Reactions of diterpenoids on solid supports II. Behavior of di- and tricyclic diterpenoids on alumina containing oxidants
The behavior of epimanool (1), epimanool oil, larixol (2), cis-abienol (3) and methyl dehydroabietate (4) on alumina impregnated with oxidants (H2CrO4 and KMnO4) has been studied. This has led to the methyl ketone (5) and norambrenolide (8) - precursors of the perfume substances 14,15,17-trinorlabdane-8,13-dione (6), 8α-hydroxy-14,15-bisnorlabd-II-en-13-one (7), and methyl 7-oxodehydroabietate (14). α-Levantenolide (11) has been synthesized in one stage from cis-abienol (3)for the first time.
Oxidising supported reagents-II-influence of the chemical and textural properties of the K2Cr2O7 supported reagents on the oxidation of menthol
Abstract We have analyzed the influence of the chemical and textural properties of the solid supports as well as the oxidising K2Cr2O7 supported reagent on the oxidation of menthol to menthone—as a reaction test—. The most active K2Cr2O7 supported reagents are obtained with amorphous solid supports with large surface areas or with microcrystalline solids, with great amounts of oxidising sites titrated by phenothiazine.
“ PARTIALLY-ACTIVATED ” FLUX RESIDUE IMPACTS ON ELECTRONIC ASSEMBLY RELIABILITIES
The reliabilities of the flux residue of electronic assemblies and semiconductor packages are attracting more and more attention with the adoption of no-clean fluxes by majority of the industry. In recent years, the concern of “partiallyactivated” flux residue and their influence on reliability have been significantly raised due to the miniaturization along with high density design trend, selective soldering process adoption, and the expanded use of pallets in wave soldering process. When flux residue becomes trapped under low stand-off devices, pallets or unsoldered areas (e.g. selective process), it may contain unevaporated solvent, “live” activators and metal complex intermediates with different chemical composition and concentration levels depending on the thermal profiles. These partially-activated residues can directly impact the corrosion, surface insulation and electrochemical migration of the final assembly. In this study, a few application tests were developed internally to understand this issue. Two traditional liquid flux and two newly developed fluxes were selected to build up the basic models. The preliminary results also provide a scientific approach to design highly reliable products with the goal to minimize the reliability risk for the complex PCB designs and assembly processes.