1800
D. J . COYLI.:
THE RADIOLYSIS OF ARALKYL KETONES’ BY D. J. COYLF;~ Georgc! Ilerberl Jones Laboratory, University of Chicago, Chicago 37, Illiriois Receiued February 21, 1963 (i:i t i i i t i : i r:idiolJ.sis of t Iic nwt, degmscd kctoncs n - t ~ r ~ t y r o ~ ~ l i ~i~ s noot ~r luc~, ~ r o ~ ~ l i :ind c i i oI~~i cr ,n ~ o ~ l c ~ ~ c ~ I c r ~ ~ r ~ ~ ~ ~ ~ i n e h:is been studied \\it11 rcg:trd to vo1:itilc products. The total G-valrtcs of products volatilc a t -7s” :It 1 1 1 dos:igc ~ indicatcd were
ri-I~~ityroi~li~~nt~nc
3.90 (6.2 x 10’U e.v./g.) 2.11 ((j2 X lO‘!’c.v./g.) 0.!)7!)((!-LO X 10l!r c.v./g.)
Isvhrityro~ltrnvnc
0.100 (62.3 x 1 0 1 9 c.v./g.) .lo.+ (310 x IO’~e.v./g.)
0.723 (5.8 X 1 0 1 g e.v./g.) l i 2 7 (6.2 X 1019 c.v./g.) .591 (31.0 X 10i9e.v./g.) ,549 ( ( 2 . 2 X lotg e.v./g.) ,475 (043.0 X l o t 9e.v./g.)
.080 (545 x IOlQe.v./g.) .OS7 (616 X IO’gc.v./g.) . l o 7 (625 X I O i Q e.v./g.)
‘L’lie tnajor vol:itile 1)roduct froin n-t~utyrophcnone\vas cthylene (8875 :Lt lowest dosagc); ac:etophcnonc \vas found in the liquid plti~scin roughly comparable arnoiints. Seither of the other ketones disphyed suc*hspccific4ty of product formation. Hydrogen, carbon monoxide, propanc, and propylene werc significant produrt s froin c;ic:h of the Itctones, but in varying proportions. Hydrogen and the olefinic products exhibited decrensin: G-vdues with increasing total radiation dosage. The products were observed in cach instance to be sirnilar to those gcneratcd by photolysis with 2637-A. radiation, except for hydrogcn, which was an insignificant product froin photolysis. Froni cotii1):irison with the mass spcctr:t and photolysis data, thc tentative conclusion wus that, tlic tticch:misins for producat. foriritition during radiolysis are similar to those of photolysis. The data are not sufficient, Iiowever, to establish B particular mechanism.
Stiidics of the radiolysis of simple aliphatic kctorics have shown that tlic products are for thc most part the same as thosc generated by ultraviolct photolysis.3 T l i ~niost important exception is the formation of liydrog:.ciias a major product of radiolysis. Tlic forniation of hydrogen is iiihibitcd in many instances by thc addition of radical scavciigcrs, and it scciiis clcar that €1 atoms arc important intcrmediatcs in the radiation chemistry of organic compounds. I’rom thc standpoint of relating products to mcchaiiism, it is ricccssary to cliininate from coiisidcratioii thosc products duc to thc secondary reactions of 11 atoms. Oiic mctliod of doing this is t o provide a builtin trap for tlic H atoms in the molecule under study. Assuming that, at lcast part of the protective effect4 attributed to aromatic substaiiccs is due t o thcir affinity6 for 11 atoms, a scrics of phciiyl alkyl kctoncs was chosen for study. The kctoncs, n-butyrophcnone, isobutyrophononc, and bciizoylcyclopropane, werc sclcctcd with particular rcgsrd for the known mechanisms of photochemical dcgradation of kctoncs.6 Thus, n-but,yrophcnoiie (n-propyl phciiyl kctone) might be cxpcctcd to dccomposc by a process analogous to thc Norrisli-Baniford Type I1 (0-clcavagc) molecular dissociation to yield acetophciioiie and cthylene. Isobutyrophciione cannot rearrange in the same maniicr and consequcntly aclcavage to benzoyl and isopropyl radicals might bc cxpectcd, with thc observed products duc t o thc reactions of thcsc fragments. Although tlic mcchanism of thc photolysis of cyclopropyl ketoiics is not understood, it is clear from thc study of 13th and Yorman’ that they (1) Tliis rescurrli WBY siiiipurtod in part b y Tlic :\cr~inibritic:~IItcscnrch I.:~boriltorics of tlic Oflira of .\crospace Ilcsaarcli a t \Vriglit-l’uttcrson Air l ~ o r c vBase. Ohio, under United Statca .iir b‘vrcc Contract . i V 33(616)-3873 witli tlie University of Chic:wo. (2) l ) c t ~ ~ ~ u u r r.Jiinr l, 14. 1963. lloqiiests for reprints sliould h c sent t o tlir 1)e~iarttnant of Clierriistr~., AIatcrials Sciences Luboratvry, Aerospace Corpvratim, 1.l Srxrtndo, Calif. ( 8 ) A r e v i e w is g i r e n hy .\. .I. S\vallow, “I2:rdiotion Chemistry of Organic Coinpoiin s k y ,.I. IJIi!/.3. Chcrn., 61, 1461 (1957). ( 5 ) I
