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Vol. 58
two recrystallizations from absolute ethyl alcohol cal.) and heat of isomerization (23,300cal.). But and alcohol-ether, melted at 220-22’ (uncorr.). it has been pointed out [Kassel, “The Kinetics of It had a specific rotation in alcohol of [ c Y ] ~ ~ D Homogeneous Gas Reactions,” p. 2851 that this -36.25’ (CY= -0.9So, c = 3.4). The analysis hypothesis is untenable as the aldehyde would revealed the formula CloH160N.HC1. A mixed decompose immeasurably fast, and, furthermore, melting point with ephedrine hydrochloride similar decompositions which result in the inter(Merck) gave no depression. Anal. Calcd. for mediate formation of an aldehyde, e. g., methyl CloHlsON.HC1: C, 59.56; H, 7.94; N, 6.96; alcohol [Fletcher, Proc. Roy. Soc. (London), C1, 17.59. Found: C, 59.81; H, 7.58: N, 7.52; A147, 119 (1934)], do not show this behavior. C1, 17.39. Now when ethylene oxide is passed through a The possibility that 1-ephedrine as such is an hot tube it is known [F. 0. Rice and K. K. Rice, alkaloid of aconitum napellus appears impos- “The Aliphatic Free Radicals,” 1935, p. 1601 that sible as the free base, being water soluble, would free radicals are produced in greater quantities remain in the mother liquors on precipitation of and at temperatures considerably lower than the whole alkaloids. In addition we were unable they are from the simple aldehydes, ketones and to detect ephedrine in aconitine, amorph., omit- ethers. It is suggested therefore that at 400’ ting the barium hydroxide distillation. one or more reactions, which constitute the first It appears probable that ephedra bases or in- and slow stage of the decomposition, take place dole derivatives are part of the molecular arrange- with the production of free radicals and aldement in aconite alkaloids. Each base, however, hydes; and that in the second stage such aldehas to be degraded individually before final con- hydes are catalytically decomposed by the free clusions can be drawn. radicals present. We have carried out tests and We express our appreciation to E. Merck, analyses which indicate that the aldehyde is Darmstadt, Germany, for a supply of the amor- mainly acetaldehyde, but that smaller quantities phous bases, to Merck and Co., Inc., Rahway, of acrolein and formaldehyde are present. The different aldehydes may be formed by alternative for crystalline aconitine. reactions of the ethylene oxide or by secondary DEPARTMENT OF CHEMISTRY WERNERFREUDENBERG FORDHAM UNIVERSITY E. F. ROGERS processes. NEWYORK As might be expected on the above hypothesis, RECEIVED FEBRUARY 8, 1936 small quantities of ethylene oxide can induce a decomposition of acetaldehyde below 500°, THE THERMAL DECOMPOSITION OF ETHYLENE analogously to azomethane, which is also known OXIDE AND AN INDUCED ACETALDEHYDE to yield free radicals [Allen and Sickman, THIS DECOMPOSITION JOURNAL, 56, 2031 (1934)l Thus we find that Sir: a t 443’ acetaldehyde at a pressure of 184 mrn. is The thermal decomposition of ethylene oxide half decomposed in the presence of its isomer [Heckert and Mack, THIS JOURNAL, 51, 2706 ethylene oxide, a t 17 mm. pressure, in three (1929)3 presents certain features which hitherto minutes; in its absence in approximately 350 have not been satisfactorily explained. It ap- minutes. This induced acetaldehyde decompopears that the reaction from 380 to 450’ proceeds sition is proportional to the square root of the in two consecutive stages with the intermediate ethylene oxide pressure, and to rather less than formation of an aldehyde; but that the aldehyde the first power of the aldehyde pressure; it is redecomposes at a temperature over 100’ lower tarded by foreign inert gases, e. g., helium (as is than that for pure aldehydes [Fletcher and Hin- the second stage of the ethylene oxide decomposhelwood, Proc. Roy. SOC.(London), A141, 41 sition), but the final pressure increase is not (1933); Fletcher, ibid.,A146, 357 (1934); Thom- changed. son and Frewing, J. Chm. Soc., 1443 (1935)J. It The presence of free radicals from ethylene OXwas originally suggested that an isomerization of ide also accounts for the induced decompositions ethylene oxide to acetaldehyde occurs, and that of methyl bromide, n-butane and isopentane the aldehyde undergoes a unimolecular decompo- found by Heckert and Mack, as, for instance, nsition in virtue of the energy it possesses when it butane is known to be sensitive to methyl radiis formed, viz., the energy of activation (52,000 cals [Frey, Ind.Eng. Chem., 26, 200 (1934)l.
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EDITOR
Further experiments to elucidate the nature of the first stage of the decomposition, and to investigate reactions induced by ethylene oxide, are in progress
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tributed between the two forms of the element. (2) IZ and Io3-, shaken together in 1 N H2S04, do not exchange with appreciable speed. After separation, the 1 0 3 - (measured as A g I 4 ) is still However, when Iz is mixed with IO3inactive. DEPARTMENT OF CHEMISTRY C. J. M. FLETCHER UNIVERSITY OF CALIFORNIA in hot 20 N H804 and immediately cooled and BERKELEY, CALIFORNIA separated] 10-15% of the activity is found in the RECEIVED NOVEMBER 20, 1935 IOa-. (3) Active IZdissolved in CzHd undergoes no exchange, and AgI precipitated from the CzHsI is quite inactive. No exchange was found beEXCHANGE REACTIONS OF IODINE BY THE METHOD OF RADIOACTIVE INDICATORS* tween these substances even when they were Sir: heated together for fifteen minutes a t 90". HowUsing the radioactive isotope of iodine [25 min. ever, when active NaI and inactive CzHJ are dishalf-life, Fermi et al., Proc. Roy. ,506. (London), solved together in alcohol and heated to 100" for A146,483 (1934)] as an indicator, we have investi- five minutes, exchange takes place. (4) IZmixed gated several types of reaction involving exchange with CHI3 in ether solution undergoes no exbetween the iodine atoms in different compounds. change. The CHL (measured as such) remains The radio-iodine is prepared by irradiating a satu- inactive after separation from the active Iz. rated solution of sodium iodate containing a little Also, a negative result was obtained when CHII iodide with the neutrons from beryllium and radon and NaI were dissolved together in alcohol solu[Amaldi et aE., ibid., A149, 622 (1935)]. Upon tion. The partial exchange found in the case of the acidifying the solution, iodine is set free and is then separated from the bulk of the solution by extrac- iodine-iodate mixture suggests an oxidation-retion with ether. The concentrated sample of duction reaction proceeding at a measurable rate. radio-iodine thus obtained is mixed with an inac- Although no net chemical reaction between these tive sample (containing approximately the same substances is possible, the present experiments number of iodine atoms) of the compound which show that a kinetic equilibrium actually exists it is desired to study. After a minute or two the in concentrated acid, and it may be possible to free iodine is separated from the compound, the measure the rate of the reaction by means of the two samples are prepared in a convenient form, radioactive indicator method. It is planned to usually as silver iodide, and the activity of each is carry out further experiments along this line, and to investigate the analogous reactions with bromeasured by means of a tube counter. mine and chlorine. The experimental details will The results obtained thus far are briefly stated be reported in a later publication. as follows: (1) IZand I-, mixed in aqueous soluSCHOOL OF CHEMISTRY D. E. HULL' tion to form the 1 3 - complex, exchange freely. UNIVERSITY OF MINNESOTA C. H. SHIFLETT After separation] the activity is found equally dis- MINNEAPOLIS, MINNESOTA S. C. LIND
* This work was supported in part by a grant from the Fluid Research Fund of the Graduate School of the Univcrsitp of Minnesota.
RECEIVED FEBRUARY 19, 1936 (1) National Research Fellow.
