The crystal structure of cephalexin monohydrate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Cephalexin monohydrate crystallizes in space group C2 (#5) with a = 27.32290(17), b = 11.92850(4), c = 16.75355(8) Å, β = 108.8661(4)°, V = 5166.99(3) Å3, and Z = 12. Although the general arrangement of molecules is similar to that in cephalexin dihydrate, the structural differences result in very different powder patterns. The crystal structure is characterized by alternating layers of hydrogen bonds and van der Waals contacts parallel to the bc-plane. The water molecules occur in clusters. Five of the six protons in the water molecules act as donors in O–H⋯O hydrogen bonds. The sixth hydrogen atom acts as a donor to two different phenyl ring carbon atoms to form bifurcated O–H⋯C hydrogen bonds. Each cephalexin molecule is a zwitterion, containing ammonium and carboxylate groups. The ammonium ions form N–H⋯O hydrogen bonds to carboxylate groups and water molecules, as well as to carbonyl groups. The powder pattern is included in the Powder Diffraction File™ as entry 00-065-1417.

中文翻译：

---

头孢氨苄一水合物的晶体结构，C16H17N3O4S(H2O)

头孢氨苄一水合物的晶体结构已使用同步加速器 X 射线粉末衍射数据进行求解和改进，并使用密度泛函技术进行了优化。头孢氨苄一水合物在空间群中结晶C2 (#5) 与一种= 27.32290(17),b= 11.92850(4),C= 16.75355(8) 埃，β= 108.8661(4)°,五= 5166.99(3) Å3， 和Z= 12. 虽然分子的一般排列与头孢氨苄二水合物中的相似，但结构差异导致粉末图案非常不同。晶体结构的特点是氢键交替层和范德华接触平行于公元前-飞机。水分子成簇出现。水分子中六个质子中的五个在 O-H⋯O 氢键中充当供体。第六个氢原子作为两个不同苯环碳原子的供体形成分叉的O-H⋯C氢键。每个头孢氨苄分子都是一个两性离子，含有铵和羧酸盐基团。铵离子与羧酸根和水分子以及羰基形成 N-H⋯O 氢键。粉末图案作为条目 00-065-1417 包含在 Powder Diffraction File™ 中。