of unconverted aniline is present. We have found this process to be exceptionally advantageous on a plant scale because of its flexibility.
  • Example I oil layer separated by meansof a conical separator The oil contained approximately monoethylaniline and 40% diethylaniline.
  • Example II The reaction described in Example I was effected with 242 parts by weight of ethyl chloride instead of 208 parts, all other proportions of reactants and conditions of time and temperature remaining the same.
  • the autogenous pressure in this case was about 200-250 pounds per square inch.
  • the oil was recovered as usual and analyzed approximately 35% monoethylaniline and diethylaniline.
  • aniline we may alkylate the homologues thereof, e. g. the toluidines, ,(metatoluidine, etc.) and Xylidines, or any other primary aromatic amines such as the naphthylamines.
  • the exact conditions of operation will depend upon the nature of the amine treated. In general, conditions subject to variation are the temperature, the time and the pressure of the reaction and the proportions of the reactants.
  • the temperature may vary within relatively wide limits, but, generally speaking, should be so regulated as to avoid ring alkylation at the higher temperatures and a low rate of alkylation at the lower temperatures.
  • ethylating anilineor its homologues we prefer to employ temperatures within the range of -190 C. and preferably HBO- C.
  • temperatures below about 130 C. are preferable.
  • the time allowedfor the reaction to take place appears to be a functionof the temperature em-- ployed. If the temperature used is relatively low, a longer period of heating is required than in cases where the reaction is carried out at relatively high temperatures.
  • the pressure of the reaction is the autogenous pressure produced by the reaction mixture.
  • the pressure is largely a function of the temperature and the proportions of amine, alkyl alcohol, and alkyl chloride used.
  • other sources of pressure may be employed such as, for example, the introduction of a compressed gas or vapor which is inert to the reactants or does not affect the reaction unfavorably. Elevated pressures tend to favor the production of alkyl aromatic amines by our process and pressures varying from slightly super-atmospheric to 1000 atmospheres are contemplated.
  • the proportions of the various reactants employed to produce monoand dialkyl substituted aromatic amines in accordance with our invention depend largely upon the ratio of monoto dialkyl amines desired. Thus, within a certain range, other things being equal, a small increase in the amount of alkyl chloride present in the reaction mixture will increase the proportion of dialkylamine formed. In general, it is preferable that the amount of alkyl chloride used should fall within the range of about 0.6-1.0mole per mole of primary aromatic amine. The use of such small alkyl chloride concentrations is a distinctive feature of the invention and a decided advantage from the economic viewpoint.
  • the proportions of alkyl alcohol employed may vary within relatively wide limits but, generally speaking, should not be. less than about one mole er mole of primary aromatic amine treated.
  • alkyl chloride used in effecting alkylations by our process should correspond to the alkyl alcohol employed, or vice versa. That is to say, the alkyl chloride and alkyl alcohol should contain the same number of carbon atoms similarly grouped. Otherwise; complex mixtures of alkylated amines may result.
  • alkyl we mean-a radicalderived from anacyclic hydrocarbon by the elimination of one atom: of hydrogen, such as, for example, propyl, isopropyl, allyl, butyl, isobutyl, etc.
  • step 4 which comprises reacting a non-phenolic primary aromatic amine of the benzene series with ethyl alcohol and ethyl chloride under super-atmospheric pressure.
  • the process of producing monoand diethylaniline which comprises reacting together in a closed vessel aniline, ethyl alcohol, and ethyl chloride in proportions corresponding to at least one mole of ethyl alcohol per mole of aniline, and 0.6 to 1.0 mole of ethyl chloride per mole of aniline, under autogenous pressure and at a temperature of to C.
  • the step which comprises heating said aromatic amine with an alkyl alcohol and the corresponding alkyl chloride under super-atmospheric pressure at an alkylation temperature below that giving rise to substantial ring alkylation of the amine.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Description

Patented Mar. 19, 1935 UNITED S A'i'hl'i' OFFICE ALKYLATIION 0F AROMATIC AItflNES No Drawing.
Application December 12, 1931,
Serial No. 580,732
17 Claims.
This invention relates in general to the alkylation of aromatic amines, and particularly to the alkylation of primary aromatic amines when the alkyl groups to be introduced into the amine contain more than one carbon atom. More particularly, the invention relates to the ethylation of aniline and its homologues.
It is Well known that by a process of alkylation, alkyl radicals may be substituted for one or both of the hydrogens in the amino group of a primary aromatic amine. With an alkyl radical such as the methyl group, this substitution takes place quite readily. For example, aniline when heated with methanol and a relatively small amount of sulfuric acid, under elevated temperature and pressure may be converted substantially completely to dimethylaniline or mixtures thereof with monomethylaniline. However, if an alkyl alcohol of higher order than methyl is used, this procedure is unsatisfactory because of side reactions and for other reasons. To a greater or less extent, other disadvantages have attended previously proposed methods for alkylating aromatic amines to a higher order than methyl. Thus, in some processes heretofore proposed for ethylating aniline, mixtures of monoand diethylaniline and unconverted aniline have been obtained. In order to'be commercially feasible, such processes customarily involve removal or recovery of the unconverted aniline, which adds to the cost of production and, in general, leaves much to be desired.
Our invention has as one of its objects a new and improved method of allzylating primary aromatic amines, particularly as regards alkylations of aniline or its homologues to a higher order than methyl, whereby mixtures of the monoand dialkyl substituted amines are obtained. A fur ther object of the invention is the provision of a flexible process for regulating the proportions of monoand disubstituted amines produced. A still further object is the ethylation of aniline to produce substantially binary mixtures of monoand diethylaniline by a method which is controllable to such an extent that a relatively small change in the conditions of ethylation will cause a marked difference in the ratio of monoand diethylaniline produced, and the amount of each product can be varied as needed. An additional object of the invention is the provision of a method for ethylating primary aromatic amines which is better from the economic standpoint than any method previously proposed. Other objects and advantages of the invention will be apparent by reference to the following description thereof.
In its broader aspects, the invention comprises producing monoand dialkyl aromatic amines by reacting a primary aromatic amine with an alkyl alcohol, preferably of a higher order than methyl, and the corresponding allcyl chloride under elevated pressure and temperature. The resultant product contains an oily mixture of monoand dialkyl aromatic amines, which may be recovered in any suitable manner, for example, by making the reaction product alkaline, whereupon the oil separates from the remainder of the liquid and may be removed by means of a conical separator or by any other convenient method. The oily mixture may be used as such in certain chemical processes. Or, if desired, the monoand dialkyl amines may be separated from each other by any suitable means, for instance, by fractional distillation or by fractional crystallization of salts of the amines.
The invention may be well illustrated by the ethylationof aniline. This is preferably accomplished by reacting aniline, ethyl alcohol, and ethyl chloride, under autogenous pressure and at an elevated temperature, while regulating the proportions of the reactants and more particularly the amount of ethyl chloride to produce a product containing a mixture of monoand diethylaniline in desired ratios, substantially no unconverted aniline being present. The resultant mixture may be recovered in any suitable manner and the two constituents separated or used as such without the difficulties and expense involved when a substantial amount of unconverted aniline is present. We have found this process to be exceptionally advantageous on a plant scale because of its flexibility.
While the invention is susceptible of considerable variation in the manner of its practical application, particularly as regards conditions of time, temperature, pressure and proportions of reactants used, the following examples Will illustrate how it may be practised.
Example I oil layer separated by meansof a conical separator. The oil contained approximately monoethylaniline and 40% diethylaniline.
Example II The reaction described in Example I was effected with 242 parts by weight of ethyl chloride instead of 208 parts, all other proportions of reactants and conditions of time and temperature remaining the same. The autogenous pressure in this case was about 200-250 pounds per square inch. The oil was recovered as usual and analyzed approximately 35% monoethylaniline and diethylaniline.
Example I]! Example I Example II Example III Time of heating (hrs.) 5 5 5 Temperature 0.- 180-185 180-185 180-185 Pressure lbs/sq.
(approximate) Y 175225 200-250 300-360 Ratio moles ethyl alcohol per mole of aniline- 1.09 1. 00 2. 46 Ratio moles of ethyl I chloride per mole of aniline 1. 0. 645 0. 0. Percent monoethylaniline in oil produced 60.0 35. 0 12. 5 Percent diethylaniline in oil produced 40. 0 65.0 87. 5
It will be seen in the above table that a change of about 0.10 moles of ethyl chloride per mole of aniline, all other conditions remaining the same approximately reverses the proportions of monoand diethylaniline produced. Since the demand for each of the products varies from time to time, the advantage of being able to modify the process to meet the demand as it arises is obvious. This has heretofore been possible only to a much more limited extent.
We wish it to be understood that the above examples are not meant to limit the scope of the invention. Instead of aniline, we may alkylate the homologues thereof, e. g. the toluidines, ,(metatoluidine, etc.) and Xylidines, or any other primary aromatic amines such as the naphthylamines. The exact conditions of operation, of course, will depend upon the nature of the amine treated. In general, conditions subject to variation are the temperature, the time and the pressure of the reaction and the proportions of the reactants.
The temperature may vary within relatively wide limits, but, generally speaking, should be so regulated as to avoid ring alkylation at the higher temperatures and a low rate of alkylation at the lower temperatures. In ethylating anilineor its homologues, we prefer to employ temperatures within the range of -190 C. and preferably HBO- C. For the ethylation of naphthylamines, temperatures below about 130 C. are preferable.
The time allowedfor the reaction to take place appears to be a functionof the temperature em-- ployed. If the temperature used is relatively low, a longer period of heating is required than in cases where the reaction is carried out at relatively high temperatures.
In practicing our invention we prefer to heat the reactants in a closed vessel so that the pressure of the reaction is the autogenous pressure produced by the reaction mixture. According to this method of procedure the pressure is largely a function of the temperature and the proportions of amine, alkyl alcohol, and alkyl chloride used. If desired, however, other sources of pressure may be employed such as, for example, the introduction of a compressed gas or vapor which is inert to the reactants or does not affect the reaction unfavorably. Elevated pressures tend to favor the production of alkyl aromatic amines by our process and pressures varying from slightly super-atmospheric to 1000 atmospheres are contemplated. As a general rule, it is preferable to employ pressures within the range of about 10-1'00 atmospheres. In ethylating aniline pressures within the range of about 1030 atmospheres have. given especially desirable results. I i
The proportions of the various reactants employed to produce monoand dialkyl substituted aromatic amines in accordance with our invention depend largely upon the ratio of monoto dialkyl amines desired. Thus, within a certain range, other things being equal, a small increase in the amount of alkyl chloride present in the reaction mixture will increase the proportion of dialkylamine formed. In general, it is preferable that the amount of alkyl chloride used should fall within the range of about 0.6-1.0mole per mole of primary aromatic amine. The use of such small alkyl chloride concentrations is a distinctive feature of the invention and a decided advantage from the economic viewpoint.
The proportions of alkyl alcohol employed may vary within relatively wide limits but, generally speaking, should not be. less than about one mole er mole of primary aromatic amine treated.
As previously indicated, the alkyl chloride used in effecting alkylations by our process should correspond to the alkyl alcohol employed, or vice versa. That is to say, the alkyl chloride and alkyl alcohol should contain the same number of carbon atoms similarly grouped. Otherwise; complex mixtures of alkylated amines may result. By alkyl we mean-a radicalderived from anacyclic hydrocarbon by the elimination of one atom: of hydrogen, such as, for example, propyl, isopropyl, allyl, butyl, isobutyl, etc.
In describing our invention, we, have referred to the production of mixed monoand. dialkyl aromatic amines, and particularly ethylated aniline and homologues thereof, which contain substantially no unconverted primary amine. In actual practise, it is difiicult to determine the amount of primaryaromatic amine in mixtures of monoand dialkyl aromatic amines when less than about 1% of the primary amine is present. By substantially no unconverted primary aromatic amine, therefore, we mean less-than'about 1% by weight. I I
We have found that the present inventionobviates many of the difiiculties formerly attending large scale alkylationsof a higher order than. methyl, and particularly ethylations; that eth ylated products of the character herein described can be produced more cheaplyby 5 our process than byany previously proposed method, and, in general,- the invention represents an advancement of "the-art".
As many apparent and widely different embodiments of this invention may be made without departing from the spirit thereof, it is to be understood that we do not limit ourselves to the foregoing examples or description except as indicated in the following claims.
We claim:
1. In a process of producing mono and dialkyl aromatic amines the step which comprises reacting a primary non-phenolic aromatic amine with an alkyl alcohol and the corresponding alkyl chloride under super-atmospheric pressure, the proportions of alkyl chloride used being within the range of 0.6 to 1.0 mole per mole of primary aromatic amine.
2. In a process of producing monoand diethyl aromatic amines the step which comprises reacting a primary non-phenolic aromatic amine with ethyl alcohol and ethyl chloride under superatmospheric pressure.
3. In a process of producing monoand diethyl aromatic amines the step which comprises reacting a primary non-phenolic aromatic amine with ethyl alcohol and ethyl chloride under superatmospheric pressure, the proportion of ethyl chloride used being within the range of 0.6 to 1.0 mole per mole of primary aromatic amine.
4. In a process of producing monoand diethyl aromatic amines of the benzene series the step which comprises reacting a non-phenolic primary aromatic amine of the benzene series with ethyl alcohol and ethyl chloride under super-atmospheric pressure.
5. In a process of producing monoand diethyl aniline the step which comprises reacting aniline with ethyl alcohol and ethyl chloride under superatmospheric pressure.
6. In a process of producing monoand diethyl aniline the step which comprises reacting aniline with ethyl alcohol and ethyl chloride under superatmospheric pressure, the proportions of ethyl chloride used being within the range of 0.6 to 1.0 mole per mole of aniline.
7. The process of producing monoand diethylaniline which comprises reacting aniline with ethyl alcohol and ethyl chloride under superatmospheric pressure and at a temperature within the range of about to about 190 C.
8. The process of producing monoand diethylaniline which comprises reacting aniline with ethyl alcohol and 0.6 to 1.0 mole of ethyl chloride per mole of aniline, under super-atmospheric pressure and at a temperature within the range of about 160 to about 190 C.
9. The process of producing monoand diethylaniline which comprises reacting together in a closed vessel aniline, ethyl alcohol, and ethyl chloride in proportions corresponding to at least one mole of ethyl alcohol per mole of aniline, and 0.6 to 1.0 mole of ethyl chloride per mole of aniline, under autogenous pressure and at a temperature of to C.
10. The process of ethylating aniline which comprises reacting together aniline, ethyl alcohol, and ethyl chloride in proportions corresponding to at least one mole of ethyl alcohol per mole of aniline, and 0.6 to 1.0 mole of ethyl chloride per mole of aniline, under super-atmospheric pressure and at a temperature of 180 to 185 C., to produce a product containing a mixture of monoand diethylaniline but substantially no unconverted aniline, and separating said mixture of monoand diethylaniline from said product.
11. In a process of producing monoand diethyl aniline the step which comprises reacting aniline with ethyl alcohol and ethyl chloride under a super-atmospheric pressure within the range of about 10 to about 30 atmospheres.
12. In a process involving replacing by an alkyl radical the hydrogen of an amino group of a non-phenolic aromatic amine, the step which comprises reacting said aromatic amine with an alkyl alcohol and the corresponding alkyl chloride under super-atmospheric pressure.
13. In a process involving replacing by an alkyl radical the hydrogen of an amino group of a non-phenolic aromatic amine which may contain alkyl substituents in the aromatic ring, the step which comprises reacting said aromatic amine with an alkyl alcohol and the corresponding alkyl chloride under super-atmospheric pressure.
14. In a process involving replacing by an alkyl radical the hydrogen of an amino group of an aromatic amine selected from the group consisting of aniline and homologues thereof, the step which comprises reacting said aromatic amine with an alkyl alcohol and the corresponding alkyl chloride under super-atmospheric pressure.
15. In a process involving replacing by an alkyl radical the hydrogen of an amino group of a nonphenolic aromatic amine which may contain alkyl substituents in the aromatic ring, the step which comprises heating said aromatic amine with an alkyl alcohol and the corresponding alkyl chloride under super-atmospheric pressure at an alkylation temperature below that giving rise to substantial ring alkylation of the amine.
16. In a process involving replacing by an alkyl radical the hydrogen of an amino group of a nonphenolic naphthyl amine, the step which com- PAUL WHI'I'IIER CARLETON. JOSEPH DONALD WOODWARD.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2766277A (en) * 1951-02-08 1956-10-09 Universal Oil Prod Co Production of negatively substituted n-tertiaryalkylarylamines and derivatives thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2766277A (en) * 1951-02-08 1956-10-09 Universal Oil Prod Co Production of negatively substituted n-tertiaryalkylarylamines and derivatives thereof

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