Multiple crossover phenomena and scale hopping in two dimensions

We study the renormalization group for nearly marginal perturbations of a minimal conformal field theory M_p with p 1. To leading order in perturbation theory, we find a unique one-parameter family of “hopping trajectories” that is characterized by a staircase-like renormalization group flow of the C-function and the anomalous dimensions and that is related to a factorizable scattering theory recently solved by Al. B. Zamolodchikov. We argue that this system is described by interactions of the form . As a function of the relevant parameter t, it undergoes a phase transition with new critical exponents simultaneously governed by all fixed points M_p, M_p−1,…, M₃. Integrable lattice models represent different phases of the same integrable system that are distinguished by the sign of the irrelevant parameter .     

Eliminative deoxygenation: the facile formation of α-trimethylsilyl vinyl sulfides from sulfoxides

Synthetically useful α-trimethylsilyl vinyl sulfides are generated in high yields by deoxygenation of the corresponding sulfoxides in the presence of excess LDA and trimethylsilyl chloride.     

Eliminative deoxygenation: A facile synthesis of α-cyano and α-carboalkoxy substituted vinyl sulfides

The faciIe eliminative deoxygenation of α-cyano and carboalkoxy sulfoxides by trimethylsilyl triflate under mildly basic conditions results in the formation of α-thiophenyl substituted α,β-unsaturated nitriles and esters in high yields.     

Engineering a Small HOMO–LUMO Gap and Intramolecular C−H Borylation by Diborene/Anthracene Orbital Intercalation

The diborene 1 was synthesized by reduction of a mixture of 1,2-di-9-anthryl-1,2-dibromodiborane(4) ( 6 ) and trimethylphosphine with potassium graphite. The X-ray structure of 1 shows the two anthryl rings to be parallel and their π(C₁₄) systems perpendicular to the diborene π(B=B) system. This twisted conformation allows for intercalation of the relatively high-lying π(B=B) orbital and the low-lying π* orbital of the anthryl moiety with no significant conjugation, resulting in a small HOMO–LUMO gap (HLG) and ultimately a C−H borylation of the anthryl unit. The HLG of 1 was estimated to be 1.57 eV from the onset of the long wavelength band in its UV/Vis absorption spectrum (THF, λ_onset=788 nm). The oxidation of 1 with elemental selenium afforded diboraselenirane 8 in quantitative yield. By oxidative abstraction of one phosphine ligand by another equivalent of elemental selenium, the B−B and C¹−H bonds of 8 were cleaved to give the cyclic 1,9-diborylanthracene 9 .     

X-Ray Investigations on Celluloses Grafted by the Thiocarbonation Method

It is a pleasure for me to contribute to the symposium held in honor of my colleague and old friend Vivian Stannett. The topic of this contribution is results of x-ray investigations on graft modified cellulose fibers.     

Water Vapour Adsorption on the Iron(111) Surface Studied by LEED and WFC

In a sample isolation and gas inlet system for aggressive gases saturation states of adsorption as a function of water vapour pressure were generated on the Fe(111)-surface at room temperature and analyzed quantitatively under ultra-high vacuum conditions using the methods LEED and WFC. There is a random adsorption layer emerging passing over into a p(1 × 1) structure when heated between 200°C and 400°C. This structure is more resistent to heat and oxygen treatment than an oxygen adsorption or oxide layer, respectively. The adsorption velocity for oxygen on the p(1 × 1)–H₂O structure amounts to only about 15% of the adsorption velocity on the p(1 × 1)–O structure. The adsorption isotherm measured can be described through a theoretical model.