Sept., 1963
RIECHANISM O F
RADIOLYSIS O F O L E F T S IS P.4HAFFIN
Before the onset of multilaycr formation, the individid isotlicrrn tends toward the inonolaycr value for
adsorption from carbon tctmchloride, but less readily for adsorption from cyclohcxane. The sharp rise in tlic isot~irrmoccurs approximately at the concentrations at which rnoiiolayrr forinat ion is oomplctc (I'ig. G and 7).
SOLUTION
1793
A comparison of adsorption from these and other related systems will be published in a subsequent paper. Acknowledgments.-We are grateful to the Cabot Corporati011 for the gift of the adsorbents7 and to Dr. G. W. Gray for help with the infrared spectra.
ILIE('I1ANTSJI O F RADIOLYSIS OF OLEFIN I N PARAFFIN SOLUTION. 1 -1'ENTENE I N ~ L - I ~ U T A N E BY C. D. WAGNER Shell Development Company, Emeryvilk, California Received February 8, 1963 I)etai!ed exnmination of products of radiolysis of a 0.5 Af solution of 1-pentene in butane confirm that most of the ole!in rewts by addition of a hydrogen atorn. The remainder reacts by hydrogen abstraction from allylic positions by hydrogen atoms and by a variety of unknown energy trangfer or charge transfer mechanisms.
It is well e~tablishedl-~ that olefins in dilute solution in paraffins are liigtily reactive under ionizing radiation, and participate i n forming the heavy products. 1;rorn a detailed examination of the effect of olefin conccntratiori on hydrogen evoluticn, I-Iardwick2 concludcd that, olefins react with hydrogen atoms generated from the alkane radiolysis. With no olcfin prcscnt, the hydrogen atoms from reaction 1, with butanc as an example CAFI1" +C4H9 *
+H
*
(1)
would abstract hydrogen from another butane molecule
H. Iii
+ c4Irl0 +c ~ H + ~ .H~
(2)
t,he presence of olefin, e.g., pentene, reaction 2 is
par1Iy replaced by
13.
11.
+ C61110 +C6HIl.
+ C61110 +C5H9* + Hz
(3) (4)
Reaction 3 results in the observed diminution of hydrogen yield. Iicactioii 4 leads to the observed formation of unsaturated hcavy products. While this set of rcmtions accounts for the disappearance of tlic hydrogcii atoms, it does not account for the disappearaiice of all of the olefin in dilutc paraffin solution. Tlic G-\ralue for hexerie formation in n-hexane was obser\wiZdto be 3.30, t,hat for lighter olefins is about 0.3,21'a i d thc C-\.aluc for hydrogen atom formation is 3.16,*ci Ohviously, tlie yield of hydrogen atoms is ins~ifricicnt,to result i i i a steady-state olefin concentration i n tlic systcrn as ii-radiatioii progresses. Yet Hardwick21, ot)scrvcd t,liat a t Iiigh dose rates the rate of formatioil of total licxriics was zcro at a 1-hexcne conccntration of' only 0.1 Ill. I'icwiiig it in another way, if we accept this stcadystate conaentration and t l i c ? reaction rate constants for hydrogen atoms with hexane and 1hexcnc (h,k n , and 1c4 of 4.9 X IOfi,8 X lo8, and 4 X (1) C. l?U.ugner, .I. f'h!is. Chem., 64, 231 (1960). (2) (a) T.J. liardwick, ibid.. 64, 1023 (1960); ( b ) i t i d . , 66, 101 (1961); (c) ibid., 66, 291 ( 1 0 6 2 ) ; (d) ibid., 66, 1611 (1962). (3) N. A . I k 4 i k o w , V. G. Ihxwkin, a n d I,. S. l'dak, .Yr/Lekhimi?/a [el, 828 (1901).
(4) It. A. IIolroyd a n d G. W. Klein, Intern. J. A p p l . R a d i a t i o n Jsolopes, 13. 493 (1962).
1oB l./mole sec., respectivcly), the yield balance at steady state is given by
where G, represents C-value for olefin formation and C, represents G for unknown processes of reactions of olefins (mainly 1-hexenc). From this it is calculated that at 0.1 1l.i hcxeiie about six-tenths of the olefin consumed is reacting with hydragcn atoms and about four-tenths by unknown processes. In order to explore this point further, a 0.54 dd solution of 1-pcntene in n-butane was used. This facilitated the interprctation, because the origins of the products are more clearly traced. Experimental Materials.-n-Butane was Phillips Research Grade, further treated b y hydrogenation over platinum on silica gel a t 75" and An:tlysis b y gas distilled several times i n vacuo from -78'. chromatography showed i t to cont:tin 0.15% isobutane and
