Fig. 4.

Structural assignment of cimetidine form B using SSNMR spectra. The SSNMR spectra were measured for a mixture of forms B and C. a 1D ¹³C and c ¹⁵N CPMAS spectra measured using 500 and 5000 scans, respectively. The CP contact time was adjusted to 2 ms for ¹³C and 1 ms for ¹⁵N. Only the spectral range of interest is displayed. b 2D ¹H–¹³C and d ¹H–¹⁵N HETCOR spectra over the full spectral range with expansions of the regions of interest as indicated by the blue and orange boxes. The atom labels are identical to those shown for CB2 in Fig. 5b. The contact time was 2 ms during the first CP transfer and 0.5 ms during the second CP transfer for both spectra. The 2D ¹H–¹³C spectrum was acquired using 40 scans and 128 rows in the indirect dimension and the 2D ¹H–¹⁵N spectrum was acquired using 24 scans and 64 rows. The ¹H–¹⁵N correlation peaks from form C are indicated with red asterisks