A HF Loaded Lewis-Acidic Aluminium Chlorofluoride for Hydrofluorination Reactions

The very strong Lewis acid aluminium chlorofluoride (ACF) was loaded with anhydrous HF. The interaction between the surface of the catalyst and HF was investigated using a variety of characterization methods, which revealed the formation of polyfluorides. Moreover, the reactivity of the HF-loaded ACF towards the hydrofluorination of alkynes was studied.     

Pomeron Fans for Finite Nuclei

Theoretical and Mathematical Physics - In perturbative QCD, we study a set of pomeron fan diagrams propagating from a projectile to A nucleons in the nucleus target for finite A and investigate its...     

New lower bounds on the size of (n,r)‐arcs in PG(2,q)

An $\left(n,r\right)$‐arc in $\text{PG}\left(2,q\right)$ is a set of $n$ points such that each line contains at most $r$ of the selected points. It is well known that $\left(n,r\right)$‐arcs in $\text{PG}\left(2,q\right)$ correspond to projective linear codes. Let $m_r\left(2,q\right)$ denote the maximal number $n$ of points for which an $\left(n,r\right)$‐arc in $\text{PG}\left(2,q\right)$ exists. In this paper we obtain improved lower bounds on $m_r\left(2,q\right)$ by explicitly constructing $\left(n,r\right)$‐arcs. Some of the constructed $\left(n,r\right)$‐arcs correspond to linear codes meeting the Griesmer bound. All results are obtained by integer linear programming.     

Towards a Certified Version of the Encyclopedia of Triangle Centers

Triangle centers such as the center of gravity, the circumcenter, the orthocenter are well studied by geometers. Recently, under the guidance of Clark Kimberling, an electronic encyclopedia of triangle centers (ETC) has been developed, it contains more than 7000 centers and many properties of these points. In this paper, we describe how we created a certified version of ETC such that some of the properties described come along with a computer checked proof of its validity.     

Splitting kernels into small summands

Let λ be a regular cardinal. An epimorphism between abelian groups is λ -pure if it is projective with respect to abelian groups of size less than λ. We show that cotorsion groups A have λ-pure projective dimension greater than 1 for all uncountable λ ≤ |A/tA|, where tA denotes the torsion subgroup of A. For λ > |A/tA|, cotorsion groups A are λ-pure projective.     

ALKYLIERUNGS,UND ARYLIERUNGSREAKTIONEN MIT GEMINALEN DITHIOLATEN

Abstract

Acylacetonitrile 1 reagieren mit Schwefelkohlenstoff in Gegenwart von Natriumhydrid zu den Dinatriumsalzen 2. Behandlung von 2 mit einem Alkylierungsreagens ergibt die offenkettigen oder cyclischen Acyl-cyanketen-S,S-acetale 3, 4, 8 bzw. 10. Arylierung zu 11 gelingt mit 2,4-Dinitrochlorbenzen. Fügt man zu² nur ein Äquivalent Methyliodid hinzu und säuert das Reaktionsgemisch an, so entstehen die monoalkylierten Verbindungen 7, während β-Hydroxythioanilide 12 durch Umsetzung von 1 mit Phenylisothiocyanat zugänglich sind. Ein Vergleich der δ-Werte zeigt, daß in 7 und 12 der gleiche Typ für die Chelatisierung des Protons der OH-Gruppe vorliegt.

Acyl acetonitriles 1 react with carbon disulfide in the presence of sodium hydride to give disodium salts 2. Treatment of 2 with an alkylation reagent yields the open chain or cyclic acyl cyanketene S,S-acetals 3,4,8 and 10, respectively. Arylation to 11 is successful with 2,4-dinitro-chlorobenzene. Adding only one equivalent of methyl iodide to 2 and acidifying the reaction mixture lead to the monoalkylated compounds 7, whereas β-hydroxythioanilides 12 are available by reaction of 1 with phenyl isothiocyanate. A comparison of the δ-values shows that there exists the same type of the proton's chelation of the OH-group in 7 and 12.     

Hexa-Coordinated Silicon Complexes Derived from Regioisomeric Aminotriphenylethanols and Their use as Dopants for Liquid Crystals

Abstract

Tridentate imine ligands that are obtained from the chiral, regioisomeric amino alcohols 2-amino-1,1,2-triphenyethanol and 2-amino-1,2,2-triphenylethanol serve for the formation of bis-chelated silicon complexes. Whereas the complex based on the former amino alcohol is obtained as a diastereomeric mixture, the complex that is derived from 2-amino-1,2,2-triphenylethanol forms in a completely diastereoselective manner, and its configuration is determined as (A,R,R), according to a crystal structure analysis. The new silicon complexes are found to be efficient dopants for the conversion of nematic liquid crystals into cholesteric phases.

GRAPHICAL ABSTRACT     

General Discussion on Thermal and Photodegradation and Stabilization

Indole-containing bifunctional monomers (diacids, dialcohols, and dialdehydes) were synthesized by using as the basic nucleus two indoles attached by a tetraethylene glycol chain. These monomers were used for the preparation of polyesters, poly-amides, and polyazomethines.