Benzene Plane Research Articles

Molecular Structure and Conformations of para-Methylbenzene Sulfonamide and ortho-Methylbenzene Sulfonamide: Gas Electron Diffraction and Quantum Chemical Calculations Study

The molecular structure and conformational properties of para-methylbenzene sulfonamide (4-MBSA) and ortho-methylbenzene sulfonamide (2-MBSA) have been studied by gas electron diffraction (GED) and quantum chemical methods (B3LYP/6-311+G** and MP2/6-31G**). Quantum chemical calculations predict the existence of two conformers for 4-MBSA with the S-N bond perpendicular to the benzene plane and the NH2 group either eclipsing or staggering the S-O bonds of the SO2 group. Both conformers possess CS symmetry. The eclipsed form is predicted to be favored by DeltaE = 0.63 kcal/mol (B3LYP) or 1.00 kcal/mol (MP2). According to the calculations, the S-N bond in 2-MBSA can possess planar direction opposite the methyl group (phi(C2C1SN) = 180 degrees ) or nonplanar direction (phi(C2C1SN) approximately 60 degrees ). In both cases, the NH2 group can adopt eclipsed or staggered orientation, resulting in a total of four stable conformers. The nonplanar eclipsed conformer (C1 symmetry) and the planar eclipsed form (CS symmetry) are predicted to be favored. According to the GED analysis, the saturated vapor over solid 4-MBSA at T = 151(3) degrees C consists as mixture of the eclipsed (78(19) %) and staggered (22(19) %) forms. The saturated vapor over solid 2-MBSA at T = 157(3) degrees C consists as a mixture of the nonplanar eclipsed (69(11) %) and planar eclipsed (31(11) %) forms.

4-Aminophenylsulfur pentafluoride

In the title compound, C6H6F5NS, the environment of the S atom is roughly octa­hedral. The axial F—S bond appears slightly elongated with respect to the four equatorial F—S bonds. Equatorial F atoms are staggered with respect to the benzene ring. The N atom is displaced from the benzene plane by 0.154 (4) Å. The F—S—C—C torsion angles differ greatly from the values observed in the related structure of 4-acetamido­phenyl­sulfur penta­fluoride. The packing is stabil­ized by weak N—H⋯F contacts.

Crystal Structure of 2-Nitro-5,6-dihydro-11H-benzo[a]carbazole

The title compound, C16H12N2O2, consists of a nitro benzoato group fused to the a-face of the carbazole skeleton, in which the planar carbazole skeleton and benzene ring are also coplanar. It belongs to the space group P21/n with cell parameters a = 12.220(4), b = 6.9647(10), c = 15.304(3)A and β = 97.414(3)°. Molecules are linked about inversion centres by N-H…O hydrogen bonds [N…O 2.965(5)A] to form centrosymmetric dimers.

Induction effects in metal cation–benzene complexes

The role of polarization in the stabilization of a series of biologically relevant alkali and alkaline-earth metal cations (Li(+), Na(+), K(+), Mg(2+) and Ca(2+)) with the pi-electron distribution of benzene is examined by means of MP2 computations using Sadlej's basis set. In all cases a full description of the energy profile for the approach of the metal cation along the axis normal to the molecular plane of benzene has been performed. Analysis of the different contributions to the interaction energy, performed within the framework of the symmetry-adapted perturbation theory (SAPT), illustrates the important role of the induction component in the definition of the geometrical and energetic properties of the pathway leading to the formation of cation-pi complex. Finally, the ability of classical polarization models based on models of implicitly and explicitly interacting distributed isotropic polarizabilities to describe the induction term has been examined and discussed in the context of the generation of new polarizable force fields.

Syntheses of novel di- and trinucleating ligands having a triethylbenzene core with N,N-bidentate tethers: their complexation toward Pd and Rh organometallic fragments

A series of di- and trinucleating ligands with a 1,3,5-triethylbenzene core connected to N,N-bidentate tethers was synthesized. The ligands readily reacted with monuclear Rh and Pd precursors to give the corresponding di- and trinuclear complexes, which were characterized by using NMR and ESI mass spectroscopy. In the solid state, the trinuclear complexes with ligands having pyridylpyrazolyl tethers adopt the most stable ababab configuration, in which the organometallic fragments are on the same side of the benzene plane. On the other hand, in solution, the linker moieties between the benzene core and the metals are flexible enough to interconvert between other configurations, that is, they exhibit dynamic behavior, and the rotational barrier was dependent on the length of the linkers. From variable temperature (VT) 1H NMR measurements, the rotational barrier for a trinuclear Rh-CO complex with a ligand having methylene linkers was estimated to be approximately 12.6 kcal mol(-1). However, no spectral changes were observed for the ethylene derivative in the temperature range of -60 degrees C to 50 degrees C, indicating that the rotation was not frozen out on the 1H NMR timescale, even at -60 degrees C.

(E)-N′-(5-Bromo-2-hydroxybenzylidene)-4-hydroxybenzohydrazide ethanol solvate

In the Schiff base mol­ecule of the title compound, C14H11BrN2O3·C2H6O, the dihedral angle between the two benzene planes is 6.10 (2)°. An intra­molecular O—H⋯N hydrogen bond stabilizes the mol­ecular structure. The Schiff base and ethanol mol­ecules are linked via weak inter­molecular O—H⋯O and N—H⋯O hydrogen bonds, forming a three-dimensional network.

Three 9-[(E)-2-(4-halogenophenyl)vinyl]-9H-carbazoles

The crystal structures of 9-[(E)-2-(4-fluorophenyl)vinyl]-9H-carbazole, C20H14FN, (I), 9-[(E)-2-(4-chlorophenyl)vinyl]-9H-carbazole, C20H14ClN, (II), and 9-[(E)-2-(4-bromophenyl)vinyl]-9H-carbazole, C20H14BrN, (III), are determined mainly by van der Waals forces. The chloro and bromo derivatives are highly isomorphous, while the fluoro derivative has a different packing mode. Weak C-H...X interactions are also involved in the crystal packing. The molecular structures of the three compounds are similar, with relatively large twist angles of ca 55 degrees between the carbazole and benzene planes.

3-Hydroxy-N′-phenylnaphthalene-2-carbohydrazide

The dihedral angle between the naphthalene and benzene planes in the title compound, C18H14N2O3, is 4.3 (2)°. The mol­ecular conformation is characterized by an N—H⋯O hydrogen bond and the crystal packing is stabilized by N—H⋯O and O—H⋯O hydrogen bonds.

(E)-4-Hydroxy-N′-(2-thienylmethylene)benzohydrazide

In the title compound, C13H12N2O2S, the dihedral angle between the thio­phene and benzene planes is 38.08 (11)°. Inter­molecular N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules into a two-dimensional network parallel to the bc plane.

2-[3,5-Bis(5,6-dihydro-4H-1,3-thiazin-2-ylsulfanylmethyl)-2,4,6-trimethylbenzylsulfanyl]-5,6-dihydro-4H-1,3-thiazine

The title compound, C24H33N3S6, contains three 1,3-thia­zin-2-yl­sulfanyl groups. Two are located on the same side of the planar benzene ring and the other is on the opposite side. The three C atoms in one of the heterocyclic rings are disordered over two sites in an approximately 0.54:0.46 ratio.

Structure and conformation of (trifluoromethyl)thiobenzene, C 6H 5SCF 3: Gas electron diffraction and quantum chemical calculations

The geometric structure and conformation of (trifluoromethyl)thiobenzene, C 6H 5SCF 3, has been determined by two independent gas electron diffraction (GED) studies at the Universities of Moscow and Ivanovo and by quantum chemical calculations. Both experimental studies result in perpendicular orientation of the S CF 3 bond relative to the benzene plane. This result is confirmed by several quantum chemical calculations (HF/6-31G(d), B3LYP/cc-pVTZ, MP2/6-31G(d), MP2/6-311+G(d,p) and MP2/cc-pVTZ) which predict single-minimum potential functions for internal rotation around the C(sp 2) S bond. A double-minimum potential function predicted by the B3LYP/6-31G(d) calculation is not compatible with the experiment. B3LYP and MP2 calculations with large basis sets (6-311+G(d,p) and cc-pVTZ) predict barriers to internal rotation around the C(sp 2) S bond between 2.4 and 2.6 kcal/mol. The geometric parameters of both experimental studies agree with each other within the experimental uncertainties, except for the C F bond distance. The effect of fluorination of the methyl group in thioanisole, C 6H 5SCH 3, i.e., conformational change from planar orientation of the S CH 3 bond to perpendicular orientation of the S CF 3 bond, is rationalized on the basis of a natural bond orbital (NBO) analysis. The predominant effect is loss of conjugation between the p-shaped sulfur lone pair and the π system of the ring upon fluorination.

1-(1-Tosyl-1H-pyrrol-2-yl)ethanone

In the mol­ecule of the title compound, C13H13NO3S, the dihedral angle between the planar benzene and pyrrole rings is 101.7 (2)°. In the crystal structure, inter­molecular C—H⋯O hydrogen bonds link the mol­ecules into chains.

3-(4-Fluorophenyl)-1,5-di-2-pyridylpentane-1,5-dione

The title compound, C21H17FN2O2, was prepared by the reaction of 4-fluoro­benzaldehyde and 2-acetyl­pridine in N,N-dimethyl­formamide under microwave irradiation. In the molecular conformation, there are three planes: a benzene plane and two pyridine planes. The dihedral angles between the benzene plane and the pyridine planes are 88.38 (15) and 83.27 (13)°, and the dihedral angle between the two pyridine planes is 8.05 (10)°. There is an intramolecular C—H⋯N hydrogen bond. In the crystal structure, a supramolecular structure is constructed by the dimeration of two molecules via an intermolecular C—H⋯O hydrogen bond.

2-Methoxybenzaldehyde azine

The mol­ecule of the title compound, C16H16N2O2, is located on a centre of inversion (at the midpoint of the N—N bond), so that only one half of the mol­ecule is crystallographically independent, and it adopts a syn structure with respect to the meth­oxy group and the aldehyde H atom. The benzene ring and adjacent N atom are coplanar (r.m.s. deviation of 0.017 Å for the non-H atoms). The meth­oxy group deviates from the benzene plane by 0.167 (4) Å for the methyl C atom.

1-(4-Nitrophenyl)pyrrolidine-2-carboxamide

In the mol­ecule of the title compound, C11H13N3O3, the average plane of the pyrrolidine ring is roughly orthogonal to the plane of the carboxamide group and almost parallel to the benzene plane. The mol­ecules are linked via N—H⋯O hydrogen bonds into layers parallel to the ac plane.

Tricarbonyl[η6-1-methyl-4-(trimethylsilyl)benzene]chromium(0)

The mol­ecule of the title compound, [Cr(C10H16Si)(CO)3], has an eclipsed orientation of the Cr(CO)3 group relative to three benzene ring atoms. The atoms attached to the benzene ring show very small deviations from the benzene plane in the direction towards the Cr atom.

1,4-Dihydroxy-4-phenylbutan-2-one

In the title compound, C10H12O3, the butyl chain shows an extended planar conformation, and makes a dihedral angle of 73.98 (16)° with the benzene plane. The crystal packing is stabilized by O—H⋯O hydrogen bonding.

Methyl 3-[3-tert-butyl-5-(6-chloro-1-oxybenzotriazol-2-yl)-4-hydroxyphenyl]propionate

In the title compound, C20H22ClN3O4, the dihedral angle between the benzotriazole plane and the benzene plane is 38.2 (7)°. Intra­molecular O—H⋯O and O—H⋯N hydrogen bonds are present.

2,4,6-Trimethyl-1,3,5-tris(2-thiazolin-2-ylsulfanylmethyl)benzene

The title compound, C21H27N3S6, was synthesized by the reaction of 2,4,6-trimethyl-1,3,5-tris­(bromo­meth­yl)benzene and thia­zoline-2-thione. In the mol­ecule, two thia­zoline rings are located on one side of the central benzene plane, while the third thia­zoline ring is located on the other side of the central benzene plane.

4-Dimethylamino-β-nitrostyrene and 4-dimethylamino-β-ethyl-β-nitrostyrene at 100 K

The structures of 4-dimethyl­amino-β-nitro­styrene (DANS), C10H12N2O2, and 4-dimethyl­amino-β-ethyl-β-nitro­styrene (DAENS), C12H16N2O2, have been solved at T = 100 K. The structure solution for DANS was complicated by the presence of a static disorder, characterized by a misorientation of 17% of the mol­ecules. The mol­ecule of DANS is almost planar, indicating significant conjugation, with a push–pull effect through the styrene skeleton extending up to the terminal substituents and enhancing the dipole moment. As a consequence of this conjugation, the hexa­gonal ring displays a quinoidal character; the lengths of the C—N [1.3595 (15) Å] and C—C [1.448 (2) Å] bonds adjacent to the benzene ring are shorter than single bonds. The mol­ecules are stacked in dimers with anti­parallel dipoles. In contrast, the mol­ecule of DAENS is not planar. The ethyl substituent pushes the nitro­propene group out of the benzene plane, with a torsion angle of −21.9 (3). Nevertheless, the mol­ecule remains conjugated, with a shortening of the same bonds as in DANS.