Canadian Science Publishing

Các tập hợp cơ sở loại cơ sở Gaussian và bộ cơ sở phụ trợ đã được tối ưu hóa cho các tính toán chức năng mật độ spin địa phương. Bài báo đầu tiên này nghiên cứu về các nguyên tử từ Bo đến Neon. Các bài báo tiếp theo sẽ cung cấp danh sách các nguyên tử từ Bo đến Xenon. Các tập hợp cơ sở đã được kiểm nghiệm khả năng đưa ra các hình học cân bằng, năng lượng phân ly liên kết, năng lượng hydro hoá, và mô men lưỡng cực. Kết quả cho thấy kỹ thuật tối ưu hóa hiện tại mang đến các tập hợp cơ sở đáng tin cậy cho các tính toán phân tử. Từ khóa: Tập hợp cơ sở Gaussian, lý thuyết chức năng mật độ, Bo–Neon, hình học, năng lượng của các phản ứng.

The thermodynamic equation (∂C_P/∂P)_T = −T(∂²V/∂T²)_P is used as a basis for relating thermal expansion to structure (at several temperatures and pressures) of water and "normal" liquids. Similar considerations lead to a relation between the sign of [Formula: see text] for solutions and classification of solutes as structure-making or structure-breaking.

Reaction of 3,4,6-tri-O-acetyl-D-galactal with excess ceric ammonium nitrate and sodium azide in acetonitrile produced 2-azido-1-nitrate addition products (53% β-galacto, 22% α-galacto, and 8% α-talo) and N-acetyl-3,4,6-tri-O-acetyl-2-azido-2-deoxy-α-D-galactopyranosylamine was formed, on hydrolysis, in 10% yield. The reaction product provides a convenient source of D-galactosamine and 3,4,6-tri-O-acetyl-2-azido-2-deoxy-α-D-galactopyranosylhalides. The crystalline β-chloride is also reported. The use of these glycosyl halides as reactants for the preparation of 2-azido-2-deoxy-α- and -β-D-galactopyranosides under conditions promoted by both mercuric cyanide and silver salts are reported.

The infrared spectra of the formate, acetate, and oxalate ions have been obtained for both the solid and aqueous solution. The Raman spectra of these ions with depolarization ratios have been obtained in aqueous solution. Vibrational assignments have been made which differ slightly for the acetate ion and more markedly for the oxalate ion from earlier work. The depolarization ratios confirm Fonteyne’s assignment for the formate ion.

The number and relative energies of nitrate combination frequencies in the 1700–1800 cm⁻¹ region of the infrared spectrum may be used as an aid to distinguish the various coordination modes of the nitrate group. The data also provide an excellent probe for the strength of the metal–nitrate interaction.

The electrochemical oxidation of aromatic heterocyclic compounds thiophene, pyrrole, and indole and benzenoid and nonbenzenoid polycyclic hydrocarbons azulene, fluorene, and pyrene yield electrically conducting polymers with conductivities of 10⁻⁵–10 S/cm. The presence of substituents affects the electrical conductivity of these films and also their electroactive properties. Furthermore, substituents determine whether electropolymerization of these compounds can occur or whether soluble products are formed. The relative importance of these pathways is dependent on the stability of the intermediate radical cation. These effects are investigated by INDO molecular orbital calculations.

The causative agent of toxicity in cultured mussels from a localized area of eastern Prince Edward Island has been identified as domoic acid, a neuroexcitatory amino acid. The toxin was isolated by a number of different bioassay-directed separation techniques including high-performance liquid chromatography, high-voltage paper electrophoresis, and ion-exchange chromatography, and characterized by a number of spectroscopic techniques including ultraviolet, infrared, mass spectrometry, and nuclear magnetic resonance. The isolation and purification methods are described in detail and some new analytical data for domoic acid are reported. Keywords: shellfish toxin, domoic acid, neurotoxin, bioassay-directed analysis.

The photolysis of H₂O₂ in aqueous solution has been used to study and characterize electron spin resonance (e.s.r.) spectra of the •OH and •HO₂ radical spin adducts with the spin traps 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and phenyl-t-butyl nitrone (PBN). At high concentrations of spin trap and low concentrations of H₂O₂ an e.s.r. spectrum is obtained which we assign to the •OH radical adduct (for DMPO, a^N = 15.3 G, a_β^H = 15.3 G, [Formula: see text] and g = 2.0060; for PBN, a^N = 15.3 G, a_β^H = 2.75 G, and g = 2.0057). At low concentrations of spin trap and high concentrations of H₂O₂• a second spin adduct spectrum is obtained which we assign to the spin adduct of the HO₂ radical (for DMPO, a^N = 14.3 G, a_β^H = 11.7 G, a_γ^H = 1.25 G, g = 2.0061; for PBN, a^N = 14.8 G, a_β^H = 2.75 G, and g = 2.0057).

The complexes [π-C₆H₆RuX₂]₂ (X = Cl, Br, I, SCN) have been prepared and characterized. They react with phosphorus donors to give the monomeric π-C₆H₆RuX₂PR₃, and with cyanide and hydride ions to give cyclohexadienyl and cyclohexadiene complexes.

General expressions are derived for line positions and relative intensities in the X spectrum for an X_nAA′X_n′ nuclear magnetic system in the case when Jx = 0. It is shown that in most cases it is possible to obtain the coupling constants involved by direct measurement of the spectrum using simple equations, but that this is not possible in certain limiting cases where the spectrum is deceptively simple.