Transferability of intensity parameters

The transferability of different kinds of intensity parameters is discussed. In order to transfer dipole moment derivatives with respect to internal or symmetry coordinates (dmd's) among similar modes in different molecules they must be split up into a mode-specific part (the dmd with respect to rotation-free reference coordinates) and a molecule-specific part (the rotational contribution). The calculation of reference coordinates and rotational contributions is discussed. The dmd's with respect to reference coordinates can be expressed in terms of first-order intensity parameters (bcp's or aop's). Expressions are given for CH₃X, propyne, butyne-2 and acetylene. The transferability of bcp's (or eop's) is tested by searching for a common set of bcp's for the following molecules: C₂H₂, C₂D₂, CH₃CCH, CD₃CCH, CH₃CCCH₃, CD₃CCCD₃. The final results are discussed in relation to the basic assumptions and the adopted constraints.     

The use of population localised orbitals to interpret molecular orbital calculations

An efficient and general method is derived to calculate population localised molecular orbitals (LMO's) from a given SCF eigenvector matrix, by reduction to an eigenvalue problem. Applications to both localised molecules (NH₃ and C₂H₂) and delocalised ones (B₂H₆, C₆H₆ and butadiene) are discussed in some detail. It is shown that unequal occupation of atomic energy levels leads to non-orthogonal LMO's. The consequences of non-orthogonal atomic hybrid orbitals are discussed, formulas for their overlap in terms of atomic occupation numbers are derived and it is shown that the occupation numbers are connected to LMO atomic orbital coefficients by various sum rules.     

Operational comparison of various thermodynamic treatments of organic substance adsorption at the electrode/solution interface

Three isotherms are considered: Frumkin's Bennes' and Mohilner's. The relationship between the interaction parameters in the first two and the adsorbate activity coefficient in the last is discussed. The significance of various standard states for the definition of ΔG° _ads is analysed. The operational derivation of ΔG°_ads in the three cases and the relationship between the resulting three quantities are illustrated. The isotherms have been used to describe the adsorption of 1,4-dioxane on a polarized Hg electrode. The analysis has been carried out both at constant potential and constant charge. The picture emerging in each of the three cases is discussed in the light of the results obtained in the other two. It is concluded that the three approaches give the same qualitative information about the interfacial behaviour of dioxane, especially as far as the effect of the electric field and the particle-particle lateral interaction are concerned. The usefulness of the Frumkin isotherm for analysing promptly experimental adsorption data is thus maintained. Limitations of the present approach are discussed.     

Recent developments in the chemistry of hofmann-type and the analogous clathrates

Based on the structural features of Hofmann-type clathraces M(NH₃)₂M'(CN)₄ · 2G (M = a divalent metal in six-coordination, M' = a divalent metal in square-planar coordination, G = a small aromatic guest molecule), several series of the analogous clathrates have been derived by appropriate replacements of the host moieties. These clathrates are designated with a general formula Cd (diam)M'(CN)₄ ·$\text{n}$G where diam refers to diammine, an ambident diamine or monoethanolamine (mea), or a pair of unidencate mea's, M'(CN)₄ is a square-planar or a tetrahedral tetracyanometallate(II), and G is a small aromatic guest molecule. The number of guest molecules, $\text{n}$, varies stepwise from 2 through $\text{3}\text{2}$ to 1 depending on the bulkiness of diam ligand which builds up the host structure. Their structural features are discussed on the two- and three-dimensional networks of the metal complex hosts. The historical background is also reviewed briefly.     

Electronic effect on the rotational energy of a diatomic molecule

The rotational hamiltonian for a diatomic molecule has been rederived from the total classical hamiltonian. This procedure directly introduces the effect of electronic motion which is ordinarily neglected in zero-order approximation. Kronig's rotational hamiltonian is discussed and shown to be an approximation of our findings. Our general result is then specialized to ¹Σ states, and the theory tested by calculating the observed fractional discrepancy between the experimentally determined H³⁵Cl energy level constant Y₀₂ and its predicted value from Dunham's theory. When all corrections are summed, the results are in good agreement with experiment.     

1H-NMR-spektroskopische konformationsanalyse von halogenierten thymidinabkömmlingen: I. konformation von thymidin, 3',5'-didesoxy-3'-chlor-5'-fluor-thymidin und 3', 5'-didesoxy-3',5'-difluor-thymidin

An improved method is given for determining the conformation of furanoid nucleosides by ¹H-NMR-spectra analysis using halogen-substituted thymidines as examples. The state of the three equilibria - ring-puckering, rotation about the C₄-C₅- bond and about the glycosidic bond - are influenced by the halogen substituents. Compared with thymidine the 3'-chlorine substituent shifts the furanose conformation to conformers, where the 3'-chlorine substituent is equatorial. The 5'-fluorine substituent increases the contribution of the G-G-rotamer and the ratio of syn-conformation. The relationships between the conformers in the pseudo-rotatory cycle and the population of the C_4'-C_5' rotamers are discussed.     

The infrared spectra of the hydrogen halide-olefin complexes in argon matrices

On the basis of Mulliken's charge-transfer theory the frequency shifts of vibration of the hydrogen halides in its complexes with olefins have been discussed. The relations between the a/b coefficient and the ionization potential of olefin, i_d, or pK_a of acid component has been found.     

Diabatic molecular states and the shielded diatomic orbital method. Evolution of two-interacting state systems for molecular hydrogen

Within Lichten's method, shielded diatomic orbitals (SDO's) are proposed as a basis for building-up diabatic molecular states in the single configurati approximation. The determination of SDO's i.e. eigenfunctions in prolate spheroidal coordinates of the two-center problem with a parametric shielding potential is extended to mono-excited states of many-electron diatomic systems, the shielding potential being obtained from simple electrostatic considerations. Four diabatic molecular states of H₂ are investigated i.e. ¹Σ_g⁺ (2pσ², 1Σ_g⁺ (1s,σ 2sσ), ¹Σ_u⁺(1sσ,4Pσ), ¹Σ_u⁺ (1sσ, 4fσ) using a minimal basis of SDO'S. The dynamical evolution of the nuclei for the two sets ¹Σ_g and ¹Σ_u⁺ of two interacting states is described in both the diabatic and the corresponding adiabatic representation.     

X-ray photoelectron spectra and electronic structure of rare-earth orthovanadates

Photoelectron spectra of 4d and valence states in RVO₄ (R = Y, Nd, Eu, Gd, Tb, Dy, Yb) have been investigated. The experimental spectra are interpreted using the results of the Xα discrete variational method calculations for orthovanadates. Transformations of electronic structure and covalency in the RVO₄ series are discussed. It is shown that lanthanide 4f orbitals significantly mix with the O 2pAO's and hybridize with the rare-earths 5pAO's. The 5p levels spin-orbital splitting in orthovanadates has been evaluated.     

The electronic structure of molecules by a many-body approach: V. Ionization potentials and one-electron properties of cyclopentadiene and 1-sila-cyclopentadiene-(2,4)

The valence ionization potentials (IP's) of cyclopentadiene and 1-sila-cyclopentadiene-(2,4) are studied by an ab initio many-body approach which includes the effect of electron correlation and reorganization beyond the Hartree-Fock approximation. The Hartree-Fock approximation gives the correct ordering of the IP's for cyclopentadiene but this ordering does not agree with the results of the previous experimental and theoretical studies. The ordering is 1a₂(π), 2b₁(π), 4b₂, 6a₁, 5a₁, 3b₂, 1b₁ (π), 4a₁, 2b₂, 3a₁. For sila-cyclopentadiene the ordering of the IP's is: 1a₂(π), 4b₂, 2b₁(π), 6a₁, 1b₁(π), 5a₁, 3b₂, 4a₁, 3a₁, 2b₂. The Hartree-Fock approximation is found to be incorrect with respect to the ordering of the 4b₂ and 2b₁(π) IP's. A number of one-electron properties are calculated in the one-particle approximation and compared with the available experimental data.     

Angular correlation functions of symmetric-top molecules influenced by coriolis coupling

The influence of the Coriolis coupling on the angular autocorrelation functions (ACF's) of symmetric-top molecules is calculated starting with the angular ACF's given by St. Pierre and Steele. As an example the theoretical ACF of the v₄ transition of CHCl₃ is compared with the experiment.     

Multiconfiguration self-consistent wavefunctions for CH4, C2H4 and C2H6

The results of several MC SCF calculations on CH₄, C₂H₄ and C₂H₆ with minimun bases of Slater type AO's are reported. The computing method is a quadratically convergent process. Better final energies are obtained if localized MO's are used.     

Zur reaktion primärer and sekundärer phosphine mit aromatischen aldehyden und alkoholen

PH-Phosphines react with aromatic aldehydes in an alcohol under P-C-O-bond formation to give α-alcoxy benzylphosphines R₂P-CH(Ph)-OR' or R-P[CH(Ph)-OR']₂ resp. In case of 4-dimethylaminobenzaldehyde or 2,4-dimethoxybenzaldehyde with diphenylphosphine or phenyl-benzylphosphine benzylidenediphosphine of the type (RR'P)₂CH-C₆H₄NMe₂ and (RP'P)₂CH -C₆H₃(OMe)₃ are obtained. The phosphines prepared are characterized through their hydrolytic and oxidative behaviour and the formation of phosphonium salts. The structures of the compounds are elucidated by their ¹H NMR spectra. The reaction pathways involving carbenium ion transition states in both cases are discussed.     

Charge-transfer properties of the hydrogen bond: Part 6. Charge-transfer theory and dipole moments of hydrogen-bonded complexes

The enhancement of the dipole moments of hydrogen-bonded complexes are discussed using Mulliken's charge-transfer theory.A linear relation is found between the ratio a/b and the ionization potential of the donor, I^V_D. This behaviour is similar to that previously found for halogen charge-transfer complexes [6].     

The νs infrared absorption band profile of isotopically diluted oh groups in crystals

We show that Wojcik and Falk's stochastic theory of the ν_s(OH) band-shape in isotopically diluted ice in a special case of Robertson and Yarwood's treatment of the ν_s(OH) band-shapes of hydrogen-bonded species in solution. There is a lattice-dynamical reason why the band is narrow in ice.     

Spectrophotometric method for the estimation of ammonium acetate with sensitized schiff's reagent

A spectrophotometric method has been described for the estimation of ammonium acetate with the help of sensitized Schiff's reagent. 1) Ammonium acetate restores the colour of fuchsin from the Schiff's reagent as shown by the same absorption maxima at 535 mμ of the coloured compound and fuchsin. 2) Standard curves of optical density versus concentration of ammonium acetate with different sets of sensitized Schiff's reagent having varying SO₂ contents have been presented. 3) There is a limit of ammonium acetate concentration beyond which the sensitivity considerably decreases. 4) Appropriate amounts of acetone along with a particular set of sensitized Schiff's reagent make the latter useful for different sensitive ranges of concentrations of ammonium acetate. 5) The method may be extended in its scope for the estimation of ammonium salts of other organic acids which are weaker than H₂SO₂.     

Oxydation anodique de iodoperfluoroalcanes dans les acides perfluoroalcanesulfoniques. Preparation de nouveaux esters sulfoniques totalement fluores RFSO3R'F a longues chaines

Perfluorinated sulphonic esters R_FSO₃R'_F and fluorosulphates FSO₃R'_F, are easily obtained by anodic oxidation of iodoperfluoroalkanes R'_FI in perfluoroalkane sulphonic acids R_FSO₃H (R_F  CF₃, C₂F₅, C₄F₉) and fluorosulphuric acid. With di-iodo compound I(CF₂)₄I, the mono and the diester can be selectively obtained. The alkaline hydrolysis of these esters produces perfluorinated carboxylic compounds. Polyfluorinated iodide R'_FCH₂CH₂I are also oxidized in similar conditions. The mechanism of the electrolytic reaction is discussed.     

On the hydroxyl ions in apatites

The possible mechanism originating the stretching and librational bands of the OH groups in ir spectra of various apatites are discussed. On the basis of relating the ν_s frequency of the V₃ hindered potential barrier, it is deduced that hydrogen bonds between the OH groups and the nearest O's of PO^3?₄ ions exist, and that they are responsible for the observed frequencies of the stretching and librational modes. The additional ir OH bands of heated nonstoichiometric hydroxylapatites are also discussed.     

The accurate determination of total sulphur and disulphide and polysulphide compounds in petroleum products by metal reduction and flame emission spectrometry

Conditions for the determination of total sulphur and disulphide/polysulphide in petroleum products are described. The sulphur is reduced by heating with sodium or Devarda's alloy under reflux with subsequent liberation of H₂S and measurement of the chemiluminescent S₂ emission intensity in a hydrogen—argon diffusion flame. The precision and accuracy are good. Applications to light distillates and waxy residues are discussed.