UH CHEM 3331 - nuclear magnetic resonance (3 pages)

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nuclear magnetic resonance



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nuclear magnetic resonance

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Lecture number:
27
Pages:
3
Type:
Lecture Note
School:
University of Houston
Course:
Chem 3331 - Organic Chemistry
Edition:
1
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CHEM 3331 1nd Edition Lecture 27 Outline of Last Lecture I Mass Spectrometry II Electromagnetic spectrum III Infrared Spectroscopy Outline of Current Lecture I NMR Spectroscopy II Number of different peaks III Positions of peaks IV Peak area V Peak splitting Current Lecture I NMR Spectroscopy NMR stands for nuclear magnetic resonance It analyzes the nuclei of H1 C13 N15 F19 and P31 Today we will only be focusing on hydrogen In all of these atoms they have an odd number of protons or neutrons protons They experience a magnetic spin where they rient themselves in an external magnetic field There are and states is high energy and is low energy E h 2 B0 gyromagnetic ratio B0 magnetic field B B0 Bshielding shielding 50 100Hz measured in ppm II Number of different peaks The number of peaks the number of kinds of H CH4 1 CH3CH3 1 CH3CH2CH3 2 H2C CH2 1 H2C CHF 3 CH3OH 2 benzyne 2 These hydrogens differ or rather don t differ due to symmetry being peripheral or internal relationship to F Br Cl and I III Positions of peaks These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute This depends on shielded or deshielded The scale goes from 0 12 but runs backwards The deshielded hydrogens are closest to twelve while the shielded H are closer to 0 We use TMS as our 0 point because it is the most shielded molecule Chemical shift difference from TMS peak Hz frequency of radiowaves MHz compound 4 3 CH3F 3 4 CH3OH 3 0 CH3Cl 2 7 CH3Br 2 2 CH3I 1 23 CH3CH2OH 0 94 CH3CH2CH2OH 3 0 CH3Cl 5 3 CH2Cl2 7 2 CHCl3 Alkanes 0 9 1 4 Alkenes 5 6 Alkynes 2 5 3 5 Carbonyl 2 41 IV Peak area CH3C OCH2OC CH3 3 3 peaks 3 2 9 The relative areas under the peaks are known as integrals and are equal to the ratio of different H CH3 2CHOCH CH3 2 2 12 2 6 1 CH2CH2OCH2CH3 2 6 4 3 2 1 5 1 V Peak splitting Peak splitting is determined by the number and kinds of neighbors an H has next to it There is the n 1 rule 3



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