Synthesis of Monosubstituted (S)-Oxiranes in High Optical Purity

✍ Scribed by Prof. Dr. Ulrich Schmidt; Dr. Jörg Talbiersky; Frank Bartkowiak; Jochen Wild

• Publisher: John Wiley and Sons
• Year: 1980
• Tongue: English
• Weight: 256 KB
• Volume: 19
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.198001981

✦ Synopsis

rate with high vapor pressure at T>2500"C, thus accounting for their low content; the high melting impurities Ta and W, on the other hand, remain in the niobium. The samples R-Nb-1 were electrolyzed; the major impurities Ta and W are thus removed, but metals such as Cr, Fe, and Co are apparently involved by contamination. The samples R-Nb-2 were additionally zone refined and annealed, which leads to a marked decrease in the Cr, Fe, and Co content.

The niobium thus obtained can be additionally characterized by its specific electrical resistivity of @ (4.2 K)=6 x 0 cm in the normal state; the total content of non-metals is about 100 ppb. These findings show that niobium of particularly high purity and structural perfection can be prepared by the above method. The analytical method developed here for the determination of Cr, Fe, and Co is characterized by its extremely high sensitivity and freedom from error regarding contamination and losses.