Summary 2 - NMR

Summary 2 - NMR - Summary of Important Concepts: NMR...

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Summary of Important Concepts: NMR Spectroscopy 1) NMR Spectroscopy detects different nuclei. 13 C NMR detects carbons, 1 H NMR detects hydrogens (referred to in NMR discussions as PROTONS). 2) The CHEMICAL SHIFT (horizontal scale of the spectrum, described as δ, units = parts per million (p.p.m.)) is determined by the amount of electron density around each nucleus. This is affected by the presence of electronegative atoms (protons near electronegative atoms are called DESHIELDED and have a larger chemical shift (also known as a DOWNFIELD shift)). It is also affected by π bonds – H and C on double bonds are even more deshielded due to the circulating field of electrons. 3) There are many important regions of the NMR scale, but SOME useful ones are: a) 1 H: δ 9-10: aldehyde; δ ~5-6: alkene; δ < 4.5 sp 3 CH. b) 13 C: δ >200 aldehyde or ketone; δ 160-185 other C=O; δ 120-160 alkene. See lecture handout – know your regions!
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Summary 2 - NMR - Summary of Important Concepts: NMR...

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