Applied Spectroscopy autumn 2014 Lampmann,Pavia, Kriz and Vyvyan, Spectroscopy Homepage for course: milne.ruc.dk/kemikurser/analytNMR

Content NMR MS IR Plus review of traditional analysis methods

Elementary analysis

Double bond equivalents DBE= (2n C n N –n H – n Hal )/2

What is NMR Nuclear Magnetic Resonance What can we solve What do we need –Powerfull magnet –Powerful Radio frequency transmitter –Sensitive Receiver –Fast computer

Follower

Usnic acid

Choline(CHo) Creatine(Cr)

Alkohol in the brain in time

General Scheme

NMR system

Superconducting NMR magnet 5 magnet coil 6. Liquid nitrogen 7. Liquid helium (4 K) 8.Vacuum 10. Dewar made of stainless steel

Beijing 2014Department of Science, Systems and Models Spins

Spin quantum numbers

Beijing 2014Department of Science, Systems and Models Resonance

Operating frequencies

Spin distribution B0B0

Excess nuclei out of a million

Boltzmann distribution Depends on the energy difference between two states For NMR the energy difference is very small The number of spin in the lower and higher energy levels are allmost the same Only few can be moved which means very poor sensitivity

Induced currents

The chemical shift =  B 0 (1-  )/2 

orillgninal NMR spectrum of alcohol

Simple NMR spectrum

Beijing 2014Department of Science, Systems and Models Methyl acetate 1H 13C

Referencing and chemical shifts TMS Beijing 2014Department of Science, Systems and Models

Solvent signals

Position of water signal

Free induction decay

Tables

Equivalence

Integrals

Chemical shift overview

Electronegativity

Effects of a single substitution

XH protons

Hydrogen bonding!!

Ring currents

Johnson-Bovey map

Anisotropic shielding of C=O groups 10 ppm shielded deshielded shielded

Shieldings caused by bonds

90MHz

360 MHz

1 H NMR spectrum of ?