Molekulare Zusammensetzung von flüssigem Schwefel. Teil 2: Qualitative Analyse und Isolierung von S7, S12, α-S18 und S20

Molecular Composition of Liquid Sulfur. Part 2: Qualitative Analysis and Preparation of S₇, S₁₂, α-S₁₈, and S₂₀ from S₈ Raman spectra of sulfur melts (115–300°C), of quenched melts and of CS₂ extracts of quenched melts show besides S₈ the presence of S₆ and S₇. Formation of S₇ from S₈ at 120°C takes more than 8 h; the S₇ equilibrium concentration increases with temperature. Pure crystalline S₇, S₁₂, α-S₁₈ and S₂₀ are prepared on a preparative scale by fractional extraction, crystallization, flotation and precipitation of quenched sulfur melts. Also a mixture of larger rings (S_x; x? = 25) has been isolated. Infrared and Raman spectra of α-S₁₈, S₂₀ and S_x are reported.     

Preparation of α-Bromo- and α-Chlorocarboxylic Acids from α-Amino Acids

Diazotization of α-amino acids in 48:52 (w/w) hydrogen fluoride/pyridine along with excess of potassium halide results in the corresponding α-halocarboxylic acids in good to excellent yields (Table 1 and 2).     

Absolute Konfiguration von α-Zeacarotin, α-Apo-8-carotinal und α-Apo-8-carotinol

α-Zeacarotene, isolated from corn gluten, has been shown to have the same absolute configuration at C(6) as natural (+)-α-carotene. Chiroptical comparison was made with the derived α-apo-8-carotenole. The same chirality has been found with δ-, ε-carotene, lutein, semi-α-carotenone, zeinoxanthin, crocoxanthin and β,ε-carotene-2-ol. Therefore, biological cyclisation of the acyclic precursor to the α-ionone ring seems to be stereospecific and is probably different (enantiomeric) to that leading to β-ionone derivatives. Cotton effects of carotenoids have for the first time been measured in the visible region. All carotenoids examined with C(6)-R-chirality show a positive effect at their longest absorption band.     

Preparation of phenylquinoxaline from α,α-diaminoketones and dimethyl-O-phenylenediamine

Amination of α,α-diaminoketones 1 by 4,5-dimethyl-o-phenylenediamine gave 6,7-dimethyl-2-phenylquinoxaline (II) in a high yield. The reaction may occur through formation of α-ketoazomethine III. The α,α-di-aminoketones were obtained by condensation of phenylglyoxal and substituted anilines.     

Polymers from 12 α-hydroxymethylabiet-7,8-enoic acid and vinyl 12 α-hydroxymethylabiet-7,8-enoate

12 α-Hydroxymethylabiet-7,8-enoic acid has been homopolymerized by melt condensation, and a partially crystalline polyester has been obtained. Vinyl 12 α-hydroxymethylabiet-7,8-enoate has been prepared from 12 α-hydroxymethylabiet-7,8-enoic acid by vinyl interchange with vinyl acetate and has been homopolymerized, copolymerized with vinyl chloride, vinyl acetate, butadiene, and acrylonitrile, and terpolymerized with styrene and acrylonitrile. Polymers thus obtained have been characterized.