Substituent Effects in Dye-sensitized Photooxidation Reactions of Furans

The problems encountered in the normal method used to determine β values (rate of decay of singlet oxygen divided by the rate of its reaction with an organic compound) are discussed. The use of dilute solutions of organic acceptors for our measurements was found to give more reproducible values and simplified kinetics. These β values were used to obtain relative rate constants for a variety of substituted furans. Hammett plots were made to quantitate the substituent effects in order to explore the nature of singlet oxygen in the dye-sensitized photooxidation reactions of these furans. The calculated ρ values were compared with other photooxidation and Diels–Alder reactions. Hammett ρ values in a series of solvents were also calculated for the reaction of singlet oxygen with 2-arylfurans and increasing ρ values were correlated with decreasing solvent polarity.

Download Full-text

ChemInform Abstract: SUBSTITUENT EFFECTS IN THE DIELS-ALDER REACTION OF SUBSTITUTED BENZYNES WITH HEXAMETHYLCYCLOHEXA-2,4-DIENONE

Chemischer Informationsdienst ◽

10.1002/chin.197808099 ◽

1978 ◽

Vol 9 (8) ◽

Author(s):

A. OKU ◽

A. MATSUI

Keyword(s):

Substituent Effects ◽

Alder Reaction ◽

Diels Alder ◽

Diels Alder Reaction

Download Full-text

Photophysical Properties of Protoporphyrin IX, Pyropheophorbide-a, and Photofrin® in Different Conditions

Pharmaceuticals ◽

10.3390/ph14020138 ◽

2021 ◽

Vol 14 (2) ◽

pp. 138

Author(s):

Bauyrzhan Myrzakhmetov ◽

Philippe Arnoux ◽

Serge Mordon ◽

Samir Acherar ◽

Irina Tsoy ◽

...

Keyword(s):

Singlet Oxygen ◽

Photophysical Properties ◽

Protoporphyrin Ix ◽

Fluorescence Emission ◽

Solvent Polarity ◽

Visible Absorption ◽

Light Dosimetry ◽

Time Resolved ◽

Pyropheophorbide A ◽

Influence Of Solvent

Photodynamic therapy (PDT) is an innovative treatment of malignant or diseased tissues. The effectiveness of PDT depends on light dosimetry, oxygen availability, and properties of the photosensitizer (PS). Depending on the medium, photophysical properties of the PS can change leading to increase or decrease in fluorescence emission and formation of reactive oxygen species (ROS) especially singlet oxygen (1O2). In this study, the influence of solvent polarity, viscosity, concentration, temperature, and pH medium on the photophysical properties of protoporphyrin IX, pyropheophorbide-a, and Photofrin® were investigated by UV-visible absorption, fluorescence emission, singlet oxygen emission, and time-resolved fluorescence spectroscopies.

Download Full-text

Kinetics of the successive chlorination of 1,2-dichloroethane in the liquid phase

Australian Journal of Chemistry ◽

10.1071/ch9691177 ◽

1969 ◽

Vol 22 (6) ◽

pp. 1177 ◽

Cited By ~ 6

Author(s):

DS Caines ◽

RB Paton ◽

DA Williams ◽

PR Wilkinson

Keyword(s):

Liquid Phase ◽

Rate Constants ◽

Relative Rate ◽

Stirred Tank ◽

Continuous Stirred Tank Reactor ◽

Alternative Pathways ◽

Tank Reactor ◽

Relative Rate Constants ◽

Continuous Stirred Tank ◽

Kinetics Of

Liquid 1,2-dichloroethane has been chlorinated by dissolved chlorine to a succession of chloroethanes up to the ultimate hexachloroethane. The results of both batch and continuous stirred tank reactor systems have been analysed by computer techniques to give a set of relative rate constants from which one can predict the product composition for a given chlorine uptake, the aim in this work being to optimize the production of tetrachloroethanes. An unusual feature of the kinetics is that 1,1,1,2- and 1,1,2,2-tetrachloroethanes provide alternative pathways between 1,1,2-trichloroethane and pentachloroethane.

Download Full-text

Kinetic study of the photochemical changes of (ZZ)-bilirubin IX α bound to human serum albumin. Demonstration of (EZ)-bilirubin IX α as an intermediate in photochemical changes from (ZZ)-bilirubin IX α to (EZ)-cyclobilirubin IX α

Biochemical Journal ◽

10.1042/bj2260251 ◽

1985 ◽

Vol 226 (1) ◽

pp. 251-258 ◽

Cited By ~ 25

Author(s):

S Itoh ◽

S Onishi

Keyword(s):

Human Serum Albumin ◽

Serum Albumin ◽

Kinetic Study ◽

Human Serum ◽

Photochemical Reaction ◽

Relative Rate ◽

Significant Preference ◽

Geometrical Isomers ◽

Relative Rate Constants

The present study was performed to elucidate why the photochemical reaction of (ZZ)-bilirubin bound to human serum albumin is singularly selective, and only one of the two (EZ)- and (ZE)-bilirubins, the (ZE)-isomer, is produced. In a kinetic study of the photochemical reaction in vitro, the sum of the relative rate constants of photochemical transformation of (EZ)-bilirubin into both (EZ)-cyclobilirubin and (ZZ)-bilirubin, with a significant preference for the former, was proved to be considerably larger than that of the transformation of (ZZ)-bilirubin into (EZ)-bilirubin. Therefore only one of the geometrical isomers, namely (ZE)-bilirubin, is apparently formed. It was concluded that (EZ)-bilirubin photochemically undergoes (EZ)-cyclization, i.e. structural photoisomerization, while bound to its high-affinity site on human serum albumin, and is an intermediate in the transformation of (ZZ)-bilirubin into (EZ)-cyclobilirubin.

Download Full-text

RECOMBINATION OF OPPOSITELY CHARGED AQUEOUS CLUSTER IONS USING ELECTROSTATICALLY MERGED ION BEAMS

Surface Review and Letters ◽

10.1142/s0218625x96001170 ◽

1996 ◽

Vol 03 (01) ◽

pp. 655-660 ◽

Cited By ~ 1

Author(s):

B. PLASTRIDGE ◽

K.A. COWEN ◽

D.A. WOOD ◽

M.H. COHEN ◽

J.V. COE

Keyword(s):

Rate Constants ◽

Cluster Size ◽

Collision Energy ◽

Relative Rate ◽

Center Of Mass ◽

Cluster Ions ◽

Charged Cluster ◽

Relative Rate Constants ◽

Oppositely Charged ◽

Electrostatic Quadrupole

A new method for studying cluster-cluster interactions is introduced which involves merging mass-selected beams of oppositely charged cluster ions with an electrostatic quadrupole deflector. Recombination is monitored by measuring the rate of fast neutral production. Relative rate constants have been measured for the reaction of H 3O+( H 2 O )n+ OH −( H 2 O )m as a function of cluster size (m=n=0–3), which display a pronounced enhancement with clustering. Relative rate constants have also been measured as a function of center-of-mass collision energy for a heavily clustered reaction (n=3, m=3) and a lightly clustered reaction (n=1, m=0) revealing that clustering produces a dramatic change in the reaction mechanism.

Download Full-text

Lifetime of Singlet Oxygen and Quenching by NaN3 in Mixed Solvents

Zeitschrift für Naturforschung B ◽

10.1515/znb-1982-0520 ◽

1982 ◽

Vol 37 (5) ◽

pp. 649-652 ◽

Cited By ~ 12

Author(s):

N. Miyoshi ◽

M. Ueda ◽

K. Fuke ◽

Y. Tanimoto ◽

M. Itoh ◽

...

Keyword(s):

Activation Energy ◽

Charge Transfer ◽

Singlet Oxygen ◽

Mixed Solvents ◽

Solvent Polarity ◽

Thermal Lensing ◽

Partial Charge ◽

Partial Charge Transfer ◽

Quenching Rate ◽

Quenching Rate Constant

Singlet oxygen was generated by the photosensitization of erythrosine. The lifetime of singlet oxygen and the quenching rate constant for singlet oxygen by NaN3 were measured by a thermal lensing method in MeOH-H2O mixed solvents. The reciprocal of the lifetime increased linearly with the increase of the H2O mole fraction. Semi-log plot of the quenching constant against the reciprocal of the solvent polarity exhibited a linear relation. The quenching of the singlet oxygen by NaN3 may proceed through a partial charge-transfer intermediate. The activation energy for the quenching reaction of N3- + 1O2 →[N3·1O2-] increased with the increase of the solvent polarity. The lifetime was also measured in MeOH-ethyleneglycol mixed solvents, and its relation with viscosity was obtained

Download Full-text

REACTION OF OXYGEN ATOMS WITH BUTADIENE

Canadian Journal of Chemistry ◽

10.1139/v60-296 ◽

1960 ◽

Vol 38 (11) ◽

pp. 2187-2195 ◽

Cited By ~ 13

Author(s):

R. J. Cvetanović ◽

L. C. Doyle

Keyword(s):

Pressure Dependence ◽

Rate Constants ◽

Room Temperature ◽

Relative Rate ◽

Excess Energy ◽

General Mechanism ◽

Arrhenius Parameters ◽

Heats Of Reaction ◽

Relative Rate Constants ◽

Oxygen Atoms

Reaction of oxygen atoms with 1,3-butadiene has been investigated at room temperature. It is found that it conforms to the general mechanism established previously for the analogous reactions of monoolefins. Only 1,2-addition occurs, and the addition products, butadiene monoxide and 3-butenal, possess excess energy when formed as a result of high heats of reaction. The pressure dependence of the formation of the addition products yields the values of the "lifetimes" of the initially produced "hot" molecules. The relative rate constants have been determined at 25 and 127 °C and from these the relative values of the Arrhenius parameters have been calculated.

Download Full-text