US3076037A - Process for the nitration of halobenzenes - Google Patents

Description

3,7d,3? Patented Jan, 29, 1%53 3,ti7d,ti37 PRGtIEdS FER THE NXTRA'HUN F HALSBENZENES Robert I. Leib, Kir'irwood, Md, assignor to Monsanto Chemical Company, dt. Louis, Mo., a corporation of Delaware No Drawing. Filed Feb. 5, 1969, Ser. No. 6,359 19 Claims. (Cl. 26%-646) This invention relates to an improved process for the preparation of nitrohalobenzenes by the nitration of the corresponding halobenzene, whereby a more favorable isomer distribution is obtained.

The present methods used in the preparation of nitrochlorobenzene, for example yield a mixture of the para and ortho isomers, in which the para/ortho ratio is generally around 1.7, i.e. it contains 63% para isomer and 37% ortho isomer. Because of the current and projected demand for the para isomer, a great oversupply of the ortho isomer will result if this need for the para isomer is fulfilled by using the current methods of making nitrochlorobenzene.

It has been found that the isomer distribution in the nitrohalobenzene product is favorably influenced when the nitration of a halobenzene compound is carried out in the presence of an amine salt. The presence of even small amounts of an amine salt markedly influences the isomer distribution in a nitrohalobenzene product and this effect is still obtained when a high concentration of amine salt is employed, i.e. Where 3 moles of amine salt per mole of halobenzene are used. Moreover, the amount of the desired isomer obtained when the nitration is carried out in the presence of an amine salt is greater than the amount obtained in the absence of an amine salt regardless of the nitrating agent or nit-rating temperature employed.

The nitrating agents which can be employed in the process of this invention include, for example, the conventional mixed acids, i.e. mixtures of nitric acid and a dehydrating acid such as oleum or sulfuric acid, which contain from about 20% to about 60% by Weight of nitric acid and from about 75% to about 35% by weight of sulfuric acid, the balance being made up by Water; a mixture of ethyl nitrate and sulfuric acid, nitrogen pentoxide and other strong nitrating agents which are conventionally employed in the nitration of a halobenzene. Mixed acids containing from about 30% to about 40% by Weight of nitric acid and from about 65% to about 55% by weight of sulfuric acid are preferred for the process of this invention.

The amine salts which are useful in the process of this invention are the amine salts of nitric acid or sulfuric acid or mixtures thereof. Any amine salt can be employed, however the amine salts in which the organic residue is not subject to nitration or oxidation under the nitrating conditions employed are preferred for the purposes of this invention.

Illustrative examples of amines which can be employed in the process of this invention in their nitrate or sulfate form are the primary aliphatic amines such as methylamine, ethylamine, propylamine, isopropylamine, n-hexylamine, dodecylamine, tetradecylamine, hexadecylamine, etc.; secondary aliphatic amines such as dimethylamine, diethylamine, diisopropylamine, di-Z-ethylhexylamine, N-methyl-dodecylamine, N-ethyl-pentadecylamine, etc.; tertiary aliphatic amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, trioctylamine, N-methyldiethylamine, N-ethyldipropylamine, N-pentyldidodecylamine, N-N-diisobutylhexylamine, etc.; the aliphatic polyamines such as 1,4-propylenediamine, 1,3-ethylenediarnine, 1,2-butylenediamine, etc.; the cycloaliphatic amines such as cyclopentylamine, cyclohexylamine, 2,4-dimethylcyclohexylamine, Z-methylcyclohexylamine, 4-ethylcyclohexylamine, cycloheptylamine, 4-methylcycloheptylamine, dicyclohexylamine, cyclohexane 1,3-diamine etc.; mixed aliphatic-cycloaliphatic amines such as N-ethylcyclohexylamine, N-butylcyclohexylamine, N-propylcycloheptylamine, N,N-diethylcyclohexylamine, etc.; the heterocyclic amines such as pyrrolidine, 2-methylpyrrolidine, Z-ethylpyrrolidine, 2,4-dimethyl-3-ethylpyrrolidine, 1,2,2- trimethylpyrrolidine, 3,4-dimethylpyrrolidine, pyrazole, Z-methylpyrazole, Z-ethylpyrazole, 2,5-dimethylpyrazole, 2,3,5-trimethylpyrazole, 3,5-dimethylpyrazole, imidazole, l-ethylirnidazole, 4-methylimidazole, 1,2,3-triazole, 4,5-dimethyl-1,2,3-triazole, 1,2,4-triazole, pyridine, 2-picoline, 3-picoline, 2-lutidine, parvoline, rubidine, 3-picoline, 2-pipecoline, 3-pipecoline, 4-pipecoline, 1,2-dimethylpiperidine, 1,4-dimethyipiperidine, 2,6-trimethylpiperidine, Z-methyl-S-ethylpiperidine, morpholine, Z-methylmorpholine, triamorpholine, 2-ethylmorpholine, pyrazine, quinoline, isoquinoline, 2,4-dimethylquinoline, 4-ethylquinoline, 2,5-pyridoquinoline, 1,3-oxazole, 1,2,4-0xadizine, 1,4,2-oxadiazine, indoloindole, 1-indeno-1,2b-pyridine, acridine, l-methylacridine, Z-methylacridine, 1,3-dimethylacridine, 2,5-dimethylacridine, phenanthridine, Z-methylphenanthridine, Z-ethylphenanthridine, 1,3-dimethylphenanthridine, 5,6-benzoquinoline, 6,7-benzoquinoline, 7,8- benzoquinoline, 6,7-benzoisoquinoline, naphtho-2,3h-quinoline, etc.

While the amines containing an aromatic residue are generally subject to nitration, they may be used in the process of this invention if an excess of the nitrating agent is employed. Illustrative examples of amines containing an aromatic residue are, for example, aniline, naphthylaniline, phenylenediamine, 3,5-dimethylaniline, 2,3,6-triethylaniline, phenanthrylamines, mixed coal tar bases, N-methylaniline, diphenylamine, N-octylphenylamine, N-butyl-p-methoxyaniline, N-cyclohexylaniline, N-Z-ethylhexylaniline, N-octylbiphenylamine, diuaphthylamine, N-rnethyldiphenylamine, N-butyldiphenylamine, benzylaniine, phenylethylamine, 2,4-dimethylbenzylamine, 3-butylbenzylamine, 4-t-butylphenylethylamine, N,N-dimethylbenzylamine, N,N-diethylbenzylamine, N,N-dipropylbenzylamine, N-ethylbenzylamine, N-hexylbenzylamine, and their homologues and analogues.

The aforementioned amines may be further substituted by one or more substituents. Typical but not limitative of such substituents are nitro, carboxy, the halogens, such as chlorine, bromine, iodine and fluorine, and other nonreactive substituents.

The lower aliphatic amines which have a tertiary allryl group attached to the nitrogen atom constitute a preferred class of aliphatic amines to be employed as their acid salts in the process of this invention. These amines have the following structure:

wherein R is an alkyl radical containing from 1 to 18 carbon atoms, e.g. methyl, ethyl, propyl and butyl.

The acid salts of heterocyclic amines containing a tertiary nitrogen atom also constitute a preferred class of acid salts to be employed in the process of this invention.

The acid salt can be prepared separately or it can be prepared in situ. For example, the free amine can be added to the nitration reaction medium and the amine converted to the acid salt form by the addition of a suificient excess of nitric or sulfuric acid to tie up the free amine. Moreover, a preferred method of carrying out the process of this invention involves adding concentrated sulfuric acid to a mixture of the halobenzene and the free amine. After all of the amine has beencon- 3 verted to the acid sulfate form, the mixed acid nitration is then started.

Effective concentrations of the amine salt in the process of this invention vary in Wide ranges depending upon the tains the amine salt and the spent acid may be dehydrated and then recycled.

The manner of carrying out the process of this invention and the excellent results achieved therefrom will be result desired, in that extremely low amounts, e.g. 0.05 5 further apparent from the following specific examples in mole of amine salt per mole of halobenzene to be nitrated which all parts and percentages are by weight unless otherwill produce the para directive effect. Moreover, as the wise specified.

number of amine salt groups per molecule is increased, EXAMPLE 1 the amount required to produce a given result is reduced proportionately. A higher para isomer concentration in T 5 Well surfed mlxture of Parts (140 mole) of the nitrohalobenzene product is achieved when the con- P P f of Chlorobenzene there centration of amine salt is within the range of from about 15 added dYOPWISe While eeol'lngi Parts mole 0.5 to about 2 moles per mole of halobenzene to be H2$ U of 953%? u f nc acld. A white flocculant prenitrated. It is even more preferred to employ about 1.0 elpltate of pg fulfate results- Thls Slurry 18 then mole of amine salt per mole of halobenzene to be nitrated. l5 heatefl to I end 190 P e mole a) More than 3 moles of amine salt per mole of halobenzene of mlhed field, I I g 33% by weight HNO 55% to be nitrated can be employed, however no significant inby Welght a 4 and 12% Water, l f Slowly e crease in para isomer content or yield results over that e 110111: P P After the field the l'eae'llen m is obtained with 1 to 2 1 mixture is maintained at a temperature of 50 to 55 C.

A preferred embodiment of this invention is the process about two e The resulting mlxtul'e 15 then P for the preparation of paranitrochlorobenzene which commiffed to Separate Into 1W0 P e and h bottom pe prises nitrating chlorobenzene with a mixed acid comprisaeld e 15 -(R The 011 layer 15 Washeq Wlth ing 30% to 35% by weight of nitric acid, 55% to 60% by two a gl contamms P of Water; two ahquots weight of sulfuric acid and 15% to 5% by Weight of containing 200 parts by weight of a 5% sodium carbonate water, in the presence of a sulfate salt of a lower aliphatic Sohlhon and he y Wlth two addlhehal ahquots amine having a tertiary alkyl group attached t th it The washed oil is then heated at reduced pressure to regen ato thereof. A furth preferred b di i move any unreacted chlorobenzene and the resldual water. volves the use of a sulfate salt of a heterocyclic amine hav- There is obtelhed 494138118 0f nitroehlorobehlehe- The ing a tertiary nitrogen atom. product contains p s Those skilled in the art will recognize that this inven- The following table represents additional examples of tion is not limited to specific reaction temperatures since the presentmvention, Wherem the pp Procedure this process can be carried out at a tempearture of from ingredients of Example 1 utilized eXleePt es 3 (3 to 100 C or more, A reaction temperature specified in the table. Generally, the temperature of the of 30 C. can be maintained, for example, b 1 reaction, the reaction time and the molar ratio of nitric ing a cooling bath comprising a slurry of solid carbon acid to chlorobenzene are the same as in Exampl dioxide in acetone and using chloroform as a reaction eeptiens t0 this pp in the column heedec1 Remarks? diluent. As will be appreciated, the rate of reaction at The q y of amine salt and the p ifi amine l are temperatures of from --30 C. to 0 C. will he somevaried as indicated therein and the percentage of yield what slow. The minimum temperature for the process of is based on the monochlorobenzene charged.

Table 1 Moles amine Percent Example Amine salt salt pet-mole Percent para Remarks oi chloroyield isomer benzene 2 pyridine sulfate 0.25 90 67. 4 Reaction time 2 hours. 3 2-plcolme sulfate 0.25 90 67.8 o.

quinoline sulfate 0.175 95 67.4 Reaction time 2 hours and 0.25 mole excess of HhgOi as mixed acid 5 nicotinic acid sulfate o. 5 95 70, 6 18 use 6... t-butylamine sulfate 0.2 95 68 7- do. 1.0 as 71 8. .d0. 3.0 70 9. .do 4.0 72 10-. triethylamlne sulfate 0.73 96 70 11 trimethylamine sulfate.-. 1.0 65

this invention is therefore that temperature just above that EXAMPLE 12 at which no reaction between the nitrating agent and the halobenzene will take place. The maximum temperature is only of economic importance, for it is dependent on economic factors rather than technical factors. For ex ample, some of the aliphatic amine salts will begin to oxidize at temperatures above 100 C. and in addition, it is necessary to supply considerable amounts of heat to achieve and maintain reaction temperatures above 90 C. Temperatures within the range of from about 30 C. to about 90 C. are desirably used, while temperatures within the range of from C. to C. are especially preferred.

After the nitration reaction is complete, the product can berecovered from the reaction by any method well known to those skilled in the art. For example, the reaction mixture is permitted to settle into two phases, i.e. an organic phase and an aqueous phase. The organic phase is then separated and the aqueous phase which con The procedure of Example 1 is repeated except that an equivalent amount of a mixed acid containing 36% nitric acid, 59% sulfuric acid and 5% water is used in place of the 33/55 mixed acid. The para isomer content of the product is about 73%.

EXAMPLE 14 The procedure of Example 1 is repeated except that an equivalent amount of pyridine nitrate is substituted for the pyridine sulfate of said example. Similar results are obtained in that the product contains about of the para isomer of nitrochlorobenzene.

EXAMPLE 15 The procedure of Example 1 is repeated except that an equivalent amount of a mixed acid containing 27% nitric acid, 59% sulfuric acid and 14% water is substituted for the 33/55 mixed acid. The para isomer content of the product is about 70%.

EXAMiLE 16 The procedure of Example 1 is repeated using in place of the pyridine sulfate, a stoichiometrically equivalent amount of a sulfate salt of each of the following amines:

In each instance the para isomer content of the prodnot is about 70%.

Dimethylamine Ethylenediamine N-ethyl-pentadecylamine Butylamine 1, l-dimethylpropylamine 1,1-dimethylbutylamine 1,1-dimethylpentylamine Cyclohexylamine N,N-diethylcyclohexylamine 2,6-dimethylcyclohexylamine Dicyclohexylamine Pyrrolidine Imidazole 1,2,3-triazole 2-pipeco1ine 2,6-dimethylpiperidine 5-ethyl-2-methylpiperidine 4-methylpiperazine 3,5 -dimethylmorpholine Morpholine Azi-ridine Thiarnorpholine isoquinoline Acridine Phenanthridine t-Dodecylamine t-Tetradecylamine t-Octylamine t-Octadecylamine t-Hexadecylamine EXAMPLE 17 The procedure of Example 10 is repeated using in place of the triethylamine sulfate about 1 mole of the sulfate salt per mole of chlorobenzene of each of the following trialkylamines:

(1) Tributylamine (2) Tripropylamine (3) Triisopropylamine (4) N-ethyl dipropylamine (5) N,N-diethylbutylamine In each case the para isomer content of the product is in excess of 70%. From the results obtained it is clear that trialkylamines wherein the alkyl groups each contain from 2 to 4 carbon atoms also constitute a preferred class of amine salts to be employed in the process of this invention.

While this invention has been described with respect to certain embodiments, it is not so limited and it is to be understood that variations and modifications thereof which are obvious to those skilled in the art may be made without departing from the spirit or scope of this invention.

What is claimed is:

1. In a process for the nitration of halobenzene, the improvement which comprises carrying out the nitration in the presence of an acid salt of an amine wherein the acid portion is derived from an acid of the group con sisting of nitric acid and sulfuric acid, said acid salt being present in an amount which is snflicient to produce a para directive effect.

2. A process of claim 1 wherein the nitrating agent is a mixture comprising nitric acid and sulfuric acid.

a 3. In a process for the mixed acid nitration of chlorobenzene, the improvement which comprises carrying out the nitration in the presence of an amine sulfate in an amount which is suiiicient to produce a para directive effect.

4. A process of claim 3 wherein the amine sulfate is derived from a heterocyclic amine.

5. In a process for the mixed acid nitration of chlorobenzene, the improvement which comprises carrying out the nitration in the presence of a sulfate salt of a tertiary alkyl amine of the formula wherein R is an alkyl radical having from 1 to 18 carbon atoms, said sulfate salt being present in an amount which is sufficient to produce a para directive effect.

6. In a process for the mixed acid nitration of chiorobenzene, the improvement which comprises carrying out the nitration in the presence of a sulfate salt of a trialkyl amine wherein each alkyl group has from 2 to 4 carbon atoms, said sulfate salt being present in an amount which is sufiicient to produce a para directive effect.

7. A process for the production of nitrochlorobenzene which comprises reacting monochlorobenzene with a mixed acid comprising from about 30% to about 40% by weight of nitric acid and from about 65% to about 55% by Weight of sulfuric acid in the presence of from about 0.5 to 2.0 moles of an aliphatic amine sulfate per mole of monochlorobenzene.

8. A process for the production of nitrochlorobenzene which comprises adding a stoichiometric quantity of a mixed acid, comprising from about 30% to about 40% by weight of nitric acid and from about 65% to about 55% by weight of sulfuric acid, to a reaction zone containing monoshlorobenzene and a sulfate salt of an aliphatic amine, the quantity of amine sulfate being Within the range of from about 0.5 to about 2 moles per mole of monochlorobenzene.

9. A process of claim 8 wherein the aliphatic amine sulfate is derived from a tertiary alkylamine of the formula wherein R is an alkyl radical containing from 1 to 18 carbon atoms.

10. A process of claim 9 wherein the nitrating temperature is within the range of from 50 C. to 60 C.

11. A process of claim 8 wherein the amine sulfate is tertiary butylamine sulfate.

12. A process of claim 8 wherein the aliphatic amine sulfate is derived from a trialkylamine wherein each alkyl group contains from 2 to 4 carbon atoms.

13. A process of claim 11 wherein the nitrating temperature is within the range of from 50 C. to 60 C.

14. A process of claim 12 wherein the amine sulfate is triethylamine sulfate.

15. A process for the production of nitrochlorobenzene which comprises adding a stoichiometric quantity of a mixed acid comprising from about 30% to about 40% by weight of nitric acid and from about 65% to about 55 by weight of sulfuric acid to a reaction zone con taining monochlorobenzene and a sulfate salt of a heterocyclic amine, the total quantity of sulfate salt being within the range of from about 0.5 to about 2 moles per mole of mo-nochlorobenzene and maintaining the temperature within the range of from about 30 C. to about C. throughout the nitration reaction.

16. A process of claim 14 wherein the nitrating tem- 19. A process of claim 15 wherein the sulfate salt is perature is within the range of from 50 C. to 60 C. 2-pico1ine sulfate.

17. A process of claim 15 wherein the sulfate salt is pyridine sulfate.

18. A process of claim 15 wherein the sulfate salt is 5 quinoline sulfate.

References Cited in the file of this patent UNITED STATES PATENTS Mares Feb. 27, 1945 Cherlow et a1. Jan. 18, 1955

Claims (1)

1. IN A PROCESS FOR THE NITRATION OF HALOBENZENE, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT THE NITRATION IN THE PRESENCE OF AN ACID SALT OF AN AMINE WHEREIN THE ACID PORTION IS DERIVED FROM AN ACID OF THE GROUP CONSISTING OF NITRIC ACID AND SULFURIC ACID, SAID ACID SALT BEING PRESENT IN AN AMOUNT WHICH IS SUFFICIENT TO PRODUCE A PARA DIRECTIVE EFFECT.