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The structure of (±)-2-[(1S,3S)-3-acetyl-2,2-dimethylcyclobutyl]-N-(p-tolyl)acetamide has been determined by single crystal X-ray diffraction analysis. The crystal belongs to triclinic system, space group P-1, a = 8.8700(18) Å, b = 10.331(2) Å, c = 10.363(2) Å, α = 71.11(3)°, β = 65.06(3)°, γ = 72.18(3)°, V = 798.6(3) ų, Z = 2, formula unit C₁₇H₂₃NO₂. The title compound has a fragment of 2,2-dimethylcyclobutane and its conformation represents semi-chair. The intermolecular hydrogen bonds N-H...O and C-H...O are revealed.

Quantum chemical calculations of compounds with a pentacoordinated nitrogen atom such as NF₂H₃ (in the CCSD(Full)/6-311++G(d,p) approximation), NF₂Cl₃ and NF₂Br₃ (in the B3LYP/6-311+G(d) approximation) are carried out. It is found that NF₂Cl₃ and NF₂Br₃ molecules are structurally stable, but thermodynamically unstable, and are isomerized to NFCl₂…FCl and NFBr₂…FBr molecular complexes respectively. The total energy of NFCl₂…FCl and NFBr₂…FBr complexes is lower than the total energy of NF₂Cl₃ and NF₂Br₃ molecules by 62 kcal/mol and 64 kcal/mol respectively. The trigonal bipyramidal form of the NF₂H₃ molecule of D_3h symmetry is structurally unstable: a first-order saddle point corresponds to it on the potential energy surface of the system. A second-order saddle point is found on the reaction path of NF₂H₃ isomerization.

Energetic, geometric and magnetic criteria were applied to examine the stability and/or aromatic character for the cyclic molecules C₄H₄M (M = O, S, Se, Te, NH, PH, AsH and SbH)
at B3LYP/6-311++G** and MP2/6-311++G** levels of theory. The isodesmic reactions and nuclear independent chemical shifts (NICS) calculations were utilized to examine the molecules for energetic and magnetic criteria, respectively. The isodesmic reaction energies reveal that thiophene (C₄H₄S, -23.269 kcal/mol) and pyrrole (C₄H₄NH, -20.804 kcal/mol) have the greatest aromatic stabilization energies and tellurophene (C₄H₄Te, -15.114 kcal/mol) and stibole (C₄H₄SbH, -1.169 kcal/mol) have the lowest aromatic stabilization energies in their corresponding groups at MP2/6-311++G**. The NICS calculations confirmed the results obtained trough isodesmic reaction energies.

Methods to calculate the enthalpy of vaporization of alkanes under normal conditions are considered using the classic Randič method and its modifications. The calculation based on modified methods is shown to be capable of predicting the vaporization enthalpy of alkanes with an error comparable with that of experimental measurements.

Models of new cubic crystals from carbon and boron-nitrogen (BN) nanotubes are proposed. Within electronic density functional theory, their structural, elastic, and electronic properties are studied. These isotropic nanotubular crystals are found to have extremely high elastic modules B (~490-650 GPa) and low compressibility β (~0.0020-0.0015 1/GPa) and maintain the conductivity typical of their "building blocks," i.e. isolated carbon and BN nanotubes.

The molecular structure of tris-hexafluoroacetylacetonates of dysprosium, holmium, erbium, and ytterbium (M(hfa)₃, M = Dy, Ho, Er, Yb) is studied in the framework of synchronous electron diffraction and mass-spectrometric experiment and also quantum-chemically. For all M(hfa)₃ complexes structural parameters r_a, r_g, and r_h1 are found. It is established that the coordination polyhedron LnO₆ has a configuration of D₃ symmetry. In experiments on superheated vapors of Dy(hfa)₃, Ho(hfa)₃, and Yb(hfa)₃ the molecular forms present in the vapor at different degrees of superheat are determined.

The IR spectra of α-glycylglycine (H₃⁺N-CH₂-CO-NH-CH₂-COO^-) are studied in the temperature range of 93 to 413 K. Changes in the spectra due to temperature variation are correlated with the previously obtained X-ray diffraction data on anisotropic compression of the structure and changes in the parameters of hydrogen bonding. Changes in the vibrational frequencies of NH⁺₃ and COO groups in the IR spectrum of α-glycylglycine are compared to changes in the vibrational frequencies of the same groups in the IR spectra of polymorphs of glycine, L- and DL-serine.

A study of the IR spectra of L- and DL-cysteine is carried out in a range of frequencies from 4000 cm^-1 to 600 cm^-1 and temperatures from 333 K to 83 K. Changes in the spectra of L- and DL-cysteine (NH⁺₃-CH(CH₂SH)-COO^-) on cooling are analyzed in comparison with the spectra of L- and DL-serine (NH⁺₃-CH(CH₂OH)-COO^-) and three polymorphs of glycine (NH⁺₃-CH₂-COO^-) previously studied under temperature variation. Changes in the IR spectrа at variable temperatures are correlated with previously obtained diffraction data on anisotropic compression of the structure and changes in the geometric parameters of hydrogen bonds. Special attention is paid to temperature regions in which anomalies were detected by vibrational spectroscopy, X-ray diffraction, and calorimetry.

By means of IR spectroscopy with the use of factor group analysis for vibrations of the B-O bond, rare-earth borates with a general formula of RM₃(BO₃)₄ (R is Nd, Gd, and Y; M is Al, Ga, Cr, and Fe) and related polytypic structures are assigned to space groups R32 or С2/c. Compounds with both almost homogeneous structures and with inclusions of the monoclinic polytype are revealed among rhombohedral borates. The latter is most typical of phases with a small octahedral Al cation. It is shown that in the monoclinic modification of NdAl and NdCr borates fragments of the rhombohedral phase are always present. Alternation of differently ordered structural fragments is determined by temperature conditions of crystallization.

NMR (¹⁹F, ¹H) methods are used to study ionic mobility in heptafluorozirconate (NH₄)_2.4Rb_0.6ZrF₇ in a range of temperatures from 150 K to 430 K. Types of ionic movements are determined, and their activation energy is evaluated. As a result of a phase transition a modification forms in which diffusion in the ammonium sublattice and isotropic reorientations of ZrF^3-₇ complex anions are observed. According to preliminary data, due to diffusion of ammonium ions the compound has relatively high ionic conductivity (σ ≈ 8.3×10^-5 S/cm at 423 K).