tailieunhanh - Nuclear Magnetic Resonance 1

NMR is an experiment in which the resonance frequencies of nuclear magnetic systems are investigated. NMR always employs some form of magnetic field (usually a strong externally applied field B0) NMR is a form of both absorption and emission spectroscopy, in which resonant radiation is absorbed by an ensemble of nuclei in a sample, a process causing detectable emissions via a magnetically induced electromotive force. | a W VILLANOVA UNIVERSITY Nuclear Magnetic Resonance 1 Lecture Date February 11th 2008 Nuclear Magnetic Resonance Reading for NMR - Chapter 19 of Skoog et al. - Handout What SSNMR can offer to organic chemists Nuclear Magnetic Resonance NMR - Nuclear spin transitions in the 5-900 MHz range - Magnetic resonance imaging MRI 1 What is NMR NMR is an experiment in which the resonance frequencies of nuclear magnetic systems are investigated. NMR always employs some form of magnetic field usually a strong externally applied field B0 NMR is a form of both absorption and emission spectroscopy in which resonant radiation is absorbed by an ensemble of nuclei in a sample a process causing detectable emissions via a magnetically induced electromotive force. A. Abragam The Principles of Nuclear Magnetism 1961 Oxford Clarendon Press. 2 Things that can be learned from NMR data. Covalent chemical structure 2D structure - Which atoms functional groups are present in a molecule - How the atoms are connected covalently bonded 3D Structure - Conformation - Stereochemistry Molecular motion Chemical dynamics and exchange Diffusion rate 3D Distribution of NMR spins in a medium - an image - Better known as MRI Plus many more things of interest to chemists. History of NMR 1920-1930 physics begins to grasp the concepts of electron and nuclear spin 1936 C. J. Gorter Netherlands attempts to study 1H and 7Li NMR with a resonance method but fails because of relaxation 1945-6 E. M. Purcell Harvard and F. Bloch Stanford observe 1H NMR in 1 kg of parafin at 30 MHz and in water at 8 MHz respectively 1952 Nobel Prize in Physics to Purcell and Bloch 1957 P. C. Lauterbur and Holm independently record 13C spectra 1991 Nobel Prize in Chemistry to R. R. Ernst ETH for FT and 2D NMR 2002 Nobel Prize in Chemistry to K. Wuthrich 2003 Nobel Prize in Medicine to P. C. Lauterbur and P. Mansfield for MRI P C. Lauterbur F Bloch E. M. Purcell R. R. Ernst Photographs from