Flash photolysis of an ortho-alkyl-benzophenone

Porter, George; Tchir, Morris F.

doi:10.1039/c29700001372

Cited by 39 publications

(26 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Table 1 shows quenching rate constants for several quenchers. These values are comparable to those reported for the quenching of the vinylketene 8 (10,48).…”

Section: B) I~ltertnoleculai-reactivitysupporting

confidence: 77%

See 1 more Smart Citation

Laser flash photolysis study of the photochemistry of ortho-benzoylbenzaldehyde

Netto‐Ferreira¹,

Scaiano²

1993

Can. J. Chem.

View full text Add to dashboard Cite

. Ketene-enols 4 and 5 have been generated by laser flash photolysis of or-tho-benzoylbenzaldehytle (3) and kinetically and spectroscopically characterized. In benzene or acetonitrile, the E ketene-enol, 4, shows absorption at 340 and 400 nm and a lifetime in excess of 1 ms, whereas the Z ketene-enol, 5 , shows maxima at 360 and 430 nrn and a lifeti~iie of only 1.5 ks. At shorter time scales we observed a weak absorption (A,,,;,, = 580 nm) tentatively assigned to biradical 6 with a lifetime of 140 ns. The E ketene-enol is readily quenched by oxygen, dienophiles, methanol, and water, with quenching rate constants ranging from 3.6 x I O M~. ' s ' (for methanol as a quencher) to 2.2 x 10' M ' s-.' (for diethyl ketomalonate). At high water concentrations (typically > 10 M) a new species, 7 , was detected showing maximum absorption at 5 10 nm and a growth lifetime of 7 ks. In deuterated water and using the same concentration as before we observed a formation lifetime for 7 of 10 ks, which results in an isotope effect of -1.5. It is proposed that 5 is the main precursor for 7 . Steady-state irradiation of 3 in deaerated methanol leads to the formation of dihydroanthraquinone (9). a strongly colored and fluorescent (A,,,,, = 475 nm. T , = 29 ns) species, whereas 3-phenylphthalide (2, R = Ph) is the main product when the irradiation is performed in benzene. Steady-state quenching of product formation by diethyl ketomalonate gives a Stern-Volmer constant of 380 M-' from which we conclude that 5 is the ketene-enol responsible for product formation, in agreement with the laser flash photolysis results. . L'irradiation a I'dtat stationnaire du compose 3 dans le methanol desaCr6 conduit a la formation de la dihydroanthraquinone (9), un composk fortement color6 et fluorescent (A,,,:,, = 475 nm, 7" = 20 ns) tandis que le phthalide de phCnyl-3 (2. R = Ph) est le produit majoritaire lorsque I'irradiation a lieu dans le benzene. Le blocage i I'etat stationnaire des produits obtenus B partir du cdtornalonate d'dthyle donne une constante de Stern-Volmer de 380 M-' qui nous porte B conclure que le composd 5 est le cdtkne-en01 responsable de la for~iiation des produits en accord avec les resultats de la photolyse flash au laser.[Traduit par la rCdaction]

show abstract

“…Table 1 shows quenching rate constants for several quenchers. These values are comparable to those reported for the quenching of the vinylketene 8 (10,48).…”

Section: B) I~ltertnoleculai-reactivitysupporting

confidence: 77%

“…. process (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). diforrnylpyridines (27), 2,3-diforrnylquinolines (27), and 2.3-…”

Section: 6 ~S )mentioning

confidence: 99%

Laser flash photolysis study of the photochemistry of ortho-benzoylbenzaldehyde

Netto‐Ferreira¹,

Scaiano²

1993

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…Similar results were reported for 4'-substituted ketone 3 (21). Long-lived transients have been observed from several di-and trialkylbenzophenones but these have not been conclusively identified (8,9,22). The triplet state of 2,4,6-trimethylacetophenone (4) has been suggested to be relatively long-lived (ca.…”

Section: Introductionsupporting

confidence: 75%

Laser flash photolysis studies of 2,4,6-trialkylphenyl ketones

Guérin¹,

Johnston²

1989

Can. J. Chem.

View full text Add to dashboard Cite

. 67, 473 (1989).2,4,6-Triisopropylbenzophenone (3), 2,4,6-trimethylbenzophenone (4), and 2,4,6-trimethylacetophenonc (5) have been examined by laser flash photolysis. Relatively long-lived triplets compared to similar mono-alkyl substituted ketones have been observed for each (280 ns, >2 ps and 220 ns in acetronitrile for 3, 4 and 5, respectively). Photoenol intermediates with A, , , 360 nm and 380 nm were also observed from ketones 3 and 5, respectively. Ketone 3 yielded a mixture of approximately equal amounts of Zand E enols in hexane. The Zen01 had a lifetime of -4 ps while the E en01 did not decay appreciably during 100 ps. Biradical intermediates were not observed from any of the three ketones. Quenching rate constants for several energy transfer and hydrogen donor substrates are reported. For example, ketones 3 and 4 react with 1,4-cyclohexadiene with rate constants of 2.8 x lo7 and 3.7 x lo7 M-Is-', respectively, to yield ketyl radicals with A,,,, -480 nm.

show abstract

“…[72] Forawhile,t heir combination with controlled polymerization methods other than radical polymerization was prevented for synthetic reasons,mainly because of the incompatibility of the functionalization of conventional chain ends encountered in ROP, for example,with alarge range of dienes and dienophiles as well as the lack of mild reactions for the deprotection of the reactive moieties. [88] Theas-generated photoenol is ah ighly reactive diene which can readily,q uantita-tively,a nd rapidly react with an electron-deficient dienophile. [78] Thep olymers were prepared by organocatalyzed-ROPo ft he corresponding lactone monomers,t hat is, lactide (LA) and e-caprolactone (e-CL), and subsequent functionalization of the end groups.I rradiation of adilute solution of the linear precursors (25 mg L À1 ) overnight with UV light at ambient temperature led to cyclo-PLA and cyclo-PCL with very high purities (> 95 %), as confirmed by the nearly quantitative disappearance of the reactive moieties in the 1 HNMR spectra as well as very clear shifts of the molecular-weight distributions observed in SEC experiments.…”

Section: Angewandte Chemiementioning

confidence: 99%

Cyclic Polymers by Ring‐Closure Strategies

et al. 2016

View full text Add to dashboard Cite

The preparation of cyclic macromolecules has always represented a challenging task for polymer science, mainly because of difficulties in connecting chain extremities together. Initiated by the pioneering studies of Jacobson and Stockmayer, preparative pathways to cyclic polymers have been considerably improved within the last two decades thanks to the advent of both controlled polymerizations and efficient coupling reactions in organic chemistry. This Review aims to provide a critical up-to-date overview and illustrate the considerable efforts that have been made in the past few years to improve the availability of macrocycles for industrial and academic investigations through the use of the ring-closure approach. Particular attention is paid to methods for the preparation of monocycles over more complex architectures, since the latter are usually derived from the former.

show abstract

Flash photolysis of an ortho-alkyl-benzophenone

Cited by 39 publications

References 0 publications

Laser flash photolysis study of the photochemistry of ortho-benzoylbenzaldehyde

Laser flash photolysis study of the photochemistry of ortho-benzoylbenzaldehyde

Laser flash photolysis studies of 2,4,6-trialkylphenyl ketones

Cyclic Polymers by Ring‐Closure Strategies

Contact Info

Product

Resources

About