NMR Spectroscopy: Introduction to Spin, Energy Levels and Radiation Absorption - Essay Sample

Introduction

The experiment is designed to introduce the concept of nuclear magnetic resonance. It entails spin, energy levels as well as the absorption of radiation. The experiment on the nuclear magnetic resonance involves a series of known samples used for introducing methods of sample preparation and operation of the nuclear magnetic resonance spectrum used for measuring the chemical shifts and the spectral intensities (Christopher Bardeen, 2020). From the experiment, the unknown spectra are recorded while determining the structure and identity of the compounds.

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Objectives

The objectives of this experiment are to understand the role of the nuclear magnetic resonance in the study of organic compounds, to develop a significant understanding of the number, positions as well as intensities and splitting of signals in nuclear magnetic resonance.

The spectroscopic methods used in this experiment is useful in structure determination. The nuclear magnetic resonance spectroscopy, therefore, implies applying the external magnetic field to bring the nucleus of a particular atom into resonance. In some cases, with the nuclei being either hydrogen or carbon, the resonance takes place at an adequate field strength, although it depends on the environment as well as the applied field strength.

The experiment attempts to explain the pattern among the acetaldehyde protons. It entails the use of the spectral parameters, including chemical shifts, as well as the coupling constants. The hypothesis tested in this experiment is that the spectrum of the nuclear magnetic resonance exhibits the resolved fine structure. In preparing the nuclear magnetic resonance samples, a glass pipette is used. It entails placing a rubber bulb on the pipette while holding the tube immediately below the point of attachment to avoid the breakage of glass. The fields generated by the nuclear magnetic resonance might have deleterious effects on watches, thus the need to leave such items in an alternative location.

The scientific question nuclear magnetic resonance experiment attempts to answer is based on the outcomes of the nuclear magnetic resonance basing on the applied field. With the number of signals indicating the number of hydrogen present, the question of how the environment affects the chemically equivalent protons is raised. As a result, the concept of the chemical shift that is measured as a percentage of the applied magnetic field is used to show the resonance that will appear at higher parts per million. Therefore, nuclear magnetic resonance provides the ability to calculate the area under the signal, which is proportional to the number of hydrogen responsible for the signal (Christopher Bardeen, 2020). It also provides the relative ratio of each hydrogen present in the molecule. The basics behind the nuclear magnetic resonance experiment include the large magnetic field, and the radio frequency applied. The correct rate and magnetic field lead to nuclear spin transitions that result in resonance.

Safety

Several chemicals are involved in the experiment thus the need for everyone to be careful while handling them to avoid harm. Besides, there is a need to measure the deuterated solvents, including the acetone-d6.

Procedure

Sample Preparation

The nuclear magnetic resonance tubes for samples both known and unknown. The samples are cleaned and made free of dust and particular matter. They are then dissolved such that the solvent formed is deuterated. The liquid samples are then diluted in a deuterated solvent. The nuclear magnetic resonance sample is 175 mm in length, and its minimum filling levels at a distance of about 3 within the tube (Christopher Bardeen, 2020). The optimal filling level of about 5 cm below the tube. The tube was put in a probe such that the position of the transmitter coil became 1 cm of the tube. The formed solvent was then dissolved in the sample material to get the desirable solution for using as a concentrated solution of about 10%. However, there are some difficult cases where the used samples could not dissolve, thus the need to find an alternative solvent. As a result, the solvents commonly used for the protons of nuclear magnetic resonance are the acetone-d6 and the Hexa-deuterodimethyl-sulfoxide. It is essential to make the sample tube clean within its surfaces. This is meant to make the particles visible since the unaided eye may degrade the resolution.

Reference Material

Providing a reference material for this experiment focused on the chemical shift in line with the spectrum involved. The reference material is essential as it helps in measuring the other signals. The standard method used for adding a reference material entailed a standard sample. The reference material selected was appropriate in such a way that it could not interact with the sample being tested. In case the samples used as a reference material was a symmetrical type, there will be a small effect. In this experiment, therefore, tetramethylsilane was found to be the most suitable reference material. It had several advantages as a reference material since the spectra line ensured higher field position as compared to the other signals. As a result, the chemical shifts of nearly all lines are measured concerning the tetramethylsilane. However, the experiment has alternative reference materials including a sealed capillary tube inserted into the tubes of the sample.

Standard Samples

With the use of four separate nuclear magnetic resonance tubes, various samples, including Acetaldehyde, Ethylbenzene, and Vinyl acetate as well as hexafluoroisopropanol, were prepared. It involved the simulation of crotonaldehyde nuclear magnetic resonance spectrum. The spectra were recorded with the chemical shifts measured.

References

Christopher Bardeen. (2020). Lecture 4 Lab II NMR [Video]. YouTube. https://www.youtube.com/watch?v=dc9ct0H6JtM&feature=youtu.be

Christopher Bardeen. (2020). NMR Chem 114 [Video]. YouTube. https://www.youtube.com/watch?v=JK6UvtuQHuM&feature=youtu.be