NMR spectroscopy - PowerPoint PPT Presentation

Loading...

PPT – NMR spectroscopy PowerPoint presentation | free to download - id: 75ead0-YzU5Y



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

NMR spectroscopy

Description:

NMR spectroscopy L.O.: State that NMR spectroscopy involves interaction of materials with low-energy radio frequency radiation. Describe the use of tetramethylsilane ... – PowerPoint PPT presentation

Number of Views:70
Avg rating:3.0/5.0
Slides: 26
Provided by: j1090
Learn more at: http://drbravochemistry.wikispaces.com
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: NMR spectroscopy


1
NMR spectroscopy
  • L.O.
  • State that NMR spectroscopy involves interaction
    of materials with low-energy radio frequency
    radiation.
  • Describe the use of tetramethylsilane, TMS, as
    the standard for chemical shift measurement.
  • State the need for deuterated solvents, e.g.
    CDCl3, when running an NMR spectrum.

2
(No Transcript)
3
  • Some nuclei have a magnetic spin 1H, 13C, 19F
  • In a strong magnetic field they can line up
    either with the field or opposed the field.

4
Different nuclear spins in an external magnetic
field
5
Excitation a nucleus in its low energy spin
state can be promoted to an upper energy
level. This energy is provided by a
radio-frequency radiation. Relaxation The
excited nucleus will drop back to the lower
energy level. Resonance the energy provided by
the radiation is the same as the energy gap
between the tow spin states.
6
  • The magnetic field felt by each nucleus depends
    on
  • the applied magnetic field
  • Chemical environment. Electrons surrounding the
    nucleus generate a magnetic field.

7
Nuclear shielding electrons modify the magnetic
field experienced by the nucleus
8
  • Chemical shift, d, is a scale that compares the
    frequency of an NMR absorption with the frequency
    of the reference peak of TMS at d0.

9
Tetramethylsilane (TMS), (CH3)4Si
10
Carbon-13 NMR spectroscopy
  • L.O.
  • Analyse carbon-13 NMR spectra to make predictions
    about the different types of carbon atoms
    present.
  • Predict the chemical shifts of carbons in a given
    molecule.

11
Carbon-13 chemical shifts
12
  • Electron withdrawing groups (O, CO, F, N) are
    less shielding.
  • The less shielding, the higher the chemical
    shift.

13
How many carbon environments?
14
Carbon-13 NMR spectra of propan-1-ol and
propan-2-ol
15
Carbon-13 NMR spectra of propan-1-ol and
propan-2-ol showing peak assignments
16
Carbon-13 NMR spectra of (a) CH3CHBrCH3 and (b)
CH3COOCH3
17
13C NMR TASK 1 For each of these compounds
indicate the number of signals in the 13C NMR
spectrum predict the approximate chemical shift
of each signal using the data sheet   a)methylprop
ene b)propene c)2-chloropropane d)Propanone e)
methylamine f)ethyl propanoate g)
1,2-dibromopropane h)dimethylethyl propanoate
i)but-2-ene
18
  • L.O.
  • Analyse carbon-13 NMR spectra to make predictions
    about possible structures for an unknown compound.

19
Carbon-13 NMR spectra of isomer of C3H6O
20
Structural isomers of the carbonyl isomers of
C3H6O showing different carbon environments
21
Carbon-13 NMR spectra of an aromatic compound
with molecular formula C8 H8
22
Structural isomers of the aromatic isomers of C8H8
23
(No Transcript)
24
13-C NMR of butane
25
(No Transcript)
About PowerShow.com