Disordered sodium alkoxides from powder data: crystal structures of sodium ethoxide, propoxide, butoxide and pentoxide, and some of their solvates

The crystal structures of sodium ethoxide (sodium ethanolate, NaOEt), sodium n-propoxide (sodium n-propanolate, NaOnPr), sodium n-butoxide (sodium n-butanolate, NaOnBu) and sodium n-pentoxide (sodium n-amylate, NaOnAm) were determined from powder X-ray diffraction data. NaOEt crystallizes in space group P421m, with Z = 2, and the other alkoxides crystallize in P4/nmm, with Z = 2. To resolve space-group ambiguities, a B ä rnighausen tree was set up, and Rietveld refinements were performed with different models. In all structures, the Na and O atoms form a quadratic net, with the alkyl groups pointing outwards on both sides (anti-PbO type). The alkyl groups are disordered. The disorder becomes even more pronounced with increasing chain length. Recrystallization from the corresponding alcohols yielded four sodium alkoxide solvates: sodium ethoxide ethanol disolvate (NaOEt · 2EtOH), sodium n-propoxide n-propanol disolvate (NaOnPr · 2nPrOH), sodium isopropoxide isopropanol pentasolvate (NaOiPr · 5iPrOH) and sodium tert-amylate tert-amyl alcohol monosolvate (NaOtAm · tAmOH, tAm = 2-methyl-2-butyl). Their crystal structures were determined by single-crystal X-ray diffraction. All these solvates form chain structures consisting of Na+, – O − and – OH groups, encased by alkyl groups. The hydrogen-bond networks diverge widely among the solvate structures. The hydrogen-bond topology of the iPrOH network in NaOiPr · 5iPrOH shows branched hydrogen bonds and differs considerabl...

Source: Acta Crystallographica Section B - January 21, 2021 Category: Chemistry Authors: Beske, M. Cronje, S. Schmidt, M.U. Tapmeyer, L. Tags: sodium alkoxide powder data solvate isopropanol B ä rnighausen tree PXRD research papers Source Type: research