(Table I) than when it is induced by the He3(n,p)H3 process. This seems to indicate that the mechanisms are different. I n the He3(n,p)H3case the formation of each carbon chain presumably is initiated by attack of a tritium ion on a CH4molecule. The many products formed in these reactions offer a valuable source of high specific activity labelled compounds when these non-parent “byproducts” can be separated in carrier-free form by gas chromatography or otherwise. This work was supported in part by the Atomic Energy Commission and in part by the Wisconsin Alumni Research Foundation.
amount of HT. ‘The addition of 0.2 mm. of iodine as a radical scavenger has little effect on the yield of CH3T but virtually eliminates the yield of higher labeled hydrocarbons and reduces the yield of HT. Studies on the slowing of charged particles passing through matter3 indicate that the tritium is uncharged on reaching its final reaction site. Taking this into account, our observations suggest two distinct modes of reaction of the tritium atom: (A) Most tritium combines by direct hot replacement reaction. For methane
+ CHI +CHaT -+ H T* + CHI +HT + CH3
T*
DEPARTMEST O F CHEMISTRY ROLLAND W. AHRENS UVIVERSITV OF WISCONSIN MYRANC. SAUER, JR. MADISON, WISCONSIN JOHS E. WILLARD Radical intermediates are definitely ruled out and RECEIVED APRIL8. 1957 Mralden inversion probably is involved. (B) Some
tritium escapes incorporation in stable molecules by hot reaction and becomes thermalized. Its reactions CHEMICAL REACTION OF RECOIL TRITIUM WITH then become sensitive to radical scavengers, such as 12. In their absence the tritium can react comGASEOUS ALKANES’ petitively to (1) abstract H to form part of the HT Sir: observed, or ( 2 ) combine with radiation produced lye have studied the reaction of high energy radicals or ions to form the higher labeled hydrotritium, as produced by nuclear reaction, with carbons. (Production of the latter probably ingaseous methane and ethane. The reactions volves hydrocarbon chains lengthened by ion moleHe3(n,p)H3 (0.78 Mev.) and Li6 (n,a)H3 (4.7 cule reaction^.^) Mev.) were used to supply the “hot” tritium. I n The results observed with ethane are consistent the He3 runs about 0.1 cm. He3 was sealed with 10- with this picture. Most of the activity appears in GO cm. CH4 in a 7 ml. quartz ampoule. In the H T and CzHjT with smaller amounts in CH3T and Li6runs a film of normal lithium nitrate formed the higher hydrocarbons. Only C3 and higher hydroinside coating of similar vessels. After irradiation carbons are eliminated by Iz. This means that in the Brookhaven reactor, carriers were added and degradation products such as CHIT from ethane the various tritium labeled species separated and are largely formed by direct hot replacement recounted, largely as described elsewhere.2 actions (type A). A summary of some of our results on the chemical I t has been demonstrated that neither radical state of the tritium following interaction with intermediates nor a solvent cage, the central conmethane is shown in Table I. This distribution of cepts of earlier theories of hot-atom reactions,6are necessary for hot reaction of hydrogen. lyhether TABLE I the reaction model postulated here holds also for recoil tritium reactions in the condensed phase reCHEMICAL STATEOF RECOILTRITIUM STOPPED IN METHASE mains to be seen. The similar product distribuExpressed as 70of total gaseous activity in absence of IZ tions in gaseous and liquid2 alkanes are suggestive. -Irradiation conditions1012.6 109.8 109.3 But the retention of configuration observed in the neutrons neutrons neutrons solid phase6would require further explanation. cm. --I sec. -1, cm. -2 sec. - 1 , cm. - 2 sec. -*,
-
Chemical state
I3T CHBT C2HsT C~HIT C3fT) hydrocarbons Higher tritiated hydrocarbons and iodides
+
no I2 present
no 1% present
11 pres-
50.6 30.9 8 2 5.0
61.9 29.1 2.9 2.4
29.8 26 0 0.1 0.2
5.3
3 7
43 9
en t
activity is independent of the source of the tritium, the pressure and the temperature (range 30200”). However, a drastic reduction of neutron flux, with accompanying decrease in radiation density, although having little effect on the production of CHBT,seems to reduce significantly tlie yields of labeled higher hydrocarbons while increasing the (1) Research supported $y t h e Atomic Energy Commission. See also accompanying communication by Cordus, Sauer and Willard, 1, 3284. ( 2 ) \Volf:nng, Erp-nel and Rowland, J Phys C k i , m . , 6 0 , 1137 (1956)
(3) S. K. Allison and S. D. Warshaw, Rev. M o d . P h s , 25, 779 (1953). ( 4 ) hleisels, Hamill and Williams, J. Chem. P h y s . , 25, 790 ( l ( J 5 7 ) . ( 5 ) J. Willard, Apin. Rev. X ‘ I L CSci., . 3, 193 (1953). ( 6 ) Rowland, Turton and Wolfgang, TEIISJ O U R N A L , 78, 2351 (1958); F. S. Kowland, prioate communication.
CHEMISTRY D E P A R T X E N T S BROOKHAVES NATIONSL LABOR.4TORV YORK ~ T O S T A F A FAHMIAMR EL SAVED FLORIDA STATEUNIVERSITY TALLAHASSEE, FLORIDA RICHARD WOLFGANG YALEUSIVERSITY KEW HAVEN,CONSECTICUT RECEIVED APRIL 22, 1957 U P T O N , NEW
DEGRADATION OF BRAIN GANGLIOSIDE TO GLUC0CEREBROSIDE Sir :
Since Klenk first described the brain gangliosides,‘ evidence has been presented that they arc (1) lT Klenk,
I: ph3szol L h e i n , 273, 76 (lYd?)
