Rules of the Day 4-5 - Rules of the Day 1-28-09 1. Adjacent...

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Rules of the Day 1-28-09 1. Adjacent nuclei have magnetic fields associated with their spins . The spins of equivalent adjacent nuclei can be either +1/2 or -1/2, and at room temperature they are found in about a 50:50 mixture at any given nucleus (very slight excess of lower energy +1/2). These can add to give n+1 different spin combinations in the proportions predicted by Pascal's triangle. Each different spin combination produces a different magetic field, which leads to n+1 splittings in the peaks of the NMR spectra of the adjacent (no more than three bonds away) nuclei. 2. The distance between peaks split in this way is called the coupling constant ("J") . Rules of the Day 1-30-09 1. THEORY: When there are two sets of adjacent H atoms, the number of peaks multiply. For example, a CH 2 group with a CH 2 group and a CH 3 group on either side should show 3 x 4 = 12 splittings! You can say this group is a "triplet of quartets" (or a "quartet of triplets"). 2.
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This note was uploaded on 09/22/2010 for the course CH 53200 taught by Professor Bocknack during the Spring '10 term at University of Texas at Austin.

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