Byproduct identification: crystal structure of potassium 2-eth-oxy-2-oxo-acetate.

Potassium 2-eth-oxy-2-oxo-acetate, K+·C4H5O4 -, was identified as a byproduct in the first step of synthesizing the shelf-stable salt potassium nitro-aceto-nitrile (KNAN). A single crystal of the title salt was obtained by recrystallization of the ethanol filtrate resulting from the purification of the intended product salt, potassium ethyl nitro-cyano-acetate. The asymmetric unit of K+·C4H5O4 -, contains a single potassium cation and a 2-eth-oxy-2-oxo-acetate anion, the ethyl group of which is disordered over two sets of sites in a 0.792 (13):0.208 (13) ratio. The packing is dictated primarily by K-O electrostatic inter-actions and comprises eight bonded oxygen atoms per cation, with distances ranging from 2.706 (2) to 3.053 (4) Å.