Related Experiment Video
Updated: Jun 5, 2026
05:51
Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
Published on: July 19, 2019
Ground-state proton-transfer dynamics governed by configurational optimization.
Sun-Young Park1, Young-Shin Lee, Du-Jeon Jang
1School of Chemistry, Seoul National University, NS60, Seoul 151-742, Korea.
Physical Chemistry Chemical Physics : PCCP
|December 22, 2010
Summary
Ground-state proton transfer (GSPT) in 7-hydroxyquinoline occurs concertedly and asymmetrically via tunneling. Alcohol properties significantly influence GSPT rates and mechanisms, with larger alcohols increasing configurational optimization.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Spectroscopy
Background:
- Ground-state proton transfer (GSPT) is a fundamental chemical process.
- Investigating GSPT in hydrogen-bonded systems provides insights into reaction mechanisms.
- 7-hydroxyquinoline serves as a model compound for studying proton transfer dynamics.
Purpose of the Study:
- To directly observe intrinsic GSPT dynamics of a 7-hydroxyquinoline-alcohol cyclic complex.
- To elucidate the influence of alcohol properties (donating ability, size) on GSPT.
- To understand the role of configurational optimization in proton tunneling.
Main Methods:
- Time-resolved transient-absorption spectroscopy.
- Systematic variation of alcohols, solvents (n-alkanes), isotopes, and temperatures.
- Formation of a cyclic complex between 7-hydroxyquinoline and two alcohol molecules.
Main Results:
- GSPT occurs concertedly, asymmetrically, and is rate-determined by tunneling.
- GSPT rate and kinetic isotope effect increase with alcohol proton-donating ability.
- GSPT rate and kinetic isotope effect decrease with increasing alcohol molecular size.
- Configurational optimization of the hydrogen-bond bridge precedes GSPT.
Conclusions:
- Intrinsic GSPT dynamics were observed directly in nonpolar media.
- Alcohol properties critically modulate GSPT rates and mechanisms.
- Increased alcohol size enhances configurational optimization, reducing GSPT asymmetry.
Related Concept Videos
01:25Transition State Theory
Transition-state theory, also known as activated-complex theory, provides a molecular-level explanation of reaction rates in both gas-phase and solution-phase reactions. It extends earlier kinetic models by considering the formation of a short-lived, high-energy configuration during a reaction.The progress of a chemical reaction can be represented using a reaction profile, which plots potential energy against the reaction coordinate. As two reactant molecules approach one another, their...
01:26Reaction Mechanisms: The Steady-State Approximation
The steady-state approximation, also referred to as the quasi-steady-state approximation to differentiate it from a true steady state, is a widely used method for simplifying calculations in complex reaction mechanisms. This approach is particularly useful when dealing with multi-step reactions that involve reverse reactions or several steps, which can significantly increase mathematical complexity and make the reactions nearly unsolvable analytically.The steady-state approximation operates on...
01:23Stability of Equilibrium Configuration
Understanding the stability of equilibrium configurations is a fundamental part of mechanical engineering. In any system, there are three distinct types of equilibrium: stable, neutral, and unstable.
A stable equilibrium occurs when a system tends to return to its original position when given a small displacement, and the potential energy is at its minimum. An example of a stable equilibrium is when a cantilever beam is fixed at one end and a weight is attached to the other end. If the weight...
A stable equilibrium occurs when a system tends to return to its original position when given a small displacement, and the potential energy is at its minimum. An example of a stable equilibrium is when a cantilever beam is fixed at one end and a weight is attached to the other end. If the weight...
01:58Cooperative Allosteric Transitions
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
01:58Cooperative Allosteric Transitions
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
01:58Cooperative Allosteric Transitions
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...