United States Patent [191 1111 3,937,703 Meredith [45] Feb. 10, 1976

[54] PREPARATION OF RDX _ 2,568,620 9/1951 Gresham et al ...... 260/248 [75] Inventor: Joseph A. Meredi‘h, Bluff City’ 3.1781430 4/1965 Thatcher ...... 260/248 Tenn. . _ . Primary Examiner—.lohn M. Ford [73] AsS'gnee: The Um‘ed States of Amenca as Attorney, Agent, or Firm——Nathan Edelberg; Robert P. represented by the Secretary of the Gibson. A_ victor Er-kkila Army, Washington, DC. ’ [ 22 1 F1'i ed : Nov . 8, 1974 [57] ABSTRACT [2i] App]. No.: 522,153 _ . RDX is produced by reacting formaldehyde and an alkyl nitriie RCN,» wherein R is an alkyl group of l to

U.S. - ~ - ~ ...... - ...... -. 3 carbon atoms, in the absence of added Solvents’ to [51] Int. Cl...... C07D 251/54 form a 1,3,5_triacylhexahydro_s_triazine and Subject_ Eleld of Search ...... the latter, without Separation thereof from the re _ action mixture, to nitrolysis by contact with concen [56] References C'ted trated nitric acid to form RDX. UNITED STATES PATENTS _ _ . 2,559,835 7/1951 Zerner et al...... 260/248 5 Clams’ N0 Drawmgs 3,937,703 1 a white solid; and when the addition was complete, the PREPARATION OF RDX slurry was quite heavy with solids, and if allowed to cool, the slurry became a very viscous semisolid. After BACKGROUND OF THE INVENTION the addition of the propionitrile-trioxane solution was RDX (1,3,5-trinitrohexahydro-s-triazine) is usually 5 complete, the slurry was added slowly portionwise to manufactured industrially by nitrolysis of hexamethy - about 10 volumes of 99% nitric acid, which was agi lenetetramine with concentrated nitric acid. This con tated in a glass ?ask cooled in an ice bath. .The agitated ventional process has the disadvantage that a substan reaction mixture was held for an additional 15 minutes tial amount of HMX (cyclotetramethylenetetranitra with ice bath cooling, allowed to warm to ambient mine) is formed as a by-product, which can exist in temperature for 15 minutes and then heated to about several polymorphic forms possessing high impact sen 60°C. for 60 minutes. The reaction mixture was then sitivity and, unless completely removed, would increase allowed to cool to room temperature and drowned into the impact sensitivity of the RDX significantly. ?ve volumes of ice water. The precipitated RDX was U.S. Pat. No. 3,178,430 discloses a process for pre ?ltered off, washed with water and dried. The RDX was paring RDX without the concurrent production of thus obtained in high purity and 21% theory yield, HMX by reacting a l,3,5-triacylhexahydro-s-triazine based on the propionitrile. with concentrated nitric acid. As disclosed in the pa tent, the 1,3,5-triacylhexahydro-s-triazine intermedi EXAMPLE 2 ate, which was reacted with the nitric acid, was previ The procedure described in example I for preparing ously prepared by the method of the Journal of the 20 the slurry of the 1,3,5-tripropionylhexahydro-s-triazine American Chemical Society, Vol. 74, pages intermediate was repeated using the following amounts 5524-5(1952), wherein formaldehyde and the nitrile of reactants: _ were reacted in the presence of carbon tetrachloride or 2.12 grams (0.04 mol)'propionitrile other solvents, and the s-triazine formed was separated 1.15 grams (0.04 mol) formaldehyde as trioxane from the reaction mixture and puri?ed by recrystalliza 25 0.05 gram (0.0005 mol) concentrated sulfuric acid. tion from a solvent. The slurry was added during 8 minutes to 50 ml of 99% nitric acid cooled in an ice bath. The agitated reaction SUMMARY OF THE INVENTION mixture was maintained in the ice bath for 15 minutes, An object of the ‘present invention is to provide a allowed to warm to ambient temperature for 15 min process for the preparation of RDX by nitrolysis of the 30 utes and then heated to about 60°C. for 60 minutes. triazine intermediate without isolation thereof from the The reaction mixture was poured over 200 grams of reaction mixture in which it is formed from formalde ice, and the precipitated RDX was ?ltered off, washed hyde and a nitrile. with water and dried. The RDX was thus obtained in Other objects will become apparent as the invention 99+% purity and 31% of theory yield, based on propio is further described. > 35 nitrile. In accordance with the process of the present inven In the foregoing example the ratio of l-lNOa volume tion, RDX is obtained in simple manner by reacting a to slurry weight was 15/1 and the total nitration reac formaldehyde, such as trioxane and paraformaldehyde, tion time was 90 minutes. When the foregoing example . with a nitrile of the general formula RCN, wherein R is was repeated except that the HNO3/slurry ratios were an alkyl group containing 1-3 carbon atoms, in the 40 7.5/1 and 10/1, the RDX was obtained in the same absence of added solvents to produce the correspond yield and quality. Lower yields of RDX were obtained ing 1,3,5-triacy1hexahydro-s-triazine, and thereafter when in the foregoing example the l-lNOalslurry ratio reacting the latter in situ, i.e., without separation was 15/1 but the total nitration reaction time was con thereof from the reaction mixture, with concentrated siderably shorter (about 25 minutes) or longer (150 nitric acid. 45 minutes). The process of the present invention is relatively The acid catalyzed reaction of nitriles and formalde simple and ef?cient, produces RDX of high purity free hyde in the absence of solvents other than the nitrile to from HMX, and eliminates the simmer purification for produce the corresponding "1,3,5-triacylhexahydro-s the destruction of linear by-products associated with triazines is known (e.g. J. Am. Chem. Soc. 70, 3079 the aforesaid conventional industrial RDX process. 50 (1948), U.S. Pat. No. 2,559,835.). The reported yield of the tripropionyl derivativeobtained from propioni DESCRIPTION OF THE PREFERRED trile is about 47% of theory based on propionitrile (see EMBODIMENTS also J. Am. Chem. Soc. 74, 5524 (1952)). Further, the ' The following examples serve to illustrate specific yields of RDX obtained by nitrolysis of 1,3,5-tripro embodiments of the method of carrying out the process 55 pionylhexahydro-s-triazine with concentrated nitric ‘of the present invention. acid as reported in U.S. Pat. No. 3,178,430 range from about 20% to about 75% of theory. It is evident from EXAMPLE 1 the foregoing that the present invention, by effecting 13.8 Grams (0.25 mol) of propionitrile and a cata the nitrolysis of the triazine intermediate without isola lytic amount (0.65 gram) of concentrated sulfuric acid 60 tion and puri?caton thereof from the reaction mixture were mixed and heated to gentle re?ux of the nitrile in in which it is formed, provides a simpler process, which a glass ?ask provided with a dropping funnel, air driven can produce RDX in high purity and without loss of agitator and re?ux condenser. A solution of 15 grams RDX yield from the initial nitrile. Further, in the pres (0.5 mol) of formaldehyde as trioxane in 13.8 grams ent process, by eliminating the use of added solvents in (0.25 mol) of propionitrile was added to the flask con 65 the reaction of the nitrile and formaldehyde to form the tents during about 30 minutes at such a rate as to main triazine intermediate, the by-product contaminants are tain the re?ux. When the addition was about one-third the respective carboxylic acid of the nitrile and/or de complete, the triazine compound began to separate as rivatives of the nitrile and formaldehyde. These by-pro 3,937,703 duct contaminants are water soluble whereas the RDX ally tends to promote the production of by-products at is water soluble, so that the RDX can be isolated in high the expense of RDX yield while an excessively short purity by diluting the nitration mixture with water and contact period results in an incomplete reaction and a separating the RDX from the aqueous mixture contain low yield of RDX. ing the dissolved impurities, e.g. by ?ltration. The foregoing disclosure is merely illustrative of the In similar manner nitriles of the foregoing general principles of this invention and is not to be interpreted formula RCN other than propionitrile, e.g. acetonitrile in a limiting sense. I wish it to be understood that I do and butyronitrile, can be reacted with formaldehyde, not desire to be limited to exact details of construction such as trioxane and paraformaldehyde, and the result shown and described, because obvious modifications ing 1,3,5-triacylhexahydro-s-triazine nitrolyzed in situ will occur to a person skilled in the art. with concentrated nitric acid. I claim: The reaction conditions for producing the 1,3,5 1. A process for preparing 1,3,S-trinitrohexahydro-s triacylhexahydro-s-triazines by acid catalyzed conden triazine, which comprises reacting formaldehyde with a sation of formaldehyde, such as paraformaldehyde and nitrile of the general formula RCN, wherein R is an trioxane, with nitriles of the foregoing general formula 15 alkyl group of l to 3 carbon atoms, in the absence of in the absence of added solvents, as well as the condi added solvents to produce the corresponding 1,3,5 tions for the nitrolysis of the triazine derivative with triacylhexahydro-s-triazine, and contacting the result concentrated nitric acid, are known and are generally ing reaction mixture containing said triazine with con suitable for use in the present process with the excep centrated nitric acid at a temperature sufficient to ef tion that in the nitration step of the present process the fect nitrolysis of said triazine to form 1,3,5-trinitrohex nitric acid is contacted with the triazine intermediate ahydro-s-triazine. without isolation of the latter from the reaction slurry 2. The process of claim 1, wherein the nitrile is aceto in which it is formed. Thus, for example, in the forma nitrile. 3. The process of claim 1, wherein the nitrile is propi tion of the triazine intermediate, the amount of nitrile 25 employed can be about 1 mol or more per mol of form onitrile. aldehyde. In the nitrolysis step the concentration of the 4. The process of claim 3, wherein about equimolec nitric acid used is preferably between 90 and 100% and ular proportions of propionitrile and formaldehyde as especially 98-100%, and the ratio of the volume of the trioxane or paraformaldehyde are reacted in the pres nitric acid to the weight of the slurry containing the ence of a catalytic amount of concentrated sulfuric triazine intermediate, is generally at least about 5 parts acid to form l,3,5-tripropionylhexahyd'ro-s-triazine, of nitric acid per part of reaction slurry. The nitric acid and the resulting reaction mixture is contacted with and triazine slurry are preferably mixed at about 98-100% nitric acid to effect said nitrolysis. 0°-20°C, prior to heating to a temperature at which the 5. The process of claim 4, wherein one part by weight of the resulting reaction mixture containing the 1,3,5 nitrolysis rate is signi?cant, i.e. at least about 40°C. and 35 up to the re?ux temperature of the nitric acid, namely tripropionylhexahydro-s-triazine is contacted with 80°—85°C. The yield of RDX produced is also affected about from 7.5 to 15 parts by volume of 98—lO0% nitric by the duration of contact of the nitric acid with the acid to effect said nitrolysis. triazine slurry in that a prolonged contact period gener * * * * * 40

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