Organic Chemistry,7th Edition L.G.Wade,Jr. induced magnetic field Chapter 13 Nuclear Magnetic Resonance Spectroscopy Copyright 2010 Pearson Education,Inc
Chapter 13 Copyright © 2010 Pearson Education, Inc. Organic Chemistry, 7th Edition L. G. Wade, Jr. Nuclear Magnetic Resonance Spectroscopy
Introduction NMR is the most powerful tool available for organic structure determination. It is used to study a wide variety of nuclei: 1H ■13C ■15N ■19F ■31P Chapter 13 2
Chapter 13 2 Introduction • NMR is the most powerful tool available for organic structure determination. • It is used to study a wide variety of nuclei: ▪ 1H ▪ 13C ▪ 15N ▪ 19F ▪ 31P
Nuclear Spin A nucleus with an odd atomic number or an odd mass number has a nuclear spin. The spinning charged nucleus generates a magnetic field. (current) spinning proton loop of current bar magnet Copyright2010 Pearson Prentice Hall,Inc. Chapter 13 3
Chapter 13 3 Nuclear Spin • A nucleus with an odd atomic number or an odd mass number has a nuclear spin. • The spinning charged nucleus generates a magnetic field
External Magnetic Field twist Bo S N Bo Bo N N N N lower energy higher energy more stable less stable Copyright2010 Pearson Prentice Hall,Inc. An external magnetic field(Bo)applies a force to a small bar magnet,twisting the bar magnet to align it with the external field. The arrangement of the bar magnet aligned with the field is lower in energy than the arrangement aligned against the field. Chapter 13 4
Chapter 13 4 External Magnetic Field • An external magnetic field (B0) applies a force to a small bar magnet, twisting the bar magnet to align it with the external field. • The arrangement of the bar magnet aligned with the field is lower in energy than the arrangement aligned against the field
Alpha-spin State and Beta-spin State. (externally applied field) a-spin state B-spin state (lower energy) (higher energy) Copyght010 Pearson Prentice Ha Inc The lower energy state with the proton aligned with the field is called the alpha-spin state. The higher energy state with the proton aligned against the external magnetic field is called the beta- spin state. Chapter 13 5
Chapter 13 5 Alpha-spin State and Beta-spin State. • The lower energy state with the proton aligned with the field is called the alpha-spin state. • The higher energy state with the proton aligned against the external magnetic field is called the betaspin state