Marker peaks, intensity ratios

Now what about the intensities Why s the middle peak larger Get out a marker and draw an A on one proton and a B on the other. OK. There s only one way for A and B to spin in the same direction—Both A and Bare plus or both A and B are minus. But there are two ways for them to spin opposite each other—A plus with B minus B plus with A minus. This condition happens two times. Both A and B plus happen only one time. Both A and B minus happen only one time. So what So the ratio of the intensities is 1 2 1. Ha You got it—a triplet. Do this whole business sitting on the —CH2— group. You get a quartet—four lines—because the —CH2— protons are adjacent to a methyl group. They are split B Y three to give FOUR lines (Fig. 138). 

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