Helping students to use the evidence available from spectroscopic techniques to determine the molecular structure of organic compounds is an important component of the study of organic chemistry. Each technique provides evidence about a different aspect of molecular structure, and together they demonstrate to students how molecular structure can be determined by recording the energy changes that occur as molecules shift between quantized energy levels (nuclear, vibrational or electronic). The process of structural elucidation requires that students engage with scientific practices, beginning with analyzing and interpreting data (what do the various peaks mean?), constructing an argument about the molecular structure based on the spectroscopic evidence (how does the proposed structure align with the spectroscopic evidence?), and eventually constructing an explanation about how and why particular substances show distinctive and predictable patterns (what factors affect the energies of different absorptions in each spectrum?). However, the ability to predict and explain molecular structure from spectroscopic evidence appears to be quite difficult for students. We will report our characterization of student ability to analyze spectral data, and discuss our attempts to elicit evidence of the reasoning students use to link proposed structures to data.