Using Forensics to Introduce IR Spectroscopy & Molecular Modeling

A student activity is reported that analyzes “medical evidence” with experimental and computational methods. The lesson demonstrates benefits of solving practical problems with integrated tools

Diammonium potassium citrate, (NH4)2KC6H5O7

The crystal structure of di­ammonium potassium citrate, 2NH(4) (+)·K(+)·C(6)H(5)O(7) (3−), has been solved and refined using laboratory X-ray powder diffraction data and optimized using density functional theory. The KO(7) coordination polyhedra are isolated. The ammonium cations and the hydro­phobic methyl­ene sides of the citrate anions occupy the spaces between the coordination polyhedra. Each hydrogen atom of the ammonium ions acts as a donor in a charge-assisted N—H⋯O, N—H⋯(O,O) or N—H⋯(O,O,O) hydrogen bond. There is an intra­molecular O—H⋯O hydrogen bond in the citrate anion between the hydroxide group and one of the terminal carboxyl­ate groups. [Image: see text