Note: Descriptions are shown in the official language in which they were submitted.
~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;
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.
~$ "
A
, ~ , .
.
.
.
~ ~ ~3 ~ ~
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
--5--
The present process is suitable for the
synthesis of alkylated diphenylamines represented by
the general formula:
~1 ~ N ~ R4
R2 R3
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
--7--
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
--8--
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
1 5
Q ~ ~
+AlC13 - ~ ~. - Al +3NaCl
~ 3
2. Then the aluminum comple~ r~acts with
the first olefin to ~orm an ortho-alkylated
intermediate product
Q-- C2H5
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.
Q-- C2H5
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
--10--
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'~
--11--
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 weight5 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
-12-
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;~
-13-
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~
-14-
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.
