The Vapor Phase Photolysis of Trifluoroacetophenone and Mixtures of

J O U R N A L OF T H E AMERICAN CHEMICAL SOCIETY (Registered in U. S. Patent Ofice)

(0 Copyright, 1966, by t h e American Chemical Society) JUNE 8, 1956

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NUMBER 11

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PHYSICAL AND INORGANIC CHEMISTRY [CONTRIBUTION FROM THE MCPHERSON CHEMICAL LABORATORY, THEOHIO STATE UNIVERSITY]

The Vapor Phase Photolysis of Trifluoroacetophenone and Mixtures of Trifluoroacetophenone and Trifluoroacetonel BY ROBERTAT. SMITH AND

JACK

G. CALVERT?

RECEIVED JANUARY 13, 1956 The gas phase photolysis of CaHsCOCFa is studied a t various temperatures, concentrations, and intensities of 3660 A,, The major gaseous products are CO, CF3H and C2F6. (C&,CO)z and C6Hs are idenlified in the condensable products. A chemically unreactive, clear polymer film formed on the reaction cell window during the photolysis. In experiments a t high absorbed light intensities, CFBHand CzF’ are formed primarily in the homogeneous reactions: CFa C‘H~COCF3 CSH C B H ~ C O C (a), F ~ and 2CF3 + CzFe (b). The activation energy difference E, - E b / 2 = 7.2 zt 0.5 kcal./mole; the ratio of collision theory P-factors P,IPb’/z is in the range 10-elO-s. A large fraction of the CF3 radicals formed photochemically do not appear in the gaseous reaction products. It is proposed that these add t o the aromatic nucleus of the parent ketone and initiate polymer formation. In the photolyses of mixtures of CsHjCOCFI and CHaCOCF3, the high temperature chain reaction of CH3COCFa involving CO and CHa-containing species is confirmed. The expected product CFBCOCFIcould not be detected in the reaction products of CH3COCF3photolyses. Thus, the previously proposed reaction sequence: CF3 4- CH3COCF3 e CH3CO(CF3b, CHsCO(CF3)2-* CHB CFaCOCFB, a m e a r s to be unimportant. The generation of CH, from CF3 radicals probably occurs by some other undefined heterogeneous path. 3130 b.,and full mercury arc light.

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This work was initiated to study the photolysis of pure CsHbCOCF3 and to determine its efficiency as a CF3 radical source in the near ultraviolet. I n view of the high extinction coefficient for C6&COCF, a t 3660 A., i t was supposed that selective photodecomposition of C6H5COCF3 in CH3COCF3 mixtures could be effected a t this wave length. If CF3 radicals could be produced in this manner, their interaction with CH3COCF3molecules could be determined to test the suggested mechanism of CH,COCF:I chain decomposition3

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CFs CHsCOCFa CHsCO(CFs)? CHjCO(CP;