Crystal structure of propane-1,3-diaminium squarate dihydrate.

Propane-1,3-diaminium squarate dihydrate, CHN ·CO ·2HO, results from the proton-transfer reaction of propane-1,3-di-amine with squaric acid and subsequent crystallization from aqueous medium. The title compound crystallizes in the tetra-gonal crystal system (space group 4) with = 2. The squarate dianion belongs to the point group and contains a crystallographic fourfold axis.

Surface accumulation and acid-base equilibrium of phenol at the liquid-vapor interface.

We have investigated the surfactant properties of phenol in aqueous solution as a function of pH and bulk concentration using liquid-jet photoelectron spectroscopy (LJ-PES) and surface tension measurements. The emphasis of this work is on the determination of the Gibbs free energy of adsorption and surface excess of phenol and its conjugate base phenolate at the bulk p (9.99), which can be determined for each species using photoelectron spectroscopy.

Crystal structure of 1,2,3,4-tetra-hydro-isoquinolin-2-ium (2,3)-3-carb-oxy-2,3-di-hydroxy-propano-ate monohydrate.

The crystal structure of 1,2,3,4-tetra-hydro-isoquinolin-2-ium (2,3)-3-carb-oxy-2,3-di-hydroxy-propano-ate monohydrate, CHN·CHO ·HO, at 115 K shows ortho-rhom-bic symmetry (space group 222). The hydrogen tartrate anions and solvent water mol-ecules form an intricate diperiodic O-H⋯O hydrogen-bond network parallel to (001). The tetra-hydro-isoquinolinium cations are tethered to the anionic hydrogen-bonded layers through N-H⋯O hydrogen bonds.

3-[(Benzo-1,3-dioxol-5-yl)amino]-4-methoxycyclobut-3-ene-1,2-dione: polymorphism and twinning of a precursor to an antimycobacterial squaramide.

The title compound, 3-[(benzo-1,3-dioxol-5-yl)amino]-4-methoxycyclobut-3-ene-1,2-dione, CHNO (3), is a precursor to an antimycobacterial squaramide. Block-shaped crystals of a monoclinic form (3-I, space group P2/c, Z = 8, Z' = 2) and needle-shaped crystals of a triclinic form (3-II, space group P-1, Z = 4, Z' = 2) were found to crystallize concomitantly. In both crystal forms, R(10) dimers assemble through N-H.