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Fig 1.-Burning velocities of ozone and ozone A oxygen mixtures (initial gas temperature = 298"K., pressure = 1 atm. abs).
pure ozone a t 1 atm. pressure and a t an initial teniperature of 298°K. (25OC.) has a burning velocity of 472 ( * 12) cni./sec.; a t 195'K. i t is 270 (f7) cm./sec. Pure ozone can be burned to oxygen for substantial periods of time without explosion and detonation, like a regular combustible gas mixture. TABLE I VELOCITIESFOR INITIALT = 298°K 1. PLAVE Mole '101 25 40 50 60 TO SO 90 Burning velocity, Vo (cm./s 41 139 214 290 349 386 411
100 430
Pure ozone was combusted with various fuel gases. The diffusion flame of pure ozone and cyanogen is extremely bright and produces a ternperature of 5ZOOOK. a t 1.0 atrn. A detailed description of our experiments will be published elsewhere.8
Vol. 79
dine, which is then nitrosated, reduced, formylated and subsequently ring-closed.2 The preparation of ?-alkyl- and 2-aryladenines is more cumbersome, since direct condensation of arnidines with malononitrile proceeds anomalously* and the desired 2substituted-4,6-diaminopyrimidinesmust be prepared by other methods4-? The synthesis of derivatives such as isoguanine (2-hydroxy-6-aminopurine) is also circuitous, since urea does not condense satisfactorily with malononitrile and the 2hydroxy group must be introduced i n d i r e ~ t l y . ~ . ~ , ~ We now wish to describe a facile synthesis of 2-substituted adenines which would appear to be generally applicable. Thermal cyclization of amidine salts of isonitrosonialononitrile (I) (R = -CH3; m.p. 141-143'. Anal. Calcd. for C5H;N5Q; C, 39.2: 11, 4,R; N, 45.7. Found: C, 39.4; H, 4.4; N, 45.4. R = -Ce,H5; m p . 14S150'. Anal. Calcd. for Clo€19NSO: C, 55.8; H, 4.3; N, 32.5. Found: C, 55.7; H, 4.0; N, 32.6. R = -NH2; m.p. 157-158'. A d . Calcd. for C4H6N60: C, 31.2; H, 3.9; N, 54.5. Found: C, 31.3; H, 3.9; N, 55.0) in 2-methyl-5-ethylpyridine yielded 2-substituted 4.6-diamino-5-nitrosopyrimidines (11) (R = -CI&5; Anal. Found: C, 39.2; H, 4.6; N, 46.1: K = -CsH,; Anal. Found: C? 55.9; H. 3.9; N, 32.6: R = --NHp;" Ami. Found: C, 30.7: H, 3.5; N, 55.0). The salts (T) were prepared readily in almost quantitative yield by mixing an aniidine hydrochloride in ethanol solution with the silver salt of isonitrosonialononitrile,I1 removing silver chloride by filtration and concentrating the ethanol. In some instances, isolation of I wa? not necessary prior to cyclization; for example, heating guanidine carbonate with potassium isonitrosomalononitrile (I1I) (m.p. 209211'; Anal. Calcd. for C3NaOK: N, 31.6. Found: N, 31.6) in dirnethylformamide yielded 2,4,6triamino-5-nitrosopyrimidine ('I1: R = -NH2) in SS% yield, and condensation of IT1 with urea in sodium ethoxide solution yielded 2-hydroxy-4,6-
diamino-5-nitrosopyrimidine. 9,12 Heating these 2-substituted 4,6-diamino-5-nitrosopyriniidines with a mixture of formamide, formic acid and sodium hydros~lfite'~ yielded 3substituted adenines in high yield. I n this manner, 2-methyladenine5*14t1h was prepared in 74% over-
(2) For a recent review of purine chemistrv, see A. Bendich in "The Nucleic Acids, Chemistry and Biology," ed. by E. Chargaff and J. N. Davidson, Vol. 1, Academic Press, New York, N. Y.,1955, p. 81. (3) G. W. Kenner, B. L?tbgoe, A. R. Todd and A. Topham, J . Chern. Soc., 388 (1943). (8) See (a) Proc. VIth International Symposium on Combustion. (4) G. W. Kenner, B. Lythgoe, A. R. Todd and A. Topham, i b i d . . Aug. 19-24, 1956, (b) Proc International Ozone Conference Chicago, 574 (1943). I l l , Nov. 28-30. 195G ( 5 ) J. Baddiley, B. Lythgoe, D. McNeil and A. R. Todd, ibid., 383 THERESEARCHINSTITUTE OF (1943). TEMPLE UNIVERSITY A. G. STRENG ( 6 ) H. R. H e m e . W. J. Clegg and C. W. Smart, J . Org. Chent., 11, PHILADELPHIA 44, PENNSYLVANIA A. V. GROSSE 1320 (1952). RECEIVEDFEBRUARY 8, 1957 (7) G. A . Howard, B. Lythgoe and A. R. Todd. J . Chem. Soc., 476 (1944). ( 8 ) H. L. Wheeler and G. S. Jamieson, A m . Chem. J . , 32,342 (1904). A FACILE SYNTHESIS OF 2-SUBSTITUTED (9) A. Bendich, J. P. Tinker and G . B. Brown. THISJOURNAL, 70, ADENINES' 3109 (1948). (10) a '. Traube, Ber.. 37, 4A-L-I (1904). (11) G. Ponzio, Gnzz. chim. itol., 61, 561 (1981). The conventional synthetic route to adenines in(12) H. Plielaiid a n d K . Liebig, A n x . , 5 5 5 , 146 ( l n i i i . volves the condensation of guanidine or thiourea (13) H. Hredereck and A . Erlenhofer. Brr , 8 8 , li30Ci (1953). with malononitrile to give a 4,6-diarninopyrimi(14) IT. W. Dion, I). G. C d k r n s and J . J I'tiffner, T H I S JOliKNAl, 1 6 , 948 (1954). (1) This investigation was supported by a research grant (C-2.551) (15) .f. Baddiley, B. 1,ythyoe aiirl A I
