CA1066295A

CA1066295A - Process for making nitrated aromatic compounds

Info

Publication number: CA1066295A
Application number: CA227,680A
Authority: CA
Inventors: Newell C. Cook; Gary C. Davis
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1974-07-08
Filing date: 1975-05-23
Publication date: 1979-11-13
Also published as: SE427032B; JPS5129450A; JPS5953258B2; FR2277797B1; FR2277797A1; DK309275A; BR7504323A; IT1039626B; DE2522818A1; DD119206A5; SE7507839L; DE2522818C2; AU8141975A; NL7508085A; GB1511345A

Abstract

ABSTRACT OF THE DISCLOSURE
Nitrated derivatives of aromatic compounds are obtained by contacting the latter, in the presence of methylene chlo-ride as a reaction medium, with concentrated nitric acid in the presence of concentrated sulfuric acid, and thereafter isolating the formed nitro derivatives.

Description

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Thl8 in~rention i~ concernet with a proce~ for making ni~rated derlvative~ o~ aromatic cosnpound~. ~ore particulsrly, the inventlon i5 concerned with a proce~s ~;
for malciTIg rlitrated aroma~ic ~ompounds containing fro~
S 6 to 18 carbon atoms, which proces~ comprise~ contacting the aroma~ic compo~d, in the preserlc~ of methyl~ne chlorlde a8 a reac~cion msdium, with from 80 l:o 100%
concentration sulfuric acid and 90 to lOOZ conc~tratlon nitric acid, ~dvan~ageously w~thln a ~cemperature range of ~rom about -20 to 50C., or ~ren som~what higher, a~d ~chereaf~er i~olating the llitro compound, e.g., by extractiotl with additiorlal methylene chlorid~
Dinitrob~nzen~ and dl~i~rotolu~nes (as well as other dinitro aromatic hydrocarbons) are important -lntermediates ln the preparation of diamino deri~ratives thereo~ which are obtained by ~he reduction with hydrog~n o ths corre~ponding dlnitro compo~md~ The~ d~mino compound~, ~or instance, m-phenylenediamine, p-phenyl~ne-diamine, ~nd tolue~e diisocyanate (which i8 mad~ from dinlt~otoluene) are important ingredients in the prepara~ion of conEIlerc~al reslnous compositions. For instance, dl~minobenzene} can be reacted with 2,2-bi~[4-(3,4~ticarboxy-phenoxy)phenyl] propane dianhydride to give polymer~
having good high temperature propertles. Polyetherimid~

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RD-74~4 polymers derived in the above manner are more particularly disclosed and claimed in U.S0 Patent 3,787,475, issued January 23, 1974, and assigned to the same assignee as the present invention~
Toluene diisocyanates are used in making resinous products by reacting the lat~er with polyols in the manner disclosed in U.S. Patents 3,781,229 and 3,781,235, both issued December 25, 1973, and in U.S. 3,801,687 issued April 2, 1974. Such resinou~
products can be converted to foams having utility as insulation in refrigerators, and can also be employed as wire enamels for conductors used ~n motor windingsO
In the past, these dinitrohydrocarbons have been prepared in large quantlties by fairly well-known techniques. However, it has become desirable not only to improve the yields of these dinitrobenzene compounds but al~o to reduce the hazards and the cost thereof by virtue of more simplified processing techniques~ Unexpectedly, we have discovered that aromatic compounds, e.g~, aromatic hydrocarbons, can be readily nltrated and the nitrated products can usually be obtained ~n almost quanti~ative yields, to give mainly the dinitro derivatives in almost reaction grade purl~y. In accordance with our invention, the aromatic compound dissolved in CH2C12 as a reaction medium, i~ contacted with concentrated nitric acid in the presence of concentrated sulfur~c acid to form the nitro

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derivatives thereof. Thereafter, the nitro derivatives are isolated from the reaction mixture, advantageously using additional methylene chloride for extraction purposes. The methylene chloride can be readily evaporated from the nitrated compound ~o leave behind the essentially pure nitrated derivative and to yield unchanged methylene chloride which can be recycled or further solvent and extraction purposes. By these techniques, we are able to fonm nitro derivatives, particularly dinitro compounds, on a continuous basis rather than the batch operation which has ~ormerly been used extensively in making dinitro compounds.
The use of the methylene ohloride as the ~olvent in the treatment of the aromatic hydrocarbon with ~he nitric acid in the sulfuric acid medium is important for a number of reasons. Methylene chloride is completely stable in nitric acid in all concentrations up to its boiling point of 40C. or somewhat higher, and was alone in being able to resist degradation or ré~ist conversion to otker products as compared to other halogenated der~vatives such as chloroform and methyl chloroform. Moreover, the aforesaid halogenated derivatives, other than methylena chloride, did not have the de~ired volatility and solubility affini~y for the reaction mixture and the nitrated products therefrom to insure efficient and rapid removal of the desired

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nitrocompoundsO Alsn, it was found that only me~hylene chloride was able to maintain its integrity sufficiently in a strongly acidic environment.
It was also found that in a number of instances, by using the methylene chloride, a limitlng temperature in the neighborhood of around 42C. could be attained, thus eliminating local hot spots and sudden temperature rises and automatically restricting the nitration of the aromatic compound to the mono or dinitro derivative and thus avoiding the formation of trinitro derivatives (which can be explosive in nature). Furthermore, the methylene chloride avoided the need for any extra care which might be required to insure that excess nitric acid was not present to cause the formation of dangerous trinitro lS derivatives.
The methylene chloride i8 completely miscible in nitric acid above 90% concentration thus facilitating reaction when nitrat~ons are slow; the methylene chloride, however, is immiscible wlth ~tric acid below 80%
concentration, thus diminiRhing side reactions when highly reactive compounds are being ni~rated.
It was also found that some of the nltrated products were solid and, previously7 difficulty was encountered in avoiding separation of the nitrated compounds during the nitration reaction. The use of the methylene chloride, because it was such a good solvent for , 1~6~29S

the nitra~ed compounds (as well as being a good solvent for unnitrated products), avoided this bothersome separa~ion.
The aromatic compou~ds which can be nitrated in accordance with our process can be any aromatic monoc~clic ~ :
or polycyclic (or ~used~ ring compound which has at least one nuclearly-bonded hydrogen capable of being replaced by a~ ~2 group and which is free of any substitution which will significantly and undesirably afect the abillty of the ~itra ion reaction to proceed~ ThuS9 these aromatic compounds may be str~ctly hydrocarbon compounds, or they may contain functional or side groups, such as9 ethers, carbonyls, carboxyls, halogens, anhydrides 3 nitriles, aliphatic or alicyclic groups, aromatic compounds containing heterocyclic groups attached thereto, etc.
Among such aromatic compounds which advantageously can be employed in the practice of the present in~ention may be mentioned, for in~tance, aromatic monocyclic and polycyclic hydrocarbon compounds ? e.g., benzene, ~oluene, xylene~ mesitylene, biphenyl, naphthalene, anthracene, diphe~yl methane, diphenyl ethane, e c.; halogenated derivatives of such aromatlc monocyclic and polycyclic hydrocarbons, for e~ample, chlorobenzene, dichloroben~ene, dibromobenzene, chloromesitylene, dichlorotoluene, various halogenated blphenyl derivatives, the various halogena~ed naphthalene derivatives, the various halogenated anthracene .

, ~L~66295 derivatives, etcD; aromatic etherg~ e~gO ~ diphenyl oxide, halogenated derivatives of such phe~yl ethers, for example, the mono- and d~chlorodiphenyl ox~de, e~c.; aliphatic substi~uted diphenyl ethers, particularly those containing from 1 to 3 carbon atoms in the aliphatic nucleus, for example, ~he mono- to tetramethyldiphenyl oxide (including its various isomers), diethyl substituted diphenyl oxide (and its various isomers), etc~; benzophenone and the various substitu~ed products ~hereof, for i~stance~ the mono- ~o tetramethyl-substituted dibenzophenone and ~he various halogenated substituted dibenzophen~nes, for instance, 3,3'-dichlorobenzophenone, etcO;: other aroma~ic compounds such as benzoic acid, phthalic anhydride, chlorophthalic anhydride, the various phthal~mides such a~ phthalimide itself, N-me~hylphthalimide,'N-ethyl-phthalimide, etc. and ~alogenated derivat~ve3 of such phthalimides, for instance, monochloro N-methylphthalimide (including the various isomers), etcO
It will be evident ~hat intended w$thin the scope o thi~ invention are both mono-nitrated and dinitrated products where there is a maximum of two nitro groups in the aromatic compound nucleus. Where there is more than one cyclic aromatic nucleus in the aromatic compound, there is correspondingly only one nitro group per aroma~ic ring.

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The amount of me~hylene chloride used as a solvent in the nitration s~ep is not critical~ Generally, however, we have found-that for each part by weight of the aromatic compound, from about 1 to 50 parts or more of the methylene chloride are advantageously employed.
Since the methylene chloride is also uqed as an extractant after the reaction is completed, the methylene chloride amo~nt initially employed for ~olvent purposes can be minimal and later the extra amount of methylene chloride 0 i8 added for the extraction stepO Generally, the minimum amount of methylene chloride used should be sufficient to limit the reaction temperature to no higher than about 42-45C. a~ atm~spheric pressure. Also the am~unt of methylene chloride used should be sufficien to permit eæs~ntially complete solution of the aromatic compound in the methylene chloride and to prevent undes~rable separat~on of the nitrated product before complete nitra~ion i8 accomplished.
W~en employing the methylene chloride for extraction purpose~, we have found that, on a weight basis for e~ch part of nitrated product, one can advantageously employ from about 0.5 to 8 part8 or more of addit~onal methylene chloride for the extrac~ion function. In all instances when carrying out ~he nitration reaction, ~tirring of the reaction mixture 3hould be carrled out ~or re intimate contact of the reac~ant~; a similar ,, , , , " - ", . , :, ', " ,' : ......... ' : ," , ., : ~ .

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RD~7454 degree of stirring should be resorted to when employing the methylene chloride for extraction purposes, The sulfuric acid solvent initially employed should be within 80 to 100% H2S04. If lower concentrations of H2S04 are employed initially, the amount of water liberated from the nitration reaction (with the nitric acid) will undesirably dilute the sulfuric acid thus causing a problem because of the decreased solubility of the nitrated products in the reaction mixture, particularly the water which is fonmed as a result of the reaction with the nitric acidO This might cause a separation problem during the step o~ extrac~ion w~th the methylene chlorideD
The concentration of nitric acid must also be within about 90 to 100% concentration in order to minimize the amount of water formed so as not to unduly dilute ~he sul~urlc acid. The amount of nitric acid used should be relatively close to the stoichiometric amount required to attach the desired number of nitro groups on the aromatic nucleus or nuclelO As pointed out above, however1 any substantial exces of nitrlc acid is not critical because the CH2C12 solvent will limit the degree of nitration thereby avoiding hazardous situations and possible explosive compositions.
In carrying out the reaction, one method comprises dlssolving the aromatic hydrocarbon in the methylene chloride and placing the solution in a reactor equipped wi~h : ~ , . , . ~ . . ....................................... ~ . , .:, , ' , ' ,':. . .' ', : ' ' a stirrer and mean~ for heating or cooling the reactorO
After heating the solution to the desired temperature (usually reflux temperature of about 40-45Co~ a mixture of concentrated nitric ac~d and concentrated sulfur~c acid is added slowly over a period of time advantageously ranging from about 15 minu~es to about one to ~wo hours or more. After stirring the mixture for a period of time rang~ng from about 30 minutes to about 2 to 3 ~ours at the reflux temperature, the mixture is cooled to room temperature at which time ~wo distinct layers are usually visible. The upper methylene chloride layer is separated and the bottom acid layer is extracted with additional methylene chloride, preferably in several fractional extractlons. The extracts and the top methylene chloride lS layers are sent through a silica gel (or other appropriate means) to remove residual acid, the methylene chlorlde removed by evaporation to give the nitrated productO
The continuous extraction of the bottom acid ~olution with methylene chloride is advan~ageously carried out in a closed loop reactor resembllng a Dean Stark apparatus and con6isting of an extraction column equipped with a ~tirrer in~o which the reaction product i5 introduced.
M~thylene chloride (extractant) i8 introduced continuously into the bottom of the extraction column. At the upper end of the extraction column i8 an arm through which the overflow _g_ , . . - . . .: . :..................................... .
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of the extractant and reaction pr~duct (separated from H2S04) is c~rried into a reservoir equipped with a heater operable within a range of about room temperatUrQ to 100C.
whose function is to evaporate the methylene chloride and concentrate the nitrated aromatic compoundO The methylene chloride vapor i8 condensed and recycled by gravity to the bottom o the extraction column and continues recycling until extraction is complete. At this point, all the nltra~ed product iQ in the methylene chloride contained i~
the reservoir.
~s pointed out previously, one of the advantages of using methylene chloride as a solvent during the nitration reaction i8 that lower temperatures can be used and there is practically no danger of eæ essive 1~ nitration to fonm compo~nds having more than two nitro groups per aromatic ring thereon which could present a hazardous condition. Generally the temperature at which the nitration i~ carried out is sufficiently productive:
within the range of from about 50 to 45C. However, lower ~emperatures can be employed beginning with about -20 to -10C. up to the reflu~ temperature of the mixture :
(or even higher especiall7 when supera~mospheric pre~sures are used).
During the entire nitration reaction, it is desirable that an inert atmosphere, for instance, a blanket of nitrogen be employed. Generally, atmospheric pressures :,. , , , . ,, , ,,:, . . . .
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are adequate for maintaining ~he reaction but it will of course be apparent to those skilled in the art that subatmospheric or even superatmospheric conditions may be employed without departing from the scope of the inventlon. Vigorous stirring is employed throughout the reaction perlod.
As a result of carrying out the reaction where d~nitro derivat~ves are intended, it has been found that for the most part a mixture of din~trated isomers is obtained in which there is a fairly constant ratio of the ortho, para, and meta isomers. This seems to be the case whéther a nonuclear hydrocaxbon or a dinuclear hydrocarbon aromatic compound is being subjected to nitration. When a mononuclear compound is being nitrated such as benzene and tolu~ne, generally about 70 to 80%
is the meta-dinitro isomer. The yields of dinitrated products are exceptionally good and in some ~nstances are quantitative~
In order tha~ those skilled in the art may be~ter understand how the present invention may be practiced, the following examples are given by way of illustration and not by way of l~mi~ation.
Unless stated otherwise, the extracted nitrated produot com~ined with the methylene chloride was passed ~hrough a column o~ silica gel to remove traces of sulfuric acid; the removal of methylene ch~oride was accomplished ,, , , , . ' , . .

~629~ RD-7454 under vacuum in a rotary film evaporator.
Example l 7.8 grams (0.1 mol) ben~ene was placed in the above-described nitration vessel together with 40 cc.
of methylene chloride. While stirring the mixture, it was brought up to reflux temperature by gentle heating (about 42 to 45C.a. At this point a mixed acid consistlng of 30 cc. o 95.5% H2S04 and 9.5 cc~ (0~22 mol) o~ 9801%
HN03 was added dropwise to the stirred solution over a period of approximately 25 minutes. The reaction mixture was then maintained at ~he reflux temperature of the mass for.a~ additional 90 minutes and then cooled to room temperature, at which po~nt the mix~ure separated into two layers, a top methyle~P chloride layer and a bottom acid laysr. These layer~ were separated and the acid layer was extracted twice with additional 40 CC7 portion~ : :
o methyle~e chlorideO The extracts and methylene chlorlde layer were the~ placed through a column of sili¢a gel, the methylene chloride removed to give a quantitative yieId of pure, mixed ortho, para, and meta dinitrobenzenes .
in the isomer ratios of about 85% of the meta~isomer, :13X of the ortho-isomer, and 2V/~ of the para-isomer.
Example 2 Employing the same equipment as described in Example 1, 9.2 gram~ (0.1 mol) toluene was formed into a ~ :~
solution with 40 cc. methylene chloride~ The 501ution was .. . . . . . . . . ........................ . ..
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.: ' ' ' , ',',, ' , ' . ' . " . . ...... ' '" '.' ': .: ' ~6~66Z~ 5 RD-7454 brought to re1ux temperature (about 42C.) and at this . .
point, a mi~ed acid consisting of ~5 ccO of 95.5% H2S04 and 9.5 cc. (0.22 mol~ 98.1% HN03 was added dropwise over a period of approximately 20 minutes. The mixture S was stirred at the reflux temperature of the mass for an additional 90 minutes and then cooled to room temperature to yield two distinct layers, a top methylene chloride layer and a bo~om acid layer. The latter layer was extracted twice with 40 cc. portions of methylene chloride and the extracts and the methylene chloride layer were treated with silica gel, and the methylene chloride solvent removed to give a quantitative yield of pure mixed dinitrotoluenes in a weight ratio of about 78% of the 2,4-isomer, 19% of the 2,6-isomer, and 3% ~;
of other isomers.
Example 3 In this example, 17 grams (Ool mol) diphenyl ~ther was added to the aforesaid reaction vessel used in the preceding examples along with 40 cc. methylene chloride.
An acid mixture consisting of 30 ccO of 85% H2S04 and 8.6 cc. (0.2 mol) of 98.1% HN03 was added dropwise over a period o~ 75 minute~ to the ~igorously stirred solution of diphenyl ether and held at a temperature from about 5 to 10C~ throughout the additionO The reaction mixture was then stirred at 15C. for an additional 180 minutes .

and then heated to 25C. and s~irred at this temperature for an additional 15 hours. The reaction mixture was extracted twice with methylene chloride (a 250 cc, portion followed by a 100 cc. portion). The extracts were S treated with silica gel and the solvent was removed to give 25.99 grams of recovered material consisting of about 90~/O of mixed dinitrodiphenylethsrs. Analysis of the product indicated that there was one nitro group on each phenyl nucleus.
Exam~le 4 In this example, a number o other aromatic : :
compounds were nitrated using the procedures described in Examples 1 to 3. The following Table I shows the ~-re~ult of such te~ts whereby two nitro groups were introduced into ~he aromatic eompound to form a dini~rated -~ -product. Where there was a single aromatic nucleus, two nitro groups fonmed on ~he single nucleusO Where, howe~er, the aromatic compound consisted o~ two aromatic nuciei, one nitro group was introduced into each aromatic . ~.
nucleus. ~11 nitratlons used 0.1 mol of aromatic compound ~:~
except for the diphenyl sul~one which used 0.025 mol.
Two equi~alents of nitric acid (98.3% concentration) were used i~ each case except ~or the monochlorobenzene which used a 5% excess o nitric acid. All the nitrated materials were readily extracted from the sulfuric acid with methylene chloride except for the dinitrodiphenyl sulfone which was ~, . . . . . . . . . .. . . . ... .

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slowerO In each instance, from 30 to 50 ccO of methylene chloride was used as the solvent medium durlng the nitration react~on. The first time tabulated under the heading "Time" is for the addition of the nitric-sulfuric acid mixture, and the following tim~s denote reaction periods at the temperatures indicated. Very little, if any, mononitrated product was obtained and such product generally ranged from about 0 to about 3%, by weight, of the total productO
TABLE I
Products ; Total H2S4 Waight - -- Reaction % ~ield % Con- TempO Time Product Dinitrated Compound cc centO (oc) (hr~ ~ Product o-Xylene 25 95.6 S loO 18.91 96.4 ~.0 Chlorobenzene 30 95.6 41 0,5 19.63 96.9

4.0 Naphthalene 30 85 10-15 1.3 19.44 89.1 2.0 Diphenyl 20 95.5 10-lS 0.5 23,97 94.7 1.0 Diphenyl~ 20 95.5 5-15 0,S 25,21 93,6 methane 41 3,5 Dibenzyl 20 95.5 5-15 0.5 27~00 94,0 1.0 Benzophenone 20 95.5 10-30 0.5 26.78 92,8 1.5 Diphenyl- 10 100 41 0.5 6.27 8103 sulfone 5.0 :, ,, ,,, , . ,., ~ ' , ., . . . , .. / . .

- ' 1a~66~9S RD-7454 10.6 grams (0.1 mol) o-xylene was dissolved in 40 cc. methylene chloride and to this was added a mixture consisting of 1205 cc. of 80% H2S04 and 4.3 ccO (Ool mol) of 98.1% HN~3. After 30 minutes of dropwise addition of the acid mixture at a temperatura of 0 to 5Co~ the mixture :-was then stirred at 25C. for an additional hourO The resulting reaction product was extracted with methylene chlorlde, the extracts treated with silica gel, and the methylene chloride solvent removed to give 14.94 grams . -.
(about an 83~/0 yiPld) o~ the mononitrated o-xyl nes mixture o which about 5~/0, by weight, thereof wa~ ~nreacted xylene.
~ . .
1601 grams (0.1 mol) N-methylphthalimide dissolved in 30 cc. 98.3% H2S0~ and 40 cc~ methylene chloride was brough~ to a slow reflux (about 41Co) at which point 4.55 cc, (0.105 mol) 98.1% HN03 was added slowly to the reaction mixture over a period of 40 minutesO There~ter, the mixture was stirred for an additional 1 hour at 41C.
while allowing some of the methylene chloride to be distilled. Therea~ter, the temperature of the reaction mlxture was raised ~o 90C. for a period of 2 hour~
at which poin~ the reaction mixture was cooled, dilu~ed with 10 cc. H20 and the solution extracted with 200 cc.

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~ 6~2~ 5 ~D-7454 portions of methylene chlorideO Evaporation of the methylene chloride solvent yielded 18.6 grams (90% o~ ~he theoretlcal yield) of which 90~/0, by weight, was a 4-nitro-N-m~thyl-phthalimide, 4% was the 3-nitro-N-methylphthalimide and 4% of unreacted N-methylphthalimideO
When N-isopropylphthalimide was reacted in the same way wi~h an equimolar amount of nitric acid, L9o8 grams of product was obtained of which 85% was the 4-nitro-N-isopropylphthalimide, 5% was the 3-nitro-N-isopropylphthalimide, and 7% was recovered ~tarting materials.
ExamPle ?
This example illustrates the mononitratio~ of phthalic snhydride at ~upera~mwspheric pressure. More particularly, 1.48 grams (0.01 mol) phthalic anhydride and 4 ccO of 100% H2S04 were added ~o a glass pressure reac~or (50 cc. volume) ~itted with a Te~loff valve pre~sure seal a~d a magnstic stirring bar. 4 ccO methylene chloride and 0.694 gram (0.011 mol) 98.1% nitric acid were added to the reactor and the valve sealedO The reaction was the~
stirred vigorously for 2 hours in a water bath held at 75C. The reaction mixture, whlch was essentially colorless, was poured into lS gramR of ice and e~tracted three times with 50 ccO portions of diethyl ether) The extract was passed over a silica gel and evaporated ~o ~62~ ~

dryness on a steam bath under nitrogen gi~ing 2012 grams of light, yellow crys~als (theoretical yield 2.11 grams of mononitrophthalic acid). Analysis of both the extract~ -and the solid showed them to contain 68% of 4-nitrophthalic acid, and 32% of 3-nitrophthalic acid without any evidence of recovered starting materials, indicating ~hat the reaction had gone essentially to completio~ to the mononitrated derivative. The 100% conversion o~ the phthalic anhydride to the mononitrated derivative and the lack of color development indicate that this process of superpressure nitration of phthalic anhydride with methylene chloride may ofifer substantial commersial ad~antages in making the mononitrophthalic anhydride.
Example 8 The :Eollowlng example shows 'che formation o~
other mononitro compounds formed from various other aromat~c compounds using the procedures of Examples 5 to 7 The follow~ng Table II ~hows the results of such tests whereby only one-nitro group was in~roduce~ into ~he aromatic compound, regard~ess o~ whether the aromat~c compound consis~ed o~ a single aromatic nuc~eus or two aromatic nuclei. All nitrations used 0.1 mol of aromatic compound. Equivalen~ amounts (0.1 mol) of 9803% nitric acld were used sxcept for acenAphthene where 70% nitric acid was used. The ben~ene reaction used a 5% molar excess of nitric acid. The first time tabulated is or the . . .

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addition of nitric acid; the following times denote heating periods at the corresponding temperatures. All the nitrated materials were readily e~tracted from the sulfuric acid with methylene chloride using 100 to`300 ccO portions excèpt for the nitroacetanilide which because it was insolu~le was extracted with diethyl ether. In each instance from 30 to S0 cc. of methylene chloride was used as solvent during the nitration per 0.1 mol of aromatic compound.
T~BL~ II
Products_ Total H2S04 Weight - Reaction. % Yield % Con- Temp. Tlme Product Mononitrated

5~E~g~ cc cent. ~C2 ~ rams~ Product Benzene 15 80 41 0.512.11 96.5 41 1.5 Toluene 15 80 41 0O513.62 96.9 41 1.5 Chlorobenzene 10 95.6 41 0.515.54 96.8 41 4.0 Benzonitrile 30 95.6 0-5 0.757.63 49.7 0 1.5 Benzaldehyde 30 95.6 0-5 0.514.68 96.1 0-5 2.0 O.S
Benzoic ac~d 15 95.6 41 00515.36 90.5 4~ 1.5 Acetanilide 30 g5.6 0-5 0.7515.00 80.3 0 2.5 Naphthalene lS 80 41 0.7517.17 94.1 o-Nitrophenol lS 80 41 0.518.39 94.0 41 1.5 Acenaphthene3.25 95.5 10 0.517.53 40 ~.~6~ 95 RD-~454 In addition to the aroma~ic compou~ds mentioned above and employed in the foregoing examples for ni~ration purpo~es, it will be apparent that other aromatic compounds . .
containing from 6 to 18 carbon atoms may be employed within the scope of this ~vention, many example of which have been given above. It will also be apparent to those skilled in the art that in addition to the conditions and ~ -~emperaturesS pressures 9 proportions ~nd concentration~ :
of ingredients employed in the foregoing examples, variations of these may be employed~ all wlthin the scope of the intended invention.
The various dinitro compounds described herein and capable of preparation by means of our process can be converted to either diamino deri~atives for use in making polymeric compositlons, for instance, through in~tial reac~ion with dianhydrides or else they can be converted to dilsocyanato compounds which can be used for making resi~ous composition~ by re~ction with polyol~. The mononitro compounds of the present invention may be treated to reduce the nitro group to the amino group and such amina~ed derivatives can be used in the preparation of various dyes~ In addition, aminated derivatives of aromatic hydrocarbons can be reac~ed with formaldehyde to form resinous compo~itions u~eful in the molding art~
Nitrophthalic anhydrides, nitrophthalimides or nitrated , , : .. .. : .. : ~

1~)66295 derivatives of the N-methylphthalimides can be employed in the preparation of polymers having good heat resistanceO
Thu~, the nitrophthallc anhydrides are first reacted with dialkali metal salts of, for instance, bisphenol-A to form a dianhydride of the formula O . ' .. . .
I 0 ~ 0 ~ C(CH3) ~ ~ C

O O

Thereafter this dianhydride can be reacted with organic diamines such as 4,4'-diaminodiphenylmethane, m-phenylene diamine, etc., to give polymers having extremely good high-temperature properties useful as housings for appliances and for motors, as brake linings, etc. The nitro deri~ativeQ o~ N-methylphthalimide can be reacted with bisphenol-A similarly as wlth the ni~rophthalic anhydrides, treated with aqueous sodium hydroxide to form lS the corresponding tetracarboxylic acid and by suitable treatment of the tetraacid with, for instance, glacial acetic acid and acetic anhydride, one can obtain the corresponding dlanhydride having ~ormula I. These again can be ~sed to make polymers by reacting with a diamino compound in the same manner as described previouslyO

Claims

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A process for the nitration of an aromatic compound to form a nitro derivative thereof wherein essentially only one nitro group is introduced in any aromatic ring, comprising forming a solution of said compound in methylene chloride;
reacting said solution with concentrated nitric acid in the presence of concentrated sulfuric acid whilst maintaining the reaction mixture at a reaction temperature up to the reflux temperature of methylene chloride;
said nitric acid being employed at close to the stoichiometric quantity;
and thereafter extracting from said reaction mixture a solution of said nitro compound, said aromatic compound comprising an aromatic hydrocarbon containing from 6 to 18 carbon atoms consisting of monocyclic hydrocarbons and polycyclic hydrocarbons wherein the rings may be fused or linked together with linking groups selected from -O-, -C(O)-, -CH2-, -CH2CH2- and -S(O2)-said hydrocarbon optionally being substituted by substituents inert to the conditions of nitration, with the proviso that there be at least one nuclearly bonded hydrogen in each ring available for nitration.

2. The process of claim l wherein said sulfuric acid has initially a concentration of at least about 90 per cent.

3. The process of claim 2 wherein said nitric acid has initially a concentration of at least about 98 per cent.

4. The process of claim 1, 2 or 3 wherein said reaction tempera-ture is maintained in the range of about -20°C to about 45°C.

5. The process of claim l, 2 or 3 wherein said aromatic compound is selected from diphenyl, diphenyl methane, dibenzyl, benzophenone, diphenyl sulfone, and diphenyl ether, wherein about 2 moles of said nitric acid per mole of said aromatic compound are employed so as to essentially mononitrate each aromatic ring.

6. The process of claim 1, 2 or 3 wherein said aromatic compound is selected from diphenyl, diphenyl methane, dibenzyl, benzophenone, diphenyl sulfone and diphenyl ether, and wherein said reaction temperature is in the range of about 0°C to about 45°C.

7. The process of claim 1, 2 or 3 wherein additional methylene chloride is added subsequent to the nitration reaction being effected to extract said nitro compound from the reaction mixture.

8. The process of claim 1, 2 or 3 wherein said methylene chloride is initially present in the proportion of about 1 to 50 parts by volume per part of aromatic compound.

9. The process of claim 1, 2 or 3 wherein said aromatic compound is N-methyl phthalimide.

10. The process of claim 1, 2 or 3 wherein said aromatic compound is phthalic acid.

11. The process of claim 1, 2 or 3 when carried out at super atmospheric pressure.

12. The process for making 4-nitro-N-alkylphthali-mide which comprises forming a solution of N-alkylphthalimide with methylene chloride and concentrated sulfuric acid having a concentration of at least 90%, treating the said phthalimide solution with concentrated nitric acid of at least 90%
concentration at a temperature of from about 40° to about 45°C, the said nitric acid being close to the stoichiometric amount required to attach one nitro group to the N-alkylphthalimide, and thereafter extracting the 4-nitro N-alkylphthalimide from the reaction mixture with methylene chloride.

13. The process of claim 12 wherein said N-alkyl-phthalimide is selected from N-methylphthalimide and N-isopropylphthalimide.

14. The process of claim 12 wherein said N-alkyl-phthalimide is N-methylphthalimide.