Reactivity of Excited States. Intramolecular Hydrogen Atom Abstraction in Substituted Butyrophenones<sup>1a</sup>

Baum, Edward; Wan, J. K. S.; Pitts, James N.

doi:10.1021/ja00964a005

Cited by 81 publications

(37 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The properties of the lowest excited triplet (T1) states of aromatic carbonyls have been the subject of numerous spectroscopic photochemical [28][29][30][31] and magnetic resonance [32][33][34][35][36][37][38][39][40][41][42] studies in recent years. In particular, properties of the aromatic carbonyls with nearby %m* and 3n~* states have attracted much attention and their spectroscopic properties and large zero-field splittings (ZFS) have been discussed in terms of vibronic and spin-orbit mixings of the 3n~r* and 3mr* states [7, 9, 13-17, 19-30, 39-45].…”

Section: Introductionmentioning

confidence: 99%

Microwave-induced delayed phosphorescence studies of the total and radiationless decay processes of³ππ* aromatic carbonyls

Harrigan

Hirota

1976

Molecular Physics

View full text Add to dashboard Cite

We have investigated the details of the radiationless decay processes of 37rTr* aromatic carbonyls of benzaldehyde type using microwave-induced delayed phosphorescence (MIDP) technique. Correlations between the decay rates from the spin sublevels and the energy separations between the 37rTr* and 3nTr* state (AETT) and those between the %r~r* and xTrTr* states (AEsT) were examined in detail for a series of systems. It is shown that the decay rates from the z and x sublevels depend on both AETT and AEsT strongly, but the y sublevel decay is independent of them. An empirical model to explain the 9 correlations among the decay rates, ZFS, AETT and AEsT is presented. It is shown that the decays from the z and x sublevels of the 3mr* aromatic carbonyls are dominantly radiationless and are primarily determined by the mixing with the lnTr* states unless AETT is very small. On the other hand, the radiationless decay from the y sublevel is likely due to the mixing with the loft* (1*to*) states. The mechanism for the radiationless decay from each spin sublevel is discussed in view of the results obtained.

show abstract

Section: Introductionmentioning

confidence: 99%

Microwave-induced delayed phosphorescence studies of the total and radiationless decay processes of³ππ* aromatic carbonyls

Harrigan

Hirota

1976

Molecular Physics

View full text Add to dashboard Cite

show abstract

“…A comparison of the photoreduction of the imine group with the extensively studied aryl ketone system could be of practical and theoretical interest. The elegant sturlies of Hammond 37 , Cohen 38 , Pitts 39 and others have indicated that intra-and intermolecular hydrogen abstraction processes in carbonyl photochemistry can be a most useful probe into the nature and reactivity of the excited state. This comparison and our interest in the chemical consequences of electronic excitation of the C-N double bond prompted a study of the photochemistry of aryl N-alkylimines.…”

Section: Introductionmentioning

confidence: 99%

“…On further irradiation (in cyclohexane) 36 and 37 are converted to triphenylpyrimidine (38) structures have been assigned as N-methoxymethyl-2,4,5-triphenyl-2,3-dihydroimidazole (39) and N -methoxymethyl-2,4,5-triphenylimidazole (40). The latter two products can be attributed to the addition of methanol to the azomethine ylide formed on irradiation of 36 ( or 37).…”

mentioning

confidence: 99%

Recent advances in the photochemistry of the carbon-nitrogen double bond

Padwa¹,

Dharan²,

Smolanoff³

et al. 1973

Pure and Applied Chemistry

View full text Add to dashboard Cite

The excited states of imines were shown nottobe reactive intermediates in the photoreduction of a series of benzaldehyde N-alkylimines. Instead, ketyl radicals were clearly implicated as the active reducing agent. These ketyl radicals were derived from carbonyl compounds present in the reaction mixture as an impurity, an added sensitizer, or as a photogenerated species. The Iack of reactivity of the excited state of simple imines suggests that the excited states undergo a very efficient non-radiative decay to ground state thereby precluding hydrogen abstraction. This facile energy deactivation is a consequence of rotation about the C-N double bond (i.e. syn-anti photoisomerization). In rigid systems, this mode of energy dissipation would not be available and these molecules would have maximum opportunity to undergo reaction from an electronically excited state.ln this regard, the photocycloaddition of arylazirenes with electron deficient olefins to give !l.' -pyrrolines has been examined in mechanistic detail. The formation of the adduct was interpreted as proceeding by way of irreversible opening of the azirene ring to form a nitrile ylide intermediate which is then trapped by a suitable dipolarophile. Irradiation of a number of substituted arylazirenes in an inert solvent gives 1,3-diazabicyclo-[3.l.O]hex-3-enes as primary photoproducts. The formation of these dimers can be rationalized by 1 ,3-dipolar addition of the initially generated nitrile ylide on to a ground state azirene molecule. Support for this conclusion was obtained by a study of the variation of the quantum yield for adduct formation as a function of the concentration of added dipolarophile. The study shows that the amount of adduct formed is dependent on the initial concentration of arylazirene and on the activity of the dipolarophile.

show abstract

“…trum m/e (re1 intensity) 163 (6), 162 (37), 147 (32), 133 (68), 119 79 (37)3 77 ( 5 5 ) 9 69 (30)9 67 ( 2 5 ) 3 65 (30)9 63 (21 1% 5 5 ( 5 6 ) 3 S3 (34)9 51 (31), 41 (IOO), 39 (50); exact mass, 162.1408 (calcd for C12Hl8: 162.1408). (1973).…”

mentioning

confidence: 99%

Photochemistry of organochalcogen compounds. 3. Photochemistry of bis(benzoylmethyl)tellurium dichloride

Marsh¹,

Chu²,

Lewicki³

et al. 1976

J. Am. Chem. Soc.

View full text Add to dashboard Cite

4,6-Diethyl-4,5-hexadien-7-yne (16a). ' H NMR (CC14) d 2.24 (m. 2 H), 1.92 (m, 6 H), 1.36 (m, 2 H), 1.20-0.72 (m, 12 H); IR (neat)(4) For a review on NMR chemical shift nonequivalence in prochiral groups, see W. B. Jennings, Chem. Rev., 75,307 (1975). (6) This compound has been prepared by derivatization of C5Li4 with dimethyl sulfate: T. L. Chwang and R . West, J. Am. Chem. Soc., 95, 3324 (1973). (7) The reported chemical shifts for compound 13 are all downfield by 0.35 ppm. This discrepancy can perhaps be explained by external Me4Si being used in ref 6. ( 5 2 ) 3 (8) This is similar to the UV spectrum of 2-methyl-2,3-heptadien-5-yne ( A, , ,220 nm in hexane); L. SkatteMl. Tetrahedron Left., 2175 (1965).(9) Similarly, J. Klein, S. Brenner, and A. Medlik, Isr. J. Chem., 9, 177 (1971), have shown that the dilithiated derivative of 5-phenyl-l-penten-4-yne reacts with alkyl halides to give exclusive formation of the unconjugated enyne iii while reaction with trimethylchlorosilane resulted in conjugated allenes as the major Droducts. i.e.. iv: 222 nm 6ooo); Inass spectrum . . Ph BaelAcknowledgment.

show abstract

Reactivity of Excited States. Intramolecular Hydrogen Atom Abstraction in Substituted Butyrophenones^1a

Cited by 81 publications

References 1 publication

Microwave-induced delayed phosphorescence studies of the total and radiationless decay processes of³ππ* aromatic carbonyls

Microwave-induced delayed phosphorescence studies of the total and radiationless decay processes of³ππ* aromatic carbonyls

Recent advances in the photochemistry of the carbon-nitrogen double bond

Photochemistry of organochalcogen compounds. 3. Photochemistry of bis(benzoylmethyl)tellurium dichloride

Contact Info

Product

Resources

About

Reactivity of Excited States. Intramolecular Hydrogen Atom Abstraction in Substituted Butyrophenones1a

Cited by 81 publications

References 1 publication

Microwave-induced delayed phosphorescence studies of the total and radiationless decay processes of3ππ* aromatic carbonyls

Microwave-induced delayed phosphorescence studies of the total and radiationless decay processes of3ππ* aromatic carbonyls

Recent advances in the photochemistry of the carbon-nitrogen double bond

Photochemistry of organochalcogen compounds. 3. Photochemistry of bis(benzoylmethyl)tellurium dichloride

Contact Info

Product

Resources

About

Reactivity of Excited States. Intramolecular Hydrogen Atom Abstraction in Substituted Butyrophenones^1a

Microwave-induced delayed phosphorescence studies of the total and radiationless decay processes of³ππ* aromatic carbonyls

Microwave-induced delayed phosphorescence studies of the total and radiationless decay processes of³ππ* aromatic carbonyls