An electron diffraction study of the molecular structure of methylthionformate in the gas phase

The molecular structure of methylthionformate in the gas phase has been determined by electron diffraction. The CS and O-CH₃ bonds are nearly eclipsed. The dihedral angle between the C-O-C and O-C-S plane is 15.8 ± 2.5°.     

An investigation of the molecular structure of cycloheptanone by gas phase electron diffraction

The electron diffraction data of cycloheptanone, collected at 371 K, can be explained using a model of partial pseudorotation, with the symmetrical twist—chair as the mean structure. Ther_g, r_α-structure is characterized by r(C-C) = 1.536 Å, r(C=O) = 1.219 Å, r(C-H) = 1.124 Å, xxxCC(sp²)C = 117.3°, xxx(CCC = 115.5° and xxx(HCH = 103.2°. Approximate values for the constants of the pseudorotation potential are included.     

The molecular structure of tetramethoxymethane in the gas phase: an electron diffraction study

The electron diffraction study of tetramethoxymethane showed that in the gas phase the molecule has S₄ symmetry, flattened along the S₄ axis. Central and peripheral C-O bond lengths are different, consistent with considerations based on the anomeric effect. Comparison is made with ab initio calculations on methanediol. The geometrical parameters (r_g(1) structure) are: central C-O bond 1.395 Å; peripheral C-O bond 1.422 Å; C-H bond 1.11 Å; O-C-O angle bisected by the S₄. axis 114.7°; C-O-C angle 114.0°; O-C-H angle 111.9°; methoxy torsional angle 63.1°; methyl torsional angle 48.5°.     

The molecular structure of tetramethoxysilane in the gas phase,an electron diffraction study

The molecular structure of tetramethoxysilane was determined in the gas phase by electron diffraction. The molecule has S₄ symmetry, slightly flattened along the axis. The SiO bonds are shorter than in methylsilylether, demonstrating the effect of electronegative substituents on the Si atom. The geometrical parameters (r_a structure) are: Si-O bond 1.613 Å; C-O bond 1.414 Å; C-H bond 1.12 Å; O-Si-O angle bisected by S₄ axis 115.5°; Si-O-C angle 122.3°; O-C-H angle 111°; methoxyl torsional angle 64°; methyl torsional angle 60°.     

An electron diffraction study of the structure of 1,1,2-trichloroethane in the gas phase

The molecular structure of 1,1,2-trichloroethane has been determined by gas phase electron diffraction. The molecule is asymmetric. The geometrical parameters (r_a structure) are: r(C-Cl) 1.776 Å; r(C-H) 0.98 Å; ∠(C-C-Cl) 107°; ∠(Cl-C-Cl) projected along the C-C bond 116°; dihedral angle (Cl-C-C-Cl) 75°. The parameters ∠(C-C-H) 102° and the projected (H-C-H) angle 136° are inaccurate. The structure is rather insensitive to the r(C-C) value, which is unusually long, 1.56 to 1.58 Å.     

An electron diffraction study of the molecular structure of BIS(trifluoromethyl) monoselenide

The molecular structure of (F₃C)₂Se has been determined in the vapour phase by the sector microphotometer method of electron diffraction. Two structures, differing essentially in the angles of rotation of the CF₃- groups about the C-Se bonds, are in good agreement with the data. The mean C-Se and C-F bond lengths are 1.978 and 1.333 Å, respectively.     

The molecular structure of p-bis(trimethylsilyl)-benzene from gas phase electron diffraction

Nearly regular tetrahedral silicon bond configuration and a considerably distorted ring characterize the p-bis(trimethylsilyl)benzene molecular geometry according to an electron diffraction study. The SiC_methyl bond is longer than the SiC_phenyl bond, in agreement with expectation but contrary to an X-ray diffraction determination. The extent of ring deformation is consistent with the electropositive character of the trimethylsilyl substituent and with the structural variations in other para-disubstituted benzene derivatives. The electron diffraction data are consistent with either free rotation around the SiC_phenyl bonds or with a rotamer deviating by about 15° from the eclipsed form. The following bond lengths (r_g, pm) and bond angles (°) have been determined with parenthesized estimated total errors: (CC)_mean 140.8(3), (C_ipso)(C_orthoC_meta) 1.6(7), (SiC)_mean 188.0(4), (SiC_methyl)(SiC_phenyl) 3.3(7), (CH)_methyl 111.3(3), CC_ipsoC 115.7(6), and C_phenylSiC_methyl 109.2(4).     

The molecular structure of diethyl(silyl)amine in the gas phase,determined by electron diffraction

The molecular structure of N(C₂H₅)₂(SiH₃) in the gas phase has been determined by electron diffraction. The SiNC₂ skeleton is a shallow pyramid, with angles CNC 114.5(12)° and SiNC 120.9(5)°, and the methyl groups lie so that one CC bond lies close to the CNC plane, but the other is almost perpendicular to it. Other important parameters (r_a) are: r(SiN) 171.5(3), r(CN) 145.6(4), r(CC) 154.3(8) pm, and ∠NCC 113.6(6)°.     

A gas electron diffraction study of the molecular structure of cis-stilbene

The cis-Stilbene molecule is found to possess C₂ symmetry and may be described as having a propeller-like conformation with the phenyl groups rotated ca. 43° about the C-φ bonds. The deviation from planarity is found to be more extensive than predicted by most theoretical calculations. The steric strain in the molecule is also revealed by large valence angles at the central carbon-carbon double bond (∠CC-C: 129.5°).     

A gas electron diffraction study of the molecular structure of trans-stilbene

The molecular structure of trans-stilbene has been studied by the gas electron diffraction method. Unlike the approximately planar structure with C_i symmetry found for the solid state, the molecule in the gas phase was found to be non-planar and to possess C₂ symmetry. The phenyl groups were found to be rotated ca. 30° about the C-φ bonds. The non-planarity of the molecule is, however, not so large as to seriously influence the resonance energy.     

An electron diffraction study of the molecular structure of hexamethyldisiloxane

An electron diffraction determination of the molecular geometry of hexamethyldisiloxane has removed much of the uncertainty concerning this structure. The length of the SiO bond and the SiOSi bond angle were determined to be 1.631 ± 0.003 Å and 148 ± 3°, respectively. The experimental data are consistent with a staggered conformation (C_2v symmetry) while a model with twist angles around the SiO bonds of about 30° cannot be excluded. The molecule is probably performing large amplitude intramolecular motion.     

An electron diffraction study of the molecular structure of meta-difluorobenzene

The molecular structure of meta-difluorobenzene in the gas phase has been determined by electron diffraction at room temperature. The carbon ring deviates slightly from D_6h symmetry. The four C-C distances adjacent to the F atoms are 1.384 Å, the two other C-C distances are slightly longer, i.e. 1.405 Å. The C-F and C-H distances are 1.324 and 1.107 Å. The C-C-F valency angle is 119.5°.     

An electron diffraction study of the molecular structure of 1,2-difluoroethane

The molecular structure of 1,2-difluoroethane in the gas phase has been determined by electron diffraction at room temperature. Only the gauche conformation was found, the dihedral angle F-C-C-F is 74.5°. The bond lengths r_g(1) are: r(C-C) = 1.535 Å, r(C-F) = 1.394 Å, r(C-H) = 1.13 Å. The valency angles are: α(C-C-F) = 108.3, α(C-C-H) = 108.3. The dihedral angle between the C-C-F and C-C-H planes is 113.6°.     

An electron diffraction study of the molecular structure of gaseous cyclobutylgermane

The molecular structure and conformation of cyclobutylgermane have been determined by gas-phase electron diffraction. Like its counterpart cyclobutylsilane (CBS) it possesses quasi-equatorial and quasi-axial conformers. The most interesting aspect of the structure of CBG is the influence of the germyl group on the ratio of equatorial to axial conformers. The predominance of the quasi-equatorial conformer (ΔG = 3.1(1) kJ mol⁻¹), the near equality of the skeleton C---C bond lengths (C---C = 1.557(3)A) (r_a value) and the values of the puckering angles for the equatorial angles form and the axial one of 25.3(3.1)° and −20.4(3.6)° respectively, all support the predictions made by Jonvik and Boggs concerning the correlation between electronegativity and structural parameters in four-membered rings. From a consideration of these predictions, a comparison of the most prominent structural factors in CBG and cyclobutylsilane indicates that the germanium atom is more electronegative than silicon. This result could be considered as the first structural evidence for the previously postulated inversion of the electronegativity order within group IV.     

The gas phase molecular structure of silyl formate,determined by electron diffraction

The structure of silyi formate, HCOOSiH₃, in the gas phase is determined by electron diffraction. The principal bond lengths and angles (r_a) are r(Si-O) = 169.5 ± 0.3 pm, r(C-O) = 135.1 ± 0.6 pm, r(C  O) = 120.9 ± 0.7 pm, ∠(C-O-Si) = 116.8 ± 0.5°, ∠(OC-O) = 123.5 ± 0.5°. The silyi group is twisted by 21° away from the planar cis conformation but there is nevertheless a very short (286.5 ±1.0 pm) non-bonded Si ·O contact.     

The molecular structure and conformation of gaseous bis(chloromethyl)dimethyl silane as determined by electron diffraction

The molecular structure of bis(chloromethyl) dimethyl silane has been investigated in the gas phase at a nozzle temperature of 60° C. The molecules exist mainly in the GG form with the presence of 30% (+10%, ?20%) AG form. The values of the principal distances (r_a) and angles with estimated error limits of 2σ are r(C-H) = 1.093 (0.009) Å, r(C-Cl) = 1.801 (0.019) Å, r(Si-C) (the average Si-C bond) = 1.875 (0.009) Å, ∠(CSiC) = 109.5°, ∠(SiCCl) = 110.5° (0.4), ∠(CCH) = 112.5° (1.8) and φ (the gauche torsion angle relative to 0° for the anti form) = 117.4° (3.8).