NMR

NMR spectroscopy is used in qualitative analysis mainly for molecular structure analysis in fields such as organic chemistry and natural product chemistry since it can estimate molecular structures from the information such as chemical shift of signals, coupling-pattern and intramolecular signal area. When electromagnetic waves are irradiated on a substance placed in a magnetic field, absorption and emission of electromagnetic waves (radio waves) at frequencies specific to the atomic nuclei in the substance occur. This phenomenon is called Nuclear Magnetic Resonance (NMR). NMR spectroscopy (also called simply NMR) is a method to record the frequencies of electromagnetic waves absorbed based on the characteristics of atomic nuclei as a function of the absorption peak intensity and the record is an NMR spectrum. In real compounds, resonant absorption occurs at different frequencies for the same type of atomic nucleus (1H, 13C, etc.) if the surrounding chemical environments are different. This is caused by the increase or decrease in the strength of the magnetic field due to shielding of the main magnetic field by a small magnetic field by electrons present near the nucleus and adjacent nuclei. The deviations in the resonance frequency thus caused are called chemical shifts. Although this frequency shift is slight, accurate measurement of this slight shift provides information on the compound.