Theoretical investigations on the solvation process

STO double-zeta SCF wavefunctions for various configurations of the H₅O ₂ ⁺ associate have been computed. Results are discussed and compared with other authors' similar calculations on gaussian bases.An electrostatic picture of the monosolvation of H₃O⁺ is proposed as a fairly satisfactory one.     

Quantum mechanical studies of environmental effects on biomolecules

Ab initia SCF calculations on the hydration of N-methylacetamide are reported and compared to the results previously obtained for formamide. The hydration energies are all slightly decreased. The angular positions of the two carbonyl sites are brought closer to the CO axis and the orientation of the water molecule on the NH site remains very flexible in spite of the a methyl group.     

Molecular structure of 9α-fluoro-11β-hydroxy-16β-propionyloxy-17-(2-ethyl-2-ethoxy-1,3-dioxan-5-one-6-yl)-pregna-1,4-dien-3-one

The title compound is orthorhombic, space groupP2₁2₁2₁,a=15.992(9),b=15.693(9),c=11.205(6) Å,Z=4. The structure was solved from diffractometer data by direct methods, and refined toR 0.085 for 1216 observed (of a total of 2421) reflections. Strain in the almost planar ringA is indicated by the endocyclic torsion angles, ringsB andC, which aretrans fused and chair-shaped, while ringD is intermediate between a 13-envelope and a 13, 14-half-chair conformation. RingE, a 2,5,6-trisubstituted 1,3-dioxane-like unit, adopts a highly distorted boat conformation. The bending of the skeleton is toward its side. TheA-ring carbonyl substituent accepts one hydrogen bond involving a symmetry-related 11-ol function [O(1)-O(2) 2.81, O(2)-H 1.0, H---O(1) 1.8 Å/ O(2)-H---O(1) 165°].We thank the Schering-Plough Research Division, Bloomfield, New Jersey, for the gift of the sample and the Istituto di Chimica e Tecnologia dei Radioelementi C.N.R., Padova, for equipment and computing facilities.     

Anodic ethylation of lead by cathodically produced diethylcadmium

o-, m- and p-Nitrophenyltrimethylsilanes and 2,4-dinitrophenyltrimethylsilane were conveniently prepared by the reactions of hexamethyldisilane with the corresponding nitrohalobenzenes catalyzed by tetrakis(triphenylphosphine)-palladium(O).     

A generalization of symplectic Pontrjagin classes to vector bundles with structure groupSp(n)·Sp(1)

Sunto Si considerano fibrati vettoriali reali con gruppo strutturale riducibile a Sp(n)· Sp(1)e a Sp(n)·tU(1)e si introducono classi caratteristiche relative a tali strutture mediante forme differenziali rappresentanti. Tali classi risultano generatori algebricamente indipenclenti dei quozienti modulo la 2-torsione degli anelli di coomologia intera dei rispettivi spazi classificanti, e si riducono mod. 2 a classi già introdotte. Si esamina in particolare il caso del fibrato tangente dello spazio proiettivo quaternionale.     

Iridium nitrosyl complexes of 2-aminophenol derivatives

Summary The synthesis and characterisation of products obtained by the interaction between [Ir(NO)(MeCN)₂(PPh₃)₂]²⁺ and 2-aminophenol derivatives are reported. Tetracoordinate d⁸complexes of the type Ir(NO)(2-ap)(PPh₃) and pentacoordinate d complexes₆of the type [Ir(2-ap)(PPh₃)₃]⁺ where 2-ap=2-aminophenol, 2-amino-4-nitrophenol, 2-amino-5-methylphenol, 2-3-aminonaphthol and 2-amino-4-methylphenol are obtained. The Ir(NO)(PPh₃)₃ complex is always present as a byproduct. Physical properties, i.r. spectra and conductivity data of the complexes are tabulated. Reaction schemes for the formation of the three complexes are proposed and discussed.