Room temperature structures and odd–even behaviour of a homologous series of anhydrous lithium n-alkanoates

Thermal and odd–even behaviour in a homologous series of lithium n-alkanoates

“…The purity of the compounds was checked by elemental analysis, using a Perkin Elmer Series II CHNSO Analyzer and by infrared analyses of samples recorded in KBr pellets on a Perkin-Elmer FT-IR 1000 spectrometer, at room temperature, in the range of 4000 cm À1 to 450 cm À1 at a resolution of 1 cm À1 . The results were in accord with expected values for the anhydrous compounds [9].…”

“…This has been attributed to differences in methods of preparation, crystallization, impurities and the presence of polymorphs [8,9]. Furthermore, no systematic attempt has been made to correlate the phase sequences observed with chain length and molecular structures of the room temperature solids.…”

“…Nevertheless, important structural information has been gleaned from X-ray powder diffraction. For example, at room temperature, the compounds are near isostructural with ionic lithium-carboxylate coordinated to asymmetric lithium-oxygen bonds [9,10]. Furthermore, the hydrocarbon chains are arranged tail-to-tail within lamellar layers and tilted with respect to the planes containing lithium ions.…”

“…However, for the short chain length compounds, at least up to lithium pentanoate, a monoclinic crystal structure with P2 1 /c symmetry is indicated [11]. Since the strength of the lithium-oxygen bond is reported to be chain length dependent [9,10,12], it is entirely reasonable to expect that the thermal behaviour of these compounds will be governed by chain length, the relative strength of van der Waals interaction between hydrocarbon chains and the arrangement of the chains within the molecular lattice.…”

Phase Diagrams of Mesogenic Binary Systems of Cobalt(II) and Univalent Metal Octanoates

“…The important carbonyl absorptions that point to a possible molecular structure are the asymmetric stretch, ν as (COO) ≈ 1570 -1560 cm −1 , and the symmetric stretch, ν s (COO) ≈ 1425 -1410 cm −1 . Additionally, the frequencies and relative positions of the symmetric and asymmetric bands (∆ν = ν as − ν s ) are interpreted by several authors as indicative of carboxylate-metal ion coordination [8,10,11]. For example, the frequency shifts of these bands relative to those of the free carboxylate ion depend on metal to Compound Frequencies of main IR bands, cm −1 ligand coordination.…”