scholarly journals Sunscreen-Assisted Selective Photochemical Transformations

Molecules ◽  
2020 ◽  
Vol 25 (9) ◽  
pp. 2125
Author(s):  
Or Eivgi ◽  
N. Gabriel Lemcoff
Keyword(s):  
Photochemical Reaction ◽  
Reaction Pathway ◽  
General Procedure ◽  
Molar Absorptivity ◽  
Photochemical Reactions ◽  
The Other ◽  
Protecting Group ◽  
Selective Reaction ◽  
Photochemical Transformations ◽  
Photolabile Protecting Group

In this review, we describe a simple and general procedure to accomplish selective photochemical reaction sequences for two chromophores that are responsive to similar light frequencies. The essence of the method is based on the exploitation of differences in the molar absorptivity at certain wavelengths of the photosensitive groups, which is enhanced by utilizing light-absorbing auxiliary filter molecules, or “sunscreens”. Thus, the filter molecule hinders the reaction pathway of the least absorbing molecule or group, allowing for the selective reaction of the other. The method was applied to various photochemical reactions, from photolabile protecting group removal to catalytic photoinduced olefin metathesis in different wavelengths and using different sunscreen molecules. Additionally, the sunscreens were shown to be effective also when applied externally to the reaction mixture, avoiding any potential chemical interactions between sunscreen and substrates and circumventing the need to remove the light-filtering molecules from the reaction mixture, adding to the simplicity and generality of the method.

scholarly journals Laser-Induced Photochemical Reaction of Maleic Acid Solutions in the Presence of Hydrogen Peroxide

1997 ◽  
Vol 17 (2) ◽  
pp. 97-108 ◽  
Author(s):  
Yuichi Shimizu ◽  
Shun'ichi Sugimoto ◽  
Shunichi Kawanishi ◽  
Nobutake Suzuki
Keyword(s):  
Hydrogen Peroxide ◽  
Maleic Acid ◽  
Photochemical Reaction ◽  
Room Temperature ◽  
Direct Synthesis ◽  
Reaction Scheme ◽  
Photochemical Reactions ◽  
The Other ◽  
Acid Solutions ◽  
Selective Formation

Targeting the selective and direct synthesis of tartaric acid (TA), the photochemical reactions of maleic acid (MA) solutions containing H2O2. in various solvents have been investigated using four wavelengths in the UV region between 193 and 351 nm, with high intensity from an excimer laser. All the laser irradiations in H2O resulted in the direct synthesis of TA with lower selectivity and it was found that, with XeF-laser (351 nm) irradiation in 1,4-dioxane, TA is selectively and directly synthesized from MA containing H2O2 of lower concentration at room temperature. On the other hand, none of the irradiations in methanol, N,N-dimethylformamide, acetonitrile, and tetrahydrofuran gave the selective formation of TA. On the basis of these results, the reaction scheme for the selective formation of TA is discussed.

Photochemical Reactions of Bromoanthracenes with N,N-Dimethylaniline in Solution

1981 ◽  
Vol 36 (7) ◽  
pp. 846-851 ◽  
Author(s):  
Jan Fulara ◽  
Tadeusz Latowski
Keyword(s):  
Photochemical Reaction ◽  
Photochemical Reactions ◽  
Medium Effect ◽  
Reaction Products ◽  
Photochemical Transformations

AbstractMajor products of the photolysis of 9-bromoanthracene and 9,10-dibromoanthracene in benzene and acetonitrile as well as photochemical reaction products of the two bromoanthracenes with N,N-dimethylaniline in these solvents have been isolated and identified. The mechanisms of partial reactions are discussed and attention is paid to the medium effect on the photochemical transformations.

Photochemical reactions of bacteriorhodopsin in Triton X-100 solution studied by low temperature spectrophotometry

1985 ◽  
Vol 63 (7) ◽  
pp. 1891-1898 ◽  
Author(s):  
Tatsuo Iwasa ◽  
Fumio Tokunaga ◽  
Tỏru Yoshizawa
Keyword(s):  
Low Temperature ◽  
Thermal Equilibrium ◽  
Photochemical Reaction ◽  
Membrane Structure ◽  
Purple Membrane ◽  
Photochemical Reactions ◽  
The Other ◽  
Other Hand ◽  
Triton X

The photochemical reaction of purple membrane solubilized with Triton X-100 (T-BR) was investigated by low temperature spectrophotometry. The batho- and meta-intermediates of T-BR were observed to resemble bacteriorhodopsin in native purple membrane. Two photoproducts characteristic of the T-BR system were found, which were named the "490-nm complex" and the "380-nm complex". The 490-nm complex was in thermal equilibrium with T-BR in the dark. Cooling T-BR to low temperature favoured the 490-nm complex, which was photoinsensitive. On the other hand, the 380-nm complex was produced by warming the batho-intermediate and reverted to the original T-BR. The meta-intermediate of T-BR may possibly be in thermal equilibrium with the 380-nm complex. On the basis of the above results, the possible role of the membrane structure was discussed

Paraquat (Methylviologen): Its Interference with Primary Photochemical Reactions

1993 ◽  
Vol 48 (3-4) ◽  
pp. 374-378 ◽  
Author(s):  
Tetsuo Hiyama ◽  
Akira Ohinata ◽  
Shin-ichi Kobayashi
Keyword(s):  
Reaction Center ◽  
Electron Donor ◽  
Photosystem I ◽  
Photochemical Reaction ◽  
Photochemical Reactions ◽  
The Other ◽  
Primary Photochemical Reaction

Paraquat(methylviologen), a widely used nonspecific herbicide, is ptoreduced in the primary photochemical reaction of photosystemI. Using two types of the photosystem I reaction center preparations, i.e. one with FeSA/FeSB and the other without, the immediate electron donor to methylviologen was determined to be FeSx (P430) rather than FeSA/FeSB.

One-electron photooxidation of N-ethylcarbazole in the presence of carbon tetrachloride. Products and mechanism of the photochemical reaction

1985 ◽  
Vol 63 (7) ◽  
pp. 1654-1665 ◽  
Author(s):  
Bogumil Zelent ◽  
Gilles Durocher
Keyword(s):  
Carbon Tetrachloride ◽  
Photochemical Reaction ◽  
Reaction Medium ◽  
Chloride Ion ◽  
Photochemical Reactions ◽  
The Other ◽  
Main Process ◽  
Reaction Products ◽  
Solvent Cage ◽  
Ct Complex

The mechanism of the photodecomposition of N-ethylcarbazole (NEC) in the presence of carbon tetrachloride has been discussed on the basis of the photoproducts identified. The photodissociation of the N-ethyl bond and the electron transfer in the transiently formed ex-CT complex, [Formula: see text], have been proposed as the primary photochemical processes involved irr the singlet excited NEC molecule. The latter, treated as the main process, leads to the radical cation of NEC, chloride ion, and trichloromethyl radical in the solvent cage, [NEC+•Cl−ĊCl3]. The other reactions in the system studied are analysed following the decomposition of NEC+• in the presence of Cl− and ĊCl3, which can occur by the N-ethyl group and (or) by the aromatic ring. The formation of intermediate products such as[Formula: see text]in the solvent cage gives rise to secondary photochemical reactions in the system studied. The polarity and chemical activity of the reaction media used strongly influence the nature of the secondary photochemical transformations both in and outside the solvent cage. The formation mechanism of the photochemical reaction products in CCl4 when ammonia was used, after and during irradiation, has been explained mainly by the transformations of the radical αr and cation αk as well as by the carbazyl radical β, which is also formed in the reaction medium. On the other hand, reaction of the cation [Formula: see text] explains the formation of the photoproducts in the irradiated solution of NEC with CCl4 in ethanol. These photochemical results have been compared to the photochemical reactions involved in the carbazole–CCl4 system.

scholarly journals A procedure for the introduction of leanness into a company

2021 ◽  
Author(s):  
Davorin Cimermančič ◽  
Janez Kušar ◽  
Tomaž Berlec
Keyword(s):  
Negative Impact ◽  
General Procedure ◽  
Portfolio Analysis ◽  
The Other ◽  
Business Operations ◽  
Step Procedure ◽  
The One ◽  
A Company

AbstractChanging a traditional company into a lean one is a very complex and time-consuming process that needs to be addressed in an appropriate way, otherwise the project of introduction of leanness into a company may fail on the one hand and even have a negative impact on business operations of the company on the other. When introducing a change, a step-by-step procedure leading to a progress may be of great help. The paper outlines a general procedure of leanness, an important part of which is a lean agent. A portfolio analysis is also used as a measure of leanness or as an indicator of the desired direction. The applied working methods were mainly active workshops and interviews with employees. The procedure has been tested on an example of a Slovene company; first, the existing situation is outlined, then the leanness steps taken according to the procedure and the final result after the first transition of the procedure.

Photolabile Protecting Group‐Mediated Synthesis of 2‐Deoxy‐Glycosides

2021 ◽  
Author(s):  
Xiaoqian Li ◽  
Zhi Ma ◽  
Rongkun Liu ◽  
Mattan Hurevich ◽  
You Yang
Keyword(s):  
Protecting Group ◽  
Photolabile Protecting Group

Photochemical reactions of azo compounds. IX. Further studies related to the photochemical reactions of bisazo compounds

1967 ◽  
Vol 20 (2) ◽  
pp. 321 ◽  
Author(s):  
NC Jamieson ◽  
GE Lewis
Keyword(s):  
Sulphuric Acid ◽  
Photochemical Reaction ◽  
Photochemical Reactions ◽  
Azo Compounds ◽  
Bisazo Compounds ◽  
First Time

The photochemical reactions of 4,4?-bis(phenylazo)biphenyl and 4- phenyl-azoazobenzene in 98% sulphuric acid have been examined, for comparison with the corresponding reactions in 22N acid. Photochemical cyclodehydrogenation of 4-phenylazoazobenzene to two benzo[c]cinnoline derivatives has thereby been effected for the first time. The observed course of the latter reaction has led, in turn, to studies of the benzidine rearrangement of 2-(2-phenylhydrazino)benzo[c]- cinnoline, of the photochemical cyclodehydrogenation of 3-phenylazobenzene, and of the photochemical reaction of 2-phenylazobenzo[c]cinnoline. The results of these investigations are now recorded and discussed.

LED Light Sources in Organic Synthesis: An Entry to A Novel Approach

2021 ◽  
Vol 18 ◽  
Author(s):  
Aparna Das
Keyword(s):  
Organic Compounds ◽  
Organic Synthesis ◽  
Photochemical Reaction ◽  
Low Cost ◽  
Environmentally Friendly ◽  
Photochemical Reactions ◽  
Light Sources ◽  
Blue Led ◽  
Oxidation Reduction ◽  
Novel Approach

: In recent years, photocatalytic technology has shown great potential as a low-cost, environmentally friendly, and sustainable technology. Compared to other light sources in photochemical reaction, LEDs have advantages in terms of efficiency, power, compatibility, and environmentally-friendly nature. This review highlights the most recent advances in LED-induced photochemical reactions. The effect of white and blue LEDs in reactions such as oxidation, reduction, cycloaddition, isomerization, and sensitization is discussed in detail. No other reviews have been published on the importance of white and blue LED sources in the photocatalysis of organic compounds. Considering all the facts, this review is highly significant and timely.

Photochemical transformations. 14. Photochemical reactions of ketones with some aliphatic ureas

1977 ◽  
Vol 42 (14) ◽  
pp. 2378-2379 ◽  
Author(s):  
Stanley J. Cristol ◽  
Richard P. Evans ◽  
Karl L. Lockwood
Keyword(s):  
Photochemical Reactions ◽  
Photochemical Transformations
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