-[2-(Tri-fluoro-meth-yl)phen-yl]maleamic acid: crystal structure and Hirshfeld surface analysis.

The title mol-ecule, CHFNO, adopts a configuration across the -C=C- double bond in the side chain and the dihedral angle between the phenyl ring and side chain is 47.35 (1)°. The -COOH group adopts a conformation (O=C-O-H = 0°), unlike the conformation observed in related maleamic acids.

Crystal structures of 2-amino-pyridine citric acid salts: CHN·CHO and 3CHN·CHO.

2-Amino-pyridine and citric acid mixed in 1:1 and 3:1 ratios in ethanol yielded crystals of two 2-amino-pyridinium citrate salts, . CHN·CHO () (systematic name: 2-amino-pyridin-1-ium 3-carb-oxy-2-carb-oxy-methyl-2-hy-droxy-propano-ate), and 3CHN·CHO () [systematic name: tris-(2-amino-pyridin-1-ium) 2-hy-droxy-propane-1,2,3-tri-carboxyl-ate]. The supra-molecular synthons present are analysed and their effect upon the crystal packing is presented in the context of crystal engineering.