Phenyl Planes Research Articles

The X-ray crystal structure of 3-ammonium-4-hydroxyphenylarsonic acid chloride dihydrate

The X-ray crystal structure of 3-ammonium-4-hydroxyphenylarsonic acid chloride dihydrate has been determined from single-crystal diffraction data. The compound crystallizes in the orthorhombic space groupPna 21 with four molecules in a unit cell of dimensionsa=17.712(7),b=13.468(4), andc=4.798(2) A. The structure was solved by the Patterson method and refined to a finalR value of 2.1%. The average C-C phenyl distance is 1.393 A, but two bonds are somewhat shorter than the others. This, coupled with the fact that the C-O and C-As bonds are shorter than normal, makes it appear as if there is a minor resonance contributor of a keto form. The C-N bond length of 1.443 A is intermediate between values found in aminophenols and other ammoniumphenols. The H2AsO3 group is nearly tetrahedral, with the double-bonded oxygen rotated 9° out of the phenyl plane about the C-As bond. There is an extensive hydrogen-bonding system, involving every one of the OH and NH hydrogens, through the chloride and the waters of crystallization.

Darstellung und Kristallstruktur des 2:3-Adduktes von Antimontrichlorid und 4-Phenylpyridin, 2 SbCl3 · 3 (C11H9N) / Preparation and Crystal Structure of the 2:3 Adduct of Antimony Trichloride and 4-Phenylpyridine, SbCl3 · 3 (C11H9N)

Abstract A congruently melting phase of molar ratio 2:3 was identified in the system SbCl3/4-phenylpyridine. The structure consists of two different types of complex units: One SbCl3 molecule is bonded to one 4-phenylpyridine ligand only, whereas the other one forms a complex with two 4-phenylpyridine ligands. The SbCl3 unit in the 1:1 species is pyramidally shaped, whereas the SbCl3 unit in the 1:2 species displays a T-shaped geometry. The mean angle between the phenyl and pyridyl planes is 33.3°; mean bond lengths are 〈Sb-Cl〉 = 247.6 pm and 〈Sb-N〉 = 241.7 pm.

Orientation and intramolecular hydrogen bonding of nitro groups in the crystal structure of picric acid, C6H3N3O7*

Abstract Crystals of Picric acid, C6H3N3O7 are orthorhombic, space group Pca21, and cell dimensions a = 9.262(1), b = 19.137(1), c = 9.714(1) Å with Dm = 1.78 g· cm−3 and Dx = 1.768 g · cm−3. There are eight molecules in the unit cell. The crystal structure was solved by a combination of multisolution technique and “dummy atom” method with three-dimensional data collected (to the limit of 2θ ∼ 165° for CuKα) by the stationary crystal-stationary counter technique on a GE XRD-6 diffractometer. The crystal structure was refined by least-squares method with block diagonal approximation to a final R value of 0.058. The two molecules in the asymmetric unit have different orientations of the nitro groups. In molecule I, the nitro groups are inclined by 17.0, 0.4, 7.7° whereas the corresponding values in molecule II are 2.7, 5.2 and 20.3° respectively. In both the molecules, there is an internal hydrogen bond from the OH group to the proximal oxygen of an adjacent nitro group (O–H… O 2.572, 2.619 Å). There appears to be no correlation between the C —N bond distance and the twist of the nitro groups from the mean phenyl plane. There is a wealth of internal short contacts between the various substituents of the phenyl ring.

The conformational preference and barrier to internal rotation of an equatorial 3,5-dichlorophenyl group by the J method. Derivatives of cyclohexane, 1,3-dithiane, 1,3-dioxane, and 1,3-dioxolane

We report the preparation and the analysis of the phenyl ring proton magnetic resonance spectra of 3,5-dichlorophenylcyclohexane and of the 2-(3,5-dichlorophenyl) derivatives of 1,3-dioxane, 1,3-dithiane, and 1,3-dioxolane. With the exception of the dioxolanes these compounds exist predominantly as the equatorial isomers. The J method is used to show that the phenyl moiety prefers the conformation in which the α C—H bond lies in the phenyl plane. The predominantly twofold barriers to rotation about the carbon–carbon bond between the two ring systems are 2.0 ± 0.3, 0.4 ± 0.2, 2.2 ± 0.3, 0.85 ± 0.3 kcal/mol for these compounds, in the order given above. The low value for the barrier in the 1,3-dioxane derivative agrees reasonably well with molecular mechanics calculations and with the results of calorimetric and X-ray studies on equatorial 2-phenyl-1,3-dioxane.

Conformation of 2,6- and 3,5-dichloroanisole from 1H and 2H nuclear magnetic resonance studies on liquid crystalline solutions

The 1H n.m.r. spectra of liquid crystalline solutions of the two dichloroanisoles labelled with 13C in the methyl groups have been analysed to yield sets of dipolar coupling constants, Dij. It is shown that the Dij values involving 13C and ring protons can be used to determine the minimum energy positions for reorientation about the ring–oxygen bonds independently of the nature of reorientation of the methyl protons about the oxygen–methyl bond. It is found that the minimum energy positions for the 3,5-dichloroanisole have all C and O atoms coplanar, whilst for the 2,6-dichloroanisole the COC and phenyl planes are orthogonal. The DCH and DHH values within the methyl groups are used to derive the HCH angles of 109.5 and 110.0 respectively, whilst using all the Dij values fixes rCH as 1.11 ± 0.03 and 1.14 ± 0.04 A respectively. The 2H and 1H n.m.r. spectra of compounds labelled with OCD3 groups yield values for the quadrupole coupling constants of the C–D bonds of 132 ± 10 for 3,5- and 144 ± 24 kHz for 2,6-dichloroanisole.

N,N'-(p-Phenylene)dibenzamide (PPDB)

C20N202H16, monoclinic, P2~/c, a = 18.065(1), b = 5.247(1), c = 8.027(1) A, fl = 93.99 (1) °, Z = 2. The crystal structure has been refined by least-squares techniques. R w = 7.3%. The structure contains planar phenyl rings which are rotated with respect to the plane of the amide group owing to steric hindrance. The molecules are connected in one dimension by means of hydrogen bonds.

Crystal Structures of Bis[N-(3-methoxysalicylidene)isopropylaminato]nickel(II) (Brown Room Temperature Phase) and -cobalt(II)

Abstract The crystal structures of two Schiff base complexes, bis[N-(3-methoxysalicylidene)isopropylaminato]nickel (II) and -cobalt(II), have been determined. Ni complex: brown, room temperature phase, monoclinic, P21/c, a=21.089, b=7.254, c=14.386 Å, β=98.40°, Z=4, final R=0.076. Co complex: red, triclinic, P\bar1, a=22.699, b=7.395, c=14.099 Å, α=107.78, β=99.03, γ=93.75°, Z=4, final R=0.13. In both crystals the metal ions have distorted tetrahedral coordinations. The two crystals are roughly isostructural, although appreciable differences exist in both of the molecular and crystal structures. The Co complex gives a unique example of the methoxy group which sticks out nearly perpendicularly from the phenyl plane.

The Crystal Structure of the 1:1 Complex of Pyromellitic Dianhydride with trans-Stilbene

Abstract The 1: 1 complex of pyromellitic dianhydride with trans-stilbene crystallizes in the space group P21/c with two pairs of the component molecules in a unit cell with dimensions of a=12.48, b=6.33, c=13.17 Å, and β=111.6°. The structure was solved from a three-dimensional |E|2 Patterson synthesis and refined by a block-diagonal least-squares method to a final R value of 0.12 for 1635 reflections. In the trans-stilbene molecule, the plane containing the central ethylene group makes an angle of 11.5° with the phenyl plane. The non-planarity of the trans-stilbene molecule seems to be largely due to a steric repulsion between the hydrogen atom attached to the ethylene moiety and that at the 6 and 6′ position in the phenyl group. The pyromellitic dianhydride molecule is approximately planar. The component molecules are stacked alternately in infinite columns along the a axis. The average spacing between the phenyl plane of trans-stilbene and the molecular plane of pyromellitic dianhydride is 3.59 Å, and these palnes make an angle of 4.8° with each other. The relative arrangement of the component molecules in the crystal differs from that observed in the crystal of the anthracene, pyrene, or perylene complex with pyromellitic dianhydride. The van der Waals forces are considered to be more important than the charge transfer force in determining the relative arrangement of the component molecules in this crystal.

Crystal structure of 5,5-dimethyl-2-p-bromophenylimino-?3-1,3,4-oxadiazoline

Oxidation of acetone-4-p-bromophenylsemicarbazone with lead tetraacetate yields only one isomer of 5,5-dimethyl-2-p-bromophenylimino-Δ3-1,3,4-oxadiazoline, C10H10BrN3O. Crystals of this compound are triclinic, space groupP¯1,a = 5·91(1),b = 9·52(1),c = 11·59(2) A, α =114·1(1) °, β = 93·5(1) ° and γ = 108·8(1) °;z = 2 and the chemical composition is C10H10BrN3O. Of 2306 independent reflexions examined, 877 were strong enough to be measured with integrated precession photographs using MoKα radiation. The structure was refined using a full-matrix least-squares program to a finalR value of 0·064. The structure consists of planar phenyl and oxadiazoline rings, with a van der Waals interaction between a phenyl hydrogen atom and oxygen atom of the five member ring preventing the two rings from being co-planar; the H(13)-O(1) separation is 2·47 A. TheZ-configuration of the product suggests a specific mechanism for the ring closure involving an organolead intermediate.

Conformational analysis and electronic structure of acetanilide

The calculations of the electronic structure and conformational analysis of the acetanilide were carried out using the CNDO/2 method. The results show that the endo form is 1.2 Kcal/mole more stable than the exo form. The most stable conformation of the exo isomer corresponds to the dihedral angle of 90 ° between the phenyl and acetamide plane, whereas the minimum energy conformation of the endo isomer corresponds to the dihedral angle 50 °–60 °. A comparison of the calculated and experimental dipole moments suggests also the dihedral angle of 50 °–60 °. A comparison with experiment indicates that this molecular orbital method is good for conformational analysis and gives electronic structure which is compatible with spectroscopic measurement. The calculated conformational analysis and electronic structure of the acetanilide are in excellent agreement with experiments.

Topochemistry. Part XXX. Crystal and molecular structures of chalcone

The crystal structure of benzylideneacetophenone (chalcone) has been solved from photographically recorded partial three-dimensional data by means of the SEARCH computer programme and refined to discrepancy indices R′= 0·017 and R= 0·055. The C–C and C–O bond lengths have been determined with estimated standard deviations of 0·009 A. The two essentially planar phenyl units are linked by a non-planar cisoid 1,3-enone bridge twisted about the C–C bond by 16·9°.The molecules are arranged in alternating layers related by the two-fold screw axis along [001]; no short (<4·3 A)CC contact exists.

The structure of acetyltriphenylgermane

Crystals of acetyltriphenylgermane, Ph3Ge·CO·CH3, are monoclinic, a= 15·30, b= 14·53, c= 7·68 A, β= 94·8°, Z= 4, space group P21/c. The structure was determined with Cu-Kα scintillation counter data from Patterson and electron-density maps and refined by least-squares methods, the final R being 0·068 for 1834 observed reflexions.The acetyl and three phenyl groups are arranged tetrahedrally around the germanium atom. The phenyl rings are oriented in a propeller fashion; the angles between the ring planes and the C(acetyl)–Ge–C(phenyl) planes are about 60° for two of the rings, and about 40° for the third ring, this deviation from a symmetrical propeller orientation being probably a result of intra- and inter-molecular steric interactions. The mean aromatic C–C distance is 1·383A, and the mean C–H length is 1·09 A.Two distinct Ge–C bond lengths are found: Ge–C(phenyl)= 1·945 A(σ= 0·008 A), and Ge–C(acetyl)= 2·011 A(σ= 0·015 A). The longer Ge–C bond can be explained by a contribution from a resonance structure in which there is no formal bond between germanium and the carbonyl carbon atom, and which is in accord with the electronegativity difference between carbon and germanium. There is no evidence for π-bonding involving germanium 4d orbitals.

NMR measurements of the anisotropy effect of the phenylimino group

Two peaks due to α-methylene protons adjacent to the phenylimino group are observed in NMR spectra of phenyliminocyclohexane, phenyliminocyclopentane and 2-phenyliminotetrahydrofuran. In order to assign these two peaks, conformation of the phenylimino group is discussed in relation to the IR, UV and NMR spectra. It is concluded that the ▪ plane is nearly perpendicular to the phenyl plane and that hybridization of the nitrogen atom is of sp 2 type. Thus the higher field signal is assigned to the syn proton and the lower field signal to the anti proton.