CA1283126C - Process for ortho- and para-alkylating diphenylamines - Google Patents
Process for ortho- and para-alkylating diphenylaminesInfo
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- CA1283126C CA1283126C CA000545984A CA545984A CA1283126C CA 1283126 C CA1283126 C CA 1283126C CA 000545984 A CA000545984 A CA 000545984A CA 545984 A CA545984 A CA 545984A CA 1283126 C CA1283126 C CA 1283126C
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- ortho
- aluminum
- para
- diphenylamine
- alkylated
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Abstract
ABSTRACT OF THE DISCLOSURE
Ortho-para-alkylated diphenylamines are prepared utilizing an improved, one-stage process wherein the diphenylamines are ortho-alkylated by reaction with a first olefin in the presence of an aluminum complex as the catalyst, and are subsequently para-alkylated by reaction with a second olefin using a Friedel-Crafts aluminum catalyst. The para-alkylation is carried out without prior isolation or solvent washing of the ortho-alkylated diphenylamine intermediates.
Ortho-para-alkylated diphenylamines are prepared utilizing an improved, one-stage process wherein the diphenylamines are ortho-alkylated by reaction with a first olefin in the presence of an aluminum complex as the catalyst, and are subsequently para-alkylated by reaction with a second olefin using a Friedel-Crafts aluminum catalyst. The para-alkylation is carried out without prior isolation or solvent washing of the ortho-alkylated diphenylamine intermediates.
Description
~3~26 IMPROVED PROC~SS F~R ORTHO- ~ND
P~RA-ALKYLATING DI~HENY~AMINES
B~CKG~OUND OE_THE INVENTION
Alkylated derivatives of diphenylamines are well known compounds that are commonly used as antioxidants ~or lubricating oils, natural and synthetic rubbers and plastics. Alkylated diphenylamine compounds include, for e~ample;
4,4'-bis(~,~-dimethylbenzyl) diphenylamine as described in U.S. patent no. 3,505,225;
P~RA-ALKYLATING DI~HENY~AMINES
B~CKG~OUND OE_THE INVENTION
Alkylated derivatives of diphenylamines are well known compounds that are commonly used as antioxidants ~or lubricating oils, natural and synthetic rubbers and plastics. Alkylated diphenylamine compounds include, for e~ample;
4,4'-bis(~,~-dimethylbenzyl) diphenylamine as described in U.S. patent no. 3,505,225;
2,2'-diethyl-4,4'-tert-dioctyldiphenylamine as described in U.S. patent no. 3,732,167;
~,2',4,4'-tetra-t-butyldiphenylamine as described in U.S. patent no. 3,655,559; and p,p~-di-tar~iary-octyl-diphenYlamine and p,p'-di-~-phenylethyl) diphenylamine as described in U.S. patent no. 2,530,769. Alkylated diphenylamines are typically prepared by alkylating a diphenylamine with ole~ins such as ethylene, heptene, octene, nonene, styrene, and diisobutylene, in the presence o a suitable alkylation catalyst. For example, U.S. patent no. 2,530,769 discloses the para-alkylation of diphenylamines using various olains and a Friedel-Crats condensation catalysk such as aluminum chloride, and U.S. Patent No.
2,943,112 discloses the alkylation of diphenylamine with heptenes, octenas, and nonenes using a Filtrol Clay as a catalyst.
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As to the ortho-alkylation step, an article in the "Journal of Organic Chemistry", Vol. 21, page 711 (1956) discloses a process and mechanism for ortho-alkylating aromatic amines using aluminum metal to form an aluminum anilide catalyst. U.S. Patent Nos. 2,762,845 and 2,814,646 also disclose the use of aluminum metal to form an aluminum anilide to effect the ortho-alkylation of aromatic amines. The 2,814,646 patent also discloses that aluminum halide used with an alkali or alkaline earth metal anilide can be used in the ortho-reaction. U.S. Patent No.
~,2',4,4'-tetra-t-butyldiphenylamine as described in U.S. patent no. 3,655,559; and p,p~-di-tar~iary-octyl-diphenYlamine and p,p'-di-~-phenylethyl) diphenylamine as described in U.S. patent no. 2,530,769. Alkylated diphenylamines are typically prepared by alkylating a diphenylamine with ole~ins such as ethylene, heptene, octene, nonene, styrene, and diisobutylene, in the presence o a suitable alkylation catalyst. For example, U.S. patent no. 2,530,769 discloses the para-alkylation of diphenylamines using various olains and a Friedel-Crats condensation catalysk such as aluminum chloride, and U.S. Patent No.
2,943,112 discloses the alkylation of diphenylamine with heptenes, octenas, and nonenes using a Filtrol Clay as a catalyst.
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As to the ortho-alkylation step, an article in the "Journal of Organic Chemistry", Vol. 21, page 711 (1956) discloses a process and mechanism for ortho-alkylating aromatic amines using aluminum metal to form an aluminum anilide catalyst. U.S. Patent Nos. 2,762,845 and 2,814,646 also disclose the use of aluminum metal to form an aluminum anilide to effect the ortho-alkylation of aromatic amines. The 2,814,646 patent also discloses that aluminum halide used with an alkali or alkaline earth metal anilide can be used in the ortho-reaction. U.S. Patent No.
3,923,892 discloses the use of an alkylaluminum halide with aromatic amines to achieve accelerated reaction rates. An article in the German journal Angewandte Chemie, ~olume 69, page 124 (1957) discloses the ortho-alkylation of diphenylamine using as a catalyst the reaction product of aluminum metal with aniline.
Ortho-para-alkylated diphenylamines are typically synthesized in a two-stage process. In the first stage, diphenylamine is alkylated at one or both of the ortho-(2 and 2') positions by reacting with a suitable olefin and typically using an aluminum catalyst. The ortho-alkylated product is then isolated, generally by fractional distillation or by washing the crude mixture with water, and subsequently para-alkylated at one or both of the para-~4 and 4') positions with additional olefin.
The '559 patent referenced above describes such a general process, wherein the ortho-alXylation is first performed by reacting diphenylamine with a 2 to 4 carbon olefin, and the para-alkylation involves the subsequent reaction of the ortho-alkylated diphenylamine with a secondary olefin having 4 to 12 carbons, such as isobutylene, 2-mathyl pentene-l, ,- , ' .
"
~ ~ ~3 ~ ~
diisobutylene and propylene trimer. Although the '559 patent discloses a preparation of a tetra-substituted product in a single-stage alkylation where the ortho- and para-substituents are the same t-butyl groups, for different alkyl substituents at the ortho- and para-positions the two-stage alkylation is disclosed.
The necessity for isolation of the ortho-alkylated diphenylamine intermediate prior to the para-alkylation introduces an undesirable step wi~h attendant disadvantageæ. The isolation step results in additional process eguipment requirements, longer preparation times, lower productivity, increa~ed catalyst usage, and increased costs. An alkylation process which can effectively produce ortho-para-alkylated diphenylamines having different ortho- and para-substituents, without the necessity for isolation of the ortho-alkylated intermediate, is most desirable.
It is an object of the present invention to provide an improved process for ortho-para-alkylation o~ diphenylamines wherein the intermediate product does not have to be isolated. It is a further object of this invention to achieve a more efficient process for the preparation of ortho-para-alkylated diphenylamines where the ortho- and para-substituents are dif ferent entitie~.
SU~RY OF TH~ I~y~M~QN
This invention i8 an improved, one-stage process for alkylation o diphenylamines which comprises 1) forming a reactive aluminum complex by the interaction of diphenylamines and aluminum, 2) ortho-alkylating ths diphenylamines by reaction with a irst olefin in the presence of the aluminum comple~, 3) adding hydrogen halide to the ~83~
ortho-alkylated diphenylamine intermediate products to form a Friedel-Crafts aluminum catalyst, and 4) subsequently para-alkylating the ortho-alkylated intermediates by reaction with a second olefin in the presence of the Friedel-Crafts aluminum catalyst, without pr~or isolation or solvent washing o~ the ortho-alkylated intermediates. Although the present inventive process is readily usable to produce alkylated diphenylamines where all the ortho- and para-substituents are the same, the process is particularly applicable to the production of alkylated diphenylamines with different ortho- and para-substituents, such as, for example, the preparation of 4,4'-bis(a,a-dimethylhenzyl)2,2'-diethyldiphenylamine.
DETAILED DESCRIPTION
This invention relates to an improved process for ortho-, para-alkylation of diphenylamines. Specifically, this invention involves an improved, one-stage process for ortho-para-alkylation of diphenylamines which comprises 1) forming a reactive aluminum comple~ by the interaction of diphenylamines and aluminum, 2) ortho-alkylating the diphenylamines with a first olefin in the presence of the aluminum complex, 3) adding hydrogen halide to the ortho-alkylated diphenylamine intermediate products to orm a Friedel-Crafts aluminum catalyst, and g) subsequently para-alkylating the ortho-alkylated diphenylamine intermediates by reacting the intermediate with a second olefin in the presence of the Friedel-Crafts aluminum catalyst, wherein the para-alkylation is carried out without prior isolation or solvent washing of the ortho-alkylated intermediates.
~ ~ 83 The present process is suitable for the synthesis of alkylated diphenylamines represented by the general formula:
~1 ~ N ~ R4 wherein Rl and R4 represent the same of different linear or branched alkyl radicals having 2 to about 12 carbon atoms or alkaryl radicals having f rom 8 to about 16 carbon atoms, and R2 and R3 represent the same or different linear alkyl radicals having from 2 to about 10 ~arbon atoms or branched alkyl radicals haYing from 3 to about 6 carbon atoms. More preferably, Rl and R4 are the same radicals and are linear or branched alkyl radicals of about 4 to about 9 carbon atoms such as t-butyl,t-octyl or nonyl groups, or alkaryl radicals of 8 to about 12 carbon atoms such as -methyl benzyl groups. Also, more preferredly, R2 and R3 are the same radicals and are ethyl groups or branched alkyl radicals of 3 to 6 carbon atoms such as isopropyl or t-butyl groups.
Alkylated diphenylamines which can be made by the present invention include, for e~ample:
2,2'-diethyl,4,4'-t-dioctyldiphenylamine;
2,2'-diethyl-4,4'-di-t-butyldiphenylamine;
2,2'-diethyl-4,4'-bis(~,-dimethylbenzyl)diphenylamine, 2,2'-diethyl-4,4'-dinonyldiphenylamine, and the like. The process i8 particularly suitable for the preparation of ortho-para-diphenylamines having different ortho- and para- substituents.
The ortho-alkylation is carried out in a closed reaction vessel by reacting the diphenylamine with a irst olefin containing 2 to 10 carbon atoms.
The ortho-alkylation is conducted at a temperature ~2~33~
from about 180C. to about 260C., at a pressure from about 50 to about 300 psig, for about 30 minutes to about 6 hours or more in the presence of an al~minum complex as the catalyst. The aluminum complex is formed by the interaction of aluminum metal with the diphenylamine. The aluminum is employed either as aluminum metal in combination with aluminum chloride which is believed to act as a catalyst, or as a combination of aluminum chloride with an alkali metal. The combination of aluminum chloride plus an alkali metal such as sodium, forms the aluminum complex faster. The total amoun~ of aluminum in the form of aluminum and/or aluminum chloride is employed in an effective amount, typically ranging from about 0.1 to about 10 mole percent of aluminum per mole of diphenylamine, and more preferably ranges from about 1 to about 8 mole percent of aluminum per mole of diphenylamine. When the ortho-alkylation catalyst is aluminum metal and aluminum chloride, the mole ratio of aluminum metal to aluminum chloride is from about 15:1 to about 1:3. More preferredly, the mole ratio of aluminum metal to aluminum chloride is about 4:1 to 1:2. When the ortho-alkylation catalyst i9 a combination of aluminum chloride and an alkali metal, the mole ratio of alkali metal to aluminum chloride is from about 3:1 to 1:2.
After the ortho-alkylation step, the reaction mixture is treated with a hydrogen halide, either as a gas, an amine salt or other suitable anhydrous salt. Suitable hydrogen halides include hydrogen chloride, hydrogen bromide and hydrogen iodide. The preferred hydrogen halide is hydrogen chloride. The hydrogen halides can be used in the form of an amine salt such as the aniline or diphenylamine salt of the halogen halide like the ~8~ 6 diphenylamine-hydrochlorlde salk. T~e hydroyen halide is used in about a 3:1 molar ratio of h~drogen halide~
to the aluminum oomplex catal~st. The hydrogen halide can be added directly to the rea¢tion mixture ~ollowing th~ or~o-alk~lation by mixlng in the ~alk ~rm or by a~pirating khe mixture wlth hydrogen halide ya~. Levels o~ hydrogen hal~de~ abo~e 3:1 may be used without adver#e e~eats. ~he temperature at which the hydrogen halide 1~ added can ranga ~rom about room temperakure up to about lOO~C. The treatment o~ the orkho-alkylated diphenylamine intermediate with hydrogen hal~des leads to the ~ormation o~ the Friedel-Cra~ts alumlnum aatalyst u~ed in the para-alkylation step.
Following the ~ormatisn o~ the Friedel-Cra~ts aluminum catalyst, the para-alkylation o~ the diphenyl-amine is carried out. In ~his step, the ortho-al~ylate~
diphenylamin~ intermediate is r~acted with a second ole~in, such as styrene, dC -methylstyrene, i~obutyl-ene, diisobutylene, or nonenes, containing from 2 to about 16 carbon atoms ~ollowing a typical Friedal-Cra~ts reaction process. A~ter the para-alkylation reaction has taken place, the ~inal ortho-para-alkylated diphenvlamine product 1~ separated ~rom the reaction m~xkure in any known and desired manner.
The meahanism o~ the ortho- and para-alkyla-tion reaations i~ po~tulated a~ ~ollows:
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~;~83126 1. First, the diphenylamine interacts with aluminum to form the reactive aluminum comples a) ( ~ ~ ) AlC13 ( or b) 3 ~ N ~+ 3 ~a ~ 3 ~ N ~ ~ ~ Fl 2 Q ~ ~
+AlC13 - ~ ~. - Al +3NaCl ~ 3 2. Then the aluminum comple~ r~acts with the first olefin to ~orm an ortho-alkylated intermediate product 2 C2H4~__C~ N . _ Al L ~ C2N5 ~3 ~'~ 83 ~ ~
3. A~ter the ortho-alkylation step, the hydroqen halide is added to the ortho-alkylated diphenylamine intermediate product to form the Friedel-Crafts aluminum catalyst for the s para-alkylation reaction.
N-H ~ AlC13 ~ ~ 2H5 4. With the addition of the second olefin, the para-alkylation occurs through a carbonium ion mechanism following a typical Friedel-Crafts reaction process.
CH3- C =CH2 CH3- -C
+ c~ NH
" " AlC13 ~
CH3-C- ~ C2~5 1 ~ ) The present inventive process is carried out 30 without isolation or solvent washing of the ortho-alkylated diphenylamine intermediate, as is disclosed in the prior art processes. The following Examples are presented to illustrate the present inventive process, but are not to be construed as 3slimiting the invention.
~33~6 EXAMPLE I
The ortho-alkylated diphenylamine intermediate was prepared as follows. 300 grams of diphenylamine were placed in a reactor equipped for agitation. 17.2 grams of AlC13 was first added for safety reasons followed by 6.0 grams of sodium metal, and the mix stirred for about 4 hours at a temperature of about 140C. During this time the H2 formed was vented. The first olefin (ethylene) was then introduced into the mixture as a gas, and the olefin and aluminum comple~ was heated to about 200C. at a pressure of about 100 psig for about 6 hours. The resultant product was not isolated and recovered but can be used as is to prepare the para-alkylated product as shown in the followinq e~amples.
EXAMP~
200 grams of (unwashed) 2,2'-diethyldiphenylamine prepared as in Example I
were charged to a dry 500 ml round-bottom flask. A
catalyst of dry aniline-hydrochloride salt ~17.75g) was added with mi~ing. The flask was purged with dry nitrogen gas to maintain an anhydrous system. The temperature of the misture increased from 24C. to 34C. in about 4 minutes indicating an e~othermic reaction. The mixture was then heated to 100C. to 140C. and 250 ml ~220g) of a-methylstyrene was added. The reaction medium was maintained at 120C.
to 125C. for about 12 hours. The product was recovered and analyzed by gas chromatographia and high performance liquid chromatographic methods, and shown to be 4.4% by weight 2,2'-diethyldiphenylamine;
~0.0% by weigh~
2,2'-diethyl-4-~,a-dimethylbenzyl)diphenylamine;
and 48.8~ by weight 2,2'-diethyl-4,4'-bis~a,a-dimethylbenzyl)diphenylamine.
1~31'~
EXAMPLE III
206.5 grams of (unwashed~
2,2'-diethyldiphenylamine prepared as in Example I
were charged to a 1000 ml round-bottom flask.
Hydrogen chloride gas was disp0nsed into the system while stirring, and tha temperature of the mi2ture rose to approximately 60C. The system was then purged with dry nitrogen gas while heated to 120C.
307.1 grams of diisobutylene (C8H16) was added to the flask and the mi~ stirred for approximately 10 hours. The product was recovered and analyzed to show 0.38% by weight 2,2'-diethyldiphenylamine;
10.12% by weight 2,2'-diethyl-4-octyldiphenylamine;
and 80.7% by weight 5 2,2'-diethyl-4,4'-dioctyldiphenylamine.
EXAMPLE IV
300 grams of (unwashed~
2,2'-diethyldiphenylamine prepared as in Example I
were treated with 6.94 grams of hydrogen chloride gas and charged into a 1.2 liter autoclave. 476 grams of a mixture of nonenes were added to the autoclave and the mix heated to lB0C. After 4 hours, 748 grams of product were obtained. The product was washed with water and unreacted nonenes were removed under vacuum. The recovered product was analyzed and shown to be 2% by weight 2,2'-diethyldiphenylamine; 33.2%
by weight 2,2'-diethyl-4-nonyldiphenylamine; and 60.1% by weight 2,2'-diethyl-4,4'-dinonyldiphenylamine.
The following comparative examples were run to demonstrate some of the unique aspects of this invention.
~/31~6 EXAMPLE A
204.0 grams of (unwashed) 2,2'-diethyldiphenylamine prepared as in Example I
were mixed with a-methylstyrene (220.3 grams) following the procedure of Example II e~cept that no hydrogen chloride was added to the mixture. No reaction of the ortho-alk~lated diphenylamine intermediate with the a-methylstyrene took place after 5 hours of heating at 90C. to 140C. This comparative example demonstrates that the hydrogen halide must be added to the ortho-alkylated diphenylamine intermediate product to form the Friedel-Crafts catalyst needed for the para-alkylation step.
EXAMPLE B
203.2 grams of (unwashed) 2,2'-diethyldiphenylamine prepared as in Example I
were mi~ed with a-methylstyrene (220.6 grams) following the procedure of E~ample II e~cept that no h~drogen chloride was added to the mi~ture. In this case, however, aluminum chloride (1.97 grams) was added to the mi~ture. After heating for five hours at 85 to 140C., no reaction of the ortho-alkylated diphenylamine intermediate took place and no para-a-methylstyrene substituted diethyldiphenylamine was found. This example shows that simple addition oE the Friedel-Crafts aluminum catalyst does not provide the para-alkylation step. One must ~irst treat the intermediate with hydrogen halide.
~YPh~_~
Z00.8 grams of 2,2'-diethyldiphenylamine prepared as in Example I was washed with water and dried. The washed mix was then added ~o a 1000 ml round-bottom flask, and 7.2 grams of hydrogen chloride gas was added to the Elask over a 30 minute : , .
~8;~
period. The temperature of the mixture rose to approximately 45C. The mixture was heated to 105C.
to 110C. and 305.0 grams of diisobutylene wa~
added. After 2.5 hours, no reaction had taken place. The washing step effectively removed the aluminum complex which is soluble in water.
The above mixture was then cooled to room temperature and 7.7 grams of p-toluenesulfonic acid were added. The mixture was reheated to 110C. for an additional 2.5 hours. Af~er this period, no reaction had taken place. This comparative example shows that, with the removal of the aluminum complex, the addition of a traditional Friedel-Crafts catalyst (p-toluenesulfonic acid) does not provide the para-alkylation step.
EXAMPLE D
200.9 grams of ~unwashed) 2,2'-diethyldiphenylamine prepared as in Example I
was added to a lO00 ml round-bottom flask. The mixture was heated to 60C. and 7.4 grams of ammonium chloride (NH4Cl) was added. The mixture was gradually heated to 150C. No evolution of ammonia gas was detected during a 1.5 hour period, indicating ~hat the ammonium chloride, as opposed to the inventor's use of hydrogen chloride, was inefective in forming the Friedel-Crafts aluminum catalyst.
Examples I, II, III and IV above demonstrate the present invention in that the diphenylamine was ortho-alkylated and para-alkylated without isolating the ~ntermediate ortho-substituted product.In the comparative examples, E~ample A demonstrates the inactive state of the aluminum comple~ after ~33~
undergoing the ortho-alkylation stage. Without addition of the hydrogen halides, the ortho-substituted diphenylamine intermediate complex is ineffective in promoting para-alkylation. Example B shows that the mere addition of a Friedel-Crafts aluminum catalyst to the ortho-alkylated diphenylamine intermediate is not an effective means for promoting the para-alkylation reaction. E~ample C shows that neither hydrogen chloride nor p-toluenesulfonic acid are effective as para-alkylation catalysts where the aluminum complex used in the ortho-alkylation has been e~tracted from the mixture. Example D shows that ammonium chloride, as opposed to hydrogen chloride, does not function to form the Friedel-Crafts para-alkylating catalyst.
Ortho-para-alkylated diphenylamines are typically synthesized in a two-stage process. In the first stage, diphenylamine is alkylated at one or both of the ortho-(2 and 2') positions by reacting with a suitable olefin and typically using an aluminum catalyst. The ortho-alkylated product is then isolated, generally by fractional distillation or by washing the crude mixture with water, and subsequently para-alkylated at one or both of the para-~4 and 4') positions with additional olefin.
The '559 patent referenced above describes such a general process, wherein the ortho-alXylation is first performed by reacting diphenylamine with a 2 to 4 carbon olefin, and the para-alkylation involves the subsequent reaction of the ortho-alkylated diphenylamine with a secondary olefin having 4 to 12 carbons, such as isobutylene, 2-mathyl pentene-l, ,- , ' .
"
~ ~ ~3 ~ ~
diisobutylene and propylene trimer. Although the '559 patent discloses a preparation of a tetra-substituted product in a single-stage alkylation where the ortho- and para-substituents are the same t-butyl groups, for different alkyl substituents at the ortho- and para-positions the two-stage alkylation is disclosed.
The necessity for isolation of the ortho-alkylated diphenylamine intermediate prior to the para-alkylation introduces an undesirable step wi~h attendant disadvantageæ. The isolation step results in additional process eguipment requirements, longer preparation times, lower productivity, increa~ed catalyst usage, and increased costs. An alkylation process which can effectively produce ortho-para-alkylated diphenylamines having different ortho- and para-substituents, without the necessity for isolation of the ortho-alkylated intermediate, is most desirable.
It is an object of the present invention to provide an improved process for ortho-para-alkylation o~ diphenylamines wherein the intermediate product does not have to be isolated. It is a further object of this invention to achieve a more efficient process for the preparation of ortho-para-alkylated diphenylamines where the ortho- and para-substituents are dif ferent entitie~.
SU~RY OF TH~ I~y~M~QN
This invention i8 an improved, one-stage process for alkylation o diphenylamines which comprises 1) forming a reactive aluminum complex by the interaction of diphenylamines and aluminum, 2) ortho-alkylating ths diphenylamines by reaction with a irst olefin in the presence of the aluminum comple~, 3) adding hydrogen halide to the ~83~
ortho-alkylated diphenylamine intermediate products to form a Friedel-Crafts aluminum catalyst, and 4) subsequently para-alkylating the ortho-alkylated intermediates by reaction with a second olefin in the presence of the Friedel-Crafts aluminum catalyst, without pr~or isolation or solvent washing o~ the ortho-alkylated intermediates. Although the present inventive process is readily usable to produce alkylated diphenylamines where all the ortho- and para-substituents are the same, the process is particularly applicable to the production of alkylated diphenylamines with different ortho- and para-substituents, such as, for example, the preparation of 4,4'-bis(a,a-dimethylhenzyl)2,2'-diethyldiphenylamine.
DETAILED DESCRIPTION
This invention relates to an improved process for ortho-, para-alkylation of diphenylamines. Specifically, this invention involves an improved, one-stage process for ortho-para-alkylation of diphenylamines which comprises 1) forming a reactive aluminum comple~ by the interaction of diphenylamines and aluminum, 2) ortho-alkylating the diphenylamines with a first olefin in the presence of the aluminum complex, 3) adding hydrogen halide to the ortho-alkylated diphenylamine intermediate products to orm a Friedel-Crafts aluminum catalyst, and g) subsequently para-alkylating the ortho-alkylated diphenylamine intermediates by reacting the intermediate with a second olefin in the presence of the Friedel-Crafts aluminum catalyst, wherein the para-alkylation is carried out without prior isolation or solvent washing of the ortho-alkylated intermediates.
~ ~ 83 The present process is suitable for the synthesis of alkylated diphenylamines represented by the general formula:
~1 ~ N ~ R4 wherein Rl and R4 represent the same of different linear or branched alkyl radicals having 2 to about 12 carbon atoms or alkaryl radicals having f rom 8 to about 16 carbon atoms, and R2 and R3 represent the same or different linear alkyl radicals having from 2 to about 10 ~arbon atoms or branched alkyl radicals haYing from 3 to about 6 carbon atoms. More preferably, Rl and R4 are the same radicals and are linear or branched alkyl radicals of about 4 to about 9 carbon atoms such as t-butyl,t-octyl or nonyl groups, or alkaryl radicals of 8 to about 12 carbon atoms such as -methyl benzyl groups. Also, more preferredly, R2 and R3 are the same radicals and are ethyl groups or branched alkyl radicals of 3 to 6 carbon atoms such as isopropyl or t-butyl groups.
Alkylated diphenylamines which can be made by the present invention include, for e~ample:
2,2'-diethyl,4,4'-t-dioctyldiphenylamine;
2,2'-diethyl-4,4'-di-t-butyldiphenylamine;
2,2'-diethyl-4,4'-bis(~,-dimethylbenzyl)diphenylamine, 2,2'-diethyl-4,4'-dinonyldiphenylamine, and the like. The process i8 particularly suitable for the preparation of ortho-para-diphenylamines having different ortho- and para- substituents.
The ortho-alkylation is carried out in a closed reaction vessel by reacting the diphenylamine with a irst olefin containing 2 to 10 carbon atoms.
The ortho-alkylation is conducted at a temperature ~2~33~
from about 180C. to about 260C., at a pressure from about 50 to about 300 psig, for about 30 minutes to about 6 hours or more in the presence of an al~minum complex as the catalyst. The aluminum complex is formed by the interaction of aluminum metal with the diphenylamine. The aluminum is employed either as aluminum metal in combination with aluminum chloride which is believed to act as a catalyst, or as a combination of aluminum chloride with an alkali metal. The combination of aluminum chloride plus an alkali metal such as sodium, forms the aluminum complex faster. The total amoun~ of aluminum in the form of aluminum and/or aluminum chloride is employed in an effective amount, typically ranging from about 0.1 to about 10 mole percent of aluminum per mole of diphenylamine, and more preferably ranges from about 1 to about 8 mole percent of aluminum per mole of diphenylamine. When the ortho-alkylation catalyst is aluminum metal and aluminum chloride, the mole ratio of aluminum metal to aluminum chloride is from about 15:1 to about 1:3. More preferredly, the mole ratio of aluminum metal to aluminum chloride is about 4:1 to 1:2. When the ortho-alkylation catalyst i9 a combination of aluminum chloride and an alkali metal, the mole ratio of alkali metal to aluminum chloride is from about 3:1 to 1:2.
After the ortho-alkylation step, the reaction mixture is treated with a hydrogen halide, either as a gas, an amine salt or other suitable anhydrous salt. Suitable hydrogen halides include hydrogen chloride, hydrogen bromide and hydrogen iodide. The preferred hydrogen halide is hydrogen chloride. The hydrogen halides can be used in the form of an amine salt such as the aniline or diphenylamine salt of the halogen halide like the ~8~ 6 diphenylamine-hydrochlorlde salk. T~e hydroyen halide is used in about a 3:1 molar ratio of h~drogen halide~
to the aluminum oomplex catal~st. The hydrogen halide can be added directly to the rea¢tion mixture ~ollowing th~ or~o-alk~lation by mixlng in the ~alk ~rm or by a~pirating khe mixture wlth hydrogen halide ya~. Levels o~ hydrogen hal~de~ abo~e 3:1 may be used without adver#e e~eats. ~he temperature at which the hydrogen halide 1~ added can ranga ~rom about room temperakure up to about lOO~C. The treatment o~ the orkho-alkylated diphenylamine intermediate with hydrogen hal~des leads to the ~ormation o~ the Friedel-Cra~ts alumlnum aatalyst u~ed in the para-alkylation step.
Following the ~ormatisn o~ the Friedel-Cra~ts aluminum catalyst, the para-alkylation o~ the diphenyl-amine is carried out. In ~his step, the ortho-al~ylate~
diphenylamin~ intermediate is r~acted with a second ole~in, such as styrene, dC -methylstyrene, i~obutyl-ene, diisobutylene, or nonenes, containing from 2 to about 16 carbon atoms ~ollowing a typical Friedal-Cra~ts reaction process. A~ter the para-alkylation reaction has taken place, the ~inal ortho-para-alkylated diphenvlamine product 1~ separated ~rom the reaction m~xkure in any known and desired manner.
The meahanism o~ the ortho- and para-alkyla-tion reaations i~ po~tulated a~ ~ollows:
~E~3' .
~;~83126 1. First, the diphenylamine interacts with aluminum to form the reactive aluminum comples a) ( ~ ~ ) AlC13 ( or b) 3 ~ N ~+ 3 ~a ~ 3 ~ N ~ ~ ~ Fl 2 Q ~ ~
+AlC13 - ~ ~. - Al +3NaCl ~ 3 2. Then the aluminum comple~ r~acts with the first olefin to ~orm an ortho-alkylated intermediate product 2 C2H4~__C~ N . _ Al L ~ C2N5 ~3 ~'~ 83 ~ ~
3. A~ter the ortho-alkylation step, the hydroqen halide is added to the ortho-alkylated diphenylamine intermediate product to form the Friedel-Crafts aluminum catalyst for the s para-alkylation reaction.
N-H ~ AlC13 ~ ~ 2H5 4. With the addition of the second olefin, the para-alkylation occurs through a carbonium ion mechanism following a typical Friedel-Crafts reaction process.
CH3- C =CH2 CH3- -C
+ c~ NH
" " AlC13 ~
CH3-C- ~ C2~5 1 ~ ) The present inventive process is carried out 30 without isolation or solvent washing of the ortho-alkylated diphenylamine intermediate, as is disclosed in the prior art processes. The following Examples are presented to illustrate the present inventive process, but are not to be construed as 3slimiting the invention.
~33~6 EXAMPLE I
The ortho-alkylated diphenylamine intermediate was prepared as follows. 300 grams of diphenylamine were placed in a reactor equipped for agitation. 17.2 grams of AlC13 was first added for safety reasons followed by 6.0 grams of sodium metal, and the mix stirred for about 4 hours at a temperature of about 140C. During this time the H2 formed was vented. The first olefin (ethylene) was then introduced into the mixture as a gas, and the olefin and aluminum comple~ was heated to about 200C. at a pressure of about 100 psig for about 6 hours. The resultant product was not isolated and recovered but can be used as is to prepare the para-alkylated product as shown in the followinq e~amples.
EXAMP~
200 grams of (unwashed) 2,2'-diethyldiphenylamine prepared as in Example I
were charged to a dry 500 ml round-bottom flask. A
catalyst of dry aniline-hydrochloride salt ~17.75g) was added with mi~ing. The flask was purged with dry nitrogen gas to maintain an anhydrous system. The temperature of the misture increased from 24C. to 34C. in about 4 minutes indicating an e~othermic reaction. The mixture was then heated to 100C. to 140C. and 250 ml ~220g) of a-methylstyrene was added. The reaction medium was maintained at 120C.
to 125C. for about 12 hours. The product was recovered and analyzed by gas chromatographia and high performance liquid chromatographic methods, and shown to be 4.4% by weight 2,2'-diethyldiphenylamine;
~0.0% by weigh~
2,2'-diethyl-4-~,a-dimethylbenzyl)diphenylamine;
and 48.8~ by weight 2,2'-diethyl-4,4'-bis~a,a-dimethylbenzyl)diphenylamine.
1~31'~
EXAMPLE III
206.5 grams of (unwashed~
2,2'-diethyldiphenylamine prepared as in Example I
were charged to a 1000 ml round-bottom flask.
Hydrogen chloride gas was disp0nsed into the system while stirring, and tha temperature of the mi2ture rose to approximately 60C. The system was then purged with dry nitrogen gas while heated to 120C.
307.1 grams of diisobutylene (C8H16) was added to the flask and the mi~ stirred for approximately 10 hours. The product was recovered and analyzed to show 0.38% by weight 2,2'-diethyldiphenylamine;
10.12% by weight 2,2'-diethyl-4-octyldiphenylamine;
and 80.7% by weight 5 2,2'-diethyl-4,4'-dioctyldiphenylamine.
EXAMPLE IV
300 grams of (unwashed~
2,2'-diethyldiphenylamine prepared as in Example I
were treated with 6.94 grams of hydrogen chloride gas and charged into a 1.2 liter autoclave. 476 grams of a mixture of nonenes were added to the autoclave and the mix heated to lB0C. After 4 hours, 748 grams of product were obtained. The product was washed with water and unreacted nonenes were removed under vacuum. The recovered product was analyzed and shown to be 2% by weight 2,2'-diethyldiphenylamine; 33.2%
by weight 2,2'-diethyl-4-nonyldiphenylamine; and 60.1% by weight 2,2'-diethyl-4,4'-dinonyldiphenylamine.
The following comparative examples were run to demonstrate some of the unique aspects of this invention.
~/31~6 EXAMPLE A
204.0 grams of (unwashed) 2,2'-diethyldiphenylamine prepared as in Example I
were mixed with a-methylstyrene (220.3 grams) following the procedure of Example II e~cept that no hydrogen chloride was added to the mixture. No reaction of the ortho-alk~lated diphenylamine intermediate with the a-methylstyrene took place after 5 hours of heating at 90C. to 140C. This comparative example demonstrates that the hydrogen halide must be added to the ortho-alkylated diphenylamine intermediate product to form the Friedel-Crafts catalyst needed for the para-alkylation step.
EXAMPLE B
203.2 grams of (unwashed) 2,2'-diethyldiphenylamine prepared as in Example I
were mi~ed with a-methylstyrene (220.6 grams) following the procedure of E~ample II e~cept that no h~drogen chloride was added to the mi~ture. In this case, however, aluminum chloride (1.97 grams) was added to the mi~ture. After heating for five hours at 85 to 140C., no reaction of the ortho-alkylated diphenylamine intermediate took place and no para-a-methylstyrene substituted diethyldiphenylamine was found. This example shows that simple addition oE the Friedel-Crafts aluminum catalyst does not provide the para-alkylation step. One must ~irst treat the intermediate with hydrogen halide.
~YPh~_~
Z00.8 grams of 2,2'-diethyldiphenylamine prepared as in Example I was washed with water and dried. The washed mix was then added ~o a 1000 ml round-bottom flask, and 7.2 grams of hydrogen chloride gas was added to the Elask over a 30 minute : , .
~8;~
period. The temperature of the mixture rose to approximately 45C. The mixture was heated to 105C.
to 110C. and 305.0 grams of diisobutylene wa~
added. After 2.5 hours, no reaction had taken place. The washing step effectively removed the aluminum complex which is soluble in water.
The above mixture was then cooled to room temperature and 7.7 grams of p-toluenesulfonic acid were added. The mixture was reheated to 110C. for an additional 2.5 hours. Af~er this period, no reaction had taken place. This comparative example shows that, with the removal of the aluminum complex, the addition of a traditional Friedel-Crafts catalyst (p-toluenesulfonic acid) does not provide the para-alkylation step.
EXAMPLE D
200.9 grams of ~unwashed) 2,2'-diethyldiphenylamine prepared as in Example I
was added to a lO00 ml round-bottom flask. The mixture was heated to 60C. and 7.4 grams of ammonium chloride (NH4Cl) was added. The mixture was gradually heated to 150C. No evolution of ammonia gas was detected during a 1.5 hour period, indicating ~hat the ammonium chloride, as opposed to the inventor's use of hydrogen chloride, was inefective in forming the Friedel-Crafts aluminum catalyst.
Examples I, II, III and IV above demonstrate the present invention in that the diphenylamine was ortho-alkylated and para-alkylated without isolating the ~ntermediate ortho-substituted product.In the comparative examples, E~ample A demonstrates the inactive state of the aluminum comple~ after ~33~
undergoing the ortho-alkylation stage. Without addition of the hydrogen halides, the ortho-substituted diphenylamine intermediate complex is ineffective in promoting para-alkylation. Example B shows that the mere addition of a Friedel-Crafts aluminum catalyst to the ortho-alkylated diphenylamine intermediate is not an effective means for promoting the para-alkylation reaction. E~ample C shows that neither hydrogen chloride nor p-toluenesulfonic acid are effective as para-alkylation catalysts where the aluminum complex used in the ortho-alkylation has been e~tracted from the mixture. Example D shows that ammonium chloride, as opposed to hydrogen chloride, does not function to form the Friedel-Crafts para-alkylating catalyst.
Claims (8)
1. An improved, one-stage process for the ortho-, para-alkylation of diphenylamines consisting essentially of forming a reactive aluminum complex by the interaction of aluminum and diphenylamine(s), (2) ortho-alkylating the diphenylamines by reacting said diphenylamine(s) with a first olefin in the presence of the aluminum complex, (3) adding hydrogen halide to the ortho-alkylated diphenylamine intermediate products to form a Friedel-Crafts aluminum catalyst, and (4) subse-guently para-alkylating the ortho-alkylated diphenyl-amine intermediates by reacting said intermediates with a second olefin in the presence of the Friedel-Crafts aluminum catalyst, wherein the para-alkylation is carried out without prior isolation or solvent washing of said ortho-alkylates intermediates.
2. A process of Claim 1 wherein the first olefin is ethylene.
3. A process of Claim 1 wherein the second olefin is selected from the group consisting of styrene, ?-methylstyrene, isobutylene, diisobutylene, and nonenes.
4. A process of Claim 1 wherein the aluminum complex is prepared by the interaction of aluminum metal with diphenylamine in the presence of aluminum chloride.
5. A process of Claim 1 wherein the aluminum complex is prepared by the interaction of diphenylamine with a combination of an alkali metal and aluminum chloride.
6. A process of Claim 5 wherein the alkali metal is sodium.
7. A process of Claim 1 wherein the hydrogen halide is hydrogen chloride.
8. A process of Claim 1 wherein the hydrogen halide is used in the form of the salt diphenylamine hydrochloride.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/904,078 US4739121A (en) | 1984-05-24 | 1986-09-04 | Process for otho- and para-alkylating diphenylamines |
| US904,078 | 1986-09-04 |
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| Publication Number | Publication Date |
|---|---|
| CA1283126C true CA1283126C (en) | 1991-04-16 |
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ID=25418503
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000545984A Expired - Fee Related CA1283126C (en) | 1986-09-04 | 1987-09-02 | Process for ortho- and para-alkylating diphenylamines |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115925556A (en) * | 2022-11-08 | 2023-04-07 | 万华化学集团股份有限公司 | Preparation method of diethyltoluenediamine |
-
1987
- 1987-09-02 CA CA000545984A patent/CA1283126C/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115925556A (en) * | 2022-11-08 | 2023-04-07 | 万华化学集团股份有限公司 | Preparation method of diethyltoluenediamine |
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