Quinolines dissolving metals

The partial reduction of alkynes provides methods that are both regio-and stereospecific. Dissolving metal reductions tend to give trans alkenes, whereas catalytic methods of reduction generate the cis alkenes (Scheme 3.3). A Lindlar catalyst (Pd/CaCOj + PbO, partially poisoned with quinoline) has been recommended for use in this context. 

Lowering the temperature, -10 to -30 C, has improved the selectivity of the Lindlar catalyst when used in the presence of quinoline dissolved in pentane, hexane or hexane/THF. However, raising the temperature increases the rate of desorption of the alkene, which appears to account largely for the resulting increase in the selectivity of the heavier Group VIII metals for the hydrogenation of the simple al-kynes. ... 

Rhenium can be analyzed by various instrumental techniques that include flame-AA, ICP-AES, ICP-MS, as well as x-ray and neutron activation methods. For flame-AA analysis the metal, its oxide, or other insoluble salts are dissolved in nitric acid or nitric-sulfuric acids, diluted, and aspirated directly into nitrous oxide-acetylene flame. Alternatively, rhenium is chelated with 8-hydroxy quinoline, extracted with methylisobutyl ketone and measured by flame-AA using nitrous oxide-acetylene flame. 

Metal-depleted medium, used in the work depicted in Plate 5, was conveniently made as follows. The required nutrient salts were dissolved in water. This solution was shaken out with a solution of dithizone in chloroform. This operation was repeated many times, and finally the solution was shaken out with chloroform (to remove the dithizone) and finally aerated (to remove the chloroform) (Piper, 1942). Other substances with a high avidity for metals have been used similarly, e.g. 8-hydroxy-quinoline for depleting bacteriological media (Rubbo, Albert, and Gibson, 1950). Thirty-eight methods of metal depletion have been compared by Donald, Passey, and Swaby (1952). 

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