Nuclear orientation study of the quadrupole interaction for Co in PdCo alloy

The angular distribution anisotropy of -radiation was measured following the decays of⁵⁸Co and⁶⁰Co oriented at low temperatures in the ferromagnetic PdCo alloy. The ratio of the electric quadrupole to magnetic dipole interaction constants for the⁶⁰Co was deduced to be P/a_o=0.001±0.003, where P=3e²qQ/4I(2I-1) and a_o=H/I.     

Internal rotation in mononitro-n-alkyl radicals

Internal rotation in the C·H₂(CH₂) _n NO₂ (n ≤ 7) type radicals has been studied. 44 potential functions of the internal rotation, V(φ), have been calculated taking advantage of the B3LYP/6-311++(3df,3pd) and MP2/6-311++(3df,3pd) methods. The trends observed in the series of parameters characterizing the internal rotation have been explained in view of the electron clouds conjugation, the inductive effect of the end groups, the gauche effect, and the rotation tops interaction. The coefficients of V(φ) have been shown to depend predominantly on the nearest surrounding of the rotation axis. Based on this, the generalized functions, V _av(φ), have been developed, their coefficients being dependent exclusively on the rotating bond position. Such functions are convenient for molecular modeling applications.     

A quantum-mechanical study of inductive and steric effects in isoalkanes

The method of “quantum mechanics of atoms in molecules” was used to find the parameters of functional groups in isopropylalkanes. The relation between such concepts of the classic theory of the structure of molecules as inductive and steric effects and electron density distribution was shown. Branching could cause deformation of the shape of an atom in a molecule accompanied by changes in volume and energy with charge conservation. The degree of damping of intramolecular steric and inductive effects was substantiated and described. An analysis of transferability of groups and the corresponding parameters was performed to obtain procedures for calculating properties by additive methods.     

Effect of free valence on the characteristics of internal rotation in <Emphasis Type="Italic">n</Emphasis>-alkyl radicals

A study of internal rotation in the radicals n-C _n H_2n+1C^·H₂, (2 ≤ n ≤ 7) was carried out for the case of rotation around the bonds not including the radical center. 21 potential functions of internal rotation V(φ) were calculated. The coefficients in V(φ) were shown to depend only on the immediate environment at the bond of rotation. Characteristics of internal rotation in n-alkyl radicals were compared with related parameters of the corresponding alkane molecules. The generalized function V _av(φ) with the coefficients defined only by the position of the bond of rotation in the hydrocarbon chain and possessing the transposition property were proposed. The functions V _av(φ) were recommended for the simulation of the structure and properties of large molecules containing hydrocarbon fragments. This work continues a systematic study on the characteristics of the internal rotation in the n-alkane molecules and the groups containing free valence in n-alkyl radicals.     

Investigation of the Electronic Structure of Alkyl Allyl Radicals

The electronic structure of the homologous series of CH₃(CH₂)_nCHCHCH₂ (n = 0÷5) allyl all radicals is studied. The obtained spin density distribution is used to determine the fragment serving as the radical center. The delocalization of spin density over the basin of the radical center is shown to be responsible for two free valencies associated with two classical canonical structures (the conjugated fragment). The conjugation phenomenon is studied and electronic parameters are determined for the “standard” conjugated fragment CHCHCH₂.     

Comparative analysis of the electronic structure and electronegativity of groups of unbranched ethers of sulphoxylate acid

Journal of Structural Chemistry - Within the quantum theory of atoms in molecules (QTAIM) the electronic structure of sulphoxylate acid HOSOH and compounds of a homological series of ethers of...     

Enthalpies of formation of organic free radicals of alcohol and ether derivatives

Numerical values of the enthalpies of formation of oxygen-containing organic radicals of alcohol and ether derivatives (Δ_f H°) were analyzed. For seven out of 25 compounds the corresponding Δ_f H° values were determined more accurately. For 35 radicals, the Δ_f H° values were determined for the first time based on the published values of bond dissociation energies in molecules and on the corresponding enthalpies of their formation. Based on the analysis of the Δ_f H° values for 60 radicals studied, a structure—property (enthalpy of formation) correlation was established, described in the framework of the group additivity scheme. The parameters for calculations of Δ_f H° values for the title radicals were recommended.     

Solution of a torsional Schrödinger equation with a periodic potential of general form. The probability amplitude and probability density

Analytic expressions for the probability density of states of a molecule with internal rotation and the probability of finding the state in the potential well are derived for the first time. Two methods are proposed for assigning conformers to potential wells. A quantitative measure of localization and delocalization of a state in the potential well is introduced. The rotational symmetry number is generalized to the case of asymmetric rotation. On the basis of the localization criterion, a model is developed for calculating the internal rotation contribution to thermodynamic properties of individual conformers with low rotational barriers and/or at a high temperature.