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Revisiting the Long-Range Perlin Effect in a Conformationally Constrained Oxocane.
Kahlil S Salome1, Cláudio F Tormena1
1Institute of Chemistry , University of Campinas - UNICAMP , P.O. Box 6154 , 13083-970 Campinas , SP , Brazil.
The Journal of Organic Chemistry
|August 14, 2018
Summary
Recent studies on oxocane derivatives reported unusual 1 JCH values, suggesting a long-range Perlin effect. Our findings contradict this, attributing J-coupling differences to increased 1 JC-Hax rather than decreased 1 JC-Heq.
Area of Science:
- Organic Chemistry
- Nuclear Magnetic Resonance Spectroscopy
Background:
- Recent reports suggested unusual 1 JCH values in oxocane derivatives, attributed to a long-range Perlin effect.
- This effect implies specific electronic interactions influencing the one-bond carbon-hydrogen coupling constants.
Purpose of the Study:
- To investigate and clarify the reported unusual 1 JCH values in oxocane derivatives.
- To re-evaluate the proposed long-range Perlin effect based on theoretical and experimental evidence.
Main Methods:
- Theoretical calculations of nuclear magnetic resonance (NMR) parameters.
- Experimental NMR spectroscopy measurements on oxocane derivatives and analogous molecules.
Main Results:
- Theoretical and experimental results do not support the previously published unusual 1 JCH values.
- The observed differences in J-couplings are primarily due to an increase in the 1 JC-Hax (axial) coupling.
- This contrasts with the previous suggestion of a decrease in the 1 JC-Heq (equatorial) coupling.
Conclusions:
- The previously reported long-range Perlin effect in oxocane derivatives is not supported by this study.
- J-coupling variations in these systems are better explained by changes in axial C-H couplings.
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