NMR Spectroscopy - Principle & Types

Dhristi JEE 2022-24

NMR Spectroscopy

Spectroscopy is a technique in which we study the interaction between matter and electromagnetic radiation. There are different types of spectroscopy such as infrared spectroscopy, UV-spectroscopy, NMR-spectroscopy, etc. In this article, we will discuss NMR- spectroscopy. In NMR-spectroscopy, we will cover the following- NMR-meaning, NMR-spectroscopy principle (or NMR-principle), NMR-instrumentation (or NMR-spectroscopy instrumentation), and application of NMR-spectroscopy. 


What is NMR-Spectroscopy? 

NMR- spectroscopy is a type of spectroscopy by which we can determine the quality and purity of a sample and the molecular structure of a compound. 


What is NMR?

NMR is an abbreviation of Nuclear Magnetic Resonance. So, NMR-spectroscopy is a spectroscopy technique based on the nuclear magnetic resonance of atoms of the sample being examined. 


NMR-Spectroscopy Principle 

It is based on the fact that the nuclei of most of the atoms show spin and all nuclei are electrically charged. NMR-spectroscopy is based on the absorption of electromagnetic radiation in the radiofrequency region 3kHz-300 GHz. Nuclei of atoms have spin and electrical charge, so they generate magnetic fields. In the presence of an external magnetic field, nuclei of atoms align themselves either in the direction of the external magnetic field or in the opposite direction of the external magnetic field. 


In the presence of an external magnetic field, energy transfer takes place between the ground state to the excited state. 


It takes place at a wavelength that matches with radio frequencies and when the electron returns from an excited state to ground state, it emits the radio wave of the same frequency. This emitted radio frequency gives NMR spectrum. This emitted radiofrequency is proportional to the strength of the applied external magnetic field.      

                

B0= external magnetic field


γ= the between the nuclear magnetic moment and angular moment.


NMR-Instrumentation – 

Sample holder used in NMR-spectroscopy is a glass tube. Generally, 8cm long. 

  • Permanent powerful magnet is used to provide a homogeneous magnetic field. 

  • Magnetic coils also generate magnetic fields. 

  • Sweep generators can modify the strength of the magnetic field. 

  • Radio frequency input oscillator produces powerful but short radio waves. 

  • Radio frequency output receiver is used to receive radio frequency signals coming from the sample.

  • System is connected with a computer to analyze and record NMR-spectrum. 

Generally, carbon tetrachloride and carbon disulphide are used as solvents for samples being examined in NMR-spectroscopy. 


Applications of NMR-Spectroscopy – 

NMR-applications are as follows- 

  1. It is used for quantitative analysis of mixtures of compounds. 

  2. It is used for quality control. 

  3. It is used to determine the molecular structure of compounds. 

  4. It is used to check the purity of samples. 

  5. It is used in food science. 

  6. It is used in the study of drugs. 

  7. It is used in the study of biofluids, cells and nucleic acids. 

 

Limitations of the NMR Spectroscopy and Ways to Overcome 

NMR spectroscopy is one of the definitive methods used in organic chemistry. However, there are certain limitations to this technique that can come in your way while experimenting. Below you will find the limitations of NMR spectroscopy and what you can do to overcome them.  


1. Sensitivity 

Even though NMR spectroscopy is a versatile technique, it often fails due to its low sensitivity. It is a huge disadvantage while examining metabolomics or other complex reactions.   

 

There are several methods to overcome the sensitivity problem in NMR spectroscopy. For example, you can use advanced hardware to improve the sensitivity during NMR experiments. 

 

2. Magnetic Field Drift

Drift in the magnetic field has a huge impact on NMR spectroscopy, leading to distorted lineshapes and spectral leaks. This can make the interpretations of the results a lot tougher. 


In such cases, you can make certain corrections in the magnetic field while recording the measurement. For this, deuterium present in NMR solvents is detected, which enables the tracking of the magnetic field drift. Subsequently, adjustments in the main field are made with the use of electromagnets at room temperatures. 

How can I Revise the NMR Spectroscopy - Principle and Types? 

Revising the concept of NMR Spectroscopy - Principle and Types will be easy if you have gone through the textbook explanations at least once. You can start revising the NMR Spectroscopy - Principle and Types from Vedantu’s website as we provide you with notes of this topic in simple language to make it easy to comprehend. Moreover, you can make notes for this concept using textbooks and reference guides and summarize the topic. This summarized version will help you during last-minute revisions. Try to answer the questions related to NMR Spectroscopy - Principle and Types and check whether you have understood this concept or not. Furthermore, during your exam preparations, have a look at the questions, based on NMR Spectroscopy - Principle and Types, in simple papers and previous year chemistry question papers to understand the pattern and difficulty level of the chemistry exam.  

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FAQs (Frequently Asked Questions)

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2. What are the techniques of NMR Spectroscopy?

Below are the various techniques of NMR Spectroscopy: 

  • Resonant frequency: It is the energy absorbed by the NMR active nuclei when placed in a magnetic field. 

  • Acquisition of spectra: In this method, a nuclear magnetic resonance response is acquired. It has a weak signal that can only be picked by sensitive radio receivers.  

  • Sample handling: An NMR spectrometer has a radio frequency emitter, a strong magnet that contains a spinning sample holder, and a receiver with a probe that is used for NMR spectroscopy. 

3. Is it necessary to study the concept of NMR Spectroscopy - Principle and Types?

Yes, it is necessary to study the concept of NMR Spectroscopy - Principle and Types as it is one of the most important topics of chemistry. Inorganic chemistry, NMR spectroscopy is the ideal method to identify monomolecular organic compounds. Moreover, even biochemists use this technique to identify protein and other molecules. If you are a student of chemistry, learning about the NMR Spectroscopy - Principle and Types will help you a great deal in your studies and improve your understanding of various concepts of organic chemistry.

4. How does the NMR Spectroscopy - Principle and Types help me?

The NMR Spectroscopy - Principle and Types will strengthen your knowledge of the chemistry subject. By learning the NMR Spectroscopy - Principle and Types, you can improve your understanding of molecules and how to determine the chemical and physical properties of an atom. Since it is a crucial concept of organic chemistry, learning it will help you score well in your exams. You can gain more knowledge on the NMR Spectroscopy - Principle and Types from Vedantu’s learning platform and understand the various techniques, instrumentation, and application of NMR spectroscopy.

5. Difference between 1H NMR and 13C NMR.

There are only two types of nuclear magnetic resonance, namely 1H NMR and 13C NMR. The major difference between 1H NMR and 13C NMR is that the former is used to determine the number of hydrogen atoms in a molecule, whereas the latter is used to determine that of carbon atoms in a molecule. 1H NMR usually has a slow process whereas the 13C NMR works much faster. The chemical shift range for 1H NMR and 13C NMR is 0-14 ppm and 0-240 ppm respectively. 

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