Conclusion

This chapter was full of numbers and values, but the most important thing to know about
spectroscopy on the MCAT is that you don’t need to know a lot of numbers. The numbers that you
do need to know have already been stressed heavily in this chapter. Know that infrared (IR)
spectroscopy is best for identifying the presence (or, more importantly, the absence) of functional
groups. A cursory understanding of ultraviolet (UV) spectroscopy and its association with
conjugation will suffice. Nuclear magnetic resonance (NMR) spectroscopy—specifically, proton (^1 H)
NMR— also helps us figure out the arrangement of functional groups. Know how to interpret IR and
NMR spectra: IR spectra have three important peaks (O–H, C=O, and N–H), but NMR spectra can be
far more complex. The MCAT can test the chemical shift of deshielded protons, which will be
downfield, or toward the left of the spectrum. Make sure that you can interpret peak splitting, which
is due to interference from neighboring hydrogens, and peak integration, which is proportional to
the number of magnetically identical hydrogens.

Spectroscopy is often tested on the MCAT in the context of experiment-based passages. As you
continue studying the reaction chemistry discussed in Chapters 4 through 10 of MCAT Organic
Chemistry Review, consider what these products would yield in different spectroscopic modalities.

This chapter focused on one method of identifying compounds based on structural characteristics
and interactions with electromagnetic energy, but spectroscopy is not the only method for
characterizing organic molecules. In the next chapter, we explore another side of laboratory
techniques: separation and purification schemes. These utilize physical differences between
molecules to allow us to isolate and describe them.