Organische Reaktionen an Aluminiumoxid-Oberflächen

Expanded Porphyrin Contraction: From [22]Triphyrin(6.6.0) to [22]Triphyrin(6.5.0)

An expanded triphyrin containing a bipyrrole moiety and annulene links, namely tetraphenyl-[22]triphyrin(6.5.0), 2, has been synthesized. The synthesis proceeded by a postsynthetic transformation of tetraphenyl-[22]triphyrin(6.6.0), 1, in a metal-free unexpected and unprecedented ring contraction during column chromatography on alumina. The observed transformation, located at the hydrocarbon chain linking the pyrrole units, formally corresponds to a subtraction of one carbon atom from an annulene circuit. In contrast to the flexible substrate 1, the product 2 is conformationally rigid, and capable of chloride anion binding in its protonated form.

Oxidation of Benzylic Alcohols to Carbonyl Compounds with Hydrogen Peroxide Catalysed by Manganeses Chloride Supported on Montmorillonite K10

Manganeses(II) chloride supported on montmorillonite K10 was found to be an efficient catalysts for the oxidation of alcohols to carbonyl compounds with hydrogen peroxide as oxidant.

Application of a novel phenylpiperazine formation reaction to the radiosynthesis of a model fluorine-18-labeled radiopharmaceutical (18FTFMPP)

The labeled serotonin agonist 3-[18F]fluoro-N-(alpha,alpha,alpha-trifluoro-m-tolyl)piperazine (18FTFMPP) was prepared rapidly using the labeling procedure for trifluorotoluenes, [18F]fluoro-for-nitro exchange, followed by an alumina-supported bis-alkylation. After normal-phase HPLC purification, the labeled product was obtained in 20-32% (n = 20) decay-corrected radiochemical yield with a radiochemical purity > 98% and a specific activity of 100 GBq/mumol. The synthesis time including purification was 3 h. The receptor binding affinity of FTFMPP to rat brain membranes was found to be similar to that of the nonfluorinated parent compound (TFMPP). Although TFMPP has been proposed by others as an agent for the imaging of serotonin receptors, only minimal receptor-mediated uptake was observed.

Sorption Properties of Aluminas in Relation to Adsorbate—Adsorbent Interaction

Five calcination products AI–AV were obtained by the calcination of alumina gel in the temperature range 673–1473 K. The adsorption of nitrogen at 77 K on these products was determined volumetrically. The chemisorption of H2, CO, CO2 and CH4 at 300, 320 and 340 K was also determined for each alumina sample.

Increasing calcination temperature caused phase changes with formation of the most stable phase α-Al2O3 starting at 1273 K and predominating at 1473 K. Chemisorption depends on the nature of the adsorbent and the adsorbate molecules. The amount adsorbed was related to the critical temperature of the gas involved while the heat of adsorption was related to the strength of the interaction between the adsorbent and the adsorbate. The polarizability of the adsorbed gas molecule is a determining factor in its chemisorption, particularly on polar surfaces.