High Resolution Proton NMR Spectroscopy Peak Splitting (n+1 Rule) explained in A-level Chemistry

**Proton NMR Spectroscopy: Explained with Examples and Applications**

In this informative video, we delve into the world of proton NMR spectroscopy. We will discuss the concept of spin-spin coupling and explore how peak splitting occurs in high-resolution NMR spectroscopy. Furthermore, we will examine the practical application of the n+1 rule through examples.

To fully grasp the intricacies of peak splitting and spin-spin coupling, it is crucial to have a solid understanding of the general theory of proton and mass spectroscopy. If you need a refresher on this topic, check out our detailed video on the subject.

Proton NMR spectroscopy is a powerful technique used for the analysis of compounds in organic chemistry. By examining the spectra produced, we can obtain valuable information about the number of unique hydrogen environments in a molecule, the arrangement of these environments, and the ratio of hydrogen atoms in each environment.

In proton NMR spectroscopy, the protons’ spin within the hydrogen atom’s nucleus is flipped against an externally applied magnetic field. This flip is achieved using radio waves, resulting in resonance. Depending on the hydrogen atom’s specific environment, varying amounts of energy are required to flip its spin. As a result, hydrogen atoms in different environments absorb different frequencies of radio waves.

High-resolution proton NMR spectroscopy enables us to understand the number of hydrogen atoms bonded to adjacent, non-equivalent carbon atoms in a molecule. Adjacent non-equivalent carbon atoms refer to carbon atoms bonded to the same carbon atom, yet not bonded to the same atoms or groups. For instance, in the molecule ethanol, the two hydrogens bonded to the first carbon (the CH2OH group) are adjacent to a carbon that is bonded to another carbon atom. This carbon atom is considered an adjacent non-equivalent carbon atom since it is bonded to different atoms and groups, making it nonequivalent.

When a hydrogen atom is bonded to a carbon, which in turn is bonded to an adjacent non-equivalent carbon atom, spin-spin coupling occurs. This interaction between the protons in each of these hydrogen atoms creates a weak magnetic field that can align with or go against the external magnetic field used in the NMR process. These situations require different amounts of energy to flip the spin of the proton, resulting in two possible frequencies being absorbed by the same proton environment. Consequently, the original hydrogen environment’s single peak in the NMR spectrum becomes split into two smaller peaks.

It’s important to note that the splitting effect becomes visible only with high-resolution NMR spectroscopy due to its sensitivity. When observing peak splitting, different numbers of hydrogen atoms bonded to adjacent non-equivalent carbon atoms can cause peaks for other hydrogen atom environments to split differently. This phenomenon follows the n+1 rule, where “n” represents the number of protons or hydrogen atoms bonded to adjacent non-equivalent carbon atoms. For example, if there are three hydrogen atoms bonded to adjacent non-equivalent carbon atoms, the main peak for that environment will split into four peaks, forming a quartet.

In this video, we provide examples of peak splitting using the molecules ethanal and ethanol. By applying the n+1 rule, we can predict the peak splitting pattern for each hydrogen environment, providing a deeper understanding of the complex nature of proton NMR spectroscopy.

For students studying AQA, OCR (A), Edexcel, and CIE, this video is an excellent resource for understanding and applying the concepts of peak splitting, spin-spin coupling, and the n+1 rule.

**Timestamps:**

– Recap: 00:23
– Adjacent, non-equivalent carbon atoms: 02:10
– Spin-Spin Coupling: 04:04
– Peak Splitting: 05:02
– Example – Ethanal: 05:11
– n+1 rule: 07:11
– Example – Ethanol: 08:01
– Summary: 10:31

**Additional Resources:**

– Check out the NMR spectroscopy section on [ChemistryStudent.com](https://www.chemistrystudent.com/NMRSpectroscopy.html) for in-depth reading on the topic.

**Relevant Videos:**

– [Proton NMR](https://youtu.be/98js-JK166c)

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*Transcript of the video:*

In the video, the speaker explains the concept of proton NMR spectroscopy, focusing on spin-spin coupling, peak splitting, and the application of the n+1 rule. Proton NMR spectroscopy is a technique used in organic chemistry to analyze compounds and gain insights into their structure and composition.

To understand peak splitting and spin-spin coupling, it is important to have a basic understanding of proton and mass spectroscopy, which is covered in a separate video. Proton NMR spectroscopy involves the flipping of the proton’s spin within the hydrogen atom’s nucleus against an externally applied magnetic field. This flip is achieved using radio waves, resulting in resonance. Different environments of hydrogen atoms within a molecule absorb different frequencies of radio waves.

High-resolution proton NMR spectroscopy provides information about the number of hydrogen atoms bonded to adjacent non-equivalent carbon atoms in a molecule. Adjacent non-equivalent carbon atoms are those bonded to the same carbon atom but not to the same atoms or groups. For example, in ethanol, the two hydrogens bonded to the first carbon (CH2OH group) are adjacent to a carbon bonded to another carbon atom. This adjacent carbon atom is nonequivalent as it is bonded to different atoms and groups.

When a hydrogen atom is bonded to a carbon atom, which is bonded to an adjacent non-equivalent carbon atom, spin-spin coupling occurs. The protons in these hydrogen atoms interact, creating a weak magnetic field. This magnetic field can align with or go against the external magnetic field used in NMR spectroscopy, resulting in two possible frequencies being absorbed by the same proton environment. Consequently, the original hydrogen environment’s single peak in the NMR spectrum splits into two smaller peaks close together, known as peak splitting.

Peak splitting can only be observed with high-resolution NMR spectroscopy due to its sensitivity. The number of hydrogen atoms bonded to adjacent non-equivalent carbon atoms can cause peaks for other hydrogen atom environments to split differently. This follows the n+1 rule, where “n” represents the number of protons or hydrogen atoms bonded to adjacent non-equivalent carbon atoms. Predicting the peak splitting pattern using the n+1 rule provides valuable insights into the structure and arrangement of atoms within a molecule.

The speaker provides examples of peak splitting in the molecules ethanal and ethanol to illustrate the application of the n+1 rule. Students studying AQA, OCR (A), Edexcel, and CIE will find this video particularly helpful in understanding and applying the concepts of peak splitting, spin-spin coupling, and the n+1 rule in proton NMR spectroscopy.

For more extensive reading on NMR spectroscopy, visit the NMR spectroscopy section on [ChemistryStudent.com](https://www.chemistrystudent.com/NMRSpectroscopy.html).

Watch the related video on [Proton NMR](https://youtu.be/98js-JK166c) for a comprehensive overview of the topic.

Thank you for watching! Remember to like and subscribe to our channel for more informative videos on chemistry topics.

Keywords/Tags: [vid_tags]

Outlining peak splitting (spin-spin coupling) and how it arrises with high resolution NMR spectroscopy. The n+1 rule is shown with examples (ethanal and ethanol) and the use of peak splitting to help identify and determine the arrangement of atoms within a given substance is explained, along with what is meant by adjacent, non-equivalent carbon atoms.

For AQA, OCR (A), Edexcel and CIE.

Data table NMR values used and shown are taken from AQA data booklet (7405).

Recap: 00:23
Adjacent, non-equivalent carbon atoms: 02:10
Spin-Spin Coupling: 04:04
Peak Splitting: 05:02
Example – Ethanal: 05:11
n+1 rule: 07:11
Example – Ethanol: 08:01
Summary: 10:31

NMR Examples in the video:
Ethanal: 05:11
Ethanol: 08:01

Pages on chemistrystudent.com:
https://www.chemistrystudent.com/NMRSpectroscopy.html

Relevant Videos:
Proton NMR – https://youtu.be/98js-JK166c

Thank you for watching – if you found the video useful, please like and subscribe!