1 / 10

NMR Spectroscopy

NMR Spectroscopy. NMR spectroscopy gives information on the type of hydrogen atoms in a molecule. Specifically, -CH 3 , -CH 2 , CH 2 OH etc, The location of peaks and the height of the peaks indicate what type of hydrogen atoms and the number of hydrogen atoms, are present respectively.

elisa
Download Presentation

NMR Spectroscopy

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. NMR Spectroscopy • NMR spectroscopy gives information on the type of hydrogen atoms in a molecule. Specifically, -CH3, -CH2, CH2OH etc, • The location of peaks and the height of the peaks indicate what type of hydrogen atoms and the number of hydrogen atoms, are present respectively.

  2. How NMR works • The nuclei of hydrogen atoms possess spin that exists in two different states of equal energy. • When a radio frequency with a varying magnetic field is applied to a molecule, the hydrogen’s spin state align themselves either with or against the magnetic field. • This alignment of the hydrogen absorbs energy. This energy comes from the absorption of radiation from the radio frequency being applied. • This absorption, or chemical shift, makes a spectrum.

  3. Why are there different absorption peaks? • Each hydrogen does not absorb the same amount of radiation because they do not all have the same bond strength between itself and the carbon to which it is bonded. Bond strength is affected by surrounding bonds. • Examples: CH3CH2CH3 • There would be two peaks, or chemical shifts on its NMR spectrum indicating two different types of C-H bonds, CH3- and CH2- . • The CH3- peak would be higher because there 6 of these H’s. There are only 2 of the other.

  4. NMR spectroscopy • Type of proton Chemical shift/ppm • R-CH3 0.9 • R2-CH2 1.3 • R3CH 2.0 • CH3COR(ester) 2.0 • R-C-CH3 (Ketone) 2.1 • R-OH 4.5 • R-C-H (aldehyde) 9.7

  5. Example: CH3CHCl2 • There are 2 peaks, or chemical shifts, indicating 2 types of Hydrogen C-H bonds: CH3-, andCHCl2, • The 2 peaks on this spectrum would not be similar in height, with the CH3- peak being higher with 3H’s the CHCl2 has only one H.

  6. NMR spectrum of 1,1dichloroethane

  7. How many peaks would there be in propane’s NMR spectrum? • CH3CH2CH3

  8. NMR spectrum for propane  CH3 • CH2  • C

  9. Summary Chart

  10. Summary continued • No single test is adequate in determining the structure of a molecule. The tests are effective when combined with each other. • The best way to identify an unknown molecule is to compare its tests results with a known molecule.

More Related