Crystal structure and aqueous solubility of ammonium d-glucarate

Ammonium d-glucarate, NH4(C6H9O8) [ammonium d-saccharate, NH4-SAC], has been synthesized, and its crystal structure solved by single-crystal X-ray diffraction methods. NH4-SAC crystallizes in the monoclinic space group P21 (#4) with cell parameters a = 4.8350(4) Å, b = 11.0477(8) Å, c = 16.7268(12) Å, β = 90.973(1)°, V = 894.34(12) Å3, Z = 3. The structure was refined by full-matrix least-squares on F2 yielding final R-values (all data) R1 = 0.0353 and Rw2 = 0.0870. The structure consists of alternating (NH4)+ and (C6H11O6)− layers parallel to the bc plane. An extended network of N-H⋯OSAC and OSAC-H⋯OSAC hydrogen bonds provide the 3-D connectivity. The aqueous solubility (Sw) has been shown to be pH independent at ambient conditions within the range 4.5 < pH < 10 with Sw = 2.19 M/L, whose value is about a factor of two lower than that of the ammonium isosaccharate analogue.