Syntheses and reactions of some fluorinated dienes,cyclobutenes and furans

There are many reports¹ of the pyrolysis of fluorinated organic compounds, including the defluorination of cyclic fluorocarbons over iron to give aromatic compounds. Extending this technique we have investigated the flow pyrolysis of some readily accessible unsaturated fluorocarbons, such as I, II, and III, and found these to be synthetically

useful routes to fluorinated dienes, cyclobutenes, and furans. Pyrolyses were carried out using a nitrogen flow over platinum, iron or caesium fluoride heated at 430–700°. The various products can all be rationalized in terms of intermediate allylic radicals, and the solid substrate influences which allylic radicals are formed.We are also investigating the chemistry of those now accessible compounds, such as IV, V, and VI, and some of the preliminary results are described.

For example the fluoride ion induced dimerisation of IV gave two major products VII and VIII via a particular interesting mechanism.

     

A structure theorem for boundary-transitive graphs with infinitely many ends

We prove a structure theorem for locally finite connected graphsX with infinitely many ends admitting a non-compact group of automorphisms which is transitive in its action on the space of ends, Ω _X . For such a graphX, there is a uniquely determined biregular treeT (with both valencies finite), a continuous representationφ : Aut(X) → Aut(T) with compact kernel, an equivariant homeomorphism λ : Ω _X → Ω _T , and an equivariant map τ : Vert(X) → Vert(T) with finite fibers. Boundary-transitive trees are described, and some methods of constructing boundary-transitive graphs are discussed, as well as some examples.     

Real-space renormalization group for Langevin dynamics in absence of translational invariance

A novel exact dynamical real-space renormalization group for a Langevin equation derivable from a Euclidean Gaussian action is presented. It is demonstrated rigorously that an algebraic temporal law holds for the Green function on arbitrary structures of infinite extent. In the case of fractals it is shown on specific examples that two different fixed points are found, at variance with periodic structures. Connection with the growth dynamics of interfaces is also discussed.     

Spatial polyhedra without diagonals

We provide new polyhedra without diagonals, and we discuss their embeddings in euclidean 3-space with maximal symmetries starting with a complete classification of their combinatorial properties: orientable neighborly 2-pseudomanifolds with 9 vertices or Mendelsohn triple systemsS ₂(2, 3, 9). This article was motivated by the longstanding and still open question: find a triangulated 2-manifold which can not be embedded in 3-space. Furthermore, we applied tested and improved algorithms for realizing oriented matroids or finding final polynomials.     

Crystal and molecular structure of geiparvarin

The structure of the antitumor agent geiparvarin was determined by direct methods from CuK diffractometer data. The crystals of synthetic geiparvarin have the space groupP2₁/c witha = 8.305(1),b = 11.077(1),c = 18.287(1) Å, = 98.79(1) °, andZ = 4. The structure was refined toR = 0.047. The chemically determined structure was confirmed. Bond distances and angles are normal and there are no unusual C-H O intermolecular contacts.IUPAC name: 7-[3-(4,5-dihydro-5,5-dimethy1-4-oxo-2-furanyl)-2-butenyi]-oxy-(2H-1-benzopyran-2-one).Camille and Henry Dreyfus Teacher-Scholar, 1978–1983; National Institutes of Health Career Development Award, 1980–1985.     

Giant resonance effects in the analysing power from inelastic proton scattering

A simultaneous analysis of the analysing power and differential cross-section for the inelastic scattering of 30.4 MeV protons to the 2^?(8.88 MeV) state in ¹⁶O confirms the importance of two step components in the reaction mechanism. These important two step processes are those in which giant multipole resonances of the target are excited.