Why is CDCl3 a Triplet?

Ever wonder why when you’re taking a 13C NMR in deuterated chloroform and look at the solvent peak – there are three evenly spaced peaks with equal intensities?

The answer can be found in your good old sophmore organic chemistry textbook (*I recommend the Marc Loudon book) and/or a physical chemistry text. It turns out that 1H has a spin of 1/2 but 2H has a spin of 1. In the case of a proton (1H) the spin state will either be +1/2 or -1/2, and in the case of a deuterium (2H) the spin state will either be +1, 0 or -1. And since we’re not running the 13C NMR in a deuterium decoupled mode – we’ll see the splitting from deuterium onto the carbon. Because there are three states: +1, 0 and -1, then we’ll see the peak split into three lines.

That’s so amazing.

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