Related Experiment Video
Updated: Jul 17, 2026
10:44
Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Intermolecular electron transfer from excited benzophenone ketyl radical
Masanori Sakamoto1, Xichen Cai, Sung Sik Kim
1The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
The Journal of Physical Chemistry. A
|January 12, 2007
Summary
This study investigated electron transfer from excited benzophenone ketyl radicals to quenchers using advanced photolysis techniques. Electron transfer rates were quantified, revealing a dependence on the driving force of the reaction.
Area of Science:
- Photochemistry
- Chemical Kinetics
- Electron Transfer Reactions
Background:
- Benzophenone ketyl radical (BPH(.-)(D(1))) is a key intermediate in photochemical reactions.
- Understanding electron transfer mechanisms is crucial for designing new chemical processes.
Purpose of the Study:
- To investigate the electron transfer from excited benzophenone ketyl radical to various quenchers.
- To determine the rate constants and driving force dependence of these intermolecular electron transfer reactions.
Main Methods:
- Utilized nanosecond/picosecond and nanosecond/nanosecond two-color two-laser flash photolysis.
- Employed transient absorption and fluorescence quenching measurements.
- Applied Stern-Volmer analysis to determine rate constants.
Main Results:
- Confirmed electron transfer from BPH(.-)(D(1)) to quenchers.
- Quantified intermolecular electron-transfer rate constants.
- Revealed a clear dependence of the electron-transfer rate on the reaction's driving force.
Conclusions:
- The study successfully characterized the electron transfer dynamics from excited benzophenone ketyl radicals.
- The findings provide valuable insights into the factors governing electron transfer reactions, particularly the role of driving force.
Related Concept Videos
01:17Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
Ideally, an unpaired electron shows a single peak in the EPR spectrum due to the transition between the two spin energy states. However, coupling interactions can occur between the spins of the unpaired electron and any neighboring spin-active nuclei. This hyperfine coupling results in hyperfine splitting, where the EPR signal is split into multiplets. The signals split into 2nI + 1 peaks, where n is the number of equivalent nuclei and I is the nuclear spin. These splitting patterns provide...
01:07Structure of Benzene: Kekulé Model
In 1865, August Kekule suggested the structure of benzene according to the structural theory of organic chemistry based on the three assertions—formula of benzene is C6H6, all the hydrogens of benzene are equivalent, and each carbon must have four bonds due to its tetravalency.
He proposed that benzene has a cyclic structure of six carbon atoms attached to one hydrogen atom each, with three alternating pi bonds.
He proposed that benzene has a cyclic structure of six carbon atoms attached to one hydrogen atom each, with three alternating pi bonds.
01:18Benzene to 1,4-Cyclohexadiene: Birch Reduction Mechanism
Birch reduction uses solvated electrons as reducing agents. The reaction converts benzene to 1,4-cyclohexadiene. The reaction proceeds by the transfer of a single electron to the ring to form a benzene radical anion. This anion is highly basic—it abstracts a proton from the alcohol to form a cyclohexadienyl radical. Another single electron transfer gives the cyclohexadienyl anion. A proton transfer from the alcohol forms 1,4-cyclohexadiene. Since this reduction occurs via radical anion...
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
00:47Radical Formation: Addition
Radicals can be formed by adding a radical to a spin-paired molecule. This is typically observed with unsaturated species, where the addition of a radical across the π bond leads to the production of a new radical by dissolving the π bond. For example, the addition of a Br radical to an alkene yields a carbon-centered radical.
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an unpaired...
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an unpaired...
01:02Radical Reactivity: Electrophilic Radicals
Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For example, the malonate radical, in which the radical center is flanked by two electron‐withdrawing groups, reacts readily with butyl vinyl ether, which consists of an electron‐donating oxygen substituent. The reaction between electrophilic malonate radical and nucleophilic vinyl ether is favored because the radical has a low‐energy SOMO, which interacts...