nuclear magnetic resonance carbon spectroscopy (NMRCS) experiment

Summary

This experiment is from the official website of College of Chemistry, Qingdao University of Science and Technology.

Operation method

nuclear magnetic resonance carbon spectroscopy (NMRCS) experiment

Principle

2. De-coupling technique: In order to simplify the NMR spectra, the direct and indirect interactions between nuclei are removed.13C NMR spectra mostly use broadband de-coupling (BB de-coupling), which is also known as full de-coupling of the proton noise.13C NMRBB de-coupling can simplify the spectra, so that multiple peaks of the overlapping couples are merged into a single peak. Each peak represents one type of carbon. At the same time, decoupling can enhance the signal-to-noise ratio, the merger of multiple peaks to enhance the signal, the general signal enhancement of 1-2 times. 4, the nuclear Overhauser (NOE) effect this phenomenon is Overhauser in 1953 in the electron spin and nuclear spin samples were first discovered. De-coupling can make the signal enhancement effect is called Overhauser (NOE) effect. The number of times the signal is enhanced is called the NOE factor. In different groups of a sample system, the NOE effect of each nucleus is different, which means that the NOE factors are different, so the multiplicity of enhancement of each peak is not equal, and therefore the heights of the peaks with the same number of carbons are not the same in the BB carbon spectroscopy experiments. Therefore, the heights of the peaks with the same carbon number are not the same in the BB carbon spectrum experiment. In other words, there is no strict quantitative relationship between the intensities of the peaks in the carbon spectrum NMR experiment.

Materials and Instruments

AV-500 CDCL3 Ethylbenzene n-octanol Sample tubes for NMR are specialized sample tubes.

Move

1. Sample tube requirements

The sample tube of nuclear magnetic resonance is a special sample tube, made of good quality temperature-resistant glass, or quartz or polytetrafluoroethylene (PTFE) material. The sample tubes are required to be non-magnetic, with straight walls and uniform thickness. The shape of the sample tube is cylindrical, and the diameter of the sample tube depends on the type of spectrometer probe, and the outer diameter can be as small as 1mm or as large as 25mm. 5mm, 10mm, and 2.5mm sample tubes are commonly used, and the length is greater than 150mm. The length of the sample tubes is required to be greater than 150mm, the sample tubes used in this instrument are 5mm.

2. Sample Preparation and Requirements

Since the signal-to-noise ratio of the 13C NMR spectrum is lower than that of the hydrogen spectrum, one of the ways to improve the signal-to-noise ratio is to increase the amount of sample. Take about 20mg of sample, add it to the sample tube, and dissolve it thoroughly with 0.5ml of deuterium reagent.

The sample should be well mixed with the reagent and the solution should be clear, transparent, and free of suspended matter or other impurities.

3. Power on

Refer to (the same as) experiment two

4. Lock field

See (same as) experiment II

5. Uniform field

See (same as) Experiment II

6. Tuning in the carbon spectrum sampling parameters

7. Adjust the sampling channel

Reference: Nuclear Magnetic Resonance Hydrogen Spectroscopy Experiment

7. Tuning the probe

At this point you can see the instrument were adjusted carbon and hydrogen resonance frequency, carbon nucleus tuned at 125MHZ, hydrogen nucleus tuned at 500.135MHZ.

8. Uniform field or gradient uniform field

Reference: nuclear magnetic resonance hydrogen spectroscopy experiment

9. Sampling

Reference: Nuclear Magnetic Resonance Hydrogen Spectroscopy Experiment

10. Data processing

Reference: Nuclear Magnetic Resonance Hydrogen Spectroscopy Experiment

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