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Updated: Jun 3, 2026
10:52
Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics
Published on: April 12, 2019
Protruding interfacial OH groups and 'on-water' heterogeneous catalysis
1Graduate School of EEWS, KAIST, Daejeon 305-701, Korea. ysjn@kaist.ac.kr
Summary
On-water catalysis is enhanced by water's protruding OH groups interacting with transition states. This study explores electronic and steric effects in cycloaddition reactions, finding water significantly accelerates reactions with good H-bond acceptors like DMAD.
Area of Science:
- Physical Organic Chemistry
- Supramolecular Chemistry
- Computational Chemistry
Background:
- 'On-water' catalysis, occurring at organic/water interfaces, shows remarkable rate enhancements.
- The mechanism is proposed to involve protruding water molecule hydroxyl (OH) groups at the interface, which stabilize transition states (TS) via hydrogen bonding.
- The cycloaddition of quadricyclane (Q) with dimethyl azodicarboxylate (DMAD) on-water exhibits over 100,000-fold rate acceleration compared to neat conditions.
Purpose of the Study:
- To investigate the role of hydrogen bonding and potential steric effects in 'on-water' catalysis.
- To compare the catalytic efficiency of water for cycloaddition reactions involving different dienophiles (DMAD vs. dimethyl acetylenedicarboxylate).
- To theoretically evaluate the influence of the dienophile's hydrogen bond accepting ability on reaction rates.
Main Methods:
- Theoretical calculations comparing on-water and neat reaction conditions.
- Analysis of hydrogen bonding interactions between water and reaction intermediates/transition states.
- Preliminary quantum mechanical/molecular mechanical (QM/MM) simulations with explicit water molecules.
Main Results:
- A related reaction with dimethyl acetylenedicarboxylate (a poor H-bond acceptor) shows minimal rate acceleration on-water compared to DMAD.
- The reduced acceleration is attributed to weaker hydrogen bonding between acetylenedicarboxylate and water at the TS.
- QM/MM simulations indicate a higher number of hydrogen bonds between the TS and water's OH groups for the DMAD + Q reaction.
Conclusions:
- Hydrogen bonding with protruding water OH groups is a key factor in 'on-water' catalysis, particularly for reactions with good H-bond acceptors.
- An intrinsic steric or orientational effect may also contribute to on-water catalysis, especially in reactions with smaller molecules.
- Both electronic (H-bonding) and steric factors likely play a role in the observed on-water catalysis for the Q + acetylenedicarboxylate reaction.
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