DiscoverFreshman Organic Chemistry 224. Higher-Order Effects, Dynamics, and the NMR Time Scale
24. Higher-Order Effects, Dynamics, and the NMR Time Scale

24. Higher-Order Effects, Dynamics, and the NMR Time Scale

Update: 2012-04-02
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Because spin-spin splitting depends on electron spin precisely at a nucleus, splitting by a C-13 depends on its orbital’s hybridization. “Higher-order effects” that give complex multiplets for nuclei with similar chemical shifts can be understood in terms of the mixing of wave functions of similar energy. Averaging of chemical shifts or spin-spin splitting may be used to measure the rate of rapid changes in molecular structure, such as changes in conformation or hydrogen bonding. Since the spectroscopic time scale depends on frequency differences, averaging is easier in NMR than in IR. A typical problem involves predicting the NMR spectrum of a compound with diastereotopic groups. In proton decoupling radio frequency irradiation of a particular proton can make it cease to split the NMR signals from nearby protons.

Complete course materials are available at the Open Yale Courses website: http://oyc.yale.edu

This course was recorded in Spring 2011.
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24. Higher-Order Effects, Dynamics, and the NMR Time Scale

24. Higher-Order Effects, Dynamics, and the NMR Time Scale

J. Michael McBride