lecture8_TOCSY_NOESY

lecture8_TOCSY_NOESY - A. S. Edison University of Florida...

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Unformatted text preview: A. S. Edison University of Florida Fall, 2009 Todays Lecture A. S. Edison University of Florida 10) Wed, Oct 23: Homonuclear 2D experiments a. TOCSY: Introduction to Isotropic mixing and effective field strength b. NOESY: Introduction to the NOE c. Phase cycling A. S. Edison University of Florida Fall, 2009 Before we get to TOCSY, lets review J coupling 1 H NMR 1D spectra of Methyl -D-Arabinofuranoside in CD 3 CN. Collected at 11.7 T by Jim Rocca in AMRIS. All of the splittings are J couplings A. S. Edison University of Florida Fall, 2009 J coupling Normal spectrum Decouple 4.93 ppm Decouple 4.05 ppm J coupling allows you to identify atoms within 3 (sometimes more) covalent chemical bonds. This will be even more powerful when we get to 2D NMR experiments. A. S. Edison University of Florida Fall, 2009 2D COSY 90x 90x t 1 t 2 As you have shown by product operators, the COSY sequence correlates resonances that are coupled together through J-coupling. Each time period ( t 1 and t 2 ) gives rise to a frequency axis in the 2D spectrum. Coupled spins can be identified by cross-peaks in the spectrum. A. S. Edison University of Florida Fall, 2009 ppm 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 ppm 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 2D COSY gives all the J-coupling information simultaneously Each pair of coupled spins shows up as a cross-peak in a 2D COSY spectrum. The diagonal peaks correspond to the 1D spectrum. A. S. Edison University of Florida Fall, 2009 TOCSY OVERVIEW TOCSY (Total Correlation Spectroscopy) is capable of correlating all spins in a coupled network (examples shown on the next slide). The working end of the TOCSY pulse sequence is an isotropic mixing sequence that is a sequence of pulses that are designed to remove all chemical shift differences and create a strong coupling environment. This is called the Hartmann-Hahn condition. Sometimes the TOCSY experiment is called HOHAHA (Homonuclear Hartmann- Hahn)....
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This note was uploaded on 07/30/2011 for the course BCH 6475c taught by Professor Edison during the Fall '09 term at University of Florida.

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lecture8_TOCSY_NOESY - A. S. Edison University of Florida...

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