Crystalline Solids of 1 1,2 -5 1,2 , 1 and 2 . Aqueous ( 2 H 2 O) solutions (~100 mM) and crystalline 1 1,2 -5 1,2 , 1 5,6 and 2 gave solution and solid-state C NMR spectra, respectively, that contained two intense signals arising from the two C-labeled carbons. Each signal was split equally into a doublet due to spin-coupling ( 1 J CC ) between the labeled carbons (see representative spectra in the Supporting Information). The measured given the smaller number of electronegative atoms appended to the C5-C6 fragment (2) than to the C1-C2 fragment (3). As found for 1 J C1,C2 , the range of experimental 1 J C5,C6 values overlapped with that calculated by DFT (Figure ). J CC values measured in aqueous solution were, in general, ~2 Hz smaller than corresponding values measured in crystalline samples (Table ).