respect to time. The establishment of the conditions for obtaining this relationship is a critical factor in the development of the quantitative aspects of this technique. Fig. I shows thc results nbtained with leucine, phenylalanine and pepsin,
THE EXCHANGE REACTION BETWEEN EUROPIUM(11) AND EUROPIUM(1II) IONS IN HYDROCHLORIC AND PERCHLORIC ACID SOLUTIONS Sir:
In view of current interest in electron transfer exchange reactions, we make this preliminary report of our studies of the measurable exchange rate between riiropium(r1) and eiiropiiim(II1) ions i n aquP/ oils solutions of hydrochloric arid perchloric acid. Solutiolis of europium(I1) chloride (perchlorate) and labelled europium(II1) chloride (perchlorate) were mixed in the appropriate acid, aliquots removed a t definite time intervals, the two oxidation states separated, and the specific activity of the europium( 11) fraction determined by counting the solirtion in a reproducible geometry with a dipping (kiger-hfueller tube, then precipitating the e l m 1)iuni and weighing i t as Eu~(C;04)3~1OH~O. Sodiuni chloride or sodium perchlorate was used, as required, to adjust the ionic strength to 2.0 in all 1 2 3 4 5 1 2 3 4 2 3 4 5 6 runs. Since europium(I1) in aqueous solution is Time of migration in hours. easily oxidized by air, and is known' to be photoFig. 1.-Movement of compounds on paper, in an electric chemically oxidized by water, all experiments were field, as a function of time: pepsin, crystallized, of porcine carried out in an opaque reaction vessel under niorigin, Armour Labs ; temperature, 23-24'. trogen freed from oxygen by passage through a 11) chloride solution. Runs were made chromium( The experiments were carried out in a modification of the apparatus previously d e ~ c r i b e d . ~Six , ~ , ~ a t 39.4 * 0.1'. Several chemical separation methods were tried, paper strips (E. & D. No. 613, 8 mm. wide) stretched across a Bakelite frame, were held in of which only the precipitation of europium(II1) place by plastic draw-bolts actuated by stainless hydroxide from the solution by ammonium hysteel coil springs. At each end of the frame, the droxide gave remoducible results. This method led ends of the strips dipped into common buffer ves- to a smdl, repGoducible induced exchange (approxisels, each containing about one liter of buffer solu- mately 12%). The tracer used was 5.2-year EulS2produced by tion. The frame, paper strips and buffer vessels the Eu(n, y) reaction in the Oak Ridge pile. were completely enclosed within a vapor-tight Lu,411 runs exhibited the usual exponential time decite chambq. The vapor space in the chamber was kept t o a minimum by replacing as much of the air pendence of exchange extent. In perchlorate meas possible with water. Electrical contact with the dium the half-time of exchange was not directly buffer solutions was made by agar-KC1 salt bridges. measurable since the europium(I1) was completely The dry paper strips were placed in the Bakelite oxidized by the perchlorate ion before the exchange frame and wetted by immersing the frame in the had proceeded more than a few per cent. However, buffer solution. The excess liquid was allowed to the exchange rate was found to be much faster in the run off, as indicated by the absence of sheen on the presence of chloride ion, and experiments showed paper; the frame was then placed in position in the that the rate constant is proportional to the first chamber. When the reading of the milliammeter, in power of the chloride ion concentration (varied by series with the paper strips, became relatively con- substituting perchlorate ion for chloride ion). In stant, 0.01 ml. of the substance under study (2-8 the presence of chloride the perchlorate oxidation of mg. per ml.) was added to the center point of each europium(I1) was not serious since the exchange rehorizontal paper strip. The PH of the buffers was action was considerably faster than the oxidation. checked before and after each run to insure against A plot of rate constant vs. chloride ion concentravariation. Ninhydrin was used to identify the tion gives a straight line extrapolating through zero amino acids, and lead acetate-bromo phenol blue for rate a t zero chloride ion concentration, implying the pepsin. The displacement of the forward edge that the rate of exchange in perchlorate medium in of the band on the paper, from the initial point of the absence of chloride is very small relative to the application of the migrating substance, was meas- rate in the presence of chloride. The change in half-time as a function of the euroured in each case. pium concentrations showed that the reaction is DEPARTMENT OF BIOCHEMISTRY HUGHJ. MCDONALD AND MATTHEW C. URBIN first order in europium(I1) and first order in euroTHEGRADUATE SCHOOL B. WILLIAMSONpium(II1). The rate is essentially independent of STRITCH SCHOOL OF MEDICIXE MARTIN LOYOLA UNIVERSITY hydrogen ion concentration in the range 0.3-1.0 f, CHICAGO 12, ILL. indicating that hydrolyzed species are apparently RECEIVED FEBRUARY 10, 1950 unimportant in the exchange. The exchange rate, (3) H. J. McDonald, M C Urbin and M B. Williamson, Scicncc, R, is then given by R = k [Eu(II)][Eu(III)][Cl-]. 112, 227 ('1950). ( 4 ) H. J McDonald, M C Urbin, and M B. Williamson, Absts , Some representative data, including the termolecniv Riol Chem , 118th Meeting, Amer Cheni Soc , p 66C (1950) ular rate constant k, are given in Table I. ( 5 ) H J McDonald M C I'rhin and M R Nilliamsoii I Col2.
l i i r l Scr
in
pre5s
'1) I )
I
I ) I , I I ~ and ~ J ' IT) R l Yo5i J C h m Phys
, 17, 1345 ( 1 W 4 )
COMMTTNICATIONS TO TIIE EDITOR
April, 1951
IS95
amphoteric and its chemical behaviors are closely analogous to I11 and IV. Copper complex salt: greenish yellow microcrystals. Picrate : yellow Total -. Halfscaly crystals, m.p. 225-226' (dec.); anal. Calcd. Eg&T Eu(II) Eu(III) H+ c1- titpe, k concn., concn., concn., min- moles-VZconcn., concn., for ClrHloOaNl: N, 15.30. Found: N, 15.42. utes min.-l f f f f f Diacetate : colorless scaly crystals, m.p. 180.50.0653 0.0244 0.0409 1.00 1 . 8 6 5.7 0.108 181'; nnal. Calccl. for CllHllOlN: N, 6.33. .os04 .om8 . o m 1 . m 1.88 40 ,107 Found. N, 6.02. ,1065 ,0683 ,om i . o o 1 . 8 4 33 .iox Application of the Saiitliiicycr reaction to 11 ,0677 . ... . . . . 1.00 .71B 132 .lo8 yields the following halogen compounds. p-Bro,0630 .... . . . . 0.30 1.87 58 .lo2 motropolone (V, X = Br); m.p. 189-190', alone or The europium used was of 99.9% purity and was in admixture with ,9-bromotropolone,3obtained as a loaned to us by Mrs. Ethel Terry McCoy to whom by-product during the synthesis of I and the posiwe express our sincere gratitude. We thank Pro- tion of its bromine atom was later established to be fessor Don b'l. Yost and Dr. David L. Douglas of a t para,b so that the amino group in I1 is also clearly the California Institute of Technology for the EuIG2 in the para position. p-Chlorotropolone : orange needles, m.p. 147-149'. p-Iodotropolone : oractivity . ange needles, m.p. 169-170'. I~BPARTMENT OF CHEMISTRY Details of the results of our studies will be reOF CALIFORNIA L)AI.R J. MEIER IJNIVERSITY 1,os ANGELES,CALIFORNIA CLIFFORII S.GARNER ported shortly. The effects of I, 11, and some of RECEIVED MARCH5, 1951 their allied compounds on E'oshida sarcoma have already been published.8 We are deeply indebted to Dr. R. Majima (EmeriON p-AMINOTROPOLONE tus Professor of this University) for his unfailing Sir : Very recently, Dewar' not only reported a molec- encouragement and to the Ministry of Education of ular orbital calculation? of tropolone (I, X = H) Japan for the financial support. (8) S Katsura, K Sat6, K Akaishi T Nozoe, e1 a1 Proc J a p a n but also predicted that paminotropolone (11, X = A c a d , 27, 31, 36 (1951) INSTITUTE TETSUOSozor: NHz), which should be obtain- CHEMICAL SlfirIC€fI S R I O FACULTY OF SCIENCE able by the reduction of its T ~HOK UNIVERSITY U SEIJIEBINB azo-compound, m'ay show interesting pharmaco- SEYDAI,JAPAY St18 I16 logical properties as a precursor in vivo of p-aminoRECEIVED FEBRUARY 25, 1951 benzoic acid. We have already reported on the syntheses of I3 (independent of other three laboratories4), a-ami- ON A NEW TYPE OF AROMATIZATION BY THE O-AMINOTROPOLONE DEn~hinokitiol,~i.e., p-amino-m-isopropyltropolone DIAZOTIZATION OFRIVATIVES (111), o-bromo-p-aminotropolone6 (IV) and other Sir : various of I. We have also recently Tropolone and its allied compounds, the troposynthesized 11, a brief account of which is given loids, possess a fair degree of aromatic properties in here. Catalytic reduction of phenylazotr~polone~ (m.p. spite of the unsaturated, seven-membered ring 161-1615'; anal. Calcd. for C13H10N202:N, structure. On the other hand, i t has also been es12.39. Found: N, 12.58) or ~-tolylazotropolone3 tablished that these compounds, when heated with (m.p. 202.5-203' ; anal. Calcd. for C14H12N202: highly concentrated alkalies, undergo benzylic reN, 11.66. Found: N, 11.42) with Adams catalyst, arrangement to carboxylic acids of benzenoid series. or their reduction with sodium hydrosulfite, yields hccording to Raistrickl and Dewar,? tropolones yellow scaly crystals (11), m.p. 177-177.5'. Anal. can be taken as precursors, in vivo, of natural benCalcd. for C T H ~ O ~ C, N :61.32; H, 5.14; N ,10.21. zenoid carboxylic acids, and recently Robinson3 has Found: C, 61.09; H, 5.32; N, 10.02; yield, 30- also discussed on the assumption of a biogenetic relation between the tropolones and various alkaloids 40%. I1 is also obtained by the similar methods or anthocyanines. These certainly seem attractive from p-nitrosotr~polone~ (X = NO), charring a t 180' .(Anal. Calcd. for C7H603N: N, 9.27. suggestions but they must be confirmed by future Found: N, 9.10) in better yield (70-80%). I1 is experimental evidence. In this connection, studies on the aromatization of tropoloid series become (1) M. J. S. Dewar, N o l n r c , 166, 790 (1950). of great significance. (2) Similar calculation and measurement of dipole moments of I and Previously, we had encountered a notable fact its related compounds have already been reported: Y . Kurita, T. Nozoe and iVf. Kubo, J . C h i n . Soc. J a p a n , 71, 543 (1950); B u l l . Chcm. that when o',p-dinitro-m-isopropyltropolone is Sot. J a p a n . in press. heated with 50% aqueous ethanol for ten minutes (3) T. Nozoe, S. Seto, Y.Kitahara, M. Kunori and Y . Nakayama, a t loo', or with absolute methanol, ethanol or isoProc. J a p a n A c a d . , 26, (7)38 (1950); presented at the Annual Meeting propyl alcohol a t 50-60' for a few minutes, i t underof the Chemical Society of Japan in Kyoto, April 2, 1950. (4) W. von E . Doering and L. H. Knox, THISJOURNAL, '72, 2305 goes rearrangement to form o',p-dinitro-m-cumic (1950); J. W. Cook and A. R. Gibb, Chemistry €9 Industry, 427 (1950); acid or its respective esters quantitatively. R . D. Haworth and J . D . Hobson, ibid., 441 (1950).
Eu(I1)-Eu(II1)
TABLEI EXCHANGERATES AT 39.4",
p
= 2.0
/x-\A,o>
(5) T. Noeoe and E. Sehe, Proc. J a p a n Acad., 16, (9) 45 (1950); T. Pu'ozoe, S. Ebine, S. It8 and A . Konishi, ibid., 2'7, 10 (1951). (6) T. Nozoe, Y.Kitahara, K. Yamane and A. Yoshikoshi, ibid., 1'7, 18 (1951); T.Nozoe,S. Seto, T. Ikemi and T. Arai, ibid., 2'7, 24 (1951). (7) T. Nozoe and S. Seto, to be published soon.
(1) H. Raistrick, Proc. R o y . SOL.( L o n d o n ) , Al99, 141 (1919). (2) M. J. S. Dewar, Nature, 166, 790 (1950). (3) R. Robinson, ibid., 166, 930 (1950). (4) T. Nozoe, Science of Drugs, 8, 171 (1949) [English translation, Sci. Rep. Tohoku Uniu., I , 84, in press (196l)I.
