Synthesis and chemistry of acyl silanes

http://www.afinitica.com/arnews/sites/default/files/techdocs/Henne%20phosphinly%20and%20phosphonateMcArdle.pdf

On the photolysis of acylphosphine oxides: 1. laser flash photolysis studies with 2,4,6- trimethylbenzoyldiphenylphosphine oxide

Localized cyclic triplet diradicals. Lifetime determination by trapping with oxygen

Preparation, properties and synthetic applications of 2h-azirines a review

Rate constants for quenching by molecular oxygen of excited singlet and triplet states, and , respectively, are reported for 12 aromatic hydrocarbons in acetonitrile. Measured values of , except in the case of fluoranthene for which = 6.6 × 109 dm3 mol-1 s-1, are in the range (2.3−4.3) × 1010 dm3 mol-1 s-1, i.e., close to 4.5 × 1010 dm3 mol-1 s-1, the average value obtained for kd, the rate constant for diffusion-controlled reactions of oxygen with aromatic hydrocarbons in acetonitrile. Values of vary from 0.24 to 5.6 × 109 dm3 mol-1 s-1. Thus, /kd was found to be less than one-ninth for 11 compounds. The efficiencies of singlet oxygen production during oxygen quenching of the excited singlet and triplet states, and , respectively, were also measured, as were the oxidation potentials of the hydrocarbons in acetonitrile. Values of were shown to be zero within experimental error for eight compounds and in the range of 0.27 ± 0.05 for the other four compounds. Three different methods, which gave good agreeme...

Charge Transfer Effects on the Efficiency of Singlet Oxygen Production Following Oxygen Quenching of Excited Singlet and Triplet States of Aromatic Hydrocarbons in Acetonitrile

Alkyl vinyl ketones have two conformations, s-cis and s-trans. The ratios of the two conformers are given by comparing their IR with NMR data. The conformer of s-cis is given by the equation, Percentage of s-cis=180. (Δδ−0.15) (%), where Δδ is the chemical shift difference between cis and trans protons for carbonyl group. The value of ΔF obtained by means of the equation is related to steric factors Esc of bearing alkyl groups. The ratio s-cis/s-trans is determined by the bulkiness of the alkyl group.

Spectroscopic Study of Alkyl Vinyl Ketones

Laser flash photolyses of (biphenyl-4-yl)chlorodiazirine (1) in 2,2,4-trimethylpentane were carried out in the presence of ethers in order to study the reaction intermediates formed from singlet carbenes and ethers. The transient species generated in the absence of ether showed an absorption maximum at 360 nm with a long life time (τ= 24.7 µs), which was assigned to singlet (biphenyl-4-yl)chlorocarbene (5). In the presence of various kinds of ethers, additional transient absorption could not be detected but the spectrum of 5(360 nm) shifted by about 15 nm to longer wavelength. The effect of ethers added to the reaction mixture was studied by means of typical singlet carbene reactions, i.e. trapping by 2,3-dimethyl-2-butene or pyridine. It was found that the rate constants of these reactions decreased by the addition of ethers and, hence, it is concluded that the reaction of 5 with ethers proceeds via oxonium glide intermediate 7. By changing the concentration of tetrahydrofuran (THF), the equilibrium constant of the reaction (5 + THF ⇌ oxonium glide) was determined to be 0.5 dm3 mol–1 at 293 K in 2,2,4-trimethylpentane (i-Oc).

Formation of oxonium ylide evidenced by the laser flash photolysis of (biphenyl-4-yl)chlorodiazirine in ethers

Laser flash photolysis of 3-(4-biphenylyl)-2H-azirine (AZ) was carried out in cyclohexane for the direct detection of a nitrile ylide (NY). Two kinds of transient species, triplet AZ (T1) and NY, have been measured. Decay rates of these species were determined to be 6.7×105 s−1 (T1) and 8×10 s−1 (NY). The rate constants for the reactions of NY toward acetone and acrylonitrile were determined to be 2.5×103 dm3 mol−1 s−1 and 2.3×106 dm3 mol−1 s−1, respectively. These results were supported by the results of pulse radiolysis of AZ in benzene and stational irradiations of AZ.

Photochemistry of 2H-Azirine—Formation of Nitrile Ylide Evidenced by Laser Flash Photolysis and Pulse Radiolysis—

Laser flash photolysis studies on homo-and copolymers of phenylisopropenyl ketone and of pivalophenone in solution

The laser-flash photolysis of propanone, butanone, and 2-pentanone were carried out in dichloromethane (265 nm, 15 ns flash duration). The emission spectra (fluorescence, phosphorescence, and P-type delayed fluorescence) and the transient absorption spectra (triplet state and acetyl radical) were recorded. From the decays of the emission and the absorption, the unimolecular (triplet decay) and bimolecular (T–T annihilation and self quenching) reaction-rate constants were determined. Oxygen quenched the triplet states with a diffusion-controlled rate constant (kO2=ca. 3×10 dm3mol−1 s−1).

Ikuo Naito

Papers

Spectroscopic Study of Alkyl Vinyl Ketones

Formation of oxonium ylide evidenced by the laser flash photolysis of (biphenyl-4-yl)chlorodiazirine in ethers

Photochemistry of 2H-Azirine—Formation of Nitrile Ylide Evidenced by Laser Flash Photolysis and Pulse Radiolysis—

Laser flash photolysis studies on homo-and copolymers of phenylisopropenyl ketone and of pivalophenone in solution

The Laser-flash Photolysis of Propanone, Butanone, and 2-Pentanone. Study of Triplet Decay Processes in Aliphatic Carbonyl Compounds