Showing papers on "Benzophenone published in 1973"

Reactivity of co-ordinated ligands. Part XV. Formation of complexes containing Group V donor atoms and metal–carbon σ-bonds

Abstract: The reactions of various palladium(II) and platinum(II) species with a number of ligands which may function as electron pair donors while simultaneously forming metal–carbon σ-bonds have been examined. Compounds containing metal–carbon σ-bonds have been obtained for NN-2-trimethylbenzylamine, N-benzylpiperid-4-one, 1-phenyl-NN-dimethylcyclohexylamine, triphenylmethylamine, N-methyltriphenylmethylamine, benzophenone phenylhydrazone, and benzo[h]quinoline. Various substitution and displacement reactions of some similar derivatives have also been examined.

Benzophenone Triplet: a New Photochemical Probe of Biological Ligand-Receptor Interactions

Abstract: PHOTO-GENERATED reagents for the covalent labelling of biological binding sites have recently been reviewed1 In principle, a photochemically activated functional group is incorporated into a biological ligand by synthesis Photolysis of this functional group while the ligand is bound to its receptor covalently links ligand and receptor allowing subsequent precise chemical location of the binding site without danger of dissociating the ligand-receptor complex A “photo-affinity probe”2 is inert until photolysis and can be directed to the receptor site of interest while still inert, unlike most chemical affinity probes which may react nonspecifically at other sites Requirements for successful photo-affinity probes include chemical stability before photolysis, chemical inertness of the activated probe to reaction with water, and negligible loss of the activated probe to rearrangement or intramolecular reaction1 These requirements are well met by aromatic ketones such as benzophenone whose triplet state apparently does not react with water, does not rearrange or react intramolecularly, and is easily generated at long wavelengths (> 320 nm)

Photopolymerizable compositions comprising polycarboxysubstituted benzophenone reaction products

Abstract: Compounds containing a benzophenone or a substituted benzophenone moiety are (a) autophotopolymerizable, (b) photopolymerizable in compositions with another photoinitiator, and (c) photoinitiating in compositions with another photopolymerizable material

Static and dynamic paramagnetism of the undistorted triplet state of benzophenone

Abstract: Existing discrepancies in reports of the EPR fine structure of triplet traps in uv‐excited benzophenone are clarified by studies of the population kinetics and the EPR of triplet benzophenone‐h10 in crystals of deuterobenzophenone. Benzophenone‐h10 provides a triplet trap of depth ≈30 cm−1 below the triplet exciton band of the deuterobenzophenone host and phosphoresces copiously at liquid helium temperatures. In deuterated crystals containing 1 mole% benzopheone‐h10, only the phosphorescence of ordinary benzophenone is detectible below 4.2°K; the quantum yield is 42%. The ordinary benzophenone traps are shown to have the same conformation as the triplet molecules formed by direct T1←S0 absorption and the molecules responsible for the excitonic phosphorescence of ordinary benzophenone crystals. The traps earlier reported by Sharnoff are shown to have nearly this conformation. The triplet states of the traps reported by Chan, Schmidt, Veeman, and van der Waals and by Winscom and Maki are shown not to have t...

Ketyl radicals in aqueous solution pulse radiolysis study

Abstract: The absorption spectra, extinction coefficients and acid dissociation constants of the ketyl radicals of benzophenone, acetophenone and its p-fluoro-, p-chloro-, p-bromo- and p-nitro-derivatives have been determined by pulse radiolysis. Rate constants for electron transfer from some simple organic radicals to the phenones were determined in alkaline solution. Studies with p-nitroacetophenone in neutral and alkaline solution show that both electron transfer and radical addition can take place, the relative proportion depending upon the structure of the radical.

Mechanism of reaction of carbon monoxide with phenyllithium

Abstract: The product mixtures obtained by reaction between phenyllithium and carbon monoxide in diethyl ether, followed by hydrolysis, include benzophenone (1). a,a-diphenylacetophenone (2), benzil (3), a,a-diphenyl- a-hydroxyacetophenone (4), benzpinacot (5), a-hydroxyacetophenone (6), 1,3,3-triphenylpropane-1,2-dione (7), 1,3,3-triphenylpropan-1-one-2,3-diol (8). and benzhydrol (9). Compounds 1, 2, 6,7, and 8 are produced in signifi- cant yields i 3,4,5, and 9 are produced in trace quantities. Spectroscopic studies establish dilithium benzophenone dianion (18) as the first long-lived intermediate formed in this reaction; qualitative correlations between the basicity of a number of organolithium reagents and their reactivity toward carbon monoxide suggests, but does not prove, that benzoyllithium is a precursor of 18. Labeling experiments indicate that the products ultimately isolated following hydrolysis of the reaction mixture are derived from at least two pathways which compete for the initially formed 18. One involves combination of l8 with 1 equiv of phenyllithium and 1 equiv of carbon monoxide, followed by elimination of I equiv of lithium oxide. yielding 17, the lithium enolate of 2; a second involves com- bination of 18 with 1 equiv of phenyllithium and 2 equiv of carbon monoxide. yielding 22,the trilithium trianion of 8. Hydrolysis of l7 yields 2 directly. Hydrolysis of 22 yields 8; reverse aldol reactions involving 8 or its pre- cursors generate 1 and 6. The mechanism proposed to account for the major products of the reaction of phenyl- lithium and carbon monoxide is outlined in Scheme III" On the basis of this scheme, plausible paths to the minor products of the reaction are proposed.

Molecular dynamics of the supercooled liquid state. Low frequency dielectric relaxation of benzophenone, cyclohexanone and fenchone in o-terphenyl

Abstract: A detailed study of the low frequency dielectric relaxation of dilute solutions of benzophenone, cyclohexanone and fenchone in o-terphenyl in the supercooled liquid state shows (i) that only a part of µ2 is relaxed by the low frequency cooperative process (ii) the cooperative process is quantitatively similar in frequency/temperature location and shape to that observed for anthrone, phthalic anhydride and camphor in o-terphenyl, (iii) the shape of the dielectric loss curves may be represented by the Williams–Watts empirical relaxation function and (iv) that the defect diffusion model for cooperative relaxation proposed by Phillips, Barlow and Lamb gives a quantitative representation of the derived experimental dipole correlation function for benzophenone, and is also fairly satisfactory for cyclohexanone and fenchone.

Electrochemical Reactions of Organic Compounds in Liquid Ammonia. I. Reduction of Benzophenone

Abstract: The electroreduction of benzophenone in liquid ammonia was studied by cyclic voltammetry. In anhydrous solutions, the reduction occurs in two reversible one-electron steps producing the anion radical and the dianion. In the presence of alcohol, the first reduction is unaffected and the second reduction wave becomes irreversible and is shifted toward positive potentials, following qualitatively the criteria for a rapid reaction of the dianion with the proton donor. iquid ammonia is an amphiprotic, very weakly L acidic, slightly ionized solvent in which solvated electrons are stable. Its unique properties have been exploited by organic chemists to achieve numerous reductions of unsaturated compounds by alkali metals dissolved in liquid ammonia. * The overall reaction can be written NH8 R + 2M + 2 H A + R H z + 2M+ + 2A(1) where R is the reducible compound, M the alkali metal, and HA a proton source (generally an alcohol) and is known as the Birch reduction in the case of the aromatic hydrocarbons or simply reduction by dissolved metals for the other compounds. The overall reaction shown in eq 1 occurs in several steps. It is generally accepted2 that the first step is the formation of solvated electrons followed by the reversible reaction of these to produce anion radicals.

Configuration and stereochemistry of photoproducts by application of the nuclear Overhauser effect. Adducts of benzophenone with methyl-substituted furans and 2,5-dimethylthiophen, and of methyl-substituted maleic anhydrides with thiophen and its methyl derivatives, and benzo-[b]thiophen

Abstract: The configurations and the stereochemistry of two series of photocycloaddition products have been elucidated by means of 1H n.m.r. spectroscopy including intramolecular internuclear Overhauser effect measurements. The first series consists of the oxetans (3)–(6) obtained by photoreactions of benzophenone with 3- and 2-methylfuran (1a and b). furfuryl alcohol (1c), 2,3-dimethylfuran (1d), and 2,5-dimethylthiophen (1e). The second series includes photocycloaddition products (9)–(18) formed in reactions of methyl-substituted maleic anhydrides (8a and b) with thiophen (7a), methylthiophens (7b–d), and benzo[b] thiophen (15).

Mechanism of the benzophenone‐sensitized photodegradation of polypropylene

Abstract: The photodegradation of polypropylene sensitized by benzophenone has been studied under accelerated light-aging conditions using a Xenotest 150. Degradation of the polymer and consumption of the benzophenone was monitored by infrared spectroscopy. The results indicate that hydrogen stom abstraction from the polymer, by photo-excited benzophenone, is the major primary process in the mechanism of sensitized photodegradation.

The benzoyl cation: The participation of isolated electronic excited states in the dissociation of molecular ions of the form [C6H5COX]+˙

Abstract: The heat of formation of the benzoyl cation generated from [C6H5COX]+˙ is found to depend on X, while the heat of formation of the phenyl ion produced therefrom is, with one exception, independent of X. The excess energy of the benzoyl cation can be accounted for by an electronic excited state of the ion in the mass spectra of benzoic acid, benzaldehyde, benzamide, methyl benzoate and possibly benzophenone; the benzoyl cation is not excited in the mass spectra of acetophenone and benzoyl chloride.

A Study on the Photochemistry of α,β-Unsaturated γ-Lactones. II. Photoisomerization of 3-Ethylidene-4,5-dihydro-2(3H)-furanone

Abstract: On irradiation of cis-3-ethylidene-4,5-dihydro-2(3H)-furanone with 2537 A light, both the cis-trans isomerization of the exocyclic double bond and transformation into the β,γ-unsaturated isomer, 3-vinyl-4,5-dihydro-2(3H)-furanone, were observed. By the use of sensitizers such as acetone, acetophenone, p-methoxyacetophenone and benzophenone, it was possible to induce cis-trans isomerization exclusively. On the basis of the solvent effect and the wavelength dependence of the reactions, transformation into the β, γ-unsaturated isomer and cis-trans isomerization were suggested to proceed via T2(n,π*) and T1(n,π) states, respectively.

Photopolymerizable compositions comprising benzophenone reaction products

Abstract: Compounds containing a benzophenone or a substituted benzophenone moiety are (a) autophotopolymerizable, (b) photopolymerizable in compositions with another photoinitiator, or (c) photoinitiating in compositions with another photopolymerizable material.