A voltammetric study of several oxygen,sulfur and selenium heterocyclic carbonium ions in acetonitrile

Cyclic voltammetric data are reported on seven new oxygen, sulfur and selenium heterocyclic carbonium ions. Each compound undergoes electrochemical reduction to form a dimer. The reaction mechanisms are discussed. The compounds with selenoethoxy substituents formed heterofulvalenes at room temperature.     

A compact differential isoperibol calorimeter with variable heat shields

The dynamic characteristics of an isoperibol solution calorimeter with electrical heating are discussed on a theoretical basis.The design requirements of a solution calorimeter are briefly reviewed. A calorimeter which satisfies these requirements was conducted and is described here. The dynamics of solutions heating by an electrical heater are mathematically developed and computer generated heating curves are compared to experimental curves.     

Fock-tani representation for the quantum theory of reactive collisions

A previously-developed second-quantization representation for nonrelativistic systems of composite bound states and their constituents is extended to any number of composite species. The result is an explicit representation for the kinematics and dynamics of reactive scattering processes (rearrangement collisions). A single Hamiltonian in the new representation simultaneously exhibits the various possible scattering and reaction channels, thus circumventing problems associated with “different Hamiltonians for different channels”. The “unperturbed” Hamiltonian describes the free propagation of all possible bound composites as well as their unbound constituents, while the interaction Hamiltonian describes only true scattering and reaction processes, each term corresponding to a collision process with specified initial and final bound composites and/or unbound constituents. The key to the generalization is a suitable ordering of the composite species and a corresponding ordered-product form of the unitary transformation to the new representation.     

The electrochemical preparation of organo nickel and palladium halides

The electrochemical oxidation of a nickel or palladium anode in the presence of certain organic halides yields the unstable RMX species, which can be stabilised by both mono and bidentate phosphorus(III) ligands. Cyanide compounds of the general formula RNiCN.L₂ can also be synthesised. The advantages of the method are outlined.     

Multilinear enumerative techniques

When S is a finite set and G a finite group acting on S, we consider the problem of rejecting isomorphs in a G-stable subset of S. In previous work we developed a linear algebraic context for this problem by constructing the finite dimensional vector spaceF^s whereF is a field of characteristic zero. When S is a finite function space, or a finite direct product of finite function spacesF^s acquires a multilinear structure By various specializations ofG and S and by applications of results which have appeared elsewhere, identities of Sheehan, deBruijn and P61ya are obtained. Furthermore, these same techniques are applied to examples which do not have a clear resolution using the more common formulas     

Dipole and Quadrupole Measurements of an Isolated Turtle Heart

An equivalent cardiac generator, specifically the multipole model, was evaluated for an isolated turtle heart located in a spherical volume conductor. The dipole and quadrupole contributions to the potential field were calculated using weighted integrals of the surface distributions. This procedure has the advantage of eliminating errors due to the truncation of the multipole series. The dipole and quadrupole effects were calculated for the QRS portion of the cardiac waveform. A significant quadrupole contribution was found to exist.     

Radical and palladium-catalyzed cyclizations to cyclobutenes: an entry to the BCD ring system of penitrem D

A novel approach toward the synthesis of the BCD ring system of penitrem D is described. The strategy capitalizes on the fast cyclization rates of aryl radicals into cyclobutenes and allows access to a variety of fused tricyclic structures. Radical/polar crossover reactions of precursors 24-29 promoted by samarium diiodide in the presence of HMPA and acetone allow access to the fully functionalized BCD ring system of penitrem D. The stereochemical implications of these processes are evaluated, and a Pd-mediated cyclization approach toward the penitrems is also introduced.     

Bicyclo[3.2.1]octane synthons from cyclopropenes: functionalization of cycloadducts by nucleophilic additions

It has been known for several decades that a highly functionalized family of tetrahalobicyclo[3.2.1]octadienes are readily available through the cycloaddition of furan or cyclopentadiene with either tetrachloro- or tetrabromocyclopropene. However, the application of these highly functionalized building blocks in synthesis has remained relatively unexplored in relation to their better-known counterparts derived through oxyallyl cation additions. As a first step toward utilizing these highly versatile intermediates in synthesis, a study of the addition of various nucleophiles to the halogenated nucleus has been conducted. It has been found that these halogenated systems are amenable to a wide range of functionalizations in high yields and with good selectivities.     

Site-selective abstraction in the reaction of 5-20 eV O+ with a self-assembled monolayer

Site-specific reaction of hyperthermal O+ with a self-assembled monolayer is described. Isotopic labeling experiments reveal the percentage of abstraction products formed from hydrogen atoms bound originally to the top three carbon atoms in the chain.