Find Symmetry in Molecules: NMR Spectra & 3D Structures

In summary, the process of finding symmetry in molecules is crucial for identifying equivalent nuclei in an NMR spectrum. Point group symmetry is a key concept to understand, and it is recommended to start with the CNPI group and refer to resources such as the book "Molecular Symmetry and Spectroscopy" by Bunker and Jensen or chapter 12 in "Physical Chemistry: A Molecular Approach" by McQuarrie for a thorough understanding.
  • #1
Big-Daddy
343
1
What is the general method for finding symmetry in molecules which would allow you to find which nuclei are equivalent in an NMR spectrum?

I know it sounds vague but it seems inevitable. Any good guides on the Internet would be great. My main issue is with larger molecules whose structures are drawn in 2D, and virtually any 3D structure (e.g. adamantane).
 
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  • #2
Are you familiar with the idea of point group symmetry?
 
  • #3
No. And looking it up leads to a list of mathematical symbols that I cannot hope to understand on my own.
 
  • #4
Personally I think the proper way to learn group theory, especially with hindsight of spectroscopic applications like NMR, is to start from the CNPI group. The classic book on that topic, with many exercises is Bunker and Jensen, Molecular Symmetry and Spectroscopy.
See also
http://www.ptc.uni-wuppertal.de/team/hochschullehrer/prof-per-jensen-phd.html
 
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  • #5
I fully agree with DrDu recommendation. That book is comprehensive and avilable from Dover Publication with a reasonable price.
But for a quick and easy to follow overview on the undergraduate level, you can consult chapter 12 in D. A. McQuarrie "physical chemistry a molecular approach."
 

1. What is the purpose of finding symmetry in molecules?

The purpose of finding symmetry in molecules is to understand their three-dimensional structure and how their atoms are arranged. This can provide important information about the properties and behaviors of the molecule, such as its stability, reactivity, and interactions with other molecules.

2. How is NMR spectroscopy used to determine symmetry in molecules?

NMR spectroscopy involves bombarding a molecule with radio waves and measuring the energy absorbed by different atoms in the molecule. By analyzing the resulting peaks in the NMR spectrum, scientists can determine the types of atoms present and how they are connected, which can reveal the symmetry of the molecule.

3. What are some common techniques used to visualize the three-dimensional structure of a molecule?

Some common techniques used to visualize the three-dimensional structure of a molecule include X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, and computational methods such as molecular modeling and molecular dynamics simulations.

4. How does symmetry affect the chemical properties of a molecule?

Symmetry can greatly influence the chemical properties of a molecule. For example, molecules with high symmetry tend to be more stable and less reactive, while molecules with low symmetry may have more varied properties. Additionally, the symmetry of a molecule can impact its polarity, which can affect its solubility and interactions with other molecules.

5. Can molecules have different types of symmetry?

Yes, molecules can have different types of symmetry, including rotational symmetry, reflection symmetry, and inversion symmetry. Some molecules may have multiple types of symmetry, while others may have little to no symmetry at all. The type and degree of symmetry can vary greatly between different molecules and can greatly impact their properties and behaviors.

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