Ragnhild Seip

Electron Diffraction Study of the Toluene Molecular Geometry

On the basis of an electron diffraction analysis, the following structural information was obtained on vapour phase toluene molecules: rg(CC)mean 1.399 ± 0.002 Å, rg(C-C) 1.511 ± 0.008 Å, the mean length of the C-H bonds is 1.117 ± 0.005 Å (rg). The methyl C-H bonds are at least 0.020 Å longer than the phenyl C-H bonds which are not longer than those in benzene

Electron-diffraction investigation of the molecular structure of sulphonyl chloride isocyanate

The electron-diffraction data for the title compound are consistent with two sets of geometric parameters differing in the relation between the CO and NC bond lengths. The other geometric parameters are: S–N 1.656(4), S–Cl 2.019(3), and SO 1.417(3)A; S–N–C 123.8(38), N–SO 108.3(22), N–S–Cl 98.0(30), Cl–SO 107.8(7), and OSO 122.8(24)°. The conformational properties may be characterised in two ways: (i) by a mixture of two forms having rotation angles of 109(4) and 70(10)°(0 ° corresponds to a form in which the S–Cl bond is anti to the OCN chain) in which the first form predominates [69(7)%]; (ii) by one form having a rotation angle of 86(3)° and a large amplitude of rotation around the S–N bond. The observed molecular geometry is consistent with structural variations found in isocyanates and in sulphonyl chlorides.

Electron Diffraction Investigation of the Molecular Structure of Trifluoromethanesulphonic acid (triflic acid)

Abstract The molecular geometry of triflic acid is characterized by the following bond lengths (rg) and bond angles from an electron diffraction study: S-C 183.3±0.5, F-C 133.2 ±0.2, S=O 141.8±0.2, S-O 155.8±0.3 pm, S-C-F 110.3 ±0.3, F-C-F 108.6 ±0.3, C-S=O 105.4±1.1, C-S-O 102.3 ±2.3, O-S= O 109.9±0.7, and O=S=O 122.0 ±1.3°. The heavy-atom-skeleton is staggered with respect to the rotation about the S-C bond with an estimated barrier of rotation of 15 kJ mol-1.

The Molecular Geometry of Trichloromethyl Sulphonyl Chloride as Studied by Electron Diffraction. Estimation of the Barrier to Internal Rotation

The molecular geometry of trichloromethyl sulphonyl chloride has been determined by electron diffraction. The sulphur bond configuration [rg(S=0) 1.421±0.003 Å, rg(S-Cl) 2.021 ±0.005 Å, rg(S-C) 1.87±0.03 Å, ∠O=S-C 108.3±0.7°, ∠C-S-Cl97.9±0.8°, ∠O=S=O 121.5±0.9° and ∠O=S-Cl 109.2±0.6°] is consistent with the characteristic structural variations observed in the sulphone series. The barrier to internal rotation around the S-C bond was estimated to be between 3.5 and 6 kcal mol-1 by means of various procedures and assumptions.

Determination of the molecular structures of tri(t-butyl)phosphine oxide and tri(t-butyl)phosphine imide in the gas phase by electron diffraction

The molecular structures of the oxide and imide of tri(t-butyl)phosphine in the gas phase have been determined by electron diffraction. For PBut3O important parameters (ra) are: r(PO) 159.0(12), r(P–C) 188.8(6), r(C–C) 151.9(3) pm, OPC 106.1(5), and CCC 109.1(4)°. The butyl groups are tilted 3.1(8)° away from each other, and twisted 15.8(7)° away from the positions in a structure with C3v symmetry, thus minimising steric interactions between the groups. For PBut3NH important parameters are: r(PN) 165.2(11), r(P–C) 191.3(6), r(C–C) 153.2(2) pm, NPC 109.6(7), and CCC 107.8(5)°, the tilt and twist angles of the butyl groups are –2.3(11) and 18.5(14)° respectively. The structures are such that the oxygen and imide group are sterically well protected from attack, thus accounting for the remarkable chemical and thermal stability of the compounds.

Determination by electron diffraction of the molecular structure of tris(trimethylsilyl)methylphosphine in the gas phase

The molecular structure of (Me3Si)3CPH2 in the gas phase has been determined by electron diffraction. Important bond lengths (ra) are Si–C 194.1(5), Si–Me 188.3(2), and P–C 180.8(9) pm. Steric strain within the tris(trimethylsilyl)methyl group is relieved by (a) compression of the methyl groups within each trimethylsilyl group, so that the Me–Si–Me angles are only 104.3(4)°, (b) tilting of the trimethylsilyl groups by 7.3(15)° away from each other, and (c) twisting of the trimethylsilyl groups by 21.2(4)° away from the fully staggered conformation.

The Molecular Structure of Benzotrifluoride as Studied by Gas Electron Diffraction

Abstract The molecular structure of benzotrifluoride has been studied by electron diffraction. The geometry of the carbon ring is essentially regular hexagonal. The bond configuration of the trifluoromethyl group considerably departs from the regular tetrahedral arrangement. The following values were obtained for bond lengths (rg) and bond angles: r(C-C)ring- 139.7 ±0.3 pm (mean value), r(Cmethyl-Cphenyl) = 150.4 ± 0.4 pm, r(C-F) = 134.5 ±0.3 pm, r(C-H) = 109.9 ± 0.5 pm and ∢ C-C-F = 111.9 ± 0.1°. The electron diffraction data are in agreement with nearly free rotation of the -CF3 group around the Cmethyi-Cphenyi axis

Determination of the molecular structure of tris(difluorophosphino)-amine by electron diffraction in the gas phase

The molecular structure of N(PF2)3 in the gas phase has been determined by electron diffraction. The molecule has a planar skeleton, with overall C3h symmetry, and ra(P–F) 157.4(2), ra(P–N) 171.2(4) pm, F–P–F 97.1(5), and F–P–N 99.0(4)°. The root-mean-square amplitude of torsion of the PF2 groups from their average positions is 17°, corresponding to a harmonic torsional frequency at 30 cm–1.