US2365981A - Production of chlorinated nitro hydrocarbons - Google Patents

Description

Patented Dec. 26, 1944 PRODUCTION OF CHLORINATED NITRO HYDROCARBONS John B. Tindall, Terrc Haute, Ind., assignor to Commercial Solvents Corporation, Terre Haute, Ind., a corporation of Maryland No Drawing. Application December 20, 1941, Serial No. 423,765

8 Claims.

The present invention relates to a process for the preparation of chlorinated nitro hydrocar-' ('11 R-C-NOz in which the substituents R and R may represent either chlorine or an alkyl group.

A sub-class of nitroalkanes falling within the group represented by the above generic formula is the group of nitroalkanes of the formula:

in which R is an alkyl group. Chloronitroalkanes included by the above formula are 1,1-dichloro-l-nitroethane, 1,1 dichloro l-nitropropane, 1,1-dichloro-l-nitrobutane, 1,1-dichlorol-nitroisobutane, 1,1 dichloro 1 nitropentane and the like.

While my invention is especially adapted to the preparation of the 1,l-dichloro-1-nitro-' alkanes, it is to be understood that it is not restricted thereto, but also includes such chlorinated nitro hydrocarbons as 2-chloro-2-nitropropane, and 2-chloro-2-nitrobutane, as well as other chlorinated nitro alkanes in which the nitro group is attached to either a primary or secondary carbon atom, and the term chlorinated nitro alkanes appearing in certain of the ac companying claims is to be so interpreted.

I am aware of the fact that chlorinated nitro alkanes, included in the class contemplated by the present invention, have previously been prepared. However', the conditions provided by the methods. formerly employed do not favor the procurement of commercially practical yields. For example, 1,1-dichloro-l-nitro-alkanes have previously been prepared by first producing the l-chloro-l-nitroalkane in accordance with any of several known methods, after which the resulting l-chloro-l-nitroalkane was introduced into an alkaline solution, such as for example, an aqueous solution of an alkali or alkaline earth metal hydroxide, preferably containing the metal hydrdxide in the amount theoretically required to produce the corresponding salt of the l-chlorol-nitroalkane. Chlorine was then introduced into the resulting solution in an amount theoretically required to convert the l-chloro-l-acinitroalkane salt into the corresponding 1,1-dichloro-l-nitroalkane. In. carrying out this reaction under such conditions,'an appreciable quantity of the l-chloro-l-aci-nitroalkane salt is present in an alkaline medium for a substantial period of time. Otherwise stated, a certain amount of the salt is present in the alkaline medium until a quantity of chlorine has been introduced which is sufficient to convert all of the salt into the corresponding 1,1-dichloro-l-nitroalkane. Such reaction conditions are definitely unfavorable with respect to the formation of the desired 1,1-dichloro-1-nitroalkanes since I have found that the metal salts of the l-chloro-l-acinitroalkanes are relatively unstable under these circumstances, and this finding has been confirmed by the comparatively low yields obtainable by the procedure mentioned immediately above. In addition to the fact that such a process gives commercially impractical yields, there is also the further disadvantage that it involves two separate and distinct steps which necessarily entail added operation costs.

, Other prior procedures for the chlorination of nitro alkanes have employed a metal h'ypochlorite as a chlorinating agent, in which the hypochlorite is produced from a suitable base, such as sodium hydroxide, in the presence of relatively large volumes of the nitro alkane. Under such circumstances, a competing reaction for the nitro alkane exists between the metal hydroxide and metal hypochlorite. Obviously, therefore, the yield of the desired chloro nitro alkane is materially decreased. In addition, the reaction of the metal hydroxide with the nitro alkane frequently leads to the formation of various complex products, the character of which is not entirely known. As a result of the presence of such products in the reaction mixture, purification of the chlorinated nitro alkane thus produced becomes considerably more difiicult.

. I have now discovered that chlorinated nitro alkanes may be conveniently prepared from the corresponding nitro alkane by means of a procedure free from the above mentioned disadvantages. A preferred embodiment of the present invention consists of first preparing an aqueous alkaline solution of a suitable metal hypochlorite by adding to a relatively strong alkaline solution sufficient chlorine to bring the pH thereof to a the chlorinated nitro alkane recovered in substantially pure form. In this connection the expression slight excess, as used in the present 1 description and claims, is to be construed as representing a quantity of hypochl orite lying intermediate the amount theoretically required to replace, with chlorine, the reactive hydrogen atom or atoms attached to the carbon holding the nitro group, and approximately a per centexcess of said theoretical amount.

A modification of the above general procedure] comprises producing an alkaline hypochlorite solution by adding sufficient chlorine to a'strong alkaline solution to bring the pH thereofto a value ofbetween about 13 and 14. -A deficiency of nitro alkane, with respect to the hypochlorite present, is then added together with suificient chlorine to reconvert the alkali, produced by the action of hypochlor-ite on the nitro alkane, to hypochlorite, which is in turn used for-chlorinatingadditional nitro alkane; In carrying out my invention in accordance with this procedure, an excess of hypochlorite overnitro alkane is always maintained, and although. the medium remains alkaline throughout the course of the reaction,

the presence of excess hypochlorite avoids the above mentioned undesirable side reactions which are obtained when the metal hypochlorite is formed in the presence of anexcess of-wnitro alkane, i

- Although in the procedure last-described, a pH of between 13 and 14 is specified, it may be said, in general, that any. means by which the pH of the medium can be 'maintained at -a value of-between 10. and 14. throughout the course'of-the re action. will resultin satisfactory yields of chlorinated nitro alkanes. The necessity of -maintaim alkane employed,.i. e., in general, the higher the carbon content of the nitro alkane, the higher the necessary reaction temperature. In the majority of instances, however, I have found that my process is most effectively carried out at tem-- peratures ranging from about 20 to not in subin which R and B may represent either hydrogen or alkyl. Examples of such nitroalkanes are nitromethane, nitroethane, 1 -nitropropane, 2-, nitropropane, l-nitrobutan'e, Z-nitrobutane, 1- nitropentane, 2-nitropentane and the like. Ad.- ditional nitro alkanes which may be chlorinated accordance with my invention are other nitro alkanesin which the nitro group is attached to either a primary orsecondary carbon atom.

The examples which follow, although typical of the high yields that are obtainable as a result, of the present invention, are in no Way to ing..the reaction medium withintheaforesaid pH hypochlorites; when in concentrations. appre ,ciablyexceeding. this. value, tend. to bereadily transformed intov the corresponding chlorates.

The. presence ofchlorates. in. the chlorinating medium, inaddition to retarding, the velocity of the action of hypochlorites on the. nitro alkane togive, the corresponding chlorinated nitro derivative, promotes the. occurrencefof objectionable oxidation reactions, causing a substantial decrease in the yield of chlorinated. nitro. alkanes. as well as also, rendering. the purification thereof much moredifficulu.

In carrying out the. present invention, itis es-. sential that sufiicient water. be .presentin themedium to facilitate the. reaction between the. alkali and chlorine, to, form the. hypochlorite, which in turn reacts; with, thenitro alkane. Likewise, it is desirable to maintain, water in, thetreaction medium I in amounts, sufficient. t dissolve. the. metal: chloride formed as a,,by:product;of.- the reaction.

The temperature at, which my. process. can be cgngri cl out, w ll, var -withlthe ature, of the nitro.

I hire wasstealm distilled and trichloronitromet-mbe considered as limiting the scope thereof.

Example I Into a solution consisting of 600 pa ts of water and 58 parts of sodium hydroxide was introduced approximately 51 parts of chlorine. The pH value of the resulting mixture was between; 12.5 and 13. Eleven and two-tenths parts of nitromethane was then slowly added with agitation at a temperature of between 20 and 25 C. After all of the nitromethane had been introduced, agitation was continued until chlorination appeared to be substantially complete as; evidenced by a decrease in-the temperature of thereaction mixture; The crude" chlorinated product, trichloronitromethane; was then steam distilled, this operation being continued untilthe distillate came over clear. The quantityof triohloronitromethane obtained in this manner amounted to a yield of 96 per cent.

Example II,

Eighty partsof sodium hydroxide in the form of a ,3.'7 normal aqueous solution wasplacedzinto a suitable reaction, flask after. which approxi=-.. matelyAB. parts of chlorine Waslintroduced. At thispoint nitromethane was added simultaneous:

1y, with the chlorine in a ratioof three moles ofz.

chlorine 130011601" nitromethane; This proce-, dure was'continued until. 1:22.71 parts, of-chlorine and 3.1 parts. Of'nitromethane had. been added; ThepH- of'themixture-durin the course ofgthe reaction remained between. wand; 14. After the,

chlorine: and. nitromethane. were: introducedv'irt thev manner described. above, the reaction. mix-,

ane obtained in 92..2-per cent yield,

- rle 1 Ffifty parts. of chlorine was introd d. into.

600 a Q W ter onta n ng e arts i; sod um. hydroxide. To this; resulting, alkaline, solution. dded, w th: tho ou h. tation; at" a. item:

'perature of 25 0., -20.8 parts of nitrcethane. The 1,1-dichloro-l-nitroethane thus produced was isolated in the manner set forth in Example I and obtained in 99.6 per cent yield.- The pH of the reaction mixture throughout the chlorination was between 11.5 and 14.

Example IV An alkaline solution of hypochlorite was prepared by introducing 162.6 parts of chlorine into 1590 parts of water containing 210 parts of sodium hydroxide, at a temperature of between 20 and 25 C. The resulting mixture was then cooled to a temperature of 18 C, after which 68.2 parts of nitroethane was slowly added with thorough agitation. During the course of the introduction of nitroethane, the temperature of the reaction mixture rose to approximately 40 C. At the conclusion of the addition of nitroethane, the crude product was steam distilled and the 1,1-dichloro-l-nitroethane obtained in a yield of -100 per cent. The pH of the mixture during the reaction was between 11.5 and 14.

Example V 1,1-dichloro-l-nitropropane was prepared by slowly introducing at a temperature of 30 (3., 24.5 parts of l-nitropropane into a solution containing600 parts of water, 64 parts of sodium hydroxide and 5.0 parts of chlorine. On steam distillation of the resulting reaction mixture, 1,1- dlchloro-l-m'tropropane, representing a 99.2 per cent yield, was recovered. The pH of the reaction mixture throughout the chlorination remained between 11.5 and 14.

Example VI 2-chloro-2-nitropropane was prepared by slowly adding 49.9 parts of 2.-nitropropane to an alkaline sodium hypochlorite solution, prepared by introducing 50 parts of chlorine into a solution Example VII To a sodium hypochlorit solution, prepared by the addition of 50 parts of chlorine to a solution consisting of 600 parts of water and 64 parts of sodium hydroxide, was added with vigorous agitation, at a temperature of 30 C., 53.5 parts of 2-nitrobutane. During the addition of 2-nitrobutane, considerable heat of reaction was evolved; however, the temperature of the reaction mixture was maintained between 45 and 50 C. by means of external cooling when necessary. After all of the 2-nitrobutane had been added, the mixture was agitated until the temperature fell to about 25 C. This mixture was then steam distilled and 2-ch1oro-2'-nitrobutane was recovered in a yield of 98.3 per cent. The pH of the mixture throughout the reaction was between 11.5 and 14.

While I have only mentioned, in the above examples, the use of sodium hydroxide as the base which may be employed in the preparation of the metal hypochlorite, I do not desire to be lim ited thereto since the water soluble alkali and alkaline earth metal hydroxides and carbonates,

in general, are equally suitable for this purpose.

Also, it is to be understood that the scope of the present invention is not limited to the specific procedures outlined by the above examples, but on the contrary, includes numerous modifications thereof.' For example, the nitro hydrocarbon, chlorine, and base may all three be added concurrently to the necessary amount of water, the only requirements being, in case such a procedure is used, that sufiicient alkali be present to maintain the pH of the reaction mixture between the value of 10 and 14 and that the quantity of chlorine added, and present in solution as hypochlorite, is always in slight excess over the nitro hydrocarbon employed. Other such modifications which involve the principles of the present invention will be evident to those skilled in the art. Therefore, it is to be understood that my invention covers all methods which are concerned with the production of chlorinated nitro hydrocarbons of the type specified by chlorinating the corresponding nitro hydrocarbon with a metal hypochlorite at a pH of between 10 and 14 wherein the chlorine, present in the mixture as hypochlorite, always remains in excess over the quantity of nitro hydrocarbon added.

Having described my invention, what I claim 1. A process for the liquid phase production of chlorinated nitro alkanes which comprises adding to a solution of a metal hydroxide selected from the group consisting of alkali and alkalineearth metal hydroxides, sufiicient chlorine to bring the pH of said solution to a value of between 10 and 14, and to produce the corresponding metal hypochlorite, adding to the resultant metal hypochlorite a nitroalkalane in which the nito group is bound to a carbon atom'having from one to three hydrogen atoms, said nitroalkane being added to said hypochlorite solution so that a slight excess of said hypochlorite is present in the reaction mixture at all times.

2. A process for the liquid phase production of chlorinated nitroalkanes of the formula:

01 R--NO:

wherein R and R each represent an alkyl group, which comprises adding to a solution of a metal hydroxide selected from the group consisting of alkali and alkaline-earth metalhydroxides, sufflcient chlorine to bring the pH of said solution to a value of between 10 and 14, and to produce the corresponding metal hypochlorite, adding to the' alkaline earth. metat hydroxides, 'suflicient ch10}- ri-ne to bring the: pH. of. said v solution to: a; Value of between 10 and. 1d and. to: produce thev corresponding metal hypochlorite, adding to the resultant metal hypochlorite solution a, nitroalkane in. which the nitro group isattached to a primary carbon atom, said nitroalkane. being; added to said hypochlorite solutionso that a slight excess of said hypochlorite is present. in the reaction mixture at. all times;

4.. A process for the. production ofi I l-(1101110130- I-nitroethane which. comprises adding to a. solution of a metal hydroxideselected from. the group consisting of alkali. and alkaline earthmetal hydroxides, suificient chlorine to bring the pH of said solution, to a value of between 10 and 14' to produce the corresponding. metal: hypochlorite, adding to the resultant metal. hypochlorite solution nitroethane,. said nitroethanev being added to said hypochlorite solution so, that. a slight excess of said hypochlorite is present in the reaction mixture at all times.

5. A process for the production of 2-- chlor o-2- nitropropane which comprises adding. to. a, solution of a metal hydroxide selected; from the group consisting of alkali and. alkaline earth metal hydroxides, sufficient chlorine to. bring the pH of said solution to a value of between 10 and 14 and to produce the corresponding, metal hypochlorite, adding to the. resultant metal hypochlorite solution Z-nitropropane, said 2-nitropropane being added to said hypochlorite solution so that a slight excess of. said; hypochlorite is present in the reaction mixture: at all. times;

6. A process for the production of. 2-chloro-2- nitrobutane which comprises adding to. a solution of a metal hydroxide selected from the groupconsisting of alkali: and. alkaline earth. metal hydroxides, sufficient chlorine: to bring the, pH of said solution to a, value of between- 10 and 14 and to producev the corresponding metal. hypochlorite, adding to the resultant metal hypochlorite solution Z-nitrobutane, said nitrobutane being added chlorinated nitroalkanesof the formula:

5855* or said hypochlorite is present in the reagtion mixture at all. times.

'7. A process for the liquid: phaseproduction of wherein R represents-an; alkyl group at less. than five carbon atoms, which comprises adding to: a

solution of a metal hydroxide selected from the chlorite solution a nitroalkane off ther'formula,

to said. hypochlorite. solution so that av slight ex.-

ing to a. solution of a metal hydroxide selected from the group consisting of alkali and alkaline earth metal hydroxides, suflicient chlorine to bring the pH of said solution to a value of between 10 and 14 and to producethe corresponding metal hypochlorite, adding to the resultant metal hypochlorite solution, chlorine and a nitroalkane excess of" hypochlorite is present in the reaction mixture at all times.

JOHN B. TINDALL' j