Molecular structure and charge density analysis of p-methoxybenzoic acid (anisic acid)

A concerted X-ray and ab initio SCF-MO study of the structure and charge density of p-methoxybenzoic acid (anisic acid) is reported. An extensive X-ray data set (7401 reflections) was measured on a single crystal using Mo Kα radiation and the structure refined with 2121 unique reflections, leading to a final R(F)-factor of 0.047 calculated for reflections with I>2σ. The molecular geometry of crystalline anisic acid, where the molecules dimerize via a moderately strong CO–H⋯O hydrogen bond, is compared with that of the isolated molecule, resulting from SCF-MO ab initio calculations. A topological analysis of the molecular charge density was performed using Bader's method to gain insight into the dominant intra- and intermolecular interactions in this compound. In particular, the effects of the substituents on the observed distortions of the benzene ring were investigated as well as the internal rotation of the methyl group

3β-Acet­oxy-lup-20(29)-en-28-yl 1H-1,2,4-tri­azole-1-carboxyl­ate

The title triterpene, C35H53N3O4, is a C-28 carbamate derivative of 3β-acet­oxy­betulin prepared in a one-step reaction from the commercially available 1,1′-carbonyl-di(1,2,4-triazole) (CDT), crystallized from acetone/n-hexane. All rings are trans fused. The carbamate and acetate substituents are in axial and equatorial positions, respectively. A quantum chemical ab initio Roothaan Hartree–Fock calculation of the equilibrium geometry of the isolated mol­ecule gives values for bond lengths and valency angles in close agreement with experimental values. The calculation also reproduces the observed mol­ecular conformation, with puckering parameters that agree well with those determined from the crystallographic study

19β,28-Ep­oxy-18α-olean-3β-ol

The title triterpene, C30H50O2, is an 18α-oleanane derivative prepared by the Wagner–Meerwein rearrangement of betulin with Bi(OTf)3.xH2O (OTF is trifluoromethanesulfonate). There are two symmetry-independent mol­ecules in the asymmetric unit that show no significant differences concerning bond lengths and angles. The conformation of the six-membered rings is close to a chair form, while the five-membered epoxide rings adopt envelope conformations. All rings are trans-fused. In the crystal, mol­ecules are held together by O—H⋯O hydrogen bonds. A quantum-mechanical ab initio Roothan Hartree–Fock calculation on the isolated mol­ecule gives values for bond lengths and valency angles close to the experimental values. The calculations also reproduce well the mol­ecular conformation with calculated puckering parameters that match well the observed values

1,5-Bis(2,5-dimethyl-1H-pyrrol-1-yl)naphthalene

In the title compound, C22H22N2, the asymmetric unit contains one half-mol­ecule. A crystallographic inversion centre is located at the mid-point of the bond common to both rings, in the central naphthalene unit. Quantum-mechanical ab initio calculations on the isolated mol­ecule showed that the minimum energy configuration occurs when the naphthalene ring system and the pyrrolyl groups deviate only slightly from perpendicularity. In the crystal, due to the effects of crystal packing, the mol­ecule deviates by approximately 4° from the a priori expected ideal value of 90° [C—C—N—C torsion angle = 86.11 (15)°]

Guanidinium 4-amino­benzoate

In the title compound, CH6N3 +·C7H6NO2 −, the cation and anion lie on crystallographic mirror planes. The 4-amino­benzoate anion is almost in a planar conformation with a maximum deviation of 0.024 (2) Å for the N atom. The bond length in the deprotonated carboxyl group is inter­mediate between those of normal single and double Csp2=O bonds, indicating delocalization of the charge over both O atoms of the COO− group. In the crystal, N—H⋯O hydrogen bonds assemble the ions in layers propagating in the bc plane. This structure is very similar to that of guanidinium benzoate

(Benzoato-κ2 O,O′)(quinoline-2-carboxyl­ato-κ2 N,O)(quinoline-2-carboxylic acid-κ2 N,O)manganese(II)

The crystal structure of the title compound, [Mn(C7H5O2)(C10H6NO2)(C10H7NO2)], contains manganese(II) ions six-coordinated in a distorted octa­hedral environment. The equatorial plane is occupied by four O atoms, two from the carboxyl­ate group of the benzoate ion, the other two from carboxyl­ate/carboxyl groups of the quinaldate/quinaldic acid mol­ecules. The axial positions are occupied by the N atoms of the quinoline ring systems. The metal ion lies on a twofold rotation axis that bisects the benzoate ligand; the quinaldate and quinaldic acid ligands are therefore equivalent by symmetry, and the carboxylate/carboxyl groups are disordered. The complexes are joined together by hydrogen bonds between the carboxyl­ate/carboxyl groups of adjacent quinaldate/quinaldic acid mol­ecules, forming zigzag chains that run along the c axis

16α,17α-Ep­oxy-5α-hydr­oxy-6β-nitrooxy-20-oxopregnan-3β-yl acetate

The title steroid, C23H33NO8, is a pregnane derivative obtained regio-, stereo- and chemoselectively from the ring opening of the corresponding 5α,6α;16α,17α-diepoxide with bis­muth(III) nitrate. There are two symmetry-independent mol­ecules in the asymmetric unit that show no significant differences concerning bond lengths and angles. All rings are trans-fused. The conformations of the six-membered rings are close to chair forms, while the five-membered ring adopts an envelope conformation. The mol­ecules are held together by an extensive O—H⋯O hydrogen-bonding network of chains runnning along the a axis

(Benzoato-κ2 O,O′)(quinoline-2-carboxyl­ato-κ2 N,O)(quinoline-2-carboxylic acid-κ2 N,O)copper(II)

The crystal structure of the title compound, [Cu(C10H6NO2)(C7H5O2)(C10H7NO2)], contains copper(II) ions five-coordinated in a distorted trigonal-bipyramidal environment. The equatorial plane is occupied by three O atoms, one from the carboxyl­ate group of the benzoate ion considered as occupying a single coordination site, the other two from two carboxyl­ate groups of the quinaldic acid and quinaldate ligands. The axial positions are occupied by the N atoms of the quinoline ring system. The metal ion lies on a twofold axis that bisects the benzoate ion. The quinaldate and quinaldic acid ligands are equivalent by symmetry, and the carboxyl­ate/carboxyl groups are disordered. The disordered H atom is shared between the carboxyl­ate groups of adjacent quinaldic acid mol­ecules. Such hydrogen bonds delineate zigzag chains that run along the c axis. The structure is very similar to that of the MnII analog

Bis[(2-quinol­yl)methane­diol-κ2 N,O](sulfato-κO)copper(II) dihydrate

In the title compound, [Cu(SO4)(C10H9NO2)2]·2H2O, the CuII ion is chelated by two (2-quinol­yl)methane­diol ligands and coordinated by a monodentate sulfate ligand in a distorted trigonal–bipyramidal environment, with O atoms occupying the equatorial sites and N atoms in the axial sites. The dihedral angle between the two essentially planar quinoline ring systems is 45.02 (9)°. In the crystal structure, an extensive O—H⋯O hydrogen-bonding network forms layers parallel to the ab plane

Bis(triphenyl­guanidinium) tetra­chlorido­cuprate(II)

The structure of the title compound, (C19H18N3)2[CuCl4], consists of square-planar [CuCl4]2− anions and triphenyl­guanidinium cations. The CuII ion occupies a crystallographic inversion centre. In the cation, the dihedral angles between the phenyl rings and the plane defined by the central guanidinium fragment are in the range 51.9 (4)–64.4 (3)°. N—H⋯Cl hydrogen bonds assemble the ions into infinite chains running along the b axis