Note: Descriptions are shown in the official language in which they were submitted.
72032-1
CARBONYLATION PROCESS
BACKGROUND OF THE INVENTION
1. Field Q~ ~he I~yQn~ion
This invention relates to a proce~s for the
carbonylation of a nitrogen-containing organlc compound by
reacting said compound with carbon monoxide in the
presence of a rhodium or ruthenium catalyst.
2. ~es~LiR~i2n-c-th~-a~
Variou~ patents have disclosed methods for
carbonylating nitrogen-containing organic compounds -
e.g., nitro compounds, amines, azo- and azoxy compounds, -:
to urethanes in the presence of a platlnum group metal-
containing catalyst usually a palladium or rhodium-
containing catalyst and most often a palladium or rhodium
halide-containing catalyst. Generally, a co-catalyst
;
. , .
~'
i6
(promoter) has been needed in combination with the
platinum ~r`oup metal-containing catalyst in order to
obtain improved rates o~ reactionO The vast majority of
prior art processes use, as a co-catalyst, a halide salt
of a metal which is redox-active under the reaction
conditions, usually iron, and most often iron chlorides.
The co-catalyst is used in substantial molar excess
compared to the main catalyst in order to obtain the
desired reaction rate. These large quantities of redox-
active metal halides are troublesome to separate ~rom the
reaction product and cause substantial corroslon problems.
A few references have taught the addition o a
primary amino compound (and/or related compounds, such as
urea, biurets, and allophanates) to urther improve the
rate and selectivity of reactions catalyzed by a platinum
group metal compound in combination with a redox-active
metal halide-cocatalyst. U.S. Patent 4rl78~455 discloses
that, in a process for converting nitroaromatic to
urethane catalyzed by a platinum, palladium, rhodium, or
ruthenium compound and a Lewis~acid promoter, the rate and
selectivity are improved by adding to the reaction, an
organic primary amino compound, a urea compound, a biuret
compound, an allophanate compound, or a mixture thereof.
The preEerred Lewis acid promo~ers are redox-active metal
: salts, especially iron chlorides. This patent illustrates
(by example) only palladium catalysts with iron chloride
promoters. A careful study of the examples reveals that
the starting nitroaromatic and the primary amino compound
(or related compound) are both converted, in net, to
urethane. Thus, when the primary amino compound or urea
compound contains the same aryl group as the starting
nitroaromatic compound the reported yield o urethane,
based on only the nitroaromatic converted, exceeds 100~.
. . .
~ ;27~
This patent also teaches the use of tertiary amines, ~.g.
pyridine, in large molar excess compared to the palladium
catalyst to prevent corrosion. See also U.S. Patent
4,169,269 wherein a tertiary amine, e.g. pyridine, in
large molar excess i5 utilized to ~uppress corrosion in a
process utilizing a catalyst system comprising (1) palladium,
ruthenium/ rhodium or compounds thereof, and ~2) a Lewis
~cid, e.gt ferric chloride. Similarly, U.S. Patents
4,219,661; 4,262,130; and 4l339,592 teach palladium
catalysts with iron oxide and iron chloride co-catalysts
in which addition of tertiary amines is one embodiment.
U.S. Patent 4,297,501 discloses a process in which
mixtures of a primary a~ine and a nitroaromatic are
carbonylated to urethane with a Group VIII noble metal
compound and an oxychloride compound capable o~ undergoirlg
redox reactions. In the preferred embodiment o~ U.S.
4,297,501, the nitroaromatic corresponds to the primary
amine, and the patent teaches the following reaction
stoichiometry:
2RNH2 + RN02 ~ 3CO ~ 3R'OH--~ 3RNEICO2R' ~ 2H20 (1)
U.S. 4,297,S01 further teaches that when
nitroaromatic is present in excess of the 1:2 ratio
relative to amine, the remaining nitroaromatic is
converted to urethane by the followlng reaction
stoichlometry:
RNO2 ~ 3CO ~ R'OH RN~CO2R' ~ 2CO2 ~2)
It can be seen from the above equations that when
primary amine is initially preseilt, in processes which
convert nitroaromatic to urethane uslng Group V~II noble
27~
metals, the primary amine is, in net, consumed to alco
make urethane. (See equation (1) above). Once the
primary amine is consumed to low levels, any rema;ning
nitrobenzene is converted to urethane via reaction
equation (2) above. Since the primary amine is already
consumed to low levels, it is no longer available to
favorably influence the rate of the process accordiny to
said reaGtion (2)o
U.S. 4,304,922 similarly discloses a process in which
mixtures of N,N'-diaryl urea and nitroaromatic are
carbonylated to urethane with the~same catalyst/co~
catalyst systems of U.S. 4,297rS01~ Illustrated by
examples are PdC12, RhC13, IrC13, PtCl~
and RUC13 as Group VIII noble metal compounds. Iron
oxychloride and several other redox active metal oxides
and chlorides are illustrated as co-catalysts. In
examples in which redox active metal oxides are used,
anilinium hydrochloride is also added to provide active
anionic chloride. In the preferred embodiment of this
patent, the N,N'-diaryl urea and nitroaromatic have the
same aryl groups, and the patent ~eaches that the
following reaction stoichiometry is obtained:
2RNHCONHR ~ RNO2 + 3CO -1 5~' OEI~ 5RNIICO2R' ~ 2E120 ~3~
It is known that N,N' diarylureas react wi~h alcohols
to produce urethane plus amins; see for Example U.S.
Patent 2,409,712, wherein the ~ollowing reactlon is
disclosed:
RNEICONEIR ~ R' OH--~ RNIIC02R' ~ RNH2 ~ 4)
.
It can be seen that once this occurs under the
reaction conditions, the same process as UOS~ 4,297,501 is
obtained according to equation (1) above. (Twice equation
(4) plus equation (1) equals equation (3)). It can
further be seen that both N,N'-diaryl urea and arylamine
are, in net, consumed in the process to make urethane.
Example 11 of U.S. Patent 4,304,922 illustrates that when
RhC13 is used as catalyst in combination with iron
oxychloride as co-catalyst, nitrobenzene and N/N'-
diphenylurea (1:2 molar ratio) are both consumed (100% and
99% conversion, respectively) to give urethane product 99~
selectivity based on nitrobenzene plus N,N'-diphenylurea).
Japan Rokai 55-7227 discloses a process in which
molecular hydrogen is added, to a process for
carbonylating nitroaromatic, in the presence of a
palladium catalyst, to increase the reaction rate. The
description of the invention specifies a palladium
catalyst, accompanied by promoters such as tertiary
amines, iron and vanadium compounds, and chlorine ions~
All illustrated examples use a supported palladium-
selenium on carbon catalyst promoted with pyLidlne and
either FeC12 or VOC13 (these are redox-active metal
chlorides), The patent ~eaches that the addition of
hydrogen causes hydrogenatlon of a fraction o~ the
nitroaromatic to generate the corresponding primary
arylamine 1LL~ . The process i5 thus generically
similar to that of U.S. 4,178~455, discussed above, which
illustrates by example the addition oE primary arylamine
to a reaction wlth a supported palladium catalyst promoted
with FeC13. Thus, it may be concluded that primary amine
generated ~rom hydrogen will in net be consumed in the
reaction to make urethane. Indeed, Japan Ko~ai 55-7227
teaches that any primary amine remalnlng at the end oE a
~ ~7~
reaction can be returned to another reaction with more
nitroaromatic, in which case the primary amine is easily
conYerted to urethane.
In U.S. Patent 4,474,978 a process is disclosed for
converting a nitroaromatic to a urethane ln the presence
o a primary amine and a catalyst system based on
palladium complexed with Group VA-chelate ligands,
including bis phosphine ligands and bis-tertiary amino-
containing ligands~ The patent teaches ~hat redox active
metal co-catalysts are not needed when these ligand~ are
used. The paten~ teaches that the primary amine and/or
urea are co-converted with the nitroaromatic to urethane.
Thus, the process, in net, consumes added amine or urea;
But, this patent does not suggest the use of ruthenium or
rhodium with said ligands.
Thus, it ls clear that, ln the processes clted above,
as the primary amine and/or urea compound ls converted, in
net, to urethane, its concentration decreases and its
effects on reaction rate and selectivity must also
decrease. Eventually, as nitroaromatic continues to be
converted, either in a ba~ch process or in a continuous
process (with recycle of the remaining amine), the primary
amine will be consumed to a low concentration. In order
to maintain t~e improved rates and selectivities, which
are obtained by the original addition oE primary amlne,
urea, hydrogen, etc., it is necessary to provide
additional`primary amine, urea, hydrogen, etc. as the
primary amine is consumed.
A few references teach the use o rhodium catalysts,
in the absence of a redox-active metal co-catalysts, for
the carbonylation of nitrogen-containing organic compounds
to urethanes. ~owever, these reEerences do not teach the
initial addition oE primary amines, ureas, hydrogen, etc.
' - ' , ' .
~ ~ 7 ~ ~ 6 ~
to obtain improved activity. For example, U.S. Patent
3,338,956 discloses a metal carbonyl catalyst
of Group VIA, VIIA, or VIII~ for this reaction. The only
such catalyst exemplified, however, is rhodium
chlorocarbonyl and the rates of reaction are relatively
slow.
U.S. Patent 3r993l685 teaches the addition of
tertiary amines, especially pyridine, to platinum group
metal catalysts to obtain improved activity in the absence
of redox-active metal co-catalysts. Rhodium chloride and
hydridocarbonyl tris (triphenyl-phosphine) rhodium in
combination with pyridine are exemplified.
U.S. Patent 4,052,437 discloses the use of rhodium
oxide as catalyst, preferentially in nitrilic solvent.
Rh6(Co)l6 as a catalyst i5 also exemplified in this
patent. There ls no suggestion that the inltial addltion
of a primary aryl amine to the process disclosed in thls
patent would improve the rate.
An article in the Journal o~ Organic Chemistry 37~
2791 (1972) describes a reaction in which nitro benzene in
the presence o~ ethanol is carbonylated in low yield to
urethane (<10~) and urea (<5%) with a catalyst comprising
Rh6(Co)l6 in pyridine solvent. The major product was
aniline. A related article in Helveti¢a Chimica Acta 55,
2637 (1972) describes a reaction in which nitrobenzene is
reacted with carbon monoxide and hydrogen to urea with a
catalyst comprising Rh6(CO)16 in pyridine solvent~ The
pyridine is used in high concentration or excess to enable
its function as a solvent for the reaction.
None of the above cited art, which discloses the use
o~ rhodium catalysts (in the absence of redox-active metal
co-catalysts) ~or the carbonylation oE nitro-organics to
urethanes, discloses the initial addition of primary
- .
6~
--8--
amine, urea~ hydrogen, etc. Moreover, the efEect of
initially adding primary amine to such catalysts is not
predictable. Finally, the result obtained by adding a
primary amine to a rhodium or ruthenium catalyst system
essentially free from redox-active metal components, is
substantially different from the result obtained when a
primary amine is added to either Group VIII metal
catalysts (including ruthenium, rhodium and palladium) in
the presence of redox active metal co-catalysts or certain
palladium catalysts in the absence of ~edox active metal
co-catalysts.
Ruthenium compounds have been utilized in the
reduction of organic nitro compounds to the cGrrresponding
amines with mixtures of hydrogen and carbon monoxide. ~t
was reported in U.S. 3,729,512 that urea is a by~roduct of
the reaction of nltrobenzene with hydrogen and carbon
monoxide to give aniline using Ru3(C0)12 catalyst. It was
also reported that the reduction of the organic nitro
compound with carbon monoxide and ethanol, in the absence
of H2, resulted in a mixtu~e Q amine ~nd a urethane. The
patentee was not concerned with the preparation of a
urethane product; therefore, there was no attempt to
increase the selectivity above ~he approximately ~2
percent, urethane, that was obtained.
It is an object of this invention to provide a
process for the conversion of nitro-~romatic to urethane
in good rate and selectivity, without requiring continual
addition of primary amine, urea, hydrogen, etc~ to
maintain the rate and selectivity.
Xt is a further object of this invention to
effectively carry out tha above process in the absence o
redox-active metal halide co-catalysts.
66
g--
Other objects and advantages of this invention will
become apparent ~rom a carcEul read;ng o~ the
specification below.
SUMM~RY OF THE INVENTI~N
It has now been surprisingly found that, in a process
for carbonylating nitrogen-containing organic compounds
selected from the group consisting of nitro, nitroso, azo
and azoxy compounds, by reacting said nitrogen~containing
organic compound, with carbon monoxide, the improvement
comprises: .
(a) reacting said nitrogen-containing compound
with carbon monoxide, in the presence of a primary
amine and a catalyst, said catalyst being essentially
free of redox active metal halide components, and
comprising ruthenium or rhodium.
Furthermore, the present invention provides a process
for converting a nitrogen-containing organic compound,
selected from the group consisting oE nitro, nitroso, azo,
and a~oxy compounds, into a carbamic acld derivative by
reacting said nitroyen-con~aining organic compound with
carbon monoxide wherein the improvement comprises the
steps of:
(a) mixing a primary amine with said nitrogen-
containing organic compound to provide a solution,
- (b) contacting ~he solution of step (a~ with
carbon monoxide, in the presence of a catalyst
essentially free of redox active metal halide
components and comprising rhodium or ruthenlum at
conditions suEficient to convert said nitrogen-
containing organic compound into sald carbamic acid
derivative .
~ ~t~6~
--10-- ,
Said carbamic acid derivative may be a urethane or a
urea (depending on whether a hydroxyl containing organic
compound is included in the solution o~ step (a~O) If the
solution of step (a) includes only the nitrogen-containing
compound and the primar~ amine --and any inert solvent--
the carbamic acid derivative will be a urea, which may be
separated and alcoholyzed to the urethane in a separate
step.
~inally, the present invention provides a process for
preparing a urethane by reacting a nitrogen-containing
organic compound, selected from the group consisting of
nitro, nitroso, azo and azoxy compounds, with carbon
monoxide and a hydroxyl-containing vrganic compound, the
improvement which comprises the steps of:
(a) adding a primary amine to a solution
comprising said nitrogen-containing organic compound,
(b) reacting said solution with carbon
monoxide, in the presence of a catalyst consisting
essentially of rhodium or ruthenium,
(c) recovering a urethane, and
(d) recovering a primary amine, in an amount
equal or greater than the primary amine in the
primary amine-containing solution of step ~a).
Whether the process of the present invention is practiced
to obtain urethane, directly, or upon separate alcoholysls
of a urea, the primary amine recovered i9 equal to or
greater than the primary amine initially provided in the
reactant solution. Thus, in a cont~nuous process, the
primary amine can be constantly recycled and no further
addition o~ primary amine, urea, hydrogen, etc. is needed
to maintain the desired rate and selectivities.
While not wishing to be bound by kheory, it appears
that, in the rhodium or ruthenium-catalyzed carbonylation
i6
o the above nitrogen-containing organic compound to the
corresponding urethane~ in the absence of a redox-active
metal halide co-catalyst, the urethane is produced by
oxidative carbonylation of the corresponding primary
amine. This oxidative carbonylation also provides
hydrogen atom equivalents for the reduction of the
nitrogen-containing organic compound to the primary amine.
These reactions which are illustrated below ~wherein [E~]
represents the rhodium or ruthenium hydrogen carrier) must
be effectively coupled to provide the desired selectivity
to the urethane.
Oxidative carbonylation: C6H5NE12 ~ C0-~CE130~ C~H5NHC02CH3-~2[H]
Reduction/hydrogenation: C6~5~02 ~ 2C0+2[H]--~C6H5NH2~2C02
Net Reaction: C6H5N2 ~ 3CO~CH30H-~C~H5NE1C02C~13~2C02
Thus, the primary amine (illustrated by aniline) is
an intermediate in the fornlation of urethane from the
nitrogen-containing organic compound, but is not in net
produced or consumed by the desired net reaction. It has
been ~ound that the primary amine is not in net consumed
and the desired reaction stoichiometry is obtained even
when pr~mary amine is initially added to the reaction. It
has been further ~ound that the rate of conversion of
nitrogen-containing organic compound to urethane and the
selectivity of the reaction are increased when the initial
amount of primary amine added to the reaction is
increased. The ini~ial amount o primary amine and itB
favorable e~ects on the rate and selectivity of the
reaction persist for the conversion o~ an inde~inite
amount of nitrogen-containing or~anic compound to
urethane.
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~.2~6~
-12-
The primary amine can be provided directly or by the
in situ alcoholysis of a urea~ bluret, or allophanate
compound. Uxea is alcoholyzed ~o form amine and urethane:
RNHCON~IR ~ E~'O~I~RNH2 t RNHC02R'
siurets and allophanates similarly provide primary
amine by alcoholysis under the reaction conditions.
In a carbonylation reaction wherein no primary amine,
urea, biuret, or allophanate is present, initially, a
fraction of the nitrogen-containing compound (e.g.
nitrobenzene) can be reduced to the primary amine
(aniline) by added hydrogen. It has been found that the
reduction of the nit~ogen-containing organic compound to a
prima~y amine in the p~e~ence of hydrogen is rapid and
provided that the molar xatio o~ hydrogen to the nitrogen-
containing organic compound is less than 1, the remainder
o~ the nitrogen-containlng organic compound is converted
to urethane by the desired reac~ion stoichiometry. The
primary amine may also be provlded in situ by the addition
of water, iD which case a fraction of the nitrogen-
containing compound is reduced to primary amine by
hydrogen equivalents obtained from shifting water and
carbon monoxide to carbon dioxide.
In the initial absence oE primary amine, hydrogen or
water in a urethane production reaction, the hydrogen
equivalents required to initially reduce nitrogen-
containing organic compound to the primary amine are
derived by dehydrogenation oE the alcohol. ~In the scheme
illustrated below R represents a hydrogen or hydrocarbyl
radical.)
.
-13~
~lcohol Dehydrogenation: R2 CHOH~ R~C=O ~ 2[~1]
Reduction/
Hydrogenation: c6i~5NO2 + 2co ~ 2[~] C6H5NH2 ~ 2C2
Net Reaction C6H5N02 ~ 2Co ~ R2C110~1 ~C6H5NH2 -~ 2C2 ~R2C=O
However, the carbonyl compounds which result from
dehydrogenation of alcohol react with the primary amine
to ~orm undesired condensation products and water.
~dditional nitrogen-containing compound may then be
reduced to the primary amine by hydrogen equivalents
derived from water by the shift reaction.
When sufficient primary amine is initially present in
the reaction solution, alcohol dehydrogenation is
undesired because it converts the nitrogen-containing
organic compound to primary amine and higher products
instead of urethane. It has been ound that methanol is
less susceptible to dehydrogenation to the aldehyde than
ethanol and higher alcohols, in the presence o~ the
ruthenium catalysts utilized in the process of the instant
invention. Therefore, the use of methanol improves the
yield of urethane obtained in the carbonylation reaction
product mixture and the combination o~ methanol and a
primary amine in the process of the instant invention
results in both an increi~sed yield o~ urethane and an
increased reaction rate
Since oxidative carbonylation of amlne to yield
urethane and dehydrogenation of alcohol to carbonyl
compound compete as sources of hydrogen equivalents ~or
reduction of the nitrogen containing organic compound, the
selectivity of urethane production is increased by
increasing the amine-to-alcohol ratio. The amine-to-
alcohol ratio is increased by increasing the am~ne
concentration and/or by decreasing the alcohol
-
7~
-14-
concentration. The primary amine may become the major
reaction solution component and act as solvent. The
alcohol concentration may be independently decreased by
using an inert solvent in place of excess alcohol in the
initial reaction solution.
It has been found that during the course of reactions
in which amine ls initially present, N,N'-disubstituted
urea is present in the reaction mixture during the
reaction. When nitrobenzene is reacted with alcohol,
aniline, or many inert solvents as solvent, the N, N'-
diphenyl-urea appears as a solid in samples of the
reaction mixture which are cooled. The solid has been
filtered rom the solution componen~s of such samples
(includ$ng the soluble catalyst), and characterized as
N,N'-diphenyl urea.
The amount of urea presen~ during the reaction
depends on the amine-to-alcohol ratio initially presentO
The higher the ratio, the higher the amount of urea
present. When enough alcohol is provided, however, little
or no urea persists to the end of the reaction. At the
end oE the reaction it is substantially reacted with
alcohol to make urethane according to equation (4). Some
or perhaps all of the urethane appears ~o be formed via
oxidative cabonylation to amine to urea, followed by urea
alcoholysis:
2C6H5Nli2 ~ CO ~ C6E15NHÇONHC6H5 ~ 2111],
- C6H5N02 ~ 2CO -~ 2[H]~ -' C6H5N~2 ~ 2C2
C6H5N02 ~ C6H5NH~ ~ 3CO ~ C6ll5NHCONHC6H5 ~ 2C02
then,
~6~15NHcoN~lc6Hs ~ ROII ~ C6H5NHCO2R ~ C6~lSNEl2
.
C6H5NO2 -~ 3CO ~ ROH ~ C6HsMHC02~ ~ 2C2
,
~.~7~
--15--
If the amine-to-alcohol ratio becomes quite high or if
insufficient alcohol is provided, urea will persis~ at the
end of the reac~ion. If little or no alcohol is provided,
urea will become the major reaction product. It can be
seen that the urea production consumes one equivalent of
initially added amine ~or each equivalent of urea
produced~ This consumed amine can be separately recovered
by reacting the urea with the alcohol to make urethane in
a ~eparate step
In a carbonylation reaction to produce urea~ wherein
no primary amineS urea, biuret or allophanate is present,
initially, a fraction o~ the nitrogen-containing organic
compound (e,~. nitrobenzene) can be reduced to the primary
amine (aniline) by added hydrogen. Again, if the molar
ratio o hydrogen to the nitrogen-containing organic
compound is less than 1, the remainder of the nitrogen-
containing oryanic compound is converted to urea by the
desired reaction stoichiometry. In a batch process, an
improved yield of urea is obtained ~hen from 50 to about
60 percent of the nitrogen-containing organic compound is
converted to primary amine, b~ hydrogenation, with the
maximum being obtained at S0 percent conversion.
Since there is no alcohol present in the urea
production reaction, side reactions of the alcohol
~dehydrogenation, dehydration) which reduce selectivity
are avoided. Thus, at the same initial amine
concentration, the yield oE urea in the absence of alcohol
can exceed the yield oE urethane in the presence of
alcohol.
Because one equivalent o~ amlne is consumed in the
urea production reaction, the amine concentration
decreases during the reaction, and the observed rate of
nitrogen-containing organic compound conversion
. . .. .. .
~ ~6~66
`1~
coeespondingly decreases during the reaction. (If the
molar ratio of nitrogen-containing organlc compound to the
primary amine is greater than 1, not all of the nitrogeJI-
containinq compound will be converted to urea~ Thus, in
the absence of alcohol, there will be unreacted nitrogen-
containing organic ccmpound left when all of the primary
amine is consumed into urea. I the amine is used in
large excess to the nitro compound (as solvent, for
example) however, the fractional changes in amine
concentration and rate of urea production are small or
insignificant.
By proYiding amine at higher concentrations in excess
of nitrogen-containing organic compoundl the rate of urea
production is increased and the nitro compound can be
conveniently 100% converted. Urea yields near 100~ may
thus be obtainedr
Since the urea alcoholysis to urethane is essentially
quantitative, the overall selectivity of urethane
synthes~s can be increased by separating the urea
synthesis and urea alcoholysis into two process steps, 80
that the selectivity reducing reactions o the alcohol in
the catalytlc carbonylation step are avoided.
76~
DETAILED DESCRIPTION OF THE INVENTION
The nitrogen-containing organic compound useful in
the process of this invention will contain at least one
non-cyclic group in which a nitrogen atom is directly
attached to a single carbon atom and through a double bond
to oxygen or another nitrogen atom. The nitrogen-
containing organic compound is selected from ~he group
consisting of nitro, nitrosor aæo and azoxy compounds.
Examples o suitable nltrogen-containing organic
compounds for use in the process o~ this invention are
compounds represented by the general formulae:
I R ~NOx)y and
II Rl-RN-N (O)z ~ ~2
wherein Rl and R2 are radicals independently selected ~rom
the group consisting o~ Cl to C2~ hydrocarbyl radicals and
substituted derivatives thereof, x is an integer of from 1
to 2, y is an integer of from 1 to 3, and z i3 an integer
of from O to 1. The substituted hydrocarbyl radical may
include hetero atoms selected from the group conslsting
of halogen, oxygen, sulfur, nitrogen and phosphorus atoms.
The nitrogen-containing compounds represented by
formula I include nitro compounds (wherein x is 2) and
nitroso compounds (wherein x is 1~. Suitable nitro
compounds are mononitro compounds such as nitrobenzene,
alkyl and alkoxy nitrobenzenes wherein ~he alkyl group
contains up to 10 carbon atoms, aryl and aryloxy
nitrobenzenes, wherein the aryl group is phenylr toyl,
naphthyl, xylyl, chlorophenyl, ~hloronitrobenzenes,
aminonitrobenzenes, carboalkoxyamino nitrobenzenes wherein
the alkoxy group has up to 10 carbon atoms, aryl and
aryloxy dinitrobenzenes, trinikro compounds such as
trinitrobenzene, alkyl and alkoxytrinitroben2enes, aryl
and aryloxytrinitrobenzenesr the substituents being any of
~ ~:76~
those already mentioned and chlorotrinitrvbenzenes as well
as similarly substituted mono and polynitro derivatives
o~ the naphthalene, diphenyl, diphenylmethane, anthracene
and phenanthrene series. Substituted or unsubstituted
aliphatic nitro compounds such as nitromethane,
nitrobutane, 2,2'-dimethyl nitrobutane, nitrocyclopentane,
3-meth~lnitrobu~ane, nitrooctadecane, 3-nitropropene-1,
phenyl nitromethane, p-bromophenyl nitromethaner p-methoxy
phenyl nitromethane,dinitroethane, dinitrohexane,
dinitrocyclohexane, di-(nitrocyclohexyl)-methane are also
suitable. The above nitro compounds may include more than
one of the above substituents (in addition to ~he nitro
group(s) such as in nitroaminoalkylbenzenes"
nitroalkylcarboalkoxyamino benzenes, etc. From this group
of nitro compounds nitrobenzene, nitrotoluene,
dinitrobenzene, dinitrotoluene, trinitrobenzene,
trinitrotoluene, mononitronaphthalene, dinitronaphthalene,
4,4'-dinitrodiphenylmethane, nitrobutane,
nitrocyclohexane, p-nitrophenylnitromethane.
dinitrocyclohexane, dinitromethylcyclohexane,
dinitrocyclohexylmethane, nitroaminotoluene and
nitrocarboalkoxyaminotoluene are pre~erred and in
particular aromatic nitro compounds especially 2,4-and
2,6-dinitrotoluenes, meta and para dinitrobenzenes, and 5-
nitro-2-methyl-carboalkoxyamino~,2-nitro-5-methyl-
carboallcoxyamino-t and 3-nitro-2-methyl~carboalkoxyamino
benzenes.
Examples of sultable nitroso compounds are the
aromatic nitroso compounds such as nitrosobenzene,
nitrosotoluene, dinitrosobenzene, dinitrosotoluene and the
aliphatic nitroso compounds such as nitrosobutane,
nitrosocyclohexane and dlnitrosomethylcyclohexane.
~ ~7 ~ ~6 ~
The nitrogen~containing compounds represented by
Formula II include both azo compounds ~wherein z is O) and
azoxy compounds ~wherein z is l)o Suitable compounds
represented by Formula II include azobenzene,
nitroazobenzne, chloroazobenæene, alkyl or aryl
substituted a~obenzener azoxybenzene, nitroazoxybenzene,
chloroazoxybenzene, etc.
The primary amine compound utilized in this invention
may be selected from the group consisting o~ compounds
xepresented by the general formula:
IV Rl (NH2)y
wherein Rl and Y are as de~ined above. Examples of such
primary amines include methylamine, ethylamine,
butylamine, hexylamine~ ethylenediamine, propylenediamine,
butylenediamine, cyclohexylamine, cyclohexyldiamlne,
aniline, p-toluidine, o-m-and p-diaminobenzenes, amino-
methylcarbanilic acid esters, especially the 5-amino-2
methyl-, 2-amino-5-methyl-, and 3-amino-2-methyl
carboalkoxyaminobenzenes, wherein said alkoxy group has up
to lO cabon atoms, o-, m- and p-nitroanilines,
nitroaminotoluenes, especially those designated above, o-
and p-phenylenediamine, benzylamine, v-amino-p-xylene, l-
aminophthaline, 2,4-and 2,6-diaminotoluenes, 4,41_
diaminodibènzyl, bis (4-aminophenyl) thioether~ bis (4-
aminophenyl) sulfone,~ 2,4,6-triaminotoluene, o-, m-and p-
chloroanilines, p-bromoaniline, l-fluoro-2,4-
diaminobenzener 2~-4-diaminophenetole, o,-m- and p-
aminoanisoles, ethyl p-aminobenzoate, 3-aminophthalic
anhydride, etc. These primary amino compound3 may be used
alone or in combination.
Among the above enumerated primary amino compounds,
those which can be derived from the startlng nitro
.
~ ;~76~
~ 20-
compound are preferred. For example, when nitrobenzene is
used as the starting aromatic nitro compound, aniline is
preferred. Similarly, 2-amlno-4-nitrotoluene, 4-amino-2-
nitrotoluene, and 2,4-diaminotoluene are preferably used
when the starting aromatic nitro compound is 2,4-
dinitrotoluene, while 2-amino-6-nitrotoluene, and 2,6-
diaminotoluene are preferably used when the starting
aromatic nitro compound is 2,6~dinitrotoluene.
The primary amine compound can be provided by the in-
situ decomposition of the corresponding urea or biuret as
represented by compounds having the general formulae:
RNH ~ NHR
and
Rl~H - ~ - N - ~ - NHR
~1 '
respectively, wherein ~1 is as defined above. Of course,
since the above urea and biuret will comprise more than
one radical, Rl may represent different radicals in the
same compound. That is non-symmetrical ureas and biurets,
e.g.
CH3NH~1 - NHC2~15
are within the scope of the invention.
In the process of this invention, no particular
limitation is placed on the amount of primary amine used~
However, it is preferably used in an amount equal to from
0.1 to 100 moles per gm-atom oE nitrogen in the
nitrogen-contalning organlc compound.
The process of the invention may be carried out in
the absence o~ solvent but the use of a sol~ent is not
precluded. Suitable solvents include, for example,
aromatlc solvents such as benzene, toluene, xylene, etc.;
~ ;~7~i~6Ei;
-21-
nitriles such as acetonitrile, benzonltrile, etc.;
s~lfolles such as sulfolane, etc.; hal~genated aliphatic
hydrocabons such as 1,1,2-trichloro 1,,2,2,-
trifluoroethane, etc.; halogenated aromatic hydrocarbons
such as monochlorobenzene, dichlorobenzene,
trichlorobenzene, etc.; ~e~ones; esters; and other
solvents such as tetrahydroEuran, 1,4-dioxane, 1,2-
dimethoxyethane, etc.
The hydroxy-containing organic compounds for use in
the process of this invention include compounds
represented by the general ~ormula
III Rl (OH)y
wherein Rl and y are de~ined above.
Hydroxy compounds suitable for use in the process of
the present invention may be, for example, mono- or
polyhydric alcohols containil3g primary, secondary or
tertiary hydroxyl groups as well as mono- and polyhydric
phenols. Mixtures o these hydroxy compounds may also be
used. The alcohols may be aliphatic or aromatic and may
bear other substituents in addition to hydroxyl gro~ps but
the substituents should texcept as hereinafter described)
preferably be non-reactive to carbon monoxide under the
reaction conditions. Especially suitable compounds are
phenol and monohydric alcohols such as methyl, ethyl, n~ ;
and sec-propyl, n-, lso, sec-and tert butyl, amyl, hexyl,
lauryl, cetyl, benzylr chlorobenzyl and methoxybenzyl
alcohols as well as diols such as ethylene glycol,
diethylene glycol, propylene glycol and dipropylene
glycol, triols such as glycerol, trimethylol propane,
hexanetriol, tetrols such as pentaerythritol and the
ethers o~ such polyols providing that at least one
hydroxyl group remains unetheriEied. The etheriying
group in such ether alcohols normally contains up to 10
carbon atoms and is preferably an alkyl, cycloalkyl or
aralkyl gro~p which may be substituted with, for example,
a halogen or an alkyl group.
The most preferrea hydroxyl-containing organic
compound for use in the process of this invention is
methyl alcohol or a similar lower alkanol, e.g. a Cl to C5
alcohol.
The process o~ this invention includes the use of any
mixture o~ nitro compounds, nitroso compound~, azo or
azoxy compounds with any mixture oE hydroxy compounds and
also the use of compounds containing both functions, l.e.
hydroxynitro compounds, hydroxynitroso compounds,
hydroxyazo and hydroxyazoxy compounds such as 2-
bydroxynitroethane, 2-hydroxynitrosoethane, nitrophenols,
nitronaphthols, nitrosophenols, nitrosonaphthols,
hydroxyazobenznes and hydroxyazoxybenzenes. Mixtures o
these nitrogen-containing compounds may also be used.
This process of the invention has been ~ound to
proceed most smoothly to give the hlghest yield~ when
employing nitro compounds. It is accordingly preferred to
use nitro compounds rather than n~troso, azo or azoxy
compounds.
The catalyst utilized in the process o~ this
invention may be selected rom the group consisting o~
rhodium or ruthenium salts, e.g. the halides, nitrate,
sulfate, acetate,~formate, carbonate, etc. and rhodium or
ruthenium complexe~ (especially rhodium or ruthenium
carbonyl complexes) including ligands capable of
coordlnating with the rhodium or ruthenium atom~ The
complex may include one or more rhodium or ruthenium atoms
and suitable ligands may include carbon-carbon unsaturated
groups as in ethylene, isobutylene, cyclohexener
norbornadiene, cyclooctatetraene. Other suitable ligands
-~3-
include acetylacetonate (acac), hydrogen atoms, carbon
monoxide, nitric oxide, alkyl-radicals, alkyl or aryl
nitriles or ison triles, nltrogen-containing heterocyclic
compounds such as pyridine, piperidine, and organo
phosphines, arsines or stilbines.
In one embodiment of this invention a rhodium or
ruthenium catalyst for use in the present process further
comprises a polyamino ligand having at least two tertiary
amino groups capable of coordinating with rhodium. For
example, such polyamino ligand may be selected from the
group o~ compounds represented by the general formula:
R3 ~ / R7
N (CR5R6)n N
R4 / ~ R8
wherein R3, R4, R7 and R8, which may be the same or
dif~erent, each represent an alkyl, aryl, alkaryl or
aralkyl group which may be substituted by one or more
inert substituents or R3 and R4 and/or R7 and ~8 may orm
a ring structure together with the atom M to which they
are attached; R5 and R6, which may be the same or
different, each represent a hydrogen atom or a lower alkyl
~roup and may form a ring struc~ure together with the atom
N and R3, ~4, R7 and/or R~ and n is an integer, pre~erably
n varies from 1 to about 5, e.g~ 1 to 3.
Examples o~ ligands according to the general ~ormula
are l,2-bis(diethylamino)ethane 1,2-
bis(dimethylamino)propane, l,2-~is(dimethylamino)ethane,
1,2-bis(di-t-butylamino)ethane, 1,2-
bis~diphenylamino)ethane, 1,2-bis(diphenylamino)propane,
1,2-bis(diphenylamino)butane, 2,2'-bipyridine, 2,2'-
biquinoline, bispyridylglyoxal, and l,10-phenanthroline and
derivatives thereof. Preference ls given to the use o
2,2'-bipyridine and l,10-phenanthroline.
,
~ ~7~
.
In another embodiment of the instant invention the
catalyst utiliæed in the process of this ~nvention may
comprise a bis-phosphino rhodium or ruthenium compound.
The bis-phosphino rhodium or ruthenium compound may also
include the above anions, i.e. sulfate, acetate,
trifluoroacetate, formate, carbonate, etc. and/or other
ligands, discussed above, cpable of coordinating with the
rhodium or ruthenium atom. The bis-phosphino rhodium or
ruthenium compound may include more than one rhodium or
ruthenium atom.
The bis-phosphino ligand of the rhodium or ruthenium
catalyst may be represented by the general formula:
(R3) (R4) P-Rg-P (R7) (Rg)
wherein ~3, R~, ~7 and R8 are as de~ined above and ~9 is a
divalent radical providing sufficient spacing to enable
both phosphorus atoms to coordinate with a rhodium or
ruthenium atom. Rg may be a hydrocarbyl having from 1 to
10 atoms or a substituted derivative thereof including one
or more heteroatoms selected rom the group connsisting of
haloyen, oxygen, sul~ur, nitrogen, and phosphorus atom.
Preferably, Rg comprises Erom 2 to G carbon atoms.
Examples of suitable bis phosphine ligands include
bis(1,2-diphenylphosphino)benzene, bis(1,2-
diphenylphosphino)-ethane, bis~3,3-
diphenylpho~phino)propane, etc.
Examples o~ ruthenium compounds which are suitable
as catalysts ~or the process o~ this invention include:
Ru(CO)3lbis(1,2-diphenylphosophino)ethane]
Ru(CO)3[bis(1,2-dlphenylphosphino)benzene]
Ru(CO)3[bis(1,3-diphenylphosphino)propane]
The rhodium or the ruthenium catalyst is preferably
utilized as a homogeneous catalyst and therefore one
criteria ~or t~e selection o~ the rhodium or ruthenium
72032-1
-25-
compound is its solubility und~r the conditlons of
reaction in the mixture QE the nitrogen-containing organic
compound and the primary amino compound (and, if desired,
the hydroxyl-containing organic compound). The rhodium or
ruthenium compound i5 also selected with a vlew toward the
catalytic activity of the compound. Mixtures of rhodium
and ruthenium compounds may be used.
The rhodium or ruthenium compound comprising a
polyamino ligand or a bls-phosphino ligand may be
preformed or formed ln~ in the reaction solution by
separately dissolving a ~hodium or a ruthenium compound
and the respectlve l~gand. Since the catalyst is utillzed
in very low concentration, it ls preferred that the
compound is preformed to ensure that uch llgand will be
coordinated with the rhodium or ruthenium during the
reaction.
The rhodlum or ruthenium catalyst may be used in
m~xture with co-catalysts or promoters 80 long as the co-
cataly3t~ unllkè the redox-actiYe metal halide co-
~o catalysts of the prior art, does not change the reactivityo~ the catalyst system to con~ume added amine~. Mono-
tertiary amines are one class of ~uitable promoter~ for
the rhodium cataly~ts o~ this invention. Suitable mono~
tertiary amlnes are ~hose descr~bed in U.S. 3~993,6~5.
Preferably the catalyst is free of halide to avoi~d
corrosion problems.
In carrying out the process of the invention, -the
hydroxyl-containing organic compound and carbon monoxide
may be used in amounts equal to at least 1 mole per
gm-atom of nitrogen in the nitrogen-containing compound.
When it is desired to obtain the urethane product,
directly, preferably the hydroxyl-containing organic
compound is used in excess. When it is desired to obtain
r~ ~
~1
~ ~7~
-26-
a urea product, then the primary amine iSJ preferably;
used in excess.
The amount oE the rhodium or ruthenium compound used
as the catalyst may vary widely according to the type
thereof and other reaction cond~ tions. However, on a
weight basis, the amount of catalyst is generally in the
range o~ from 1 X 10-5 to 1 part, and preferably from 1 X
10-4 to 5 X 10~1 parts, per gram-atom of nitrogen in the
startin~ nitrogen~containing organic compound when
expressed in terms of its metallic component.
The reaction temperature is generally held in the
range of 80 to 230 COt and preferably in the range of
from 100 to 200 C.
The reaction pressure, or the initial carbon monoxide
pressure, is generally in the range of ~rom 10 to 1,~00
kg/cm2G, and preEerably from 30 to 500 kg/cm2G.
The reaction time depends on the nature and amount of
the nitrogen-containing organic compound used, the
reaction temperature, the reaction pressure~ the type and
amount of catalyst used, the type of reactor employed, and
the like, but is generally ln the range oE from S mlnutes
to 6 hours. After completion of the reaction, the
reaction mixture is cooled and the gas is discharged from
the reactor. Then, the reaction mixture is subjected to
any conventional procedure including filtratlon,
distillation, or other suitable separation steps, whereby
the resulting urethane or urea is separated from any
unreacted materialsr any by-products, the solvent, the
catalyst, and the like.
The urethanes and the ureas prepared by the process
of the invention have wlde applications in the manufacture
o~ agricultural chemicals, isocyanates, and polyuretllanes.
~ ;~7~
-27-
The invention is more fully illustrated by the
f ollowing examples. However, they are not to be construed
to limit the scope oE the inven~ion.
In each of the following examples9 the reaction was
conducted in batch mode in a 300 ml stainless steel
autoclave reactor equipped with a stlrring mechanlsm which
provides constant dispersion o~ the gas through the liquid
solution. Heating of the reaction is provided by a
jacket-type furnace controlled by a proportioning
controller. The autoclave is equipped with a high
pressure sampling system for removal of small samples of
the reaction solution during the reaction in order to
monitor the reaction progress. Reaction solutions were
prepared and maintained under anaerobic conditions.
Reaction samF~es were analyzed by gas chromatography.
The ~ollowing examples are shown for the purpose o~
illustration only and should not be deemed as limitlng the
scope o~ the invention.
~ .
75 ml o~ a solution conta~ning 12.31g (0.100 mole)
nitrobenzene, 4.66g (0.050 mole) aniline~ and 2068g t-
butylbenzene (internal sandard for gas chromatographic
analysls~ in methanol and 0012~g (0.20 mlllimole)
Ru3(C0)12 were placed in the reaction vessel. The gas
volume in the vessel was replaced with carbon monoxide at
1000 pslg at ambient temperature. The reactor contents
were then heated to 160C. Complete conversion of
nltrobenzene occurred over 805 hours at 160C and yielded
0.076 mole methyl N-phenyl carbamate (76~ selectivity
based on nitrobenzene) and 0~067 mole aniline (17~
selectivity to additlonal aniline based on nitrobenzene).
The balance consis~ed o~ undesired side-products formed
-~8-
by aniline-formaldehyde condensations and ensuing
reactions.
,
x~m~l~ 2
The procedure was the same as for Example 1 except
that 9.32g ~0.100 mole) aniline was lnitlally provided to
the reaction. The volume of methanol ws reduced so that
the total solution volume was again 75 ml. Complete
conversion of nitrobenzene occurred over 3.5 hours at
160C and yielded 0.088 mole methyl N-phenylcarbamate
(88~ selectivity based on nitrobenzene) and 0.112 mole
aniline ~12~ selectivi~y to additional aniline based on
nitrobenzene).
~omparativ~ E~ample 1
The procedure was the same as or Example 1 with the
exception tha~ no aniline was introduced to the reaction.
Complete nitrobenzene conversion re~uired 26 hours at
lG0~ Selectivities based on nitro~enzene were 38 pecent
to methyl N-phenylcarbamate, 32 percent to aniline, 12 percent
total to formylidene aniline and N-methylaniline. The
balance was converted to higher molecular weight products
derived from aniline.
It can be seen by comparison oE Examples 1, 2 and
Comparative Example 1 that the rate and selectivity oE the
reaction are improved by intially pro~lding increasing
amounts o~ amine to the reaction.
Relative to Example 1 and 2, the amine concentration and
amine-to-alcohol ratio may be further increased by
replacing more alcohol in the initial solution with
amine. Amine may become the major reaction solution
component and thus act as solvent for the reaction.
. ~ . ' . .
. !
~ ~7~l6~i
-29-
The amine-to-alcohol ratio may also be increased by
simply replacing some of khe excess alcohol with an lnert
solvent.
Example 3
~ he procedure was the same as ~xample 1 except only
6.40g (0.200 mole) methanol was initially provided to the
reaction solution. Toluene was added as an lnert solvent
to again give a total solution volume of 75 ml. Complete
conversion of nitrobenzene occurred in 8.5 hour~ at 160C
yielding 0.095 mole methyl N-phenyl carbamate 195~
selectivity based in nitrobenzene) and 0.054 mole aniline
(4~ selectivity to additional aniline based on
nitrobenzene).
It can be seen by comparison of Examples 1 and 3 that
reducing the alcohol concentration in the solution, for
example by using an inert solvent, increases the
selectivity of the reaction without any decrease in the
rate of urethane production. Thus, in Example 1, wherein
the ratio of methanol to nltrobenzene was 15.1, the
selectivity was 76~, while in this Example, wherein the
ratio of methanol to nitrobenzene was 2:1, the ~electlvity
was increased to 95~. (Decreasing the ratlo of methanol
to nitrobenzene to almost 1:1, would be expected to
further increase selectivity.) In view o~ the above, it
is preferable to provide a ratio of methanol (or other
hydroxy-containing organic compound) to nitrobenzene (or
other nitroyen~containing organic compound) of less than
15:1, more preferably a rakio of from l:I to 5sl, mosk
preferably a ratio of from 1:1 to 3~1, e.g. about 2:1~
The procedure was the same a~ for Example 3 except
that no methanol is provided to the reaction. ~dditional
-30-
toluene solvent was added to again give 75 ml total
reaction solution. AEter 10 hours at 160C, 0~048 mole
nitrobenzene and 0.008 mole aniline remained (52~ and 42%
conversion, respectively). The mixture contained copious
amounts o a white organic colid. ~fter cooling, the
solid was filtered and characterized (IR, NMR) as
predominantly N,N'-diphenyl urea. The spectra and the
excess consumption of nitroben~ene over aniline indicate
that N,N',N"-triphenylbiuret was also present.
Durin~ the course of the urea synthesis of Example 4,
the observed rates of nitrobenzene and aniline conversion
decreased as the aniline was consumed. However, the
aniline-dependent rate of nitrobenzene conversion to urea
in this experiment was approximately equal to the anil~ne-
dependent rates of nitrobenzene conversion to urethane in
the experiments o Examples 1 and 4. This shows ~hat urea
synthesis is kinetically competent to account for all of
urethane synthesis in ~he presence o alcohol.
Example_5
10.60g (0.050 mole) N,N'-diphenylurea and methanol to
gi~e 75 ml total mixture volume were heated from room
temperature to 160C over approximately one hour~ On
reaching 160C, the mixture contained 0.035 mole each of
methyl N-phenyl carbamate and aniline~ and unreacted
N,N'-diphenylurea. ~fter 45 minutes at 160C, the
solution contained 0.050 mole each of methyl N-phenyl
carbamate and aniline! representing quantitative urea
alcoholysis.
From this example, it can be seen that the urea
alcoholysis occurs in the absence of an added catalyst.
The data obtained also indicate tha~ uncatalyzed urea
alcoholysis is klnetically competent to account or all Of
~31-
the urethane synthesis in the catalytic conversion of
nitro compounds in the presence of alcoholO
Example 6
The procedure was the same as for Example 1 except
that 0.23y (1.40 millimole) tetraethylammoniumchloride
was also provided to the reaction. Complete conversion of
nitrobenzene occurred over 6.0 hours at 160C and yielded
O.Q77 mole methyl N-phenylcarbamate (77% selectivity based
on nitrobenzene) and 0.071 mole aniline ~21% selectivity
to additional aniline based on nitrobenzene)c
Comparative Example 2
The procedure was the same as for Example 6 except
t~at no aniline was initially provided to the reaction
Commplete nitrobenzene conversion required 15 hours at
160C. Selectivities based on nitrobenzene were 60% to
methyl N-phenylcarbamate and 34% to aniline.
Comparison of Example 6 with Comparative Example 2
shows that the rate and selectivity oE the reaction are
improved by initially providing primary amine to the
reaction, when the reaction also includes chloride ion.
Example 6 also shows that the amine is not, in net,
consumed when the reaction contains chloride lon. Thus,
in the prior art processes in which the amine is consumed
in the presence o~ redox-active metal chloride co-
catalysts, it is the additional presence of the redox-
active metal which causes the amlne consumption.
, .
Example 7
75 ml o~ a solution containing 3.07g (0 025 mole)
nitrobenzene, 11.6~ (0.125 mole) aniline, and 2.74g t-
butylbenzene ~internal standard) in toluene and 0.1289
';
..
~.~76~
32-
(0.20 mlllimole) Ru3(CO~12 were placed in the reaction
vessel. The gas in the vessel was replaced with carbon
monoxide at 1000 psig at ambient temperature~ The reactor
contents were then heated to 160C. ~fter 1.5 hours at
160Cr the reactor contents were cooled to am~ient
temperature. The sampling system was clogged with solld
~,N'-diphenylurea 30 ml of methanol was then injected
into the vessel and the gas in the vessel was vented and
replaced with nitrogen at 1000 psig. The reactor contents
were then reheated to 1~0C. After 1.0 hour at 160C, the
reactor contents were cooled. The resulting solution
contained no nitrobenzene, 0.023 mole methyl N-
phenylcarbamate (92% selectivity on nitrobenzene) and
0.126 mole aniline.
.
Comparative Exam~le 3
The procedure was the same as ~or Example 7 except
that no aniline was lnitially provided ~o the reaction.
Additional toluene solvent was added to again give a total
initial solution volume of 75 ml. After 1.5 hours at
160C under carbon monoxide, 0.023 mole ~itrobenzene
remained and no products were observed by the gas
chromatographic analytical system. The mixture was
cooled, methanol was added, and the gas was changed to
nitrogen as in Example 7. Ater 1.0 hours at 160C under
nitrogen, the solution contained O.Q13 mole nitrobenzene,
0.003 mole aniline, O.OQl mole N-methylene aniline, 0.004
mole N-methyl aniline, and less than 0.001 mole methyl N-
phenyI carbamate.
.
