Substituent effects in the intramolecular photoredox reactions of benzophenones in aqueous solution

2007 ◽  
Vol 85 (9) ◽  
pp. 561-571 ◽  
Author(s):  
Nikola Basarić ◽  
Devin Mitchell ◽  
Peter Wan
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Acid Catalysis ◽  
Secondary Alcohol ◽  
Substituent Effects ◽  
Phenyl Substituent ◽  
Aqueous Acid ◽  
Single Compound ◽  
Acid Catalyzed

A number of α-hydroxy-3-benzylbenzophenones 7–11 have been synthesized for the purpose of studying the effect of a phenyl substituent on the intramolecular photoredox reaction of 3-(hydroxymethyl)benzophenone (5) discovered in our laboratory. This latter compound was found to undergo a unimolecular (formal) intramolecular redox reaction upon photolysis in aqueous acid that results in clean reduction of the benzophenone ketone (to secondary alcohol) and oxidation of the alcohol to aldehyde. Three of the phenyl-substituted compounds with simple phenyl (7), p-methylphenyl (8), and p-methoxyphenyl (9) were found to undergo the acid-catalyzed intramolecular photoredox reaction with the observation that 9 also undergoes a residual photoredox reaction that is not acid-mediated and may involve initial photoinduced electron transfer, which is supported by LFP data. The m-methoxyphenyl (10) compound did not undergo the reaction. The trend in observed relative reactivity may be partially rationalized by examining changes in molecular orbital coefficients observed in the calculated HOMOs and LUMOs. The photoredox reaction has also been applied twice in succession in a single compound 11, demonstrating that the photoredox reaction may be useful for sequential photoredox reactions in a multifunctional compound.Key words: intramolecular photoredox, acid catalysis, meta effect, benzophenone photochemistry.

The hydration of mesitylketene in aqueous solution: detection of acid catalysis for an aromatic ketene

1995 ◽  
Vol 73 (4) ◽  
pp. 539-543 ◽  
Author(s):  
J. Andraos ◽  
A.J. Kresge ◽  
N.P. Schepp
Keyword(s):  
Aqueous Solution ◽  
Carbon Atom ◽  
Perchloric Acid ◽  
Reaction Rate ◽  
Acid Catalysis ◽  
Sodium Perchlorate ◽  
Nucleophilic Attack ◽  
Acid Solutions ◽  
Uncatalyzed Reaction ◽  
Acid Catalyzed

Mesitylketene was generated flash photolytically in aqueous solution by the photo-Wolff reaction of 2,4,6-trimethyldiazoacetophenone and also by rearrangement of mesitylynol obtained through photodecarbonylation of mesitylhydroxycyclopropenone, and rates of hydration of this ketene were measured in dilute perchloric acid, sodium perchlorate, and sodium hydroxide solutions as well as in concentrated sodium perchlorate and perchloric acid solutions. In dilute solution only an uncatalyzed reaction and a sodium-hydroxide-catalyzed process were observed, both of which could be attributed to nucleophilic attack, by water and by hydroxide ion, respectively, at the ketene carbonyl carbon atom. In concentrated sodium perchlorate solutions, a mild decrease in reaction rate with increasing salt concentration was observed, as expected on the basis of decreasing water activity and a consequent slowing of the uncatalyzed reaction. A similar mild decrease was found in perchloric acid solutions up to [Formula: see text] but this then gave way to a rate increase that became dominant above [Formula: see text] This appearance of acid catalysis indicates a change in reaction mechanism from nucleophilic attack of water to an electrophilic process involving rate-determining protonation on the β-carbon atom of the ketene group. Analysis of the acid-catalyzed reaction rate by the Cox–Yates method gives the catalytic coefficient [Formula: see text] This, when compared with [Formula: see text] for ketene itself, shows that the mesityl group retards acid-catalyzed hydration by a factor of 2200, and consequently the acid-catalyzed reaction of this, and other aromatic ketenes as well, becomes apparent only under strongly acidic conditions. Keywords: mesitylketene, ketene hydration, acid catalysis, Cox–Yates excess acidity correlation.

Self-assembly of phosphorescent quantum dots/boronic-acid-substituted viologen nanohybrids based on photoinduced electron transfer for glucose detection in aqueous solution

RSC Advances ◽  
2016 ◽  
Vol 6 (11) ◽  
pp. 8588-8593 ◽  
Author(s):  
Yanming Miao ◽  
Maoqing Yang ◽  
Guiqin Yan
Keyword(s):  
Aqueous Solution ◽  
Quantum Dots ◽  
Electron Transfer ◽  
Self Assembly ◽  
Boronic Acid ◽  
Photoinduced Electron Transfer ◽  
Room Temperature ◽  
Glucose Sensor ◽  
Glucose Detection ◽  
Room Temperature Phosphorescence

We synthesized boronic-acid-substituted viologens (BBV) and designed a glucose sensor based on room-temperature phosphorescence (RTP) quantum dots (QDs) and BBV.

Substituent Effects on Redox Properties and Photoinduced Electron Transfer in Isoxazolo-Fullerenes

2000 ◽  
Vol 2000 (3) ◽  
pp. 455-465 ◽  
Author(s):  
Hermann Irngartinger ◽  
Peter Walter Fettel ◽  
Thomas Escher ◽  
Philip Tinnefeld ◽  
Simon Nord ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Substituent Effects ◽  
Redox Properties

Photoinduced electron transfer across an organic molecular wall: octa acid encapsulated ESIPT dyes as electron donors

2017 ◽  
Vol 16 (6) ◽  
pp. 840-844 ◽  
Author(s):  
Fabiano S. Santos ◽  
Elamparuthi Ramasamy ◽  
V. Ramamurthy ◽  
Fabiano S. Rodembusch
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Proton Transfer ◽  
Photoinduced Electron Transfer ◽  
Electron Acceptors ◽  
Water Soluble ◽  
Electron Donors ◽  
Octa Acid

Efficient photoinduced electron transfer from proton transfer dyes encapsulated within water soluble supramolecular host octa acid to electron acceptors present outside the capsule was observed in aqueous solution.

Kinetics of acid-catalyzed hydration in aqueous solution of 1-methoxy- and 1-methylthio-2-phenylethyne and some related acetylenes

1987 ◽  
Vol 65 (2) ◽  
pp. 441-444 ◽  
Author(s):  
N. Banait ◽  
M. Hojatti ◽  
P. Findlay ◽  
A. J. Kresge
Keyword(s):  
Aqueous Solution ◽  
Proton Transfer ◽  
Isotope Effect ◽  
Rate Constants ◽  
Acid Catalysis ◽  
The Other ◽  
Buffer Solutions ◽  
Hydronium Ion ◽  
Acid Catalyzed ◽  
Kinetics Of

The rates of conversion of C6H5C≡COCH3 to C6H5CH2CO2CH3 were measured in dilute HClO4/H2O, DCIO4/D2O, and H3PO4–H2PO2−/H2O buffer solutions, and the rates of conversion of C6H5C≡CSCH3 to C6H5CH2COSCH3, C6H5C≡CH to C6H5COCH3, 2,4,6-(CH3)3C6H2C≡CH to 2,4,6-(CH3)3C6H2COCH3, and p-CH3OC6H4C≡CCH3 to p-CH3OC6H4COCH2CH3 were measured in concentrated HClO4/H2O solutions, all at 25 °C. The reaction of C6H5C≡COCH3 showed general acid catalysis and gave the isotope effect [Formula: see text], which indicates that it proceeds through rate-determining proton transfer from catalyst to substrate. The hydronium ion catalytic coefficient for this reaction is [Formula: see text], and those for the other four, in the order given above, are [Formula: see text], and 8.5 × 10−6 M−1 s−1. Relative reactivities based on these rate constants are discussed.

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