K. Sunil

2-Bromo-N `-(E)-4-hydroxybenzylidene]-5-methoxybenzohydrazide

The geometric parameters of the title compound, C15H13BrN2O3, are in the usual ranges. The C = N double bond is trans configured. The C= N-N-CO- group itself is planar, with an r. m. s. deviation of 0.044 angstrom, and makes a dihedral angle of 10.73 ( 19) degrees with the hydroxyphenyl ring, but forms a dihedral angle of 67.90 ( 8)degrees with the other aromatic ring. The crystal packing is stabilized by N-H center dot center dot center dot O, O H center dot center dot center dot O and O-H center dot center dot center dot N hydrogen bonds.

1-(2,6-Dimethylphenyl)thiourea

The geometric parameters of the title compound, C9H12N2S, are in the usual ranges. The thiourea group is almost perpendicular to the aromatic ring dihedral angle = 80.75 ( 7)degrees]. The crystal packing is stabilized by N-H center dot center dot center dot S hydrogen bonds linking the molecules into layers perpendicular to the c axis. Only two of the three amino H atoms are involved in hydrogen bonding.

1,5-Bis[(1E)-3,4-dimethoxybenzylidene]thiocarbonohydrazide tetrahydrate

Geometric parameters of the title compound, C19H22N4O4S center dot-4H(2)O, are in the usual ranges. Both C = N double bonds are trans configured, while only one of the C-N single bonds shows a trans configuration (with the other one being cis configured). The crystal packing is stabilized by N-H center dot center dot center dot S, N-H center dot center dot center dot O, O-H center dot center dot center dot S and O-H center dot center dot center dot O hydrogen bonds.

Bis{4-[(Z)-N′-(4-hydroxy­benzyl­idene)hydrazino]-8-(trifluoro­meth­yl)quinolinium} sulfate dihydrate

The title compound, 2C17H13F3N3O+·SO4 2−·2H2O, crystallizes with four independent cations (A, B, C and D) in the asymmetric unit, which is composed of two groups of two cations, one anion and two water molecules (Z′ = 2). The dihedral angle between the mean planes of the 4-hydroxyphenyl and quinolinium groups is 8.9 (7)° in A, 30.1 (6)° in B, 28.8 (8)° in C and 12.8 (1)° in D. The crystal packing is stabilized by intermolecular O—H⋯O and N—H⋯O hydrogen bonding between H atoms from 4-hydroxyphenyl O atoms and the O atoms of nearby water molecules and sulfate anions, as well as H atoms from the N atom of the hydrazino group to O atoms of neighboring sulfate anions, linking the components into chains with the 4-hydroxyphenyl and quinolinium rings parallel to the (011) plane. There is also an extensive array of intermolecular hydrogen bonds between water molecules themselves and with sulfate O atoms, as well as hydrogen-bond interactions between H atoms from the hydrazino group and sulfate O atoms. In addition, intermolecular π–π stacking interactions occur between nearby 4-hydroxyphenyl and quinolinium groups, with distances between the centroids of interacting rings in the range 3.4140 (9)–3.9659 (9) Å.

4-[(1E)-Benzyl­ideneamino]-3-methyl-2,4-dihydro-1H-1,2,4-triazole-5-thione

The acyclic C=N double bond of 4-[(1E)-benzylideneamino]-3-methyl-2,4-dihydro-1H-1,2,4-triazole-5-thione, C10H10N4S, is trans configured. The mol. is almost planar. The angle between the 2 rings is just 10.25(7)°. The crystal packing is stabilized by N-H···S H bonds and I€-I€ interactions. [on SciFinder(R)]

(1Z)-1-(4-Methoxyphenyl)ethan-1-one thiosemicarbazone

Geometric parameters of the title compound, C10H13N3OS, are in the usual ranges. There are two similar molecules (r.m.s. deviation 0.131 angstrom for all non-H atoms) in the asymmetric unit. The crystal packing is characterized by sheets in the (202) plane. The molecules in the sheets are connected by N-H center dot center dot center dot O and N-H center dot center dot center dot S hydrogen bonds.

Facile and Sensitive Spectrophotometric Determination of Chromium

Abstract A simple, sensitive, and selective spectrophotometric method is developed for the determination of trace amounts of chromium(VI) in various samples. The method is based on oxidation of 2,4-dinitrophenylhydrazine (DNPH) by chromium in an acidic medium and coupling with β-naphthol to give a red-colored dye, having an absorbance maximum at 663 nm, and/or coupling with α-naphthol to give a violet-colored dye, having an absorbance maximum at 503 nm. The method obeys Beers law in the concentration range 0.02–4.0µg mL−1 and 0.05–9.0 µg mL−1, respectively. The optimum reaction conditions and other important analytical parameters were established. Interference caused by various nontarget ions was also investigated. The proposed method is applied to the analysis of chromium(VI) in environmental, pharmaceutical, and steel samples. The performance of the proposed method is evaluated using the students t and F -tests.

4‐[1‐(4‐Chlorophenyl)‐3‐oxobutylamino]benzoic acid

Geometric parameters of the title compound, C17H16ClNO3, are in the usual ranges. The two aromatic rings are almost perpendicular, with a dihedral angle of 89.26 ( 5)degrees. The carboxyl group is coplanar with the aromatic ring to which it is attached dihedral angle = 1.70 ( 17)degrees]. The packing involves inversion-symmetric dimers bridged via hydrogen bonding of the carboxyl groups. In addition, there is an N-H center dot center dot center dot O hydrogen bond between the amino group and the carbonyl O atom.

(2E)-1-(4-Bromophenyl)-3-(4-nitrophenyl)- prop-2-en-1-one

In the approximately planar molecule of the title compound, C15H10BrNO3, the dihedral angle between the two benzene rings is 4.97 (18)degrees. Intermolecular C-H center dot center dot center dot O interactions help to form chains of molecules in the crystal structure.