V. N. Petrova

Molecular Structure and Conformations of para-Methylbenzene Sulfonamide and ortho-Methylbenzene Sulfonamide: Gas Electron Diffraction and Quantum Chemical Calculations Study

The molecular structure and conformational properties of para-methylbenzene sulfonamide (4-MBSA) and ortho-methylbenzene sulfonamide (2-MBSA) have been studied by gas electron diffraction (GED) and quantum chemical methods (B3LYP/6-311+G** and MP2/6-31G**). Quantum chemical calculations predict the existence of two conformers for 4-MBSA with the S-N bond perpendicular to the benzene plane and the NH2 group either eclipsing or staggering the S-O bonds of the SO2 group. Both conformers possess CS symmetry. The eclipsed form is predicted to be favored by DeltaE = 0.63 kcal/mol (B3LYP) or 1.00 kcal/mol (MP2). According to the calculations, the S-N bond in 2-MBSA can possess planar direction opposite the methyl group (phi(C2C1SN) = 180 degrees ) or nonplanar direction (phi(C2C1SN) approximately 60 degrees ). In both cases, the NH2 group can adopt eclipsed or staggered orientation, resulting in a total of four stable conformers. The nonplanar eclipsed conformer (C1 symmetry) and the planar eclipsed form (CS symmetry) are predicted to be favored. According to the GED analysis, the saturated vapor over solid 4-MBSA at T = 151(3) degrees C consists as mixture of the eclipsed (78(19) %) and staggered (22(19) %) forms. The saturated vapor over solid 2-MBSA at T = 157(3) degrees C consists as a mixture of the nonplanar eclipsed (69(11) %) and planar eclipsed (31(11) %) forms.

Gas electron diffraction and quantum chemical studies of the molecular structure of 2-nitrobenzenesulfonic acid

A combined gas electron diffraction and quantum chemical (B3LYP/6-311+G**, B3LYP/cc-pVTZ) study of the molecular structure of 2-nitrobenzenesulfonic acid (2-NBSA) is performed. Quantum chemical calculations show that the 2-NBSA molecule has five conformers, and the Gibbs energy of one of them is lower by more than 4.5 kcal/mol than the energy of the other conformers. It is found experimentally that the saturated vapor of 2-NBSA at T = 394(5) K contains only the low-energy conformer that has an intramolecular hydrogen bond between the H atom of the hydroxyl group and one of the O atoms of the NO2 group. The C-C-S-O(H) torsion angle determining the position of the S-O(H) bond is −72(7)°, while the NO2 group is substantially turned relative to the benzene ring plane (C1-C2-N-O = 40(5)°). The following experimental values of the internuclear distances are obtained for this conformer (Å): rh1(C-H)av = 1.07(2), rh1(C-C)av = 1.401(4), rh1(C-S) = 1.767(6), rh1(S=O)av = 1.412(4), rh1(S-O) = 1.560(6), rh1(N-O)av = 1.217(5), rh1(C-N) = 1.461(8), rh1(O-H) = 0.99(3).

Structures and intriguing conformational behavior of 1- and 2-naphthalenesulfonamides as determined by gas-phase electron diffraction and computational methods.

The saturated vapors of 1- and 2-naphthalenesulfonamides (1-NaphSA and 2-NaphSA) were studied by the gas-phase electron diffraction/mass-spectrometric method at 413(9) and 431(9) K. According to quantum chemical calculations (DFT/B3LYP and MP2 with cc-pVDZ, aug-cc-pVDZ, cc-pVTZ, and aug-cc-pVTZ basis set) 1-NaphSA possesses four conformers with different orientations of the SO2NH2 fragment relative to the naphthalene frame and eclipsed or staggered orientation of the N-H and S═O bonds, whereas 2-NaphSA possesses only two conformers with different orientations of the N-H and S═O bonds. It was experimentally established that vapors over 1-NaphSA and 2-NaphSA exist predominantly (up to 75 mol %) of low-energy conformers of C1 symmetry in which the C-S-N planes deviate from perpendicular orientation relative to the naphthalene skeleton with near eclipsed orientation of the N-H and S═O bonds of the SO2NH2 fragment. The following geometrical parameters (Å and degrees) of the dominant conformers were derived: r(h1)(C-H) = 1.089(4), r(h1)(C-C)av = 1.411(3), r(h1)(C-S) = 1.761(10), r(h1)(S-O)av = 1.425(3), r(h1)(S-N) = 1.666(10), ∠C-C1-C = 119.8(2), ∠C1-S-N = 104.5(22), C9-C1-S-N = 69.5(30) for 1-NaphSA; r(h1)(C-H) = 1.083(5), r(h1)(C-C)av = 1.411(3), r(h1)(C-S) = 1.780(7), r(h1)(S-O)av = 1.427(4), r(h1)(S-N) = 1.668(6), ∠C-C2-C = 123.0(3), ∠C2-S-N = 103.6(19), C1-C2-S-N = 110(10) for 2-NaphSA. The connection between nonequivalence of the C-C bonds in the naphthalene frame and spatial orientation of the substituents SO2NH2 is discussed. Transition states between conformers and enantiomers were determined.

Gas electron diffraction and quantum chemical study of the structure of a 2-nitrobenzenesulfonyl chloride molecule

A combined gas electron diffraction and quantum chemical (B3LYP/6-311+G**, B3LYP/cc-pVTZ, B3LYP/cc-pVTZ, midix (Cl), and MP2/cc-pVTZ) study of the structure of a 2-NO2-C6H4-SO2Cl molecule is performed. It is found experimentally that at a temperature of 345(5) K the gas phase contains two conformers of the C1 symmetry. Conformer I with a nearly perpendicular arrangement of the S-Cl bond with respect to the benzene ring plane (the C(NO2)-C-S-Cl torsion angle is 84(3)°) is contained predominantly (69(12)%). In conformer II, the S-Cl bond is located near the benzene ring plane (the C(NO2)-C-S-Cl angle is 172(3)°). The following experimental internuclear distances (Å) are obtained for conformer I: rh1(C-H) = 1.064(15), rh1(C-C)av = 1.397(3), rh1(C-S) = 1.761(6), rh1(S-O)av = 1.426(4), rh1(S-Cl) = 2.043(5), rh1(N-O)av = 1.222(4), rh1(C-N) = 1.485(16). In both conformers, the NO2 group is turned by more than 30° relative to the benzene ring plane.

Simultaneous electron diffraction and mass spectrometric studies of molecular structure of manganese trifluoride

It is shown that two geometrical models of the MnF3 molecule equally fit experimental electron diffraction data: a pyramidal model of C3v symmetry and a planar model with nonequivalent F-F distances of C2v symmetry.

Electron diffraction study of molecules of niobium and tantalum pentafluorides

Gas-phase electron diffraction has been used in studying the structure of monomeric molecules of niobium and tantalum pentafluorides. For both molecules, in the course of the structural analysis, it was found that the model with D /SUB 3h/ symmetry was preferable.

Structure and force field of the NbOCl3 molecule

The structure of the NbOCl3 molecule is studied by electron diffraction at 743(6) K. It is established that the molecule is characterized by C3v symmetry and the following structural parameters: rα(Nb=0) 1.682(6) Å, rα(Nb−Cl) 2.276(5) Å, ∢(ONbCl) 107.5(5)°, and ∢(ClNbCl) 111.3(4)°. Comparison with the other niobium oxytrihalide molecules shows that these values of the Nb=O bond and the bond angles are characteristic. The assignment of the ϕ3 frequency of the NbOCl3 molecule is refined, and the vibration frequencies of the NbOF3 molecule are estimated.

Electron diffraction study of structure of iron trifluoride molecule

The saturated vapor over FeF 3 at 1037 K has been investigated by a combination of electron diffraction and mass spectrometry. It has been established that molecules of iron trifluoride and difluoride are present in the vapor, in an 83:17 ratio according tO the mass spectrometric data and a 72:28 ratio according to the electron diffraction data. Parameters have been determined for FeF 3 molecules with an equilibrium configuration that is planar (D3h) or slightly pyramidal (C3v ~ angle F-Fe-F 112~

An electron-diffraction study of the structure and force field of the zirconium tetrachloride molecule

This study on zirconium tetrachloride completes a systematic study of the structures in the halides of the titanium subgroup. The previous electron-diffraction and spectroscopic studies of this compound and of other titanium-subgroup tetrahalides indicate that the equilibrium configurations in these compounds are tetrahedral. The purpose of the present study was to refine the observed molecular component of the scattering intensity in order to use it to determine the total force field of the ZrCl/sub 4/ molecule.

Molecular structure of WO2Br2

Molecular structure of WO2Br2 has been studied by electron diffractometry. Structural parameters for the molecule with C2v symmetry are: rα(W=O)=1.710(6) Å, rα(W−Br)=2.398(5) Å, rα(O−O)=2.815(30) Å, rα(Br−Br)=4.021(16) Å, rα(O−Br)=3.347(10) Å. The OWO and BrWBr bond angles are close to tetrahedral:LαOWO=110.8(2.0)°, LαBrWBr=113.9(1.0)°. The W=O bond was found to be characteristic in the series of tungsten dioxyhalides.