"Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei."
A technique to study the structure of molecules and the interaction of molecules with their surroundings.
Magnetic Resonance: Magnetic resonance is a phenomenon that occurs when an atomic nucleus is placed in a strong magnetic field and subjected to radiofrequency radiation.
Nuclear Spin: Nuclear spin is the angular momentum of the nucleus. It affects the magnetic behavior of the nucleus and is a key player in NMR.
Chemical Shift: Chemical shift is the displacement of an NMR signal from the reference standard. It arises from the magnetic environment of the nucleus being different from the standard.
Spin-Spin Splitting: Spin-spin splitting is a phenomenon in which one NMR resonance signal is split into multiple signals due to the interaction between nearby spins.
Relaxation: Relaxation refers to the rate at which nuclear spins return to their original state after being perturbed by radiofrequency radiation.
Pulse Techniques: Pulse techniques are methods used to manipulate the magnetic fields experienced by the nuclei to excite and detect NMR signals.
Fourier Transform NMR: Fourier transform NMR is a technique used to convert time-domain NMR signals into frequency-domain spectra, which are easier to interpret.
2D NMR: D NMR techniques use two orthogonal radiofrequency pulses to correlate signals from different types of nuclei, providing additional structural information.
Nuclear Overhauser Effect: The nuclear Overhauser effect is the transfer of nuclear spins from one nucleus to another through dipolar coupling, providing information about molecular structure.
Chemical Exchange: Chemical exchange is the process in which two or more species interchange rapidly, resulting in different NMR signals. It is used to study dynamic processes in solution.
Solid-State NMR: Solid-state NMR is a technique used to study the structure and dynamics of molecules within solid materials.
Paramagnetic NMR: Paramagnetic NMR is a technique used to study the interactions between nuclear spins and paramagnetic species, such as metal ions or free radicals, leading to the elucidation of complex structures.
Relaxation Editing: Relaxation editing is a technique used to separate NMR signals from different relaxation times, enabling the study of molecular dynamics.
NMR Imaging: NMR imaging is a technique used to obtain multi-dimensional images of the internal structure of large objects, such as the human body, by exploiting differences in relaxation properties.
Applications of NMR: NMR spectroscopy is used in a wide variety of fields, including chemistry, medicine, biology, and materials science, to characterize molecular structures and dynamics.
Proton Nuclear Magnetic Resonance (1H NMR): This is the most widely used NMR technique in analytical chemistry, and it provides information about the chemical structure, concentration, purity, and stereochemistry of organic compounds. It is based on the interaction between the magnetic field of the NMR instrument and the spin of hydrogen nuclei in a molecule.
Carbon Nuclear Magnetic Resonance (13C NMR): This technique provides structural information for organic and organometallic compounds by detecting the resonant absorption of the 13C isotope in a molecule. It can be used to determine the number and type of carbons in a compound.
Fluorine Nuclear Magnetic Resonance (19F NMR): This technique is used to study organic and organometallic compounds that contain fluorine atoms. It provides information on the molecular structure, electronic environment, and intermolecular interactions of the molecule.
Nitrogen Nuclear Magnetic Resonance (15N NMR): This technique is used to analyze compounds containing nitrogen. It provides information on the number and types of nitrogen atoms in a molecule, as well as the molecular structure and properties.
Phosphorus Nuclear Magnetic Resonance (31P NMR): This technique is used to study organic and organometallic compounds containing phosphorus atoms. It provides information on the molecular structure, electronic environment, and intermolecular interactions of the molecule.
Two-Dimensional Nuclear Magnetic Resonance (2D NMR): This technique is used to analyze complex molecules and determine the connectivity between different atoms in the molecule. It involves the acquisition of two separate spectra that are related by a pulse sequence.
Solid-State Nuclear Magnetic Resonance (SSNMR): This technique is used to analyze samples that are in a solid-state, such as crystals or powders. It provides information on the molecular structure, dynamics, and interactions in the solid-state material.
Time-Domain Nuclear Magnetic Resonance (TD-NMR): This technique is used for the characterization of liquids, powders, and polymers. It provides information on the molecular mobility and relaxation properties of the material.
Diffusion-Ordered Nuclear Magnetic Resonance (DOSY NMR): This technique is used for the separation and differentiation of multiple species in a mixture. The NMR signals are separated based on their diffusion constants.
Relaxation-Edited Nuclear Magnetic Resonance (RELAX NMR): This technique is used to analyze complex mixtures containing overlapping signals. It can be used to separate the signals of different components in the mixture based on their relaxation properties.
"The principle of NMR usually involves three sequential steps: The alignment (polarization) of the magnetic nuclear spins in an applied, constant magnetic field B0. The perturbation of this alignment of the nuclear spins by a weak oscillating magnetic field, usually referred to as a radio-frequency (RF) pulse. Detection and analysis of the electromagnetic waves emitted by the nuclei of the sample as a result of this perturbation."
"The sample is placed in a magnetic field and the NMR signal is produced by excitation of the nuclei sample with radio waves into nuclear magnetic resonance, which is detected with sensitive radio receivers."
"NMR spectroscopy provides detailed information about the structure, dynamics, reaction state, and chemical environment of molecules."
"The most common types of NMR are proton and carbon-13 NMR spectroscopy, but it is applicable to any kind of sample that contains nuclei possessing spin."
"NMR spectra are unique, well-resolved, analytically tractable and often highly predictable for small molecules. Different functional groups are obviously distinguishable, and identical functional groups with differing neighboring substituents still give distinguishable signals."
"A disadvantage is that a relatively large amount, 2–50 mg, of a purified substance is required, although it may be recovered through a workup [...] The timescale of NMR is relatively long, and thus it is not suitable for observing fast phenomena, producing only an averaged spectrum."
"Correlation spectroscopy is a development of ordinary NMR. In two-dimensional NMR, the emission is centered around a single frequency, and correlated resonances are observed. This allows identifying the neighboring substituents of the observed functional group, allowing unambiguous identification of the resonances."
"Modern NMR spectrometers have a very strong, large and expensive liquid helium-cooled superconducting magnet, because resolution directly depends on magnetic field strength. Less expensive machines using permanent magnets and lower resolution are also available, which still give sufficient performance for certain applications such as reaction monitoring and quick checking of samples."
"NMR spectrometers are relatively expensive; universities usually have them, but they are less common in private companies."
"Between 2000 and 2015, an NMR spectrometer cost around 500,000 - 5 million USD."
"NMR can be observed in magnetic fields less than a millitesla."
"Low-resolution NMR produces broader peaks which can easily overlap one another causing issues in resolving complex structures."
"In modern organic chemistry practice, NMR spectroscopy is the definitive method to identify monomolecular organic compounds."
"Similarly, biochemists use NMR to identify proteins and other complex molecules."
"NMR spectroscopy provides detailed information about the structure, dynamics, reaction state, and chemical environment of molecules."
"The most common types of NMR are proton and carbon-13 NMR spectroscopy."
"Preferably, the sample should be dissolved in a solvent, because NMR analysis of solids requires a dedicated magic angle spinning machine and may not give equally well-resolved spectra."
"Although large amounts of impurities do show on an NMR spectrum, better methods exist for detecting impurities, as NMR is inherently not very sensitive - though at higher frequencies, sensitivity is higher."
"NOE spectroscopy allows for the relaxation of resonances to be observed, and by quantifying the NOE for each nucleus, a three-dimensional model of the molecule can be constructed."