Crystal and molecular structure of 1-azabicyclo[3.2.0]heptane-1-methyl chloride

The structure of the compound, 1-azabicyclo[3.2.0]heptane-1-methyl chloride has been determined by a single crystal x-ray diffraction study. The compound crystallizes in space group C_mcm with four formula weights in a unit cell of dimensions a = 8.53, b = 10.30, c = 9.27 ± .01 Å. The molecular cations fit in large holes between the chloride anions and consequently are disordered about the cation positions. The five-membered ring portion is non-planar and bears a strong resemplance to other five-membered rings in bicyclic-fused compounds. The azetidine portion of the molecule is planar. The basic fused ring structure is contrasted to that found in penicillin salts. A final value of R = 0.10₆ for the 305 independent reflections was obtained.     

Electron diffraction study of the thionyl fluoride molecular structure

The electron diffraction study of thionyl fluoride yielded the following geometrical parameters (r_a structure): S-O 1.420±0.003 Å, S-F 1.583±0.003Å, O-S-F 106.2±0.2° and F-S-F 92.2±0.3°. The average structure (r_α°) is also given. Some of the variations in the molecular geometries of SOX₂ and SO₂X₂ molecules (X = F or Cl) involving the valence shell electron pair repulsion theory are discussed.     

Vibronic spectra and S1 excited electronic state molecular structures for acetyl chloride and acetyl fluoride

Vapor-state absorption spectra have been recorded for acetyl fluoride and acetyl chloride and also for deuterated derivatives with path lengths up to 40 m. The origins of the S₁S₀ transitions have been derived, together with the torsional-vibration energy levels in the ground state S₀ and excited singlet state S₁. Fitting the calculated and observed rotational contours of the vibronic bands has been used to estimate the geometrical parameters in the S₁ states. The carbonyl groups in the S₁ states are nonplanar. The internal-rotation potentials have been determined for acetyl fluoride and acetyl chloride in the S₁ and S₀ states. The relative intensities of the torsional transitions in those states indicate that the minima in the potential energy are appreciably displaced along the torsional coordinate in the S₀ and S₁ states.Chemical Faculty, Lomonosov Moscow University. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 1, pp. 26–30, January–February, 1993.     

Electronic structure and molecular topology of boron and aluminum suboxides

Semiempirical and ab initio calculations on the suboxides B₂O, B₂O₂, Al₂O, and Al₂O₂ predict linear BOB, linear OBBO, linear AlOAl, and cyclic OAlOAl molecular structures. These structures could not have been predicted on the basis of a set of simple topological rules. The calculations provide additional evidence that the tentative structures adopted on the basis of the available thermochemical and spectroscopic data are correct.     

Quasiparticle band structure of infinite hydrogen fluoride and hydrogen chloride chains

We study the quasiparticle band structure of isolated, infinite (HF)(infinity) and (HCl)(infinity) bent (zigzag) chains and examine the effect of the crystal field on the energy levels of the constituent monomers. The chains are one of the simplest but realistic models of the corresponding three-dimensional crystalline solids. To describe the isolated monomers and the chains, we set out from the Hartree-Fock approximation, harnessing the advanced Green's function methods local molecular orbital algebraic diagrammatic construction (ADC) scheme and local crystal orbital ADC (CO-ADC) in a strict second order approximation, ADC(2,2) and CO-ADC(2,2), respectively, to account for electron correlations. The configuration space of the periodic correlation calculations is found to converge rapidly only requiring nearest-neighbor contributions to be regarded. Although electron correlations cause a pronounced shift of the quasiparticle band structure of the chains with respect to the Hartree-Fock result, the bandwidth essentially remains unaltered in contrast to, e.g., covalently bound compounds.     

Crystal and molecular structure of 1-(3-ammoniopropyl)silatrane chloride

By single crystal X-ray diffraction the crystal and molecular structure of 1-(3-ammoniopropyl)silatrane chloride (I) is determined. One of three cations in the asymmetric unit of the crystal of I differs from the other two by the length of the coordination N → Si bond. The opposite electronic effects in two geometrically similar cations are transferred inductively through a three-carbon chain.     

The molecular structure of benzene sulphonyl chloride

An electron diffraction structure analysis was carried out on benzene sulphonyl chloride, C₆H₅SO₂Cl, utilizing data from concurrent vibrational spectroscopie calculations. The following bond lengths (r_a parameters): C-H 1.14 ± 0.03 Å, C-C 1.403 ± 0.010 Å, S-O 1.417 ± 0.012 Å, C-S 1.764 ± 0.009 Å and S-Cl 2.047 ± 0.008 Å and bond angles (r parameters): C-S-C1 100.9 ± 2.0°, C-S-O 110.0 ± 2.5°, O-S-O 122.5 ± 3.6° and O-S-Cl 105.5 ± 1.8° were determined for an asymmetric model in which the benzene ring is rotated by 75.3 ± 5.0° relative to the plane containing the sulphur-chlorine bond and bisecting the O-S-O angle. The experimental data could equally well be approximated by a symmetric model with the benzene ring perpendicular to the reference plane described previously, if a particularly large amplitude of vibration was associated with the shortest rotation-dependent carbon-chlorine distance. The bond configuration around the sulphur atom in benzene sulphonyl chloride is consistent with the structural variations observed for a series of sulphone molecules.     

Fluorescent boron bis(phenolate) with association response to chloride and dissociation response to fluoride

Addition of chloride ions to boron bis(phenolate) 5 in dichloromethane solution produces a selective fluorescence decrease. The fluorescence change is believed to be caused by associative hydrogen bonding between the chloride ion and two boronic acid groups. While addition of fluoride ions to bis(phenolate) 5 generates a purple colorimetric response, the colorimetric response is caused by fluoride induced B-O bond cleavage and air oxidation of the phenolate anion formed by this dissociation.     

Rearrangement in the reaction of oxindole with o-nitrobenzyl chloride

The alkylation of oxindole with o-nitrobenzyl chloride produces three products, 5a, 6, and 10. The N-hydroxyindoloquinolone 5a probably arises by rearrangement of an initial alkylation product as shown in Scheme 1. The indoloquinolone 6 is formed by base-catalyzed elimination of o-nitrobenzaldehyde from the dialkylation product 10 and also apparently by a thermal process most simply considered as a 1,5-sigmatropic rearrangement of 10 → 12.     

Electron diffraction study on the molecular structure of methane sulphonyl fluoride

The molecular structure of methane sulphonyl fluoride in the vapour state was studied by electron diffraction. Assuming a value of 2.480A?for the distance between the oxygen atoms from a microwave determination, the following geometrical parameters (r_a structure) have been obtained: r(C-H) = 1.093±0.010Å, r(S-O) = 1.410±0.003Å, r(S-F) = 1.561 ±0.004Å, r(S-C) = 1.759±0.006Å, ∠F-S-C = 98.2±1.5°, ∠-S-F = 106.2±0.4°, ∠-O-S-O = 123.1 ±1.5° and ∠H-C-H = 112.9±1.9°. All the observed variations in the molecular geometries of (CH₃)₂SO₂, CH₃SO₂Cl, CH₃SO₂F and SO₂F₂ may be accounted for by the valence shell electron pair repulsion theory. It is particularly advantageous to combine electron diffraction and microwave data in studying sulphone molecular geometries.     

Supramolecular fluoride and chloride anions

The Cambridge Structural Database has been searched for supramolecular anions of the form H_nX_n + 1⁻ where X is fluorine (n = 1 to 6) and chlorine (n = 1 to 5); no credible evidence was found for comparable bromine or iodine species. Several structural isomers have been identified, and an experimental measure has been developed which seems to distinguish between two-centre and three-centre bonded species. There are also examples of suprafluoride and suprachloride anions as ligands in organometallic complexes. Most of these anions have not been previously described.     

Rotational spectroscopy and molecular structure of 1,1,2-trifluoroethylene and the 1,1,2-trifluoroethylene-hydrogen fluoride complex

Fourier transform microwave rotational spectra in the 6-22 GHz region are obtained for the complex formed between 1,1,2-trifluoroethylene and hydrogen fluoride, including the normal isotopomer, the two singly substituted 13C species, and the complex obtained with DF. A unique planar structure for the complex is determined from a combined analysis of the rotational constants derived from the spectra and atomic positions obtained using Kraitchman [Am. J. Phys. 21, 17 (1953)] substitution coordinates. Consistent with this structure, no hyperfine splitting of rotational lines due to the nuclear quadrupole coupling interaction is observed for the D-containing species. Although the primary interaction in the complex is a hydrogen-fluorine hydrogen bond, as is the case for all previously studied Lewis acid-fluoroethylene complexes, the CF2CHF-HF complex adopts a distinctly different geometry in which both the primary and secondary interactions occur between the HF molecule and a F atom and a H atom, respectively, bonded to the same carbon of CF2CHF. The 2.020(41) A hydrogen bond has hydrogen fluoride as the donor and 1,1,2-trifluoroethylene as the acceptor and forms a 109.0(13) degrees C-F...H angle. The secondary interaction between the hydrogen fluoride F atom and the H atom geminal to the acceptor F atom causes the hydrogen bond to deviate 41.6(51) degrees from linearity. Structural comparisons with analogous complexes formed with mono- and difluorinated ethylenes suggest that the primary hydrogen bond strength and the fluoroethylene fluorine atom basicity both decrease with increasing fluorine substitution. In the course of this work, it was necessary to obtain additional rotational spectra for the 1,1,2-trifluroethylene monomer and to improve the precision of the values of the structural parameters for this molecule.