(E)-2-Hydr­oxy-6-[(4-propyl­phenyl)­iminiometh­yl]phenolate

The title compound, C16H17NO2, crystallizes with three crystallographically independent zwitterionic mol­ecules in the asymmetric unit which differ significantly in the orientations of the propyl side chains. The dihedral angles between the two benzene rings in the three mol­ecules are 6.17 (7), 6.75 (7) and 23.67 (7)°, respectively. In each independent mol­ecule, an intra­molecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, each independent mol­ecule exists as part of an O—H⋯O hydrogen-bonded centrosymmetric R 2 2(10) dimer

1-{5-[(E)-(2-Fluoro­phen­yl)diazen­yl]-2-hy­droxy­phen­yl}ethanone

Theere are two independent mol­ecules in the asymmetric unit of the title compound, C14H11FN2O2, each with a trans configuration with respect to the azo double bond. The dihedral angle between the aromatic rings is 17.21 (2)° in one mol­ecule and 19.06 (2)° in the other. Each of the independent mol­ecules has an intra­molecular O—H⋯O hydrogen bond. In the crystal, mol­ecules are stacked along [100]

(E)-2-Acetyl-4-[(3-methyl­phenyl­)diazen­yl]phenol: an X-ray and DFT study

The title compound, C15H14N2O2, an azo dye, displays a trans configuration with respect to the N=N bridge. The dihedral angle between the aromatic rings is 0.18 (14)°. There is a strong intra­molecular O—H⋯O hydrogen bond. Geometrical parameters, determined using X-ray diffraction techniques, are compared with those calculated by density functional theory (DFT), using hybrid exchange–correlation functional, B3LYP and semi-empirical (PM3) methods

4-{2-Meth­oxy-6-[(4-methyl­phen­yl)imino­meth­yl]phen­oxy}phthalonitrile

In the mol­ecule of the title compound, C23H17N3O2, the methoxy­phenyl ring is oriented at dihedral angles of 13.34 (12) and 88.83 (12)° with respect to the methyl­phenyl and phthalonitrile rings, respectively; the dihedral angle between methyl­phenyl and phthalonitrile rings is 89.67 (10)°. In the crystal structure, weak inter­molecular C—H⋯N inter­actions link mol­ecules into chains. A weak C—H⋯π inter­action is also found.

(E)-2-[(2-Ethyl­phen­yl)iminiometh­yl]-6-hydroxy­phenolate

The mol­ecule of the title compound, C15H15NO2, crystallizes in a zwitterionic form, and displays an E configuration about the C=N bond. The dihedral angle between the two aromatic rings is 5.59 (6)°. An intra­molecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal structure, pairs of mol­ecules are linked into centrosymmetric R 2 2(10) dimers by pairs of O—H⋯O hydrogen bonds. Aromatic π–π inter­actions are observed between the benzene rings of adjacent dimers [centroid–centroid distance = 3.4808 (7) Å]

1-{5-[(E)-(4-Propyl­phen­yl)diazen­yl]-2-hy­droxy­phen­yl}ethanone

The mol­ecular geometry of the title compound, C17H18N2O2, displays an E configuration with respect to the azo group. The dihedral angle between the aromatic rings is 10.39 (4)°. In the mol­ecule, an intra­molecular O—H⋯O hydrogen bond generates an S(6) ring motif

2-[(4-Chloro­phen­yl)imino­meth­yl]hydro­quinone

The title compound, C13H10ClNO2, exists in the phenol–imine form in the crystal, and the aromatic rings are oriented at a dihedral angle of 2.82 (9)°. An intra­molecular O—H⋯N hydrogen bond results in the formation of a planar six-membered ring. In the crystal structure, inter­molecular O—H⋯O hydrogen bonds link the mol­ecules into chains

Removal of phenol and chlorophenols from water with reusable dye-affinity hollow fibers

Reactive Green HE 4BD carrying polyamide hollow fibers were investigated as dye-affinity adsorbents for removal of chlorophenols (i.e., phenol. o-chlorophenol, p-chlorophenol and 2,4,6-trichlorophenol). Adsorption rates of chlorophenols were very high. Equilibrium was achieved in about 30 min. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. Results suggest that chemisorption process could be the rate-limiting step in the adsorption process. The maximum adsorption values of chlorophenols onto the Reactive Green HE 4BD carrying hollow fibers were 145.9 mu mol/g for phenol, 179.2 mu mol/g for 2,4,6-trichlorophenol, 194.5 mu mol/g for p-chlorophenol and 202.8 mu mol/g for o-chlorophenol. The affinity order was as follows: o-chlorophenol > p-chlorophenol > 2,4,6-trichlorophenol > phenol. The adsorption capacity of chlorophenols decreased with increasing pH. Desorption of chlorophenols was achieved using methanol solution (30%, v/v). The Reactive Green HE 4BD-carrying hollow fibers are suitable for repeated use for more than 10 cycles without noticeable loss of adsorption capacity