Photoreactivity of. cap alpha. -fluorinated phenyl alkyl ketones

Journal Article · Wed Nov 26 04:00:00 EST 1986 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00284a042· OSTI ID:7202291

Wagner, P J; Thomas, M J; Puchalski, A E

The photoreactivities of the mono-, di-, and tri-..cap alpha..-fluorinated acetophenones have been compared to that of acetophenone itself. All four ketones have similar triplet excitation energies; the three fluorinated ketones have reduction potentials 0.5-0.7 eV lower than that of acetophenone. Triplet reactivity toward alkylbenzenes keeps increasing with fluorine substitution, since the rate-determining step becomes charge-transfer complexation as the ketone reduction potential decreases. The primary/tertiary C-H selectivity toward p-cymene increases with the number of fluorines. Triplet reactivity toward cyclopentane also is increased by fluorination but peaks at two fluorines, since the lowest triplet switches from n,..pi..* to ..pi..,..pi..* with two or three fluorines and ..pi..,..pi..* triplets are unreactive in simple hydrogen atom abstraction. In contrast, ..cap alpha..-fluorination of valerophenone does not significantly increase the rate of triplet ..gamma..-hydrogen abstraction. The inductive effect on reactivity apparently is offset by a conformational effect. The ..cap alpha..-fluorinated phenones give predominantly cyclobutanols instead of Norrish type II elimination. ..cap alpha..-Fluoroacetophenone forms predominantly acetophenone and HF when irradiated with 2-propanol, in what appears to be a short chain process involving electron transfer to ketone followed by fluoride ion loss. Finally, the radical coupling products in these reactions are formed in varying yields, depending on solvent and additives.

• Research Organization: Michigan State Univ., East Lansing
• OSTI ID: 7202291
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:24; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
400500* -- Photochemistry
ACETOPHENONE
ALKYLATED AROMATICS
AROMATICS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
CHEMISTRY
CUMENE
CYMENE
DATA
ELECTRON TRANSFER
EXPERIMENTAL DATA
FLUORINATED ALIPHATIC HYDROCARBONS
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROCARBONS
HYDROGEN TRANSFER
INFORMATION
KETONES
KINETICS
MULTIPLETS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC SOLVENTS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
RADICALS
REACTION KINETICS
REDUCTION
SOLVENT PROPERTIES
SOLVENTS
TOLUENE
TRIPLETS
YIELDS