Chapter13 - 13. Structure Determination: Nuclear Magnetic...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
13. Structure Determination: Nuclear Magnetic Resonance Spectroscopy Based on McMurry’s Organic Chemistry , 6 th edition ©2003 Ronald Kluger Department of Chemistry University of Toronto
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
McMurry Organic Chemistry 6th edition Chapter 13 (c) 20 2 The Use of NMR Spectroscopy Used to determine relative location of atoms within a molecule Most helpful spectroscopic technique in organic chemistry Related to MRI in medicine (Magnetic Resonance Imaging) Maps carbon-hydrogen framework of molecules Depends on very strong magnetic fields
Background image of page 2
McMurry Organic Chemistry 6th edition Chapter 13 (c) 20 3 13.1 Nuclear Magnetic Resonance Spectroscopy 1 H or 13 C nucleus spins and the internal magnetic field aligns parallel to or against an aligned external magnetic field (See Figure 13.1) Parallel orientation is lower in energy making this spin state more populated Radio energy of exactly correct frequency (resonance) causes nuclei to flip into anti-parallel state Energy needed is related to molecular environment (proportional to field strength, B ) – see Figure 13.2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
McMurry Organic Chemistry 6th edition Chapter 13 (c) 20 4 13.2 The Nature of NMR Absorptions Electrons in bonds shield nuclei from magnetic field Different signals appear for nuclei in different environments
Background image of page 4
McMurry Organic Chemistry 6th edition Chapter 13 (c) 20 5 The NMR Measurement The sample is dissolved in a solvent that does not have a signal itself and placed in a long thin tube The tube is placed within the gap of a magnet and spun Radiofrequency energy is transmitted and absorption is detected Species that interconvert give an averaged signal that can be analyzed to find the rate of conversion
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
McMurry Organic Chemistry 6th edition Chapter 13 (c) 20 6 13.3 Chemical Shifts The relative energy of resonance of a particular nucleus resulting from its local environment is called chemical shift NMR spectra show applied field strength increasing from left to right Left part is downfield is upfield Nuclei that absorb on upfield side are strongly shielded. Chart calibrated versus a reference point, set as 0, tetramethylsilane [TMS]
Background image of page 6
McMurry Organic Chemistry 6th edition Chapter 13 (c) 20 7 Measuring Chemical Shift Numeric value of chemical shift: difference between strength of magnetic field at which the observed nucleus resonates and field
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 01/03/2012.

Page1 / 23

Chapter13 - 13. Structure Determination: Nuclear Magnetic...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online