NMRspektroskoopiat

NMRspektroskoopiat is a scientific technique that uses nuclear magnetic resonance to investigate the structure, composition and dynamics of molecules. When placed in a strong external magnetic field, certain atomic nuclei with spin, most commonly hydrogen-1 (1H) and carbon-13 (13C), occupy distinct energy levels. A radiofrequency pulse perturbs these nuclei, and the subsequent relaxation emits signals that are recorded as free induction decay and translated by Fourier transformation into a spectrum.

Spectra present chemical shifts, measured in parts per million (ppm), which reflect the electronic environment around nuclei, and signal intensities that relate to the number of nuclei. Splitting patterns from spin-spin coupling reveal neighboring atoms, enabling connectivity and stereochemical information. Two or more-dimensional experiments (2D NMR) such as COSY, HSQC, HMBC, NOESY reveal through-bond or through-space relationships and are powerful for complex molecules.

Common nuclei include 1H, 13C; others such as 15N, 19F, 31P. Samples are typically dissolved in deuterated solvents; lock and reference scales often use TMS. Modern spectrometers operate at high magnetic fields (often 400–1000 MHz for 1H) to improve resolution and sensitivity. Data processing includes phasing, baseline correction, and peak assignment; software assists in structure elucidation.

Applications include determining molecular structure, conformations, dynamic processes, purity, reaction monitoring, and metabolomics or pharmaceutical analysis. Limitations include relatively low sensitivity for less abundant nuclei and the need for nonzero spin isotopes; large or flexible molecules may yield overlapping signals. The technique has a long history beginning with discoveries by Bloch and Purcell, leading to widespread use in chemistry, biochemistry and materials science.