Ureas As Amine Substrates for Hydrazine & Alkylhydrazine

Indian Journal of Chemistry Vol. 19A, September 1980, pp. 825-828

Ureas as Amine Substrates for Hydrazine & Alkylhydrazine Synthesis-Reaction of Chloramine with Monomethylurea & Formation of I-Methyltriazane

HARI PRAKASH· Inorganic Chemistry Division, National Chemical Laboratory, Pune 411 008

and

HARRY H. SISLER Graduate School, University of Florida, Gainesville, Florida, 32611, USA

Received 8 October 1979; re~'isedand accepted 1 February 1980

Reaction of chloramine with monomethylurea has been shown to yield monomethylhYlirazlne and several side products, e. g., formaldehyde monomethylhydrazone, 1,1-dimethylhydrazine, methyliminotarazane, and methanol, originating from the further oxidation of mODomethylhydrazine with cbloramine. Evidence for the existence of 1• methyltriazane, CH3NHNHNH., is presented for the first time.

the present paper, reaction of chloramine with HEREASfrom thenucleophilicelectrophilicdisplacementchloramine ofto chlorid.give hy•e monomethylurea is reported to test this hypothesis W.draziniumand triazanium1,2, phosphonium and demonstrate the feasibility of the chloramine• and arsonium3,. chlorides is reminiscent of ammonia, monomethylurea reaction as a potential synthetic alkylamines and hydrazines, tertiary phosphines and route for monomethylhydrazine. arsines, oxidative coupling, of phosphine, primary and secondary phosphines and their arsenic analogues Materials and Methods in which an active hydrogen is attached to the group V donor atom, is the preferred mode of reaction of Reagent grade solvents were used. Monomethyl• chloramine5,8. The reaction is general and leads to urea (Aldrich Chemicals) was used as obtained. the oxidative dimerization of a variety of active Chloramine was produced in the gas phase by the hydrogen compounds via H-atom abstraction by ammonia-chlorine reaction using the generator des• chloramine. Typical examples are the chloramine• cribed by Sisler, et alP. Ether solutions of chlora• induced oxidative dimerization of alkyl and aryl mine were made ammonia-free by passing through a padding of anhydrous copper sulphate. The con• mercaptans and their selenium analogues7,S, aro• centration of the chloramine in the ether solutions matic phenols9, and sulfamide1o• The oxidative dimerization, typically of aromatic phenols, follows was determined iodometrically. The identities of a radical pathway in which a proton is transferred the products were established by PMR spectra or from the aromatic phenol, followed by a redox comparison of their retention times with known reaction giving the phenoxy and aminium radical samples recorded on a Perkin Elmer gas chromato• and chloride ion9• No examples of the reactions of graph (GC) model 800 using a 1/4" X 12' K 20M chloramine with urea or alkylureas in which the 15% KOH 5% Chrom P80/100 column maintained nitrogen substrate atom bearing the active hydrogen at lOO°C. Helium was used as the carrier gas at a flow rate of lO ml per 29.0 ± 0.4 sec. PMR is coupled with the 7t-orbital system of the )C=O spectra were recorded on a Varian Associates A-60 function and provides the donor site for the electro• instrument. Deuterated solvents for PMR measure• philic chloramine, are known. The ureas thus ments were used as obtained. The chemical shifts make interesting amine substrates in which the are reported in 8(ppm) from TMS as an internal aminating and the oxidative coupling abilities of reference. chloramine can be tested and successfully exploited Reaction of chloramine with monomethylurea in for the syntheses of hydrazine and alkylhydrazine. water-ether Media - Monomethylurea (104 mmol) It is conceivable that the alkyl substitution at the was dissolved in deionized water (50 ml) contained nitrogen would enhance the basicity of the otherwise in a 1000-ml three-necked flask fitted with a nitrogen much less basic urea and make alkylureas eligible inlet tube, a 500-ml pressure equalizing funnel, and for attack by the electrophilic chloramine to give a dry ice-acetone condenser with a nitrogen bubbler. hydrazinium salt intermediates which on hydrolytic Chloramine solution (96.6 mmol in 480 ml ether) cleavage would yield the free alkylhydrazine. In was filtered into the pressure equalizing funnel

825 INDIAN J. CHEM., VOL. 19A, SEPTEMBER 1980 through ~ padding of anhydrous copper sulphate. and dissolved in absolute ethanol (20.1 ml). Am• The app ratus was purged with nitrogen for 15 min monia-free chloramine solution (37.4 mmol) in with dry ice-acetone slush in the condenser cold ether (200 ml) from the pressure equalizing funnel finger. he chloramine solution from the funnel was quickly added under nitrogen purge to the stir• was dro ise added during 1 hr to the stirred mono• red urea solution cooled in ice-water bath. An methylur a solution with the reactor flask immersed immediate reaction occurred with the precipitation in a wa r-bath. An aliquot was withdrawn after of a white solid. The reaction mixture was stirred three an one quarter hours. The aliquot showed for 80 min. Sodium hydroxide pellets (200 mmol) a produ t component peaking at 7.1 min retention were added to the reaction mixture. The gas chro• time, id ntity of which was established as methy• matogram of the liquid phase at the end of an eleven• liminota azane, CHa N=N-N=CH2 on the basis hour reaction period showed several products. The of PMRI and IR spectra12 and from the coincidence major product peaked at 15.4 min retention time which coincided with the 15.45 min. retention time chroma gram of a deuterated chloroform solution peak traced to formaldehyde monomethylhydrazone, of the roduct formed in the mono methylamine• CHaNH-N=CH2 contained in a distillate fraction chloramof its re~ntionne reaction.time of Another7.1 min observedaliquot wasin thewith•gas from the monomethylurea-sodium hypochlorite re• drawn after a five-hour period and this showed two action gas chromatographed under similar con• ditions1a• retentio times. These products were charac• Deionized water (50 ml) was added to the hetero• terizedadditioials monomethylhydrazineproducts peaking at 11.3and and1,l-dimethyl•5.95 min geneous reaction mixture, stirred at room tem• perature for 1 hr and ether distilled under nitrogen times w th those of the authentic specimens; authen• at atmospheric pressure. The composition of the tic mo omethylhydrazine gas chroma tographed in distillate fractions following the ether fraction was ether.hYdraZi~e,I herespectivelyreaction appearedby comparingto b{: slowthe asretentionnearly complex and showed formaldehyde monomethyl• half of I the originally used chloramine was present hydrazone and 1,l-dimethylhydrazine as identifiable in the reaction mixture. Sodium hydroxide pellets components in the gas chromatogram. The gas (199.8 tnmol), dissolved in deionized water (20 ml) chromatogram of the aqueous pot residue was also and copIed, were added to the reaction mixture. complex from which monomethy1hydrazine peaking at 13.8 min and 1, l-dimethylhydrazine at 6.35 min deioniz d water (10 ml). At the end of 7 hr, vir• retention times could be identified. Because of small amounts of the products and separation difficulties, stoppe , the flask sealed, and left overnight. The the distillate fractions and the aqueous pot residue tuallyether 1 yer11thewaschloramineseparated hadandreacl:ed;shown stirringto containwas could not be resolved into individual components. The7.0 mrejidualn componentsolution wasas washedmethyliminotarazanewith more of and t e 11.3 min component originating from Results and Discussion mono ethylhydrazine, Ether was distilled from the The results of this study demonstrate the feasibi• aqueo s reaction mixture under nitrogen and at• lity of amination of monomethylurea by chloramine mosph ric pressure. After the removal of ether, a seco d fraction was observed to reflux at 60.5-61°C. to give monomethylhydrazine and side products, The Ii uid in the column was dissolved in carbon e.g. formaldehyde monomethylhydrazone, methyl• iminotarazane, 1,l-dimethylhydrazine, methanol, tetrac loride and identified as 1"l-dimethylhydra- and methyltriazane originating from the oxidation zine, Ha}zN-NH2(PMR: 2.42, 6H, CHa; 3.20, of monomethylhydrazine by chloramine. Absence 2H, 2; CHa(NH2 proton ratio==3(1) and ether. of any 1,2-dimethylhydrazine in the products ex• Furth r distillation of the aqueous pot residue under cludes oxidative coupling of monomethylurea by nitrog n and atmospheric pressure yielded 0.114 g chloramine via H-atom abstraction. Instantaneous of a distillate fraction, b.p. 46-85°C. Its PMR reaction of chloramine in ether occurs with mono• spectr m in CDCla indicated the presence of ether, methylurea dissolved in absolute ethanol at 1/2.00 traces of methanol (oCH3=3.40) and exhibited two• chloramine to monomethylurea mole ratio initially proto singlets at 0=2.68 and 0==2.45 in the 1.77 by yield a white solid insoluble in the solvent media. to 1 ea ratio, tentatively assigned to NH and CHa The solid is cleaved by sodium hydroxide base to give proto s, respectively. Addition of concentrated hy• droch oric acid to the solution in the PMR tube formaldehyde monomethylhydrazone an oxidation product of monomethylhydrazine by chloramine frequently detected in the monomethylhydrazine meth lamino group and appearance of a signal at synthesis by the Sisler process involving chloramine• 0= 7. 2 due to hydrazine dihydrochloride; the che• monomethylamine reaction14• In addition, an un• micalresul~..shiftd in fora vigorousan authenticreactionsampleand cleavageof N2H4.2HClof the known product peaking at 11.2 minute retention time in the gas chromatograph of the ethanol-ether fiedoccuq;~sat1-methyltriazane,7.04. The compoundCHaNHNHNH2•is tentatively identi• reaction mixture corresponds to monomethylhy• drazine authentic sample gas chromatographed in etha l-ether media - A 250-ml flask was fitted with ether under similar conditions. The aqueous pot a 50- 1 pressure equalizing funnel, a side arm tube residue after diluting the ethanol-ether reaction mix• withReftiOnrubberof septumchloramineand awithnitrogenmonomethylureagas bubbler viain ture with water and removal of ether by distillation ahy~odermicneedle. Monomethylurea (74.80 mmol) also showed monomethylhydrazine peaking at 13.8 was transferred'. to the flask through a glass funnel minute retention time and several unidentified pro-

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IIII I,~I ! I PRAKASH & SISLER :. REACI'ION OF CHLORAMINE WITH MONOMETHYLUREA

ducts, one of which was l,l-dimethylhydrazine, a how l,l-dimethylhydrazine is formed in the hydroly• side product in the monomethylhydrazine synthesis sis of methyliminotarazane. We assume that hy• by Sisler process.a The isolation of what is be• drazine, formed in a base-catalyzed hydrolysis of lieved to be methyltriazane, CHaNH-NH-NH2 methyltriazene or in a heat-induced decomposition in detectable amounts in the distillate fraction also of methyltriazane also yielding methylnitrene, containing ether from the reaction of monomethyl• urea with chloramine in water-ether media at mono• CHaN< ' undergoes methylation by methyltriazene methylurea/chloramine/sodium hydroxide mole stoi• or methylnitrene yielding I, l-dimethylhydrazine. chiometry of 1.08/1/2;07, evidently indicates that In our mechanistic model for the oxidation of amination of monomethylurea by chloramine should monomethylhydrazine by cWoramine, the formation involve chloramination as first step to give a methyl• of a methylhydrazide radical CHaNH-NH from the hydrazinium chloride intermediate (1) according to Eq. (1). The methylhydrazinium chloride inter• one-electron oxidation of monomethylhydrazine by mediate (I) chloramine is envisaged. This radical eventually completes destruction of monomethylhydrazine and accounts for the formation of a wide range of side products in the following reactions : (i) It undergoes o - ci + NH2CI - 0 = ci CI- further oxidation by chloramine to yield methyl- "- "- NH.NHCH3 [ NH.NH(CH3)NH.]+ diazine, CHaNH-N( and diazomethane. The fre• (I) quently observed side product, formaldehyde mono• .. (1) methylhydrazone is formed by the transmethylation of methyldiazine analogous to the scheme proposed by Sisler and coworkers for the formaldehyde di• methylhydrazone, (CHa)2 N-N=CH2 from dimethyl• o= c( CI- + H.O ~ CH3NH-NH. + diazine16 or from the reaction of carbene, : CH; [ NH.NH(CH3)NH.]+ generated from diazomethane with methyldiazine + NH.CI .. (2) co. and I, l-dimethylhydrazine. The I, l-dimethyl• is cleaved hydrolytically in the presence of chlora• hydrazine is formed by the methylation of methyl• mine with and without the hydroxide base in which dydrazine by methyldiazine or diazomethane (ii) monomethylhydrazine is formed according to Eq.(2) . Methyl-hydrazyl radical undergoes dimerization to Further, but rapid oxidation of monomethylhydra• 1,4-dimethyltetrazane, CHaNH-NH-NH-NHCHa fol• zine by chloramine accounts for the formation of lowed by dismutation to monomethylamine and formaldehyde monomethylhydrazone, I, l-dimethyl• nitrogen via the formation of methyltriazene, CHeN = hydrazine, methyliminotarazane, methyltriazane, and N-NH2 or its tautomer CRaNR-N=NHI6 (iii) Finally methanol side products identified in this study. methylhydrazyl radical reacts with monomethy• The present study provides the first evidence for lamine to give 1, 3-dimethyltriazane, CHaNH-NH• the existence of l-methyltriazane, CHaNH-NH-NH2• NHCHa; its subsequent one-electron oxidation by Its I-methyl structure is supported by the PMR chloramine via H-atom abstraction and formation spectrum, decomposition to hydrazine dihydrochlo• of aminium radical leads to the formation of 1,3• ride upon treatment with hydrochloric acid, and dimethyltriazene and methyliminotarazane, CHaN = thermally to give hydrazine observed to peak at 22.3 N-N=CH2• min retention time, in close agreement with the In conclusion, amination of monomethylurea by 22.47 min retention time of an authentic sample of chloramine occurs to yield monomethylhydrazine hydrazine gas chromatographed in chloroform. It and monomethylhydrazine-based oxidation products. appears to be stabilized through hydrogen bonding Feasibility of this reaction as a potential synthetic interactions with diethyl ether co-distilling with it. route for monomethylhydrazine and other alkyl• The formation of methyltriazane is quite unusual hydrazines from alkylureas depends in avoiding and occurs with I, l-dimethylhydrazine and methanol further oxidation by chloramine of the hydrazines during distilliation of the pot liquid containing only formed. methyliminotarazane; the 1,l-dimethylhydrazine fraction preceding the methyltriazane fraction also Acknowledgement containing traces of methanol. We, therefore, as• sume that hydrolysis of methyliminotarazane, CHaN = This work was done at the University of Florida, N-N=CH2 yielding methyItriazene, CH2N=N• Gainesville, USA. One of the authors (R. P.) is NH2 and formaldehyde as initial products. Much grateful to Air Force Office of Scientific Research, of the methyltriazane decays to methylamine and USA for financial assistance during his tenure as a nitrogen in a manner analogous to the decay of Postdoctoral Associate at the University of Florida. triazene and dimethyItriazene reported by Hayon and Simic which can also regenerate hydrazine in References an OH- ion-catalyzed hydrolysis of triazene15• We 1. SISLER, H. H., BAFFORD, R. A., OMIETANSKI, G. M., RUDNER, postulate reduction of methyltriazene by either for• B. & DRAGO, R. S., J. org. Chem., 24 (1959), 859. maldehyde or the hydrazine generated from the 2. UTVARY, K. & SISLER, H. H., Inorg. Chem.,7 (1968), 698. base-catalyzed hydrolysis of methyltriazene yielding 3. SISLER, H. H.. SARKIS, A., DRAGO, R. S. & SMITH, N. L.• methyltriazane. We are uncertain at this point J. Am. chem. Soc .• 81 (1959),2982.

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INDIAN J. CHEM., YOLo 19A, SEPTEMBER 1980

4. SISLER,H. H., & STRA'ITON,C., [norg. Chem., 5 (1966), 12. SISLER,H. H. & PRAKASH,H., On the synthesis and decom• 2003. position of monomethylhydrazine in the monomethy• 5. HIGHSMITH,R. E. & SISLER,H. H., [norg. Chem., 7 (1968), lamine-chloramine reaction-Novel routes for the syn• 1740. thesis of triazenes, tarazanes, and 2-tetrazenes. Evidence 6. KRANNICH,L. K. & SISLER,H. H., [norg. Chem., 8 (1969), for the formation of I-methyltriazanium chloride and 1032. I-methyltriazane, Project Progress Report, February• September, 1978. 7. SISLER,H. H. & KonA, N. K., J. org. Chem., 36 (1971), 1700. 13. PRAKASH.H. & SISLER,H. H., On the synthesis of mono• 8. SISLER,H. H., KOTIA, N. K. & HIGHSMITH,R. E., J. org. methylhydrazine by sodium hypochlorite-monomethylurea Chem., 35 (1970), 1742. reaction, unpublished results. 9. PACQUETIE,L. A. & FARLEY,W. C., J. org. Chem., 32 14. MARTIN MARIE'ITACoRPORATION,FINAL REPORT, Amine (1967), 2718. fuels production feasibility Demonstration, MCR-75-466, October 1976. 10. PRAKASH,H., Chloramination of some unsaturated systems, Ph.D. Dissertation, University of Florida, Gainesville, 15. HAYON.E. & SIMIC,M .• J. Am. chem. Soc., 94 (1972). 42. 1969, 34. 16. SISLER,H. H. & MATHUR. M. A., Synthesis of hydrazine 11. SISLER,H. H., NETH, F. T., DRAGO, R. S. & YANEY,D., and its derivatives, Proc. Conf. Env. Chern. Hydrazine J. Am. chem. Soc., 76 (1954), 3906. Fuels, Tyndall AFB. 13 September 1977.

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