Carbon site exchange

Facilities are available for disposal and regeneration of spent activated carbon, and the vendor can coordinate transportation and on-site exchange requirements. 

Br/Mg exchange converts 1,2-dibromocyclopentene into the p-bromoalkenyl-magnesium chloride (LiCl complex), which reacts normally with carbonyl compounds. It is possible to peform a copper-mediated coupling at the p-carbon site while retaining the C-MgCl unit. ... 

C and — 50°C C-spectrum 0.898-0.670 ppm, between — 80°C and —46°C), whereas the remaining methylene protons show a small upheld shift. The two CH2-carbons are shielded between 0.607 (—80°C) and 0.536 ppm (—46°C) relative to the unlabelled cation. The relative upheld and downheld C-shift ratio of 1 2 (corrected for an intrinsic upheld shift) conhrms that a fast two-site exchange is taking place between a singly populated highheld site and a doubly populated lowheld site. 

By contrast, in dihuorosilicates no huorine-site exchange is obso-ved even at elevated temperatures, as a result of the higher stability of complexes with huorine atoms in apical positions replacement of an apical huorine by a carbon ligand is too costly in toms of energy, and is not observed . 

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