Photochemical Reactions of Microcystin-LR Following Irradiation with UV Light

Photochemical reactions of microcystin-LR, a toxic compound produced by some blue green algae, were investigated. Ultraviolet absorption of microcystin-LR was assessed. Time-dependent density functional theory (TDDFT) calculations indicated that absorption peak at 238 nm was mainly due to excitation of electrons from the linear chain structure Adda of microcystin-LR. Irradiation of microcystin-LR with UV light resulted in the reduction of the 238 nm absorption peak and the appearance of a new peak at 300 nm. Density functional theory (DFT) and TDDFT calculations with a model molecule suggested that this 300 nm peak was due to tricyclo-Adda microcystin-LR, an intermediate in photochemical reactions of microcystin-LR. Analysis of the rate of this photochemical reaction showed that it was a first order reaction.

Photochemical reactions of poly(3-butoxythiophene-2,5-diyl) with chloroform

Photochemical reactions of poly(3-butoxythiophene-2,5-diyl) with chloroform under irradiation with light were studied. The reactions were separately carried out under air, oxygen, and nitrogen. The obtained results showed that this reaction belongs to the pseudo-first-order reaction with a rate constant kobs of 1.4×10?5 s?1 at room temperature. The presence or absence of air, oxygen, and nitrogen did not have obvious effects on the reaction rate under irradiation with light.

Photochemical reactions as synthetic tool for pharmaceutical industries

In the quest for new agrochemicals and pharmaceuticals,chemists seek access to reliable and mild synthetic techniques to allow for the systematic modification of chemical structures,exploration of unexplored chemical space,and facilitation of practical synthesis in their search for novel agrochemicals and pharmaceuticals.In this regard,photocatalytic reactions enabled the synthesis of intricate and more functionalized compounds.This review overviews the developed synthetic methodologies and their utility in the chemical synthesis of pharmaceuticals.This review also offers in-depth insights into contemporary photoredox reactions such as allylic additions,cyclization,reductive cross-coupling,C–H activation,ring opening,oxidative cross-coupling,dehydrogenation,desulphonation,and decarboxylation.It provides a positive outlook for the promising future of this field.

Enhanced secondary organic aerosol formation during dust episodes by photochemical reactions in the winter in Wuhan

To investigate the effect of frequently occurring mineral dust on the formation of secondary organic aerosol(SOA),106 volatile organic compounds(VOCs),trace gas pollutants and chemical components of PM_(2.5) were measured continuously in January 2021 in Wuhan,Central China.The observation period was divided into two stages that included a haze period and a following dust period,based on the ratio of PM_(2.5) and PM_(10) concentrations.The average ratio of secondary organic carbon(SOC)to elemental carbon(EC)was 1.98 during the dust period,which was higher than that during the haze period(0.69).The contribution of SOA to PM_(2.5) also increased from 2.75% to 8.64%.The analysis of the relationships between the SOA and relative humidity(RH)and the odd oxygen(e.g.,O_(X)=O_(3)+NO_(2))levels suggested that photochemical reactions played a more important role in the enhancement of SOA production during the dust period than the aqueous-phase reactions.The heterogeneous photochemical production of OH radicals in the presence of metal oxides during the dust period was believed to be enhanced.Meanwhile,the ratios of trans-2-butene to cis-2-butene and m-/p-xylene to ethylbenzene(X/E)dropped significantly,confirming that stronger photochemical reactions occurred and SOA precursors formed efficiently.These results verified the laboratory findings that metal oxides in mineral dust could catalyse the oxidation of VOCs and induce higher SOA production.

Review of heterogeneous photochemical reactions of NOy on aerosol-A possible daytime source of nitrous acid (HONO) in the atmosphere

As an important precursor of hydroxyl radical, nitrous acid （HONO） plays a key role in the chemistry of the lower atmosphere. Recent atmospheric measurements and model calculations show strong enhancement for HONO formation during daytime, while they are inconsistent with the known sources in the atmosphere, suggesting that current models are lacking important sources for HONO. In this article, heterogeneous photochemical reactions of nitric acid/nitrate anion and nitrogen oxide on various aerosols were reviewed and their potential contribution to HONO formation was also discussed. It is demonstrated that HONO can be formed by photochemical reaction on surfaces with deposited HNO3 , by photocatalytic reaction of NO2 on TiO2 or TiO2 -containing materials, and by photochemical reaction of NO2 on soot, humic acids or other photosensitized organic surfaces. Although significant uncertainties still exist in the exact mechanisms and the yield of HONO, these additional sources might explain daytime observations in the atmosphere.

Successive construction of cucurbit[8]uril-based covalent organic frameworks from a supramolecular organic framework through photochemical reactions in water

Functional framework materials have been developed for many applications including adsorption, asymmetric catalysis, sensing,drug delivery, optical device, and so on. Here, we report the successive construction of two cucurbit[8]uril-based covalent organic frameworks(COFs) including tetraphenylethene-based COF(COF-1) and phenanthrene-based COF(COF-2) from a two-dimensional(2D) periodic cucurbit[8]uril-based supramolecular organic framework(SOF-1) as the prearranged structure via the intermolecular photocycloaddition of the coumarin units and the intramolecular photocyclization of the tetraphenylethene(TPE) units under ultraviolet(UV) irradiation(365 nm) in water. In this case, oxygen(O_(2)) plays an important role in the photocyclization of the TPE units into the phenanthrene units in the transform process from SOF-1 or COF-1 to COF-2. As the TPE units further form phenanthrenes after UV-irradiation, COF-2 exhibits aggregation-caused quenching effect and weak green emission, while COF-1 displays a strong yellow emission due to the aggregation-induced emission. Besides, the adaptive chirality of cationic COF-1 as a biomolecular sensor can be efficiently induced by chiral anionic biomolecules including adenosine-5′-triphosphate(ATP) and adenosine-5′-diphosphate(ADP) to exhibit sensitive negative circular dichroism responses in water. This supramolecular approach to construct COF from SOF via photochemical reactions may open a new opportunity for the construction and application of the water-soluble COFs with well structural controllability, unique photophysical properties,and favorable biocompatibility.

The Photochemical Study of HSA and BSA with Resonance Light Scattering and Fluorescence Spectra

The resonance light-scattering (RLS) of human serum albumin (HSA) and bovine serum albumin (BSA) is reported for the first time, and applied to study photochemical reaction of HSA and BSA. The fact of photocrosslinking self-association effect in HSA and BSA solutions is identified by the enhancement of RLS. The fluorescence quenching at about 350 nm and 700 nm proves that tryptophan (Trp) residues are one of the photochemical activity sites in HSA and BSA molecules. The Rayleigh scattering (RS) spectra of HSA and BSA that were neglected in fluorescence spectra before are found at about 296 nm, 592 nm and 888 nm for the first time, and are of adventageous to studying the aggregation of HSA or BSA. The possible photochemical reaction mechanism is also proposed.

Environmental chamber study of the photochemical reaction of ethyl methyl sulfide and NO_x

A series of experiments were conducted in a self-made smog chamber at （300 ＋ 1） K and 1.01 × 10^5 Pa to simulate the photochemical reaction of ethyl methyl sulfide （EMS） and NOx. The results showed that the higher the initial concentration of EMS, the more ozone was generated in the simulative reactions. It was found that the light intensity plays a very important role in the evaluation of ozone formation potential for EMS. The parameters of d（Oa-NO） and IR （incremental reactivity） were used to quantify the potential of EMS on ozone formation. The obtained maximum IR values in this article for the five simulative reactions were 1.55 × 10^-2, 0.99 × 10^-2, 1.36 × 10^-2, 2.47 × 10^-2, and 1.65 × 10^-2, respectively. A comparison between the results we obtained here and the results we obtained previously for di-tert-butyl peroxide and acetylene showed that the potential reactivity of EMS on ozone formation was at a relatively low level.

Photochemical reaction between magnesium tetraphenyl porphyrin and oxygen

The photochemical reaction of magnesium tetraphenyl porphyrin （MgTPP） with O2 was studied in CH2Cl2 by steady-state fluorescence, UV-vis absorption, FTIR and MALDI-TOF MS measurements. These spectra indicate that O2 can react with MgTPP excited by irradiation, forming the stable 1：1 coordinated adduct of MgTPP-O2. In the adduct, the oxygen atoms of O2 may insert in the Mg-N bonds in MgTPP and bind with the nitrogen atoms of MgTPP to form N-O-Mg bonds.

Photochemical reaction of magnesium tetraphenyl porphyrin with sulfur dioxide

The photochemical reaction of magnesium tetraphenyl porphyrin（MgTPP） with sulfur dioxide（SO_2） was investigated in dichloromethane（CH_2Cl_2） by steady-state fluorescence,UV-vis absorption,MS,and XRD spectroscopic techniques.These spectra showed that under irradiation MgTPP reacted with SO_2 to form 1：1 molecular adduct at first step.During the process of keeping irradiation and maintaining the flow of SO_2,SO_2 was reduced into S^（2-） by MgTPP and the results were detected using MS and XRD techniques.Understanding the photochemical reaction of MgTPP with SO_2 is of key interest in elucidating fundamental photochemical reaction mechanisms associated with this class of chlorophyll in the presence of SO_2.

Theoretical Study of the Photochemical Reaction Mechanism of Bicyclo[4.1.0]heptane

The photochemical reaction of bicyclo[4.1.0]heptane was studied at the complete active space SCF（CASSCF） level with a 6-31G^＊ basis set. A muhireference MP2 algorithm that has been implemented in the Gaussian program was used to correct the energetics for the dynamic correlation. Starting from the Franck-Condon excitation of bicyclo [ 4.1.0 ] heptane, the reaction is via two bonds＇ breakage to give rise to 1,6-heptdiene. One internal conversion （IC） and two intersystem crossing points（ISC） were located and are discussed separately. The reaction proceeds to its own characteristic product on the ground state.

THE SOLID STATE CONTROLLED PHOTOCHEMICAL REACTION OF NITROBENZALDEHYDE WITH INDOLE

The solid state photochemical reaction of nitrobenzaldehyde with indole was investigated. Seven hey products were identified by IR, MS,^(1)H HMR and elemental analysis.

Biobased Aromatic-Aliphatic Polyols by Thiol-Ene Reactions of Propoxylated Mercaptanized Cardanol

Aromatic-aliphatic polyols were obtained previously from the thiol-ene reactions of propoxylated cardanol with hydroxyalkyl mercaptans;these aromatic-aliphatic polyols were then utilized in the preparation of rigid polyurethane foams with excellent properties.The current work describes a variant of cardanol polyol synthesis by thiol-ene reactions in three steps.The first step is propoxylation of cardanol by reacting cardanol with propylene oxide;the second step is mercaptanization of propoxylated cardanol by reacting double bonds with hydrogen sulfide;and the third step involves the addition of the thiol groups of mercaptanized propoxylated cardanol to the double bonds of allyl alcohol,glycerol-1-allyl ether,and trimethylolpropane allyl ether.Thus,obtained polyols were characterized by standard analytical methods.Rigid polyurethane foams prepared from these polyols show promising physical-mechanical properties.The rigid polyurethane foams can be used for various applications such as thermo-insulation of freezers,storage tanks and pipes for food and chemical industries,wood substitutes and flotation materials.

THE PHOTOCHEMICAL SYNTHESIS OF THE PYRIDINE ADDUCT OF TETRAPHENYLPORPHYRINATORHODIUM(Ⅱ)AND THE MECHANISM OF PHOTOCHEMICAL REACTION

A new rhodium(Ⅱ)porphyrin complex was isolated by chromatography from the photochemical reac- tion of(μ—tetraphenylporphyrinato)bis[dicarbonylrhodium(Ⅰ)]with pyridine in benzene and has been charac- terized.From the results,the reaction mechanism is proposed.

Photochemical reaction of particle-bound 1-nitropyrene under simulated atmospheric condition

Photoreaction of particle-bound 1-nitropyrehe (1-NP) under simulated atmospheric condition has been studied. When 1-NP coated on the surface of silica gel was suspended in a stream of nitrogen, oxygen or air, respectively, and exposed to intensive light of xenon lamp, photochemical reaction took place. The result of kinetic study showed it to be of the second order. The photoreaction products were identified by off-line HPLC/MS as 1,6-pyrenequinone, 1,8-pyrenequinone, trinitro-hydroxypyrene, dinitrohydroxypyrene, 6,6'- dipyrenenone, etc. The mutagenicity of photochemical reaction products is higher in oxygen and air, and lower in nitrogen than that of the precursor 1-NP, as detected by the Ames Bioassay.

Photochemical kinetics for holographic grating formation in phenanthrenequinone doped poly (methyl methacrylate) photopolymer

The photochemical kinetics of phenanthrenequinone （PQ） doped poly （methyl methacrylate） photopolymer in holographic recording was studied theoretically and experimentally. The diffusion of PQ molecules during holographic recording was negligible because of its small diffusion coefficient at room temperature. A photochemical reaction kinetics model of PQ/PMMA was established. The analytical expressions for the temporal variations of transmittance and diffraction efficiency were derived. By fitting the experimental curves, some parameters related with the polymer components were obtained by the proposed model, which can be used to analyze the photochemical process and will be helpful to the optimization of material preparation.

Photochemical Reaction of 9,10-Anthraquinone Labeled Bovine Serum Albumin Conjugate

Bovine serum albumin (BSA) was labeled with 9,10-anthraquinone and the photochemical fluorimetric reactivity of the covalently conjugated 9,10-anthraquinone was remarkably improved. The mechanism for the enhancement in the photochemical reactivity of conjugated 9,10-anthraquinone with BSA was discussed.

Coupled Transport Phenomena in Corrugated Photocatalytic Reactors

Corrugated reactors are known for their use in applications requiring UV-exposure, whereby media flowing within the corrugated channel react with a photo-active catalyst impregnated on the surface （i.e. TiO2）. The performance in these systems is dependent on catalyst properties and reactivity for a given light source, in conjunc-tion with the coupled transport of reactants within the media and photons falling incident to the catalyst surface. Experimental and computational analyses of local mass transfer and radiation pattems for a broad range of corrugation angles, depths, and non-idealities introduced during manufacture （i.e. fold curvature） are thus integrated to the design and optimization of these systems. This work explores techniques for determining incident energy distribu-tions on the surface of corrugated reactor geometries with non-ideal cross-sectional profiles, and the local and overall mass transfer rates obtained using computational fluid dynamics and experimental analysis. By examining the reaction kinetics for the photo-degradation of 4-chlorophenol over a TiO2 catalyst, the effects of surface area, energy incidence with photon recapture, and local mass transfer on overall reactor performance are presented to highlight ootimization concerns for these tvoes of reactors.

ACTIVE INTERMEDIATES IN PHOTORADICAL AGING OF POLYMERS

The data referring to the mechanism and efficiency of electronically excited macroradical and radical anionreactions, the important role of photochemical chain reactions in polymers are presented, It was found that by varying photonenergy, temperature, photolysis time and competition between thermal and photochemical reactions, it is possible to change the functional composition and molecular weight distribution of polymers.

Nitrogen Dioxide and Ozone Pollution in the Chicago Metropolitan Area

Ground-level ozone is a harmful air pollutant associated with several health issues. Ozone concentrations have exceeded the National Ambient Air Quality Standards (NAAQS) in the Chicago metropolitan area on hot summer days for many years because of nitrogen oxide and volatile organic compound emissions. Annual fourth highest 8-hour ozone concentrations have been between 0.070 and 0.084 ppm at several monitoring sites in Cook county, during the 2016-2018 time period. The continuous measurement of nitrogen dioxide (NO2) and ozone (O3) was conducted in several communities in Chicago in 2017. The air pollution impacts the health of all who live in the area. The data were used to analyze correlations between the O3 distribution and its association with ambient concentrations of NO2 from transportation emissions. Higher concentrations in NO2 and O3 occurred in succession in the daytime. The diurnal variation of O3 concentration was analyzed. The daily cycle of NO2 concentration reaches a maximum in the late morning and has smaller nighttime concentrations. The daily cycle of ozone concentration reaches the maximum in the afternoon and also becomes smaller for nighttime concentrations. In addition, relationships were found between O3 and NO2. Monthly variations of ozone and NO2 are presented. Some options to reduce ozone pollution are presented.