Solid-state chemistry and crystal structure of cefaclor dihydrate.

Cefaclor [7-(D-2-amino-2-phenylacetamido)-3-chloro-3-cepham-4-carboxy lic acid] crystallizes as the dihydrate. Crystals belong to space group P21, with a = 10.626(3), b = 7.1288(9), c = 14.124(3), and beta = 121.6(2). The structure was solved using direct methods and refined to an R of 0.0535. The bond lengths, angles, and conformation determined are as expected for cephalosporins. The two water molecules are held in the crystal differently. The 13C solid-state NMR spectrum of cefaclor dihydrate is also reported and is consistent with its crystal structure.