US2883433A

US2883433A - Process for the preparation of nitro derivatives

Info

Publication number: US2883433A
Application number: US653073A
Authority: US
Inventors: Spaeth Charles Philip
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1957-04-16
Filing date: 1957-04-16
Publication date: 1959-04-21
Anticipated expiration: 1976-04-21

Description

United States Patent PROCESS FOR THE PREPARATION OF NITRO DERIVATIVES Charles Philip Spaeth, Woodbury, NJ., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application April 16, 1957 Serial No. 653,073

14 Claims. (Cl. 260--644) The present invention relates to a process for the preparation of nitro derivatives of alkanes, cycloalkanes, and aryl-substituted alkanes. More particularly, the present invention relates to a process for the liquid-phase nitration of alkanes, cycloalkanes, and aryl-substituted alkanes by an alkyl or cycloalkyl nitrite.

Nitro derivatives of such hydrocarbons are useful as solvents and as chemical intermediates, particularly as intermediates for valuable amines. Heretofore, the nitro derivatives were prepared generally by processes involving the use of nitric acid as the nitrating agent. This nitrating agent, however, has not been entirely satisfactory from an economical viewpoint. Not only does the corrosive action of the agent necessitate the use of expensive chrome-steel or glass-lined storage and handling equipment, but also in most nitrations by nitric acid, large amounts of undesirable oxidation products are formed, thus decreasing the yield of desired nitro compounds. In addition to the economic disadvantages incurred by the use of nitric acid, the nitric acid-hydrocarbon system is a two-phase system, and vigorous agitation must be used to bring about the required intimate contact of the reactants. Moreover, in the nitric acid processes of the prior art the substitution of the nitro group cannot be limited solely to the alkyl side-chain of an aryl-substituted alkane; in these processes, the nitro substituent also is introduced on the aromatic ring, giving undesirable by-products and lower yields of the desired products.

Accordingly, an object of the present invention is to provide a simple and economical process for the nitration of alkanes, cycloalkanes, and aryl-substituted alkanes. Another object of the present invention is to provide a process whereby the hydrocarbons are nitrated in a homogeneous system and in intimate contact with the nitrating reagent. A further object of the present invention is to provide a nitration process whereby nitro substituents can be introduced readily into the alkyl sidechain of aryl-substituted alkanes without attendant ring nitration.

I have found that the foregoing objects may be achieved when I react an alkyl or cycloalkyl nitrite with an alkane, cycloalkane, or aryl-substituted alkane at a temperature within the range of 140 and 300 C. and at a pressure of at least 125 p.s.i. ga.

ICC

In accordance with the process of the present invention, an alkyl or cycloalkyl nitrite is admixed with a molar excess of an alkane, cycloalkane, or aryl-substituted alkane, and the mixture is maintained at a temperature within the range of and 300 C. and a pressure of at least 125 p.s.i. ga., said hydrocarbon being maintained substantially in the liquid phase. 7

The following examples serve to illustrate specific embodiments of the method of carrying out the process of the present invention. However, they will be understood to be illustrative only and not as limiting the invention in any manner.

EXAMPLE 1 Cyclohexane was introduced into a reactor which had previously been flushed with nitrogen, the reactor was pressurized to 400 p.s.i. ga. with nitrogen, and the cyclohexane was heated to about C. Then, a mixture of n-butyl nitrite and cyclohexane was pumped into the reactor over a period of about 8 minutes, during which time the temperature and pressure were maintained sub stantially at the initial levels. After the addition of the mixture was complete, additional hydrocarbon was fed through the pump and feed lines over a period of about 2 minutes to clear the pump and lines of substantially all the nitrite-cyclohexane mixture. The mole ratio of total cyclohexane to n-butyl nitrite used in this experiment was 21. The charge then was cooled to about 35 C. and the reactor was vented. The product mixture was removed, washed with dilute sodium bicarbonate solution, dried, and analyzed. The analysis showed that nitrocyclohexane in 32% yield and oxidation products in 5.6% ,yield were obtained.

When this procedure was repeated with the exception that the reaction temperature was maintained at 125 C., no nitration occurred.

EXAMPLE 2 The procedure of Example 1 was repeated with the exception that the reaction temperature and pressure were maintained at C. and 125 p.s.i. ga., respectively. The analysis of the product mixture showed that nitrocyclohexane in 48% yield and oxidation products in 11% yield were obtained.

EXAMPLE 3 The procedure of Example 1 again was repeated with the exception that the reaction temperature and pressure were maintained at about 205 C. and 550 p.s.i. ga., respectively. The product mixture was shown by analysis tocontain nitrocyclohexane (41% yield) and oxidation products (10% yield).

EXAMPLE 4 In a series of experiments made in accordance with the afore-described procedure, various hydrocarbons were nitrated by means of n-butyl nitrite. The reaction conditions and results are summarized in the following table.

Table I Mole Ratio Reaction Yield of Experi- Hydrocarbon of Hydro Temp. 'Iime N ltro Derivative N itro ment; carbon] 0.) (mln.) Derlv.

N itrlte (percent) n-Nonane 18 ca. 213 Mixt. of primary and sec- 38 ondary mononitrononanes. n-Decane 9 ca. 205 12 Mixt. of primary and sec- 35 ondary mononitrodecanes. Ethylbenzene 25 ca. 215 7 l-Nltro-l-phenylethane.-. 37 Toluene ca. 222 10 Nitrophenylmethane 27 Ohlorocyc1ohexane 11 ca. 205 5 l-Ohloro-2-nitrocycl0hexane 27 p-Xylene 20 ca. 205 10 a-Nitro-p-xylene 29 Methylcyclohexane- 21 ca. 214 10 l-Methyl-l-nitroeyclohexane. 32 Secondary mononitro de- 24 rivative. 2,3Dimethylbutane" 14 ca. 212 8 2,3-Dimethy1-2-nitrobutane-. 25 Prifliary mononltro derlv- 13 a ve. Oumene 17 ca. 216 9 2-Nitro-2-phenylpropane...- 38 Cyclohexane 26 ca. 210 25 N itrocyclohexano 1 In experiments A-E and K, the reaction pressure was maintained at 410 p.s.1. ga.; in the other experiments the pressure was maintained at 400 p.s.i. ga.

EXAMPLE 5 In another series of experiments carried out according to the procedure of Example 1, cyclohexane was nitrated by means of various nitrites under the following reaction conditions: temperature, ZOO-210 C.; pressure, 400 psi. ga.; and reaction time, 8-9 minutes. The results of these experiments are summarized in Table II.

As may be seen by reference to the foregoing examples, the nitration process of the present invention proceeds smoothly and rapidly to give nitro compounds to the major product without ring nitration and without the formation of appreciable quantities of undesired oxidation products. As has been illustrated, the nitration does not proceed at temperatures below about 140 C. However, good results are obtained at temperatures of from 140 C. up to about 300 C.; at higher temperatures, tar begins to be formed and yields are correspondingly decreased.

Pressure is applied to the reaction system in order to maintain the hydrocarbon substantially in the liquid phase. The exact pressure applied, therefore, is dependent upon the temperature maintained in the reaction zone. Generally, the reactor will be pressurized to at least 125 p.s.i. ga., a minimum pressure of 125 p.s.i, ga. usually being required to maintain the liquid phase at the temperatures used in the process. The maximum pressure employed is governed only by the mechanical limitations of the available equipment. However, because the use of extremely high pressures, i.e. above 1000 atmospheres, does not result in any advantages from the standpoint of yield, this figure represents the practical upper limit of pressure. The reactor can be pressurized with any inert gas, inasmuch as the specific inert gas used is not critical. In addition to the nitrogen which was exemplified, carbon dioxide and helium also can be used.

In carrying out the nitration, a molar excess of the hydrocarbon is used, the unreacted hydrocarbon simply being recovered and reused without deleterious effects upon the economics of the process. More ratios of hydrocarbon-alkyl nitrite within the range of 5 to 44 have been exemplified and essentially equivalent results were obtained. Therefore, the extent of the excess of the bydrocarbon is not critical to the process of the present invention, nor is the reaction time. The reaction time was varied from 5 to 25 minutes without seriously effecting the yield of nitro hydrocarbon. Since the re action proceeds so rapidly, good results are obtained in a matter of minutes and extensive reaction periods are not required.

Although the process has been exemplified by the use of cyclohexyl, n-butyl, isobutyl, and tert-butyl nitrites, any alkyl or cycloalkyl nitrite is suitable for use as the nitrating agent, the nitrite group of the molecule being the portion of the molecule which eifects the nitration. Other suitable nitrating agents include ethyl nitrite, n-propyl and isopropyl nitrite, mixed amyl nitrites, hexyl nitrite, and .1,4-butyl dinitrite among others.

The process of the present invention is general for alkanes, cycloalkanes, and aryl-substituted alkanes which can be maintained in the liquid phase under the reaction conditions. In addition to the hydrocarbons used in the experiments described in the forgoing examples, various other hydrocarbons can be nitrated by the process of the present invention. For example, additional nitro paraflins can be prepared readily from the corresponding parafiinic hydrocarbons, e.g. n-hexane, neohexane, and isooctane. Other cycloalkanes which can be nitrated by the present invention include, among others, cycloheptane and cyclopentane. The term cyeloalkane as used throughout the specification and claims also includes, of course, alkylsubstituted cycloalkanes such as the exemplified methylcyclohexane and others, e.g., alkylated cycloheptanes and cyclopentanes. Additional aryl-substituted alkanes, suitable for use in the process of the present invention are, for example, cymene, durene, and diisopropylbenzene. Furthermore, nonhydrocarbon substituents, such as nitro or halo groups, present on the hydrocarbons to be nitrated do not interfere in the carrying out of the process of the present invention, and compounds such as nitrocyclohexane, chlorodecane, bromopentane, etc. constitute suitable starting materials. Of course, when a nitro-substituted hydrocarbon is used as the starting material, a poly-nitro derivative is obtained which contains an additional nitro group.

Although the preceding examples illustrate the process as a batchwise process, equally feasible is the carrying out of the process in a continuous manner. For example, the alkyl or cycloalkyl nitrite and the hydrocarbon may be introduced continuously into a reaction zone maintained at the desired operating conditions, while the product mixture is continuously withdrawn.

The invention has been described in detail in the foregoing. It will be apparent to those skilled in the art that many variations are possible without departure from the scope of the invention. For example, the hydrocarbon to be nitrated may be admixed with a diluent, e.g. benzene or acetonitrile, which is inert to the alkyl or cycloalkyl nitrite under the reaction conditions. I intend therefore, to be limited only by the following claims.

I claim:

1. A process for the preparation of nitro derivatives of alkane, cycloalkane, and simple mononuclear aryl-substituted alkane hydrocarbons which comprises admixing a nitrite selected from the group consisting of the lower alkyl nitrites and cycloalkyl nitrites with a molar excess of said hydrocarbons in a reaction zone maintained at a temperature within the range of 140 and 300 C. and at a pressure of at least 125 p.s.i. ga., said hydrocarbons being maintained substantially in the liquid phase.

2. Process according to claim 1, wherein the nitrite is cyclohexyl nitrite.

3. Process according to claim 1, wherein the nitrite is is a butyl nitrite.

4. Process according to claim 1, wherein the reaction zone is pressurizedwith an inert gas selected from the group consisting of nitrogen, helium, and carbon dioxide.

5. A process for the preparation of nitrocyclohexane which comprises admixing a nitrite selected from the group consisting of the lower alkyl nitrites and cycloalkyl nitrites with a molar excess of cyclohexane in a reaction zone maintained at a temperature within the range of 140 and 300 C. and at a pressure of at least 125 p.s.i. ga., said cyclohexane being maintained substantially in the liquid phase.

6. Process for the preparation of nitro derivatives of n-decane which comprises admixing a nitrite selected from the group consisting of the lower alkyl nitrites and cycloalkyl nitrites with a molar excess of n-decane in a reaction zone maintained at a temperature within the range of 140 and 300 C. and at a pressure of at least 125 p.s.i. ga., said n-decane being maintained substantially in the liquid phase.

7. Process for the preparation of l-nitro-l-phenylethane which comprises admixing a nitrite selected from the group consisting of the lower alkyl nitrites and cycloalkyl nitrites with a molar excess of ethylbenzene in a reaction zone maintained at a temperature within the range of 140 and 300 C. and at a pressure of at least 125 p.s.i. ga., said ethylbenzene being maintained substantially in the liquid phase.

8. Process for the preparation of a-nitro-p-xylene which comprises admixing a nitrite selected from the group consisting of the lower alkyl nitrites and cycloalkyl nitrites with a molar excess of p-xylene in a reaction zone maintained at a temperature within the range of 140 and 300 C. and at a pressure of at least 125 p.s.i. ga., said p-xylene being maintained substantially in the liquid phase.

9. Process for the preparation of nitrophenylmethane which comprises admixing a nitrite selected from the group consisting of the lower alkyl nitrites and cyc1o alkyl nitrites with a molar excess of toluene in a reaction zone maintained at a temperature within the range of 140 and 300 C. and at a pressure of at least p.s.i. ga., said toluene being maintained substantially in the liquid phase.

10. Process for the preparation of l-chloro-Z-nitrocyclohexane which comprises admixing a nitrite selected from the group consisting of the lower alkyl nitrites and cycloalkyl nitrites with a molar excess of chlorocyclohexane in a reaction zone maintained at a temperature within the range of and 300 C. and at a pressure of at least 125 p.s.i. ga., said chlorocyclohexane being maintained substantially in the liquid phase.

11. Process for the preparation of nitro derivatives of methylcyclohexane which comprises admixing a nitrite selected from the group consisting of the lower alkyl nitrites and cycloalkyl nitrites with a molar excess of methylcyclohexane in a reaction zone maintained at a temperature within the range of 140 and 300 C. and at a pressure of at least 125 p.s.i. ga., said methylcyclohexane being maintained substantially in the liquid phase.

12. Process for the preparation of nitro derivatives of 2,3-dimethylbutane which comprises admixing a nitrite selected from the group consisting of the lower alkyl nitrites and cycloalkyl nitrites with a molar excess of 2,3-dimethylbutane in a reaction zone maintained at a temperature within the range of 140 and 300 C. and at a pressure of at least 125 p.s.i. ga., said 2,3-dimethylbutane being maintained substantially in the liquid phase.

13. Process for the preparation of 2-nitro-2-phenylpropane which comprises admixing a nitrite selected from the group consisting of the lower alkyl nitrites and cycloalkyl nitrites with a molar excess of cumene in a reaction zone maintained at a temperature within the range of 140 and 300 C. and at a pressure of at least 125 p.s.i. ga., said cumene being maintained substantially in the liquid phase.

14. A process for the preparation of nitro derivatives of n-nonane which comprises admixing a nitrate selected from the group consisting of the lower alkyl nitrites and cycloalkyl nitrites with a molar excess of n-nonane in a reaction zone maintained at a temperature within the range of 140 and 300 C. and at a pressure of at least 125 p.s.i. ga., said n-nonane being maintained substantially in the liquid phase.

No references cited.

'3 I 8 'UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 4 Patent N00 2,883,433 April 21, 1959 Charles Philip Spaeth It is hereby certified thet error appearsjjin the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below, i 5

Column 3, line 42', for "compounds to" read compounds es line '72,

for "More" read Mol'e v--\-,

Signed and sealed this 13th day of October 1959.

,- (SEAL) KARL H. AXLINE Attest:

., ROBERT c. WATSO Ni Attesting'Officer Comnissioner of Patent 'UNITED STATES PATENT OFFICE v CERTIFICATE OF CORRECTION Pasnt "N5. 2,883,433 April 21, 1959 Charla; Philip Spaeth It is'hreby certified @1151; error appearin the printed specification of the above numbered. patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 42', for ompounds to" read compounds is line 12 fdf "More" rezad Mole" si ed and .sg zialeq this 13th d of October 1959 V (SEADI At fieet: v v r v H X I r ROBERT c. WATSONi Attesting; Officer (blm'lissioner of Patent UNITE-D STATES PATENT OFFICE CERTIFICATE OF CORRECTION Paini "Na. 2,883,433 April .21, 1959 Charles Philip spaeih It jig hereby cert:uf'ied that error 'apparsjjin the printed specification of the above numbred patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 42,- for' oompounds to" read compounds as fcir "More" read Mole" PM. I

si ned and; .sgaieq this 13th day of October 1959.

(SEAL) Atffiest:

' K RL X I Attesting; Officer ROBERT c. wATsori Cunniasioner of Patents line 72

Claims

1. A PROCESS FOR THE PREPARATION OF NITRO DERIVATIVES OF ALKANE, CYCLOALKANE, AND SIMPLE MONONUCLEAR ARYL-SUBSTITUTED ALKANE HYDROCARBONS WHICH COMPRISES ADMIXING A NITRITE SELECTED FROM THE GROUP CONSISTING OF THE LOWER ALKYL NITRITES AND CYCLOALKYL NITRITES WITH A MOLAR EXCESS OF SAID HYDROCARBONS IN A REACTION ZONE MAINTAINED AT A TEMPERATURE WITHIN THE RANGE OF 140 AND 300* C. AND AT A PRESSURE OF A LEAST 125 P.S.I. GA., SAID HYDROCARBONS BEING MAINTAINED SUBSTANTIALLY IN THE LIQUID PHASE.