NMR Lecture 3 - splitting associated with it This...

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Why Splitting Occurs 1
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Why Splitting Occurs
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Simple Proton-Proton Coupling Patterns 1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1 1 6 15 20 15 6 1 singlet (s) doublet (d) triplet (t) quartet (q) pentet (p) sextet (s) septet (sp) 0 1 2 3 4 5 6 Multiplicity n Intensity Ratio For simple coupling, peak multiplicity is given by n +1, where n is the number of equivalent protons attached to adjacent carbons (note that -OH and NH protons frequently do not couple).
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Coupling Constants The spacing between adjacent peaks of a splitting pattern is the coupling constant ( J ) The value of J is reported in Hz Two coupled protons must have the same value of J The coupling constant does not vary with the operating frequency of the spectrometer R H H R H R H R R R H H J = 11-18 Hz (commonly 16) J = 6-14 Hz (commonly 10) J = 0-3 Hz (commonly 2) Vicinal trans Vicinal cis Geminal
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Multiplicative Splitting
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Multiplicative Splitting
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Multiplicative Splitting 7
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Splitting Diagram 8
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NMR Spectra of Alcohols Splitting can occur between -protons and OH Water, acid, or base reduces the O-H resonance to a single line and eliminates any
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Unformatted text preview: splitting associated with it This phenomenon is called chemical exchange 9 NMR Spectra of Alcohols 10 Dynamic Systems 11 Chapter 9 12 13 C accounts for only 1.1% of naturally occurring carbon 12 C has no magnetic spin and produces no NMR signal One Peak for Each Unique Carbon Atom there is only a 1 in 10,000 chance that two 13 C atoms will occur next to each other in a molecule. The low probability of adjacent 13 C atoms leads to no detectable carbon-carbon splitting 1 H and 13 C do split each other, but this splitting is usually eliminated by adjusting the NMR spectrophotometer accordingly The process of removing the coupling of 1 H to an attached carbon is called broadband (BB) proton decoupling Carbon-13 NMR Spectroscopy Carbon-13 NMR Chemical Shift Ranges Proton-Decoupled 13 C NMR 14...
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NMR Lecture 3 - splitting associated with it This...

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