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Related Concept Videos

Keto–Enol Tautomerism: Mechanism01:14

Keto–Enol Tautomerism: Mechanism

8.1K
The keto and enol forms are known as tautomers and they constantly interconvert (or tautomerize) between the two forms under acid or base catalyzed conditions. Both the reactions involve the same steps—protonation and deprotonation— although in the reverse order.
8.1K
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution00:52

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

1.4K
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
1.4K
Conformations of Cyclohexane02:11

Conformations of Cyclohexane

16.8K
Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal...
16.8K
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR01:15

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

1.8K
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
1.8K
Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

1.6K
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
1.6K
[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement01:21

[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement

3.6K
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
3.6K

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Updated: Mar 14, 2026

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
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Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method

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Force-induced tautomerization in a single molecule.

Janina N Ladenthin1, Thomas Frederiksen2,3, Mats Persson4

  • 1Department of Physical Chemistry, Fritz-Haber Institute of the Max-Planck Society, Faradayweg 4-6, 14195 Berlin, Germany.

Nature Chemistry
|September 23, 2016
PubMed
Summary
This summary is machine-generated.

Applying mechanical force can trigger chemical reactions in single molecules. This study demonstrates force-induced tautomerization in porphycene using scanning probe microscopy, revealing insights into molecular mechanical activation.

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Area of Science:

  • Chemical Physics
  • Surface Science
  • Nanotechnology

Background:

  • Chemical reactions are commonly activated by heat, electricity, or light.
  • Mechanical force is an understudied activation method, poorly understood at the single-molecule level.

Purpose of the Study:

  • To investigate force-induced tautomerization in a single porphycene molecule.
  • To understand the mechanism of mechanical activation at the molecular level.

Main Methods:

  • Scanning probe microscopy (SPM) at 5 K.
  • Force spectroscopy with submolecular resolution.
  • Density functional theory (DFT) calculations.

Main Results:

  • Quantified the force required for tautomerization.
  • Revealed how a copper tip modifies the reaction pathway and barrier.
  • Demonstrated that a xenon-terminated tip cannot induce the reaction due to weak interaction and tip relaxation.

Conclusions:

  • Mechanical force can induce chemical transformations in single molecules.
  • The interaction between the tip and molecule is crucial for force-induced reactions.
  • SPM and DFT are powerful tools for studying single-molecule mechanical activation.