12 research outputs found
Drying activity of oxovanadium(IV) 2-ethylhexanoate in solvent-borne alkyd paints
Oxovanadium(IV) 2-ethylhexanoate was established as a new primary drier for alkyd-based paints. A series of experiments has demonstrated an excellent drying activity toward solvent-borne alkyd resins of different oil length at considerably lower metal concentration than optimal for commercial cobalt(II) 2-ethylhexanoate. The behavior in real paint was simulated on formulations bearing inhibitor of autooxidation. The detailed studies of the drying process have shown that the relatively slow initial step of autooxidation reaction, when compared with cobalt compounds, is compensated for by the absence of the induction times. Furthermore, the active oxovanadium(IV) species are not consumed during the drying processes as evidenced by EPR spectroscopic measurements.2-ethylhexanoatu oxovanadiÄŤitĂ˝ vykazuje vlastnosti typickĂ© pro primárnĂ sikativy. UvedenĂ© experimenty ukazujĂ vĂ˝bonou sikativaÄŤnĂ aktivitu vĹŻÄŤi alkydovĂ˝m pryskyĹ™icĂm rĹŻznĂ© olejovĂ© dĂ©lky pĹ™i vĂ˝raznÄ› nižšĂch koncentracĂch neĹľ je běžnĂ© u komerÄŤnĂch 2-ethylhexanoatu kobaltnatĂ©ho. ChovánĂ v reánĂ© formulaci bylo simulováno na sysytĂ©mech s inhibitory autooxidace
Double Bond Stereochemistry Influences the Susceptibility of Short‑Chain Isoprenoids and Polyprenols to Decomposition by Thermo‑Oxidation
Alcohols are common constituents of
living cells. They are usually assigned a role in the adaptation
of the cell to environmental stimuli, and this process
might give rise to their oxidation by reactive oxygen
species. Moreover, cellular isoprenoids may also undergo
various chemical modifications resulting from the physicochemical
treatment of the tissues, e.g., heating during food
processing. Susceptibility of isoprenoid alcohols to heat
treatment has not been studied in detail so far. In this study,
isoprenoid alcohols differing in the number of isoprene units
and geometry of the double bonds, β-citronellol, geraniol,
nerol, farnesol, solanesol and Pren-9, were subjected to
thermo-oxidation at 80 °C. Thermo-oxidation resulted in the
decomposition of the tested short-chain isoprenoids as well
as medium-chain polyprenols with simultaneous formation
of oxidized derivatives, such as hydroperoxides, monoepoxides,diepoxides and aldehydes, and possible formation of oligomeric derivatives. Oxidation products were monitored by GC-FID, GC-MS, ESI-MS and spectrophotometric methods. Interestingly, nerol, a short-chain isoprenoid with a double bond in the cis (Z) configuration, was more oxidatively stable than its trans (E) isomer, geraniol. However, the opposite effect was observed for medium-chain polyprenols, since Pren-9 (di-trans-poly-cis-prenol) was more susceptible to thermo-oxidation than its all-trans isomer, solanesol. Taken together, these results experimentally confirm that both short- and long-chain polyisoprenoid alcohols are prone to thermo-oxidation